Hot Start problem, sometimes, when it is hot outside...

[rothsean]

So the summer is here in TX for sure, and so is my occasional hot start problem.

Sometimes after the car sits for 10+ minutes it takes a good 10 seconds of cranking for the engine to turn on, then it runs rough at about 400 rpm for 5 seconds or so then settles smoothly at 900 rpm after about 10 seconds. That is all without touching the gas pedal.

This does not happen all of the time, but it seems to happen more when the outside air temp is above 80.


I have new injectors, new all-in-one fuel pump, new accumulator, no fuel leaks, new o-ring in fuel distributor. I just don't understand what is causing this, rich maybe?? It smells rich after it finally starts.

[DavidProehl]

Sounds like you've replaced the right parts. Perhaps there is an electrical problem causing your TTS to short thus causing extra gas to spray in when warm rather than only when cold? Maybe the TTS itself is broken and is always on. Just brainstorming here. Not sure I've ever heard of that happening, but it would explain it running rich when first starting up warm.

[DavidProehl]

To test the above theory, when the car is warm, unplug the wire going to the TTS before restarting. If it starts up fine, then that might be the culprit.

[rothsean]

To test the above theory, when the car is warm, unplug the wire going to the TTS before restarting. If it starts up fine, then that might be the culprit.

Ok, that sounds like a good idea. Where is the TTS? What does that stand for?

[DavidProehl]

ThermoTime Switch (TTS), it is connected to your water pump. #24 in the linked diagram

http://store.delorean.com/c-270-1-3-0-water-pump.aspx

There is a plug that connects to it that you would pull. The purpose of the TTS is to trigger the spraying of gas into the manifold when the car is cold. Typically when the TTS is broken you have cold start issues because you never get the extra gas, but since you say it is starting rich I'm thinking maybe you are always getting the extra gas. Maybe your TTS is closed rather than open. Again, I'm not even sure if it is even possible for it to break in such a manner.

[Bitsyncmaster]

Just unplug the CSV. Easy to get to that one.

[DavidProehl]

Just unplug the CSV. Easy to get to that one.

True, that is simpler. The Cold Start Valve (CSV) is what the TTS fires. That would be the plug going into this blue guy:

19304

[David T]

It's worth trying that and if it doesn't help just continue and do the plug swap to confirm no rest pressure. If the plug swap gets it started the first thing I would suspect is the check valve at the fuel pump.
David Teitelbaum

[Rich]

....I have new injectors, new all-in-one fuel pump, new accumulator, no fuel leaks, new o-ring in fuel distributor......

+1 on David T's post - possible fuel pump check valve leak.

There's a reported rash of problems with some of the new fuel pumps - bad check valves. If it's leaky this problem will persist til you replace the valve or the pump and valve. Call your all-in-one fuel pump vendor.

Recent thread that may or may not be a similar situation, including a clever troubleshooting method to go with it:
LINK: http://dmctalk.org/showthread.php?7202 (http://dmctalk.org/showthread.php?7202-Rest-pressure-troubleshooting-Sanity-check-me&highlight=fuel+pump)

[rothsean]

+1 on David T's post - possible fuel pump check valve leak.

There's a reported rash of problems with some of the new fuel pumps - bad check valves. If it's leaky this problem will persist til you replace the valve or the pump and valve. Call your all-in-one fuel pump vendor.

Recent thread that may or may not be a similar situation, including a clever troubleshooting method to go with it:
LINK: http://dmctalk.org/showthread.php?7202 (http://dmctalk.org/showthread.php?7202-Rest-pressure-troubleshooting-Sanity-check-me&highlight=fuel+pump)



The thing that I don't understand about the lack of fuel pressure would be is that when I turn the key on the fuel pump goes on and gives pressure immediately all the time. Even if it was losing pressure wouldn't it just build back up right away when the key is turned on?

Also, if it was a loss of pressure it would consistently do this, even when it is cold outside right?

[rothsean]

True, that is simpler. The Cold Start Valve (CSV) is what the TTS fires. That would be the plug going into this blue guy:

19304

You say just unplug the CSV wire to test this possibility?

