Weird cold and hot start issues

[Magnus86]

Hey guys,

so i've tried several things for now but maybe you have any idea what could be the problem on my Delorean.

The symptoms:
My Car seems to randomly have cold or hot start issues. Sometimes it starts cold just fine, and sometimes it even starts hot fine when the car was sitting for some time.
But most of the time it's hard to start the car cold or hot..sometimes even just 5 minutes after i stopped the engine when hot. When i turn the key you can hear the engine firing for about a second...and then i have to crank it a lot to get it running. Once it is running everything is fine.
I can accelerate the cranking-process when i spray some starter fluid into the air intake (with the air filter housing off).
The problem first occurred about 3-4 weeks ago. Before there were no cold or hot start issues and the car always started without any problems

What happened so far:
When i got the car about a year ago i noticed that it was pretty hard to start when hot. It turned out that my cold start valve primes every time, even with a hot engine. To solve this issue i disconnected the electric connector of the csv. It seems like my thermo time switch is damaged. With the disconnected CSV i had no more hot start problems, and even with a cold engine the car started all the time without any problems.

About half a year ago i replaced my fuel pump with a new one (old style) because my fuel tank was pretty dirty and the filter on the fuel pumps intake hose was clogged up. I cleaned the tank, installed a new fuel pump with a fresh hose and the reinforcement spring

Later that year i also cleaned my bulkhead-connectors with a brass brush and some contact cleaner. I renewed the bulhead ground connection as the original screw was pretty rusty and i even added the "optimized" inertia switch ground (cut the original ground wire and reconnected a new ground wire to the frame).

Of course i replaced all the fuses in the relay compartment and also replaced some of the relays, even the rpm-relay.

About a month ago i fixed my shifting computer (governor).I removed it from the car, resoldered all the solder joints and replaced two of the capacitors. Since my repair, shifting is working great.


What i already tried/tested:

1. I thought maybe i messed something up while i removed and reinstalled the shift computers wires, as they are sitting next to the ballast resistors. I checked the wires on the resistors, jiggled them around but it seems like that made no difference with my cold/hot start issues. I also cleaned the connectors of the ballast resistor and the relay next to it and tightend all the wire-plugs around the ballast resistor. Maybe i forgot to check something else here that i knocked loose?

2. I replaced the new RPM Relay with my original old one to check if the new RPM-Relay has a problem. Problem occurs with both relays

3. i removed the injectors, checked the spray pattern with jumpered RPM-Relay (and pushing the air flap down) and even searched for leaks on them. What i did notice was that one of the fuel lines to one of the injectors sometimes seem to leak a little bit from the inside, but not all the time. I still got the old fuel lines and just ordered the new stainless braided ones to sort that out.

4. I renewed the O-Rings on the primary pressure valve inside the fuel distributor even though the old rings looked good. Of course i reused the little thin spacer inside the valve.

5. I liftet the fuel distributor and checked if the plunger is stuck. It was working fine, but i cleaned it anyway.

6. I removed one Spark Plug wire, put a spark plug on and checked if i got a spark on the spark plug. As the car starts with starter fluid i was sure that a missing spark won't be the problem, but just to make sure i did the test.

7. I checked and readjusted my dwell. It was a bit off. Cold it's now at 45 and with a hot engine it's swinging between 35-45

8. I did a pressure test for the primary pressure (i think) with a non running cold engine. Hooked the Gauge up between the WUR and the main fuel line that goes on top of the distributor. I closed the valve to the WUR so that i just get the pressure coming from the distributor (primary pressure, right?). With a priming pump (jumper for rpm relay) i get about 70PSI:

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After one hour with no fuel pump running i get about 45PSI:

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And after 2 hours i still get 35 PSI:

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What i did notice is that even with a rest primary pressure (?) of 45 or 35 there is almost no more resistance on the air flap?
I'm not that much into the k-jet fuel pressure stuff, but shouldn't the air flap has some good resistance when the primary pressure still has 35-45PSI?
As i did some earlier tests with the air flap i know how a "good" air flap resistance feels.

Currently i have no possibility for testing fuel pressure with a hot and running engine as i'm currently waiting for my new fuel lines.
But can one faulty fuel line to one of the injector cause the loss of pressure on the air flap while the gauge still shows around 40PSI or is that not possible?
As i get this pressure for about 2 hours..i think my fuel accumulator and the valve inside of the fuel pump are okay so far?

