Fuel Pressure at Injector?

[nwotank]

I'm trying to diagnose on my Delorean with my mechanic, does anyone know what the fuel pressure is supposed to read at the Injector?

My car dies when its put into gear, acts as though its running out of fuel. It has a new fuel distributor, warm up regulator and frequency valve so far. Fuel pressure seems good from the pump, but trying to figure out if its the same when it reaches the injectors. The return line has been checked for any clogs. Doesn't seem to have any vacuum leaks.

[sdg3205]

Can you describe the situation in more detail? If the engine runs nicely in neutral, at idle and with a blip of the throttle, then your fuel pressure isn't disappearing when you put it in gear. Automatic, I take it?

[nwotank]

Can you describe the situation in more detail? If the engine runs nicely in neutral, at idle and with a blip of the throttle, then your fuel pressure isn't disappearing when you put it in gear. Automatic, I take it?

Yep its automatic, it revs up just fine in neutral, trying to figure out what the fuel pressure is supposed to be at the fuel injectors because it seems fine from the fuel pump.

[sdg3205]

I'm not sure how to do that. CIS gauges are done in line with the FD and WUR. You can verify system pressure and control pressure this way. If your pressure is within range here, then try and throw it in gear and see what happens. If it drops because the car stops, that would be normal. Now you'd be lookin at rest pressure. So you can't attribute loss of fuel pressure to the fuel system because the pump stops when it loses tach.

Can you post a video? It would seem to me that you might have a tranny issue that is loading the engine to the point of stopping. I'm not a pro though, but I can't think of a reason why the pump would stop just because the car is put in gear.

[DMCVegas]

I'm trying to diagnose on my Delorean with my mechanic, does anyone know what the fuel pressure is supposed to read at the Injector?

That worries me. The whole entire point of sending a vehicle to a mechanic is to pay for their accrued knowledge in how to fix something. You having to tell them what to do is a bad sign.

In order to test the pressure, you need to connect each individual injector up to a CIS Fuel Injector Tester. It's a tool that you fill with gasoline (or mineral spirits to clean), and hydraulically pump fuel through. There is a pressure gauge that will tell you how many PSI or Bar the fuel is up to. You then keep pumping until you see the injector crack open, and then record the pressure on the gauge. Compare it to what your Workshop Manual has, and you can tell if your injector is functioning properly.

The second way is by it's spray pattern.

I don't have my Workshop Manual with me to reference, so I'm not going to comment on what the pressure should be since I cannot verify it. But it should be right there in your's.

[nwotank]

There's not a lot of mechanics with knowledge about this fuel system and car in my area, in fact most of them refused to work on it, plus i'm just trying to get my car fixed so whatever I can do to help the mechanic out I'm trying to do. This shop has been successful at working on it before its just an odd issue. The car seems to work perfectly fine while its parked and has the right fuel pressure. When its placed in drive and given some gas it dies as though its starving for fuel. So the mechanic is attempting to determine whether its a fuel pressure issue or something completely different thats causing it, thats why he's trying to figure out what the fuel pressure should read from the injectors.

[Bitsyncmaster]

Maybe your auto is stuck in third gear. Does the problem show up in reverse?

[DMCVegas]

There's not a lot of mechanics with knowledge about this fuel system and car in my area, in fact most of them refused to work on it, plus i'm just trying to get my car fixed so whatever I can do to help the mechanic out I'm trying to do. This shop has been successful at working on it before its just an odd issue. The car seems to work perfectly fine while its parked and has the right fuel pressure. When its placed in drive and given some gas it dies as though its starving for fuel. So the mechanic is attempting to determine whether its a fuel pressure issue or something completely different thats causing it, thats why he's trying to figure out what the fuel pressure should read from the injectors.

Fair enough. Admittedly though, you'd probably just as good working on this car yourself. And for the price of labor involved, you'd get all the free tools that you'd need. Mechanics are great when it comes to certain things that you can't do because of tool requirements. Like replacing a clutch for example. As for the rest of it, just following directions to return everything to operating specifications is all you need, and you can certainly do this.

So you've got a car that starts, but won't move under it's own power. The way to fix this is going to be to get back to basics and ensure that everything is within spec. The Workshop Manual will help you do this, so make sure that you have a copy. The first order of business of course is going to be to test the fuel pressure.

But before we get into that...