[lorentbj]

You said when I turn the key on my fuel pump comes on. I should have fuel pressure.I would think you are right?
Turning the key on does not help when it is warm.Maybe someone can explain this?Is the problem air in fuel system,or the way fuel pressure is regulated?
Thanks,bob

[Ron]

The thing that I don't understand about the lack of fuel pressure would be is that when I turn the key on the fuel pump goes on and gives pressure immediately all the time. Even if it was losing pressure wouldn't it just build back up right away when the key is turned on?Yes it would, BUT, when it's hot, the fuel needs to be held under pressure (this prevents the liquid fuel from becoming a gas (which will compress in the lines making the delivery system fail...liquids will not compress....) .


Also, if it was a loss of pressure it would consistently do this, even when it is cold outside right?yes, but it don't matter (as long as the leak does not go into the engine v/s just returned to the tank) because the fuel will not turn to gas (vapor) when it is cold. (It will actually like it, up to a point, when cold).

When you said it does not leak, is this because you don't see any fuel leaking or because you checked the air plate and know it holds good pressure for a couple of hours or so?

And yes, unplugging the CSV will prevent the TTS from turning it on......but it (or the injectors, if bad or the CO is set to rich) could still have a leak dripping into the engine while it is shut off, which could cause the rich smell when it finally fires up (check the air plate pressure time to know for sure).

[Rich]

...Maybe someone can explain this?Is the problem air in fuel system,or the way fuel pressure is regulated?


Ron has you on the right track.

The DMC Workshop Manual explains it:
LINK: http://dmctalk.org/showthread.php?7204-K-Jet-Rest-Pressure (http://dmctalk.org/showthread.php?7204-K-Jet-Rest-Pressure)

To answer your question the problem is not air in the fuel system, it is vaporized fuel in the fuel system, as noted by Ron and this reference page. Fuel vapor won't meter like liquid fuel so you get a super-lean charge. And a hard start or no start until the vapor is purged or the fuel system cools enough.

Back in the days of carburetors the condition in question would have been called vapor lock.

Keeping the fuel rest pressure up, as the system is designed to do, completely eliminates it.

[rothsean]

Ron has you on the right track.

The DMC Workshop Manual explains it:
LINK: http://dmctalk.org/showthread.php?7204-K-Jet-Rest-Pressure (http://dmctalk.org/showthread.php?7204-K-Jet-Rest-Pressure)

To answer your question the problem is not air in the fuel system, it is vaporized fuel in the fuel system, as noted by Ron and this reference page. Fuel vapor won't meter like liquid fuel so you get a super-lean charge. And a hard start or no start until the vapor is purged or the fuel system cools enough.

Back in the days of carburetors the condition in question would have been called vapor lock.

Keeping the fuel rest pressure up, as the system is designed to do, completely eliminates it.


Ok, so it seems like I need to test the fuel pressure first in order to make sure that the rest pressure is staying up. Where do you attach the fuel pressure gauge on this car?

[Ron]

D:02:01 in the Work Shop Manual (http://dl.dropboxusercontent.com/u/13720563/DeLorean%20and%20Volvo%20Manuals/DMC-WorkshopManual-Hybrid.pdf) goes through the procedure (including control pressures). D:02:02 shows the hook up. (You can check the rest pressure with a regular gauge inline there if you don't have access to one with a valve, or, probably check the air plate pressure (http://dmctalk.org/showthread.php?3119-Hot-start-problem&p=42743&viewfull=1#post42743) since it sounds bad enough to show up...)

Less likely, but I'd check the CO too, if not first, since it is an easy test -- It may be that it is set rich and runs/starts ruff until it clears out/goes into closed loop where the system can compensate some automatically.

[DeLorean03]

Find the fuel line that goes from the top of the fuel distributor to the warm up regulator (WUR). Disconnect the end that goes to the warm up regulator. Insert one of the hose ends into the WUR. Hook the other end into the metal fuel line. The test gauges should have all the appropriate fittings you need to do this. You have a setup like this, right ? I am pretty sure the side that has the valve latch goes closer to the WUR.

19312

[Ron]

I am pretty sure the side that has the valve latch goes closer to the WUR.
Yep!

[rothsean]

Find the fuel line that goes from the top of the fuel distributor to the warm up regulator (WUR). Disconnect the end that goes to the warm up regulator. Insert one of the hose ends into the WUR. Hook the other end into the metal fuel line. The test gauges should have all the appropriate fittings you need to do this. You have a setup like this, right ? I am pretty sure the side that has the valve latch goes closer to the WUR.

19312

Where did you get that kit? I would rather buy a kit that fits a lot of cars.....

[jawn101]

Where did you get that kit? I would rather buy a kit that fits a lot of cars.....