Is it possible that the fuel accumulator just fails when it's hot outside or the fuel is warm?

I don't really know what else could be the problem. Do i need to check control pressure to make sure (open valve to the WUR)?
Thanks a lot in advance.

[David T]

Intermittent problems are always tough to solve because you can't be sure you got it. When was the last time a tune-up was done changing the spark plugs, ignition wires, cap, and rotor? Sounds like you already did everything in the fuel system.

[Ron]

If any one of the injectors/lines leak the rest pressure will fall.
If starting fluid always helps it start, it's too lean -- Not enough fuel, OR, too much air- check for vacuum leaks.
Yes, valve shut for measuring primary pressure, open for control pressure.
The heat in the fuel will get the accumulator hot even in the winter.


I'd think you should install the new lines then sort out the problems with the CSV/CPR/TTS, since they, and everything else, work in concert with each other. Maybe start with the CPR/WUR pressures (with the engine dead cold)...

Always set the dwell last!

[Magnus86]

Thanks for your replies :)

@David:
I haven?t done a Tuneup since i owned the car. All the parts like distributor cap, spark plugs etc have been changed by the previous owner about 3 years ago. The complete engine has been rebuilt in that time as well.

@Ron:
It?s a bit strange with that leaking fuel line. First i thought that my injector was leaking as i let them sit in empty jars for a day and on one of them there was a bit of fuel in the jar the next day. But after inspection i noticed that the fuel came out of the protective rubber of the fuel line on the injectors side. So i built up pressure (with the fuel pump) and jiggled around with that fuel line but there was no fuel coming out of it and there was no loss of fuel pressure. Is it normal to have about 45PSI on the gauge but a flap that has almost no resistance? I always thought the flap test gives a good first indication about the fuel pressure. So to really check for fuel rest pressure i need to open the valve to the WUR which gives me the control pressure right? But i heard that for control pressure test you need to run the engine?

Regarding vacuum leaks:
What are the areas to check?
I repaired my ac selector switch a few weeks ago as i couldn?t change the modes with the switch. Can a loss of vacuum in the switch cause vacuum problems on the engine or is this vacuum independent from the engine?s vacuum?

[Ron]

It?s a bit strange with that leaking fuel line. First i thought that my injector was leaking as i let them sit in empty jars for a day and on one of them there was a bit of fuel in the jar the next day. But after inspection i noticed that the fuel came out of the protective rubber of the fuel line on the injectors side. So i built up pressure (with the fuel pump) and jiggled around with that fuel line but there was no fuel coming out of it and there was no loss of fuel pressure. Is it normal to have about 45PSI on the gauge but a flap that has almost no resistance? I always thought the flap test gives a good first indication about the fuel pressure. So to really check for fuel rest pressure i need to open the valve to the WUR which gives me the control pressure right? But i heard that for control pressure test you need to run the engine?

Regarding vacuum leaks:
What are the areas to check?
I repaired my ac selector switch a few weeks ago as i couldn?t change the modes with the switch. Can a loss of vacuum in the switch cause vacuum problems on the engine or is this vacuum independent from the engine?s vacuum?
Showing 45 psi and having ~no resistance at the plate is odd. What does the pressure do when you press the plate.


You can read the rest pressure with the valve open or shut (engine not running).
Yes, if you want to watch the control pressure while the WUR/CPR warms up, the engine has to be running...

The vacuum is is not independent. A leak at the AC mode switch can cause problems for the engine (lean), but that alone shouldn't keep it from starting (especially when the engine is warm...starting fluid should compensate for that small of a leak).

[Bitsyncmaster]

I ran the non running control pressure test (valve open). After running the pump for about 10 seconds, my pressure read 28 PSI with ambient temp at 69 deg/F. It did slowly increase to 34 PSI in about 9 minuets where it peaked. After about one hour pressure was reading 10 PSI.

By the way an 8 oz fishing sinker will open my flap at 8 PSI and below. It will not move the flap above 8 PSI. That sinker is placed on the flap at the side closest to the rear bumper.

[Ron]

I ran the non running control pressure test (valve open). After running the pump for about 10 seconds, my pressure read 28 PSI with ambient temp at 69 deg/F. It did slowly increase to 34 PSI in about 9 minuets where it peaked. After about one hour pressure was reading 10 PSI.