I, like everyone else here wants to see you succeed with your car repair. Below is a video that will go a long way with helping you understand how BOSCH CIS/K-Jetronic Works on your car. Myself, I do better with visual aids, and feel that this is an excellent starting point with which to learn from.
Before you watch however, there are a few variances to keep in mind for the DMC-12 application as you encounter them in the video:

We use the single Fuel Pump system.
System Pressure Regulating Valve = Primary Pressure Regulator.
In the cross-section of the Accumulator, you will see a hole beneath the spring. This is for the 3rd hose that connects to the Fuel Return line. Otherwise, gasoline would just spill on the ground.
Depicted here is a Updraft (or Updraught for you folks across the pond) Air Meter where the metering plate goes up. We instead have the Downdraft type where the airflow plate goes down.
We do not use an Auxiliary Air Valve. We utilize the more advanced Constant Idle Speed System which utilizes an Idle Speed Motor for idle air flow regulation.
Because of the Constant Idle Speed System, ALL idle speed screws are meant to be closed.
No depicted is the LAMBDA emissions control system. But, once you understand how the Warm-Up Regulator functions (or Warm-Up Valve as called in this video), you now know how the LAMBDA circuit functions. Same operation of fuel pressure manipulation, just with an electronic valve (picture an EFI injector) that opens and closes at different speeds to adjust fuel pressures, in order to adjust the amount of fuel fed into the engine.
Our WUR is includes the 2nd diaphragm for vacuum enrichment.



https://www.youtube.com/watch?v=a4fJAfXYxWk

[nwotank]

Maybe your auto is stuck in third gear. Does the problem show up in reverse?

Yes the problem does show up in reverse, I got stuck a few times trying to reverse out of a driveway, when I gave it gas it would die.

[nwotank]

Fair enough. Admittedly though, you'd probably just as good working on this car yourself. And for the price of labor involved, you'd get all the free tools that you'd need. Mechanics are great when it comes to certain things that you can't do because of tool requirements. Like replacing a clutch for example. As for the rest of it, just following directions to return everything to operating specifications is all you need, and you can certainly do this.

So you've got a car that starts, but won't move under it's own power. The way to fix this is going to be to get back to basics and ensure that everything is within spec. The Workshop Manual will help you do this, so make sure that you have a copy. The first order of business of course is going to be to test the fuel pressure.

But before we get into that...

I, like everyone else here wants to see you succeed with your car repair. Below is a video that will go a long way with helping you understand how BOSCH CIS/K-Jetronic Works on your car. Myself, I do better with visual aids, and feel that this is an excellent starting point with which to learn from.
Before you watch however, there are a few variances to keep in mind for the DMC-12 application as you encounter them in the video:

We use the single Fuel Pump system.
System Pressure Regulating Valve = Primary Pressure Regulator.
In the cross-section of the Accumulator, you will see a hole beneath the spring. This is for the 3rd hose that connects to the Fuel Return line. Otherwise, gasoline would just spill on the ground.
Depicted here is a Updraft (or Updraught for you folks across the pond) Air Meter where the metering plate goes up. We instead have the Downdraft type where the airflow plate goes down.
We do not use an Auxiliary Air Valve. We utilize the more advanced Constant Idle Speed System which utilizes an Idle Speed Motor for idle air flow regulation.
Because of the Constant Idle Speed System, ALL idle speed screws are meant to be closed.
No depicted is the LAMBDA emissions control system. But, once you understand how the Warm-Up Regulator functions (or Warm-Up Valve as called in this video), you now know how the LAMBDA circuit functions. Same operation of fuel pressure manipulation, just with an electronic valve (picture an EFI injector) that opens and closes at different speeds to adjust fuel pressures, in order to adjust the amount of fuel fed into the engine.
Our WUR is includes the 2nd diaphragm for vacuum enrichment.



https://www.youtube.com/watch?v=a4fJAfXYxWk


Thank you for the information, a lot easier to understand than the 200 page Bosch book, I appreciate any suggestions as my car has been in the shop since Sept.

[RamblinDMC]

Have you replaced the fuel pump? My auto had a similar issue until it was replaced. It pulls nicely now. Before it would stumble and die under any load

Sent from my XT1049 using Tapatalk

[DMCVegas]

Thank you for the information, a lot easier to understand than the 200 page Bosch book, I appreciate any suggestions as my car has been in the shop since Sept.

The BOSCH book isn't so bad. But, are you in possession of a DeLorean Workshop Manual?

[nwotank]

Have you replaced the fuel pump? My auto had a similar issue until it was replaced. It pulls nicely now. Before it would stumble and die under any load

Sent from my XT1049 using Tapatalk


I haven't replaced the pump in a few years, it seems to test out alright though as far as providing fuel pressure while its in idle. Was yours testing out well also?

[nwotank]

The BOSCH book isn't so bad. But, are you in possession of a DeLorean Workshop Manual?

Yes, actually I've got that and the Volvo book as well, both are pretty good resources. Its a frustrating issue to nail down because everything works well as long as its parked.

[DMCVegas]

Yes, actually I've got that and the Volvo book as well, both are pretty good resources. Its a frustrating issue to nail down because everything works well as long as its parked.

It is frustrating, I know. You've got the pieces, but nothing is coming together. Been there, done that too. BUT, you can overcome this.

Testing the fuel system:
You've got your Workshop Manual. So you've got your fuel pressures specifications written in there. So of course what you're going to need next will be to perform the pressure tests with a CI Tester. Getting those readings will tell you if your system is working properly, diagnose a bad Warm-Up Regulator, Control Pressure Regulator, and identify hot-start issues. That is going to be a given. If you have a doubt about the fuel system, this is the place to start.