I think that one's from Special T, but keep in mind that the CIS pressure testing kits are very different than kits that will test more modern engines.

[rothsean]

Yes it would, BUT, when it's hot, the fuel needs to be held under pressure (this prevents the liquid fuel from becoming a gas (which will compress when the pump in the lines making the delivery system fail....) .

yes, but it don't matter (as long as the leak does not go into the engine v/s just returned to the tank) because the fuel will not turn to gas (vapor) when it is cold. (It will actually like it, up to a point, when cold).

When you said it does not leak, is this because you don't see any fuel leaking or because you checked the air plate and know it holds good pressure for a couple of hours or so?

And yes, unplugging the CSV will prevent the TTS from turning it on......but it (or the injectors, if bad or the CO is set to rich) could still have a leak dripping into the engine while it is shut off, which could cause the rich smell when it finally fires up (check the air plate pressure time to know for sure).


I still don't understand how even if I am losing pressure in the fuel system after shutdown, how the fuel pump turning back on would not boost the pressure back up again?


Also, the next time I am having this issue I should just unplug the CSV blue electric hookup? Is the valve always closed and the electricity makes it open? So in this test I am making sure that it is staying closed and not flooding the motor out during start?

[Bitsyncmaster]

I still don't understand how even if I am losing pressure in the fuel system after shutdown, how the fuel pump turning back on would not boost the pressure back up again?

If the problem is a hot start problem due to loss of rest pressure, the 6 fuel lines going to the injectors get vapor pockets. So even when your prime the system, those six lines do not get purged. If they did, you could not run the fuel pump (engine not running) without filling the cylinders with fuel.

[rothsean]

If the problem is a hot start problem due to loss of rest pressure, the 6 fuel lines going to the injectors get vapor pockets. So even when your prime the system, those six lines do not get purged. If they did, you could not run the fuel pump (engine not running) without filling the cylinders with fuel.

Ok, so the vapor lock does not let fuel by? It has to work it way out somehow, hence my cranking the starter for 10 seconds? How does the vapor lock eventually give way?

[DeLorean03]

Where did you get that kit? I would rather buy a kit that fits a lot of cars.....

You can get it from here:

http://paceperformance.com/i-5926816-cta3420-fuel-injection-pressure-tester-bosch-k-jetronic-c-i-s.html

Food for thought, the DeLorean has some unique stuff like the fuel system. This is just me: I buy tools specifically just for this car. For me, it is a peace of mind knowing that I have the tools that fit this and just this car. Things like wrenches, spark plug pullers, oil filters, and what not - I can understand getting things that are more universal - but for this fuel injection system - I would strongly recommend biting the bullet and getting what you KNOW is the right equipment.

Just my thoughts.

[Rich]

Ok, so the vapor lock does not let fuel by? It has to work it way out somehow, hence my cranking the starter for 10 seconds? How does the vapor lock eventually give way?

Two things:

1. Check the rest pressure the easy way to start with. After hot shutdown wait the same amount of time it takes for you to experience a hot-start problem but do not restart it. Check the air plate pressure the way Ron mentioned via that link in this thread. It will indicate which way to go.
2. It doesn't matter how the vapor lock goes away if the car isn't maintaining rest pressure. Millions of K-Jet cars run completely fine, hot starting and all, when the primary circuit of the fuel system isn't leaking down and rest pressure is maintained long enough. The short answer is the vapor either condenses back to liquid fuel or it gets purged. Same as with a vapor-locked car with carbs.

We still don't know if there is a rest pressure problem or not. Lack of rest pressure is the typical symptom of hot-start problems with K-Jet cars like this.

Tell us how the air plate test goes.

[rothsean]

Two things:

1. Check the rest pressure the easy way to start with. After hot shutdown wait the same amount of time it takes for you to experience a hot-start problem but do not restart it. Check the air plate pressure the way Ron mentioned via that link in this thread. It will indicate which way to go.
2. It doesn't matter how the vapor lock goes away if the car isn't maintaining rest pressure. Millions of K-Jet cars run completely fine, hot starting and all, when the primary circuit of the fuel system isn't leaking down and rest pressure is maintained long enough. The short answer is the vapor either condenses back to liquid fuel or it gets purged. Same as with a vapor-locked car with carbs.

We still don't know if there is a rest pressure problem or not. Lack of rest pressure is the typical symptom of hot-start problems with K-Jet cars like this.

Tell us how the air plate test goes.



This is the procedure that is on that link, is this right?

"Just pull the air cleaner off so you can test if your problem is due to rest pressure time.

Start the engine, then shut it off. Go lightly press on the air plate and feel it has pressure. Don't press it down, just test for pressure. Keep doing this at intervels (15 min) until it moves easily. Your looking for 4 hours of holding rest pressure so you don't have any warm start issues.

Your problem may not be related to rest pressure. "



My question about it is, how do I test the plate for pressure if I do not press it down? Also, do I start the engine at every 15 minute interval? What am I looking for during this test and how do I know if it is a successful test or not?

How does this test the fuel system and what does it diagnose?

[jawn101]

This is the procedure that is on that link, is this right?

"Just pull the air cleaner off so you can test if your problem is due to rest pressure time.

Start the engine, then shut it off. Go lightly press on the air plate and feel it has pressure. Don't press it down, just test for pressure. Keep doing this at intervels (15 min) until it moves easily. Your looking for 4 hours of holding rest pressure so you don't have any warm start issues.

Your problem may not be related to rest pressure. "



My question about it is, how do I test the plate for pressure if I do not press it down? Also, do I start the engine at every 15 minute interval? What am I looking for during this test and how do I know if it is a successful test or not?

How does this test the fuel system and what does it diagnose?

You don't press the plate down. It will either yield to the slightest pressure and bounce around (no rest pressure and thus no fuel will be expelled) or it will be firmly held in place. If you press hard enough to overcome the rest pressure holding the plate firm, it will pump fuel into your cylinders.

Take the air cleaner off and you'll see. It's just 3 bolts and should take 30 seconds to remove.

Edit: For clarity. Get the motor started and running. Run it for a few seconds, it doesn't really matter. Shut it back off. Remove the air cleaner (3 10mm bolts at the corners) and feel the resistance offered by the plate. Don't press it down or you will pump out fuel and compromise the integrity of the rest of the test. Wait 15 minutes. Feel the resistance offered by the plate again. Come back 15 minutes later, try again. See how long it takes for the resistance to go away. It should be a good long time, 2 hours or more. If it is a short period of time you have a rest pressure issue, which is the most common cause of hot start problems.

[rothsean]

You don't press the plate down. It will either yield to the slightest pressure and bounce around (no rest pressure and thus no fuel will be expelled) or it will be firmly held in place. If you press hard enough to overcome the rest pressure holding the plate firm, it will pump fuel into your cylinders.

Take the air cleaner off and you'll see. It's just 3 bolts and should take 30 seconds to remove.

Yeah, I have seen it and touched it before, it is sensitive if I remember right. What exactly am I testing? If it moves easily does that mean there is a fuel leak or air leak?


This is all after I just cold start the car and let it run 5 seconds or so, then shut it off and test this air plate?

[jawn101]

Yeah, I have seen it and touched it before, it is sensitive if I remember right. What exactly am I testing? If it moves easily does that mean there is a fuel leak or air leak?


This is all after I just cold start the car and let it run 5 seconds or so, then shut it off and test this air plate?

I edited my above response to include more or less the full test procedure. If you have rest pressure you'll know it. If it feels 'sensitive' then there is no rest pressure and you have a fuel pressure problem, most commonly a bad accumulator or check valve at the pump.

[rothsean]

I edited my above response to include more or less the full test procedure. If you have rest pressure you'll know it. If it feels 'sensitive' then there is no rest pressure and you have a fuel pressure problem, most commonly a bad accumulator or check valve at the pump.

Cool, I see. Thanks for the clarity.

So in a normal working fuel system, what is putting the pressure on that air plate to make it stiff?

[jawn101]

Cool, I see. Thanks for the clarity.

So in a normal working fuel system, what is putting the pressure on that air plate to make it stiff?

Fuel, held in the lines by the accumulator or the check valve.... :)

[jawn101]

I posted this in the resources section some time ago, and I think *every* DeLorean owner should be required to watch it in its entirety :) It's a little dry but the information is invaluable.


http://www.youtube.com/watch?v=a4fJAfXYxWk&feature=youtu.be

Edit: when I say "every" I mean those of us with stock K-Jet, of course :) This video will only enrage and incur wrath from the carb and EFI crowds!

[rothsean]

I posted this in the resources section some time ago, and I think *every* DeLorean owner should be required to watch it in its entirety :) It's a little dry but the information is invaluable.


http://www.youtube.com/watch?v=a4fJAfXYxWk&feature=youtu.be

Edit: when I say "every" I mean those of us with stock K-Jet, of course :) This video will only enrage and incur wrath from the carb and EFI crowds!