To test the Fuel Injectors, you need an Injector Tester. You can buy them, or even build it yourself. It looks something like this:

http://www.peachparts.com/shopforum/attachments/general-information/60936d1226706069-how-build-diesel-injector-pop-tester-poptester.jpg

For Gasoline, you would replace the gauge with a 100 PSI unit for an accurate reading. Anyhow... What you do is remove the injectors from the engine one at a time, connect them to the tester, and then start pumping. The fuel pressure will raise until the injectors crack open under pressure. Watch the gauge to see when they open up. That's Part 1 of knowing if you have a good injector: What is the PSI they're opening at. Part 2 is checking the spray pattern to ensure it's a proper mist with no drips, proper degree of spray, etc. If the injector fails any of these two items, you've got to replace it.

If you don't have the tools, a proper BOSCH service center should be able to perform the injector tests for you, and even diagnose your fuel system as well. Looking at a map of where I think you live, this place might be your best bet for proper testing equipment: http://franksautomotiveinc.net/

[SS Spoiler]

DMCVEGAS, nice set up for injector testing, but i'm not following
how the jack is applying pressure to the fluid?

[DMCVegas]

Quick Answer: In this instance, the person used a simple funnel instead of a graduated tank. But in either case, the fluid passes down into the chambers, and the jack applies hydraulic pressure as you pump it. Normally when the fluid enters into the next chamber after pumping, it's oil that pushes the hydraulic ram UP to lift a vehicle. In this case after having been modified, the supply of fluid instead goes up and out of the opening and into the plumbed pipe. And the fluid in this case is gasoline or mineral spirits.

There is of course a "T" in the line with one side going to a pressure gauge, and the other to the Fuel Injector. The gauge will tell you what the pressure is inside of the lines. Pressure naturally rises of course until the spring inside of the injector is pushed open and the needle valve begins to spray.

Verifying how much pressure (PSI or BAR) is needed to open the valve will tell you if the spring inside is any good any more. The second thing is to observe the spray pattern inside of the glass jar.

http://rennlist.com/forums/attachments/924-931-944-951-968-forum/531697d1303827474-wtb-bosch-universal-crush-filter-fuel-injector-spray-pattern-c-specialtauto.jpg

If the injector is cracking, or opening under too little pressure, discard it. If it is cracking under too high of a pressure, or you have a poor spray pattern, you can try and clean it with the injector tester by pumping some mineral spirits through it to try and clean it. That may, or may not work. But in either case, I can absolutely attest that proper testing will save you TONS of money.

Pulling the spark plugs out of the chambers to check for fowling is also a great indicator of where to start looking for potentially bad plugs or even ignition problems.

Now there are alternatives as well of Pneumatic Fuel Injector Testers like this:

http://ecx.images-amazon.com/images/I/51T%2BXIDUm8L._SX300_.jpg

Instead of physical pumping, these units can give you VERY precise control over the pressure by instead connecting to an air compressor and turning a knob. They also come with a volley of accessories as well and will also work on modern cars too. Just as you can slowly turn a dial to increase pressure to test an injector, you can also simulate a fuel pump too. So it's great for cleaning entire fuel systems too. You could for example plug it into the schrader valve on your EFI lines on top of your engine after killing power to the pump.
http://i01.i.aliimg.com/img/pb/471/619/108/108619471_006.jpg

If you were to EVER do something like this however to clean out the fuel distributor and the valves, plan on replacing the Primary Pressure Regulator's O-Rings.

[nwotank]

So I've ordered a new fuel pump to see if thats the issue with my car dying upon acceleration, but I read someone had a similar issue with the ignition coil. My mechanic says once the car starts up, the ignition coil wouldn't affect performance. Is this correct or does the ignition coil continue to serve a purpose while the car is running? My issue seemed electrical to me because sometimes it would lose RPMs suddenly then go back to normal.

[sdg3205]

So I've ordered a new fuel pump to see if thats the issue with my car dying upon acceleration, but I read someone had a similar issue with the ignition coil. My mechanic says once the car starts up, the ignition coil wouldn't affect performance. Is this correct or does the ignition coil continue to serve a purpose while the car is running? My issue seemed electrical to me because sometimes it would lose RPMs suddenly then go back to normal.

I think your mechanic meant that once the car starts, the ignition coil could be ruled out. There's no way he thinks it doesnt get involved after a start..... i hope!

Yes, the ignition coil produces spark voltage and continues so long as your car is running and ignition is on HOWEVER coils do crap out, but typically it takes a while (30 min or more) for that to happen.

[Bitsyncmaster]

So I've ordered a new fuel pump to see if thats the issue with my car dying upon acceleration, but I read someone had a similar issue with the ignition coil. My mechanic says once the car starts up, the ignition coil wouldn't affect performance. Is this correct or does the ignition coil continue to serve a purpose while the car is running? My issue seemed electrical to me because sometimes it would lose RPMs suddenly then go back to normal.

Ignition coil runs the engine all the time. They don't fail that often but sometimes when they get hot they won't put out enough power to run higher RPMs. It's pretty cheap and easy to change so a spare coil is a good thing to have.