Does our tank have a ventilation valve?

[jawn101]

Does our tank have a ventilation valve?

#74.... (https://store.delorean.com/p-6585-vent-tube.aspx) - leads to the charcoal canister

https://store.delorean.com/images/Category/large/2-1-0.jpg

[Rich]

Cool, I see. Thanks for the clarity.

So in a normal working fuel system, what is putting the pressure on that air plate to make it stiff?

You can see the fuel rest pressure on the other side of the air meter plate in this post:

http://dmctalk.org/showthread.php?7204-K-Jet-Rest-Pressure-Schematic

[rothsean]

You can see the fuel rest pressure on the other side of the air meter plate in this post:

http://dmctalk.org/showthread.php?7204-K-Jet-Rest-Pressure-Schematic



I will try that air plate pressure test tomorrow. Thanks to everyone for great info and a good video.



So when it comes to checking the mixture, how does a dwell meter work if it does not plug into the fuel system and is only an electrical item? I am just curious. I am going to borrow a friends dwell meter next week and his fuel pressure tester.

[jawn101]

I will try that air plate pressure test tomorrow. Thanks to everyone for great info and a good video.



So when it comes to checking the mixture, how does a dwell meter work if it does not plug into the fuel system and is only an electrical item? I am just curious. I am going to borrow a friends dwell meter next week and his fuel pressure tester.

The dwell meter checks the duty cycle of the frequency valve, which adjusts the mixture based on input from the lambda probe, which in turn measures exhaust gas. Checking the dwell just allows you to read what the "brains" of the K-Jet system is already seeing, but hiding from you.

[rothsean]

The dwell meter checks the duty cycle of the frequency valve, which adjusts the mixture based on input from the lambda probe, which in turn measures exhaust gas. Checking the dwell just allows you to read what the "brains" of the K-Jet system is already seeing, but hiding from you.

So is the dwell meter all I need to check mixture? If it is not reading the fuel quantity going thru the lines how does it know if mixture is good?

[jawn101]

So is the dwell meter all I need to check mixture? If it is not reading the fuel quantity going thru the lines how does it know if mixture is good?

Like I said... the duty cycle is based on input from the lambda probe, which measures exhaust gas.... to oversimplify, it checks for the quantity of unburned fuel in the exhaust.

I would not recommend fiddling with your mixture until you are absolutely sure that:
a) You fully understand the principles at work in the Lambda system
b) You are certain that all the components of your system are functioning properly

[rothsean]

Like I said... the duty cycle is based on input from the lambda probe, which measures exhaust gas.... to oversimplify, it checks for the quantity of unburned fuel in the exhaust.

I would not recommend fiddling with your mixture until you are absolutely sure that:
a) You fully understand the principles at work in the Lambda system
b) You are certain that all the components of your system are functioning properly


I don't want to change the mixture, but I would like to know if it is correct or at least close to the right setting.

[Ron]

I don't want to change the mixture, but I would like to know if it is correct or at least close to the right setting.
Yes! Just check it as it could contribute to the problem. Like Jon said, don't change it -- the engine has to be warm and everything else correct (plug gap, timing, idle, etc....this is the root of K-Jet naysayers IMHO) or it is basically useless -- The CO is ALWAYS the last adjustment made.

==========

FWIW- I think it is great how members work together and pick up questions before another has a chance to answer, and more important, without ego and BS, making it easy for someone wanting to understand as well as get their car right and not feel intimidated/uncomfortable about asking questions!

:thumbup: Guys!

It may not be a hot start/pressure problem, but we'll nail it....

[rothsean]

Very true...

[jawn101]

Yes! Just check it as it could contribute to the problem. Like Jon said, don't change it -- the engine has to be warm and everything else correct (plug gap, timing, idle, etc....this is the root of K-Jet naysayers IMHO) or it is basically useless -- The CO is ALWAYS the last adjustment made.

==========

FWIW- I think it is great how members work together and pick up questions before another has a chance to answer, and more important, without ego and BS, making it easy for someone wanting to understand as well as get their car right and not feel intimidated/uncomfortable about asking questions!

:thumbup: Guys!

It may not be a hot start/pressure problem, but we'll nail it....

It's all about paying it forward... I've been helped countless times in the same way. It's only fair!

Did you try the rest pressure test? My gut tells me it's going to be very revealing.

[Ryan S.]

Have you tested the check valve, yet? I learned this from Dave S. You can use a pair of vice-grips to pinch of the fuel pressure line coming out of the pump at the same time as you turn off the car. If this causes any change (i.e. slows down the pressure loss or car starts ok after 20 minutes) the pump is bad.

Fuel pressure gauge is a very useful tool to have.

[Beachdrifter]

This is a great thread, really helped me understand better the hot start issue. Also the video was great! Now the Bosch K-Jet is less of a "magic box".

Thanks,

[jawn101]

This is a great thread, really helped me understand better the hot start issue. Also the video was great! Now the Bosch K-Jet is less of a "magic box".

Thanks,

Totally a worthwhile video. Glad it helped.

[DMCMW Dave]

[COLOR=#1F497D][FONT=arial]Have you tested the check valve, yet? I learned this from Dave S. You can use a pair of vice-grips to pinch of the fuel pressure line coming out of the pump at the same time as you turn off the car. ]

BTW Don't do this on the OEM or common orange fuel lines or you'll be replacing them right away. The rubber lines in common use now will take this, but the older style Teflon lines will crack.

But they ought to have been replaced by now anyway.

[rothsean]

I am out of town until Monday but I will try the pressure test when I get back.

[DMC5180]

Great Video, I always wondered what the difference was between an IAC (Idle Air Control) valve and our ISM (Idle Speed motor).

[DavidProehl]

Great Video, I always wondered what the difference was between an IAC (Idle Air Control) valve and our ISM (Idle Speed motor).

Agreed. Somehow I had never seen this video before. I now feel like I understand how K-Jet is supposed to work.

[DeLorean03]

Such an outstanding video. I am watching it now in its entireity. I have always had a bit of a "question mark box" on the CPR. I'm currently watching it a couple times to get how it, as well as the rest of K-Jet, works.

It's always been difficult for me to sit through this video. Like others said, it is a bit dry. When your car starts being weird though, it quickly gets to be a more interesting video ;).

[Rich]

Excellent video link indeed. A very useful addition.

On a related note if not referenced elsewhere Bosch provided a Technical Instruction Manual for K-Jetronic.

One place to access it is here:
LINK: Bosch-K-Jetronic-fuel-injection-manual (http://www.slideshare.net/guestceff35/bosch-k-jetronic-fuel-injection-manual)


"This manual will describe the K-Jetronic's function and its particular features."

[DeLorean03]

Excellent video link indeed. A very useful addition.

On a related note if not referenced elsewhere Bosch provided a Technical Instruction Manual for K-Jetronic.

One place to access it is here:
LINK: Bosch-K-Jetronic-fuel-injection-manual (http://www.slideshare.net/guestceff35/bosch-k-jetronic-fuel-injection-manual)


"This manual will describe the K-Jetronic's function and its particular features."

Time to print THAT at work ;).

[Ron]

:confused0: I posted that as a PDF in the Resources Section HERE (http://dmctalk.org/showthread.php?352-K-Jetronic-System) almost a year ago....

(No need for a FaceBook account to D/L it. lol....I HATE those people with a passion).

[Dangermouse]

It's probably been done a dozen times, but a K-Jet refresher course at the next DCS would be very useful.

[DeLorean03]

:confused0: I posted that as a PDF in the Resources Section HERE (http://dmctalk.org/showthread.php?352-K-Jetronic-System) almost a year ago....

(No need for a FaceBook account to D/L it. lol....I HATE those people with a passion).

I'm sorry, Ron D: ... I have them on my portable HD at home. I don't have a printed copy yet D: ...

[Ron]

:cheers1:

[rothsean]

Update -

I did the air plate pressure test today. After turning the car off, 25 minutes later I could move the air plate with minimal pressure, like barely touching it. I guess that means pressure is leaking somewhere.

So is that fuel pressure kit that SpecialTAuto sells only for DeLoreans?

[jawn101]

Update -

I did the air plate pressure test today. After turning the car off, 25 minutes later I could move the air plate with minimal pressure, like barely touching it. I guess that means pressure is leaking somewhere.

So is that fuel pressure kit that SpecialTAuto sells only for DeLoreans?

You mean the PPR O-Ring kit? You should rule out all other potential sources of pressure loss before changing that guy out... the accumulator, check valve at the pump, hoses, etc

[rothsean]

You mean the PPR O-Ring kit? You should rule out all other potential sources of pressure loss before changing that guy out... the accumulator, check valve at the pump, hoses, etc

No, I mean the fuel pressure test guage/kit. I would like to buy tools that I can use on a lot of cars, not just the D. Are there any fuel pressure testers that I can use on the D and other cars?

[jawn101]

No, I mean the fuel pressure test guage/kit. I would like to buy tools that I can use on a lot of cars, not just the D. Are there any fuel pressure testers that I can use on the D and other cars?

Oh, ok. The pressure tester is specific for K-Jet CIS systems. So if you had another car with CIS you could use it there, sure. But not on a car with EFI. Similarly, kits that can test EFI systems will not work on CIS systems.

[rothsean]

What is the best way to take the fuel pump out of the equation? While lines do I clamp, both the pressure and return?


Do I just start the car, shut it off, then clamp both lines right away and see if fuel pressure drops?


I am thinking that I have a bad check valve in the unit. I have the new all-in-one unit from DMCH, bought last Aug.

[DeLorean03]

Here is what you do:

Gain access to the sender combo unit. Take a set of strong vice grips and wrap the jaws in electrical tape. This will keep the jaws of the vice grip from damaging the feed hose. I wrapped each jaw about 8-10 times. Experiment with how tight or loose the jaws should be when locked in place. I did this by locking the vice grips down on the hose without the fuel pump running at all before a cold-start of the engine. Once I was happy with how the vice grips locked down on a hose with minimal to no fuel in it, I had Jessica start the car, and I let it run for a minute or so. Then I had her turn the car off, and I immediately clamped down on the feed line with the vice grips. You have now, in essence, made the vice grips a "check valve."

**- Personal example details While that was going on, I walked back and checked my residual fuel pressure - it held at about 41 PSI for over 15 minutes. Previously without the vice grips, I had gone down to nearly 25 PSI in 12 minutes. -**

So anyways, after you're satisfied with how long the vice grips have been on, remove the vice grips. If the check valve is faulty, the pressure will begin to fall. Actual mileage may vary - some people have reported the pressure drop to fall like a rock. For me, it took 2-5 minutes, and then the pressure fell quickly.

There are variables to these instructions. Some people have used strong C-clamps or vice-grips with C-clamp style ends. Others may have a way to do this without having the fuel gauges.

[Ron]

Put a shut off valve at the pump, jump the RPM relay, shut the valve (remove jumper). If the air plate holds pressure longer than before, the pump is bad.

(Consider the age of your lines/hoses before clamping them...)

[Bitsyncmaster]

Remember you can not do this with OEM fuel lines. Those have a hard plastic core that will be damaged by clamping them.

[Farrar]

Take a set of strong vice grips and wrap the jaws in electrical tape. This will keep the jaws of the vice grip from damaging the feed hose. I wrapped each jaw about 8-10 times.

FWIW, I use a piece of 3/8" fuel hose on each side of the tool. Less messy than tape if you ever need to remove it.

Also, what Dave said -- you cannot clamp a plastic (or metal, obviously) fuel line. Take care...

[DeLorean03]

I am thinking that I have a bad check valve in the unit. I have the new all-in-one unit from DMCH, bought last Aug.

Hey guys, he said he has this. That comes with new rubber fuel lines.

[rothsean]

With the fuel pressure gauge hooked up the pressure dropped to 0 BAR within 24 minutes. At 10 minutes it was at 1.2 BAR.



When I isolated the fuel pump, it dropped to 1.9 BAR at 10 minutes and at 30 minutes it was 1.6 BAR.




So it means that the fuel pump check valve is bad, but it also seems to me that there is a small leak somewhere else.

In addition, my max psi at idle was 50psi. Is that normal?

[DeLorean03]

No, 50 psi is definitely not normal. You were probably measuring control pressure; control pressure is in the 44 psi to 52 psi area. The gauges should have an open/close valve handle near where the "T" of the gauges meet. Check to see if when you turn the valve handle if you get higher than 50psi. Ideally, you should be reading 78 psi.

Reference this video to see my gauges and the valve handle I am referring to.


http://www.youtube.com/watch?v=h7drhxjJ2mg

[Bitsyncmaster]

With the engine running, you are reading control pressure which will run around 50 PSI when warmed up. When you shut down the engine that pressure will drop to about 45 PSI which is your rest pressure. With the valve closed and RPM relay jumpered (engine is off) you should read 75 PSI primary pressure.

[rothsean]

No, 50 psi is definitely not normal. You were probably measuring control pressure; control pressure is in the 44 psi to 52 psi area. The gauges should have an open/close valve handle near where the "T" of the gauges meet. Check to see if when you turn the valve handle if you get higher than 50psi. Ideally, you should be reading 78 psi.

Reference this video to see my gauges and the valve handle I am referring to.


http://www.youtube.com/watch?v=h7drhxjJ2mg

I don't have that type of tester kit. Mine is a universal Kit (STAR 443 I think) and it has a banjo fitting and a hose with the gauge at the end that hooks up to the fitting, just like a hose would hook to an air compressor.

I never looked at the pressure without the engine running.

[Bitsyncmaster]

I don't have that type of tester kit. Mine is a universal Kit (STAR 443 I think) and it has a banjo fitting and a hose with the gauge at the end that hooks up to the fitting, just like a hose would hook to an air compressor.

I never looked at the pressure without the engine running.

Those quick connect fittings would be leaky so rest pressure time testing would not be valid.

[Grover]

It's the new all in one fuel pump. The check valve goes bad on the new pumps. After speaking to DMCH, there is a new version coming out later this week with an entirely different pump in the unit to solve the issue. This will be my third one of the new unit, so hopefully the new pump version fixes the design flaw.

[jawn101]

It's the new all in one fuel pump. The check valve goes bad on the new pumps. After speaking to DMCH, there is a new version coming out later this week with an entirely different pump in the unit to solve the issue. This will be my third one of the new unit, so hopefully the new pump version fixes the design flaw.

Well that's good info... I wonder if they will be contacting any or all of the previous purchasers to suggest fixes or perhaps send out replacements? Mine doesn't seem to be bad... yet... but another local owner has already gone through 3 (or maybe 4?) of them

[rothsean]

If the car holds 1.2 BAR rest pressure for a few hours is that enough to not have a hot start issue?

[Ron]

From WS Manual D:02:01
Rest Pressure — 3.3 Bar
Minimum pressure after 10 min. — 1.7 Bar

One of those "probably, but ..." answers.

Do you know when it drops below 1.7 Bar?

[rothsean]

From WS Manual D:02:01
Rest Pressure — 3.3 Bar
Minimum pressure after 10 min. — 1.7 Bar

One of those "probably, but ..." answers.

Do you know when it drops below 1.7 Bar?

At 30 minutes it was at 1.6 BAR.

[rothsean]

Those quick connect fittings would be leaky so rest pressure time testing would not be valid.


It did not seem to leak, no gas coming out near the fitting.

[Bitsyncmaster]

If your pressure drops from the book values 3.3 bar to 1.7 in 10 min. You will have hot start problems. What I find is rest pressure holds pretty steady at 44 PSI for a few hours and when it starts dropping it goes pretty quick (about 30 min) to zero. Not sure if that is how all our cars perform but mine will consistently do that.

[Rich]

If the car holds 1.2 BAR rest pressure for a few hours is that enough to not have a hot start issue?

If you wait "a few hours" then the engine is probably not hot anymore. So would that be a hot start situation?

Most folks who suffer a hot start problem, like at a gas station after a fill-up, find that the car starts up fine half an hour later right?

When the fuel is no longer vaporized (boiling) in the circuit things work well.

[Ron]

At 30 minutes it was at 1.6 BAR.

My D holds like Bitsy's....Every D I have checked that did not have a problem held at least 2 Bar/30 psi for a couple of hours


Since you have a universal tester, you can try this:

Connect the tester close to/at the fuel pump, with the shut off valve between the gauge and pump.
Open the valve.
(Do not start the engine.)
Remove the RPM relay and jump it as seen below:

http://dmctalk.org/attachment.php?attachmentid=3414&d=1313080726&thumb=1

Record the pressure.
Shut the valve.
Immediately remove the jumper and record the pressure.
Watch and record the pressure closely for 15 minutes.
Record the pressure every 15 minutes thereafter until none.
Post results.

This will eliminate the fuel pump and check valve...
Combined with the previous information, it will tell us if you have other leaks.

fyi- Reversing this gauge hookup will test the check valve and pump (can be a bit hard on the pump and not necessary at this point).


Don't change anything yet, but since you have new injectors, I'm wild guessing you have a bad check valve and maybe the CO set just rich enough to let the injectors leak (and slightly flood the engine when hot, causing the roughness and rich smell right after it starts)....But again don't change anything.