By the way an 8 oz fishing sinker will open my flap at 8 PSI and below. It will not move the flap above 8 PSI. That sinker is placed on the flap at the side closest to the rear bumper.
28 PSI @ 69?F sounds right. But I don't see why the control pressure would change while the WUR/CPR temp does not (engine off).
???

[Bitsyncmaster]

28 PSI @ 69?F sounds right. But I don't see why the control pressure would change while the WUR/CPR temp does not (engine off).
???

Yes that is strange.

[Magnus86]

Showing 45 psi and having ~no resistance at the plate is odd. What does the pressure do when you press the plate.


You can read the rest pressure with the valve open or shut (engine not running).
Yes, if you want to watch the control pressure while the WUR/CPR warms up, the engine has to be running...

The vacuum is is not independent. A leak at the AC mode switch can cause problems for the engine (lean), but that alone shouldn't keep it from starting (especially when the engine is warm...starting fluid should compensate for that small of a leak).


When i press the plate with 45PSI rest pressure nothing happens. Pressure stays the same. But i will try again today.
I always wondered a bit: When the fuel pump is priming and i press down the plate (good resistance) i get the injectors to spray. Once i shut off the fuel pump and press the plate down (still with good resistance) none of the injectors sprays. Is that normal? Seems like as soon as the pump isn't running there isn't enough pressure to get the injectors opening.

@Dave:
I'm gonna check the control pressure today as well. I just have to hook up another hose for the gauge as on my current hose the valve for opening/closing the access to the WUR is leaking. I'll add a normal T-Hose to the gauge and see what the control pressure says.

[Ron]

When i press the plate with 45PSI rest pressure nothing happens. Pressure stays the same. But i will try again today.
I always wondered a bit: When the fuel pump is priming and i press down the plate (good resistance) i get the injectors to spray. Once i shut off the fuel pump and press the plate down (still with good resistance) none of the injectors sprays. Is that normal? Seems like as soon as the pump isn't running there isn't enough pressure to get the injectors opening.That's normal -- The injectors open at 50-60 PSI.

[Bitsyncmaster]

That's normal -- The injectors open at 50-60 PSI.

I thought they opened at 40 PSI but that may be counting the engine vacuum.

[Jonathan]

It seems like my thermo time switch is damaged.

Did you ever fix or replace the thermo time switch?

http://support.delorean.com/kb/a60/cold-start-issues.aspx

[82DMC12]

Vacuum leaks can be hard to find, especially minor leaks. I suggest borrowing or buying a smoke machine. Seal the air meter flap with a latex balloon and large zip tie. Then plug the smoke machine into the PCV / metal mesh cap. Let 'er rip and you'll very quickly find any vacuum leaks. Eventually the smoke has to go somewhere if you keep pumping it in and it will start to exit the oil dipstick tube, but that's OK.

Fix all the leaks, but also check for proper vacuum routing AND make sure the vacuum solenoid is working (no vacuum to the distributor when the car is at idle). The vacuum system, and how it changes depending on idle on/ idle off and engine hot / cold is all explained in the shop manual in the Fuel & Emissions section.

[Ron]

I thought they opened at 40 PSI but that may be counting the engine vacuum.
FWIW- I remember it by 55 +/- 5 PSI Manual says 3.5 to 4.1 Bar.

[Magnus86]

Vacuum leaks can be hard to find, especially minor leaks. I suggest borrowing or buying a smoke machine. Seal the air meter flap with a latex balloon and large zip tie. Then plug the smoke machine into the PCV / metal mesh cap. Let 'er rip and you'll very quickly find any vacuum leaks. Eventually the smoke has to go somewhere if you keep pumping it in and it will start to exit the oil dipstick tube, but that's OK.

Fix all the leaks, but also check for proper vacuum routing AND make sure the vacuum solenoid is working (no vacuum to the distributor when the car is at idle). The vacuum system, and how it changes depending on idle on/ idle off and engine hot / cold is all explained in the shop manual in the Fuel & Emissions section.

Where do i find the PCV metal mesh cap? Sorry if i ask, but i cant translate pcv into german and i'm not sure what to look for. Furthermore: Could a vacuum leak really causea no starting engine? I would suggest this must be a pretty big vacuum leak then?!

[82DMC12]

Sorry, we call it PCV (positive crankcase ventilation) but I don't think it's actually referred to that in the manual.

It's the black cap you have to remove to add oil to the engine.

A major vacuum leak could cause the engine to fail to start under all conditions, but probably not intermittently like you have. Still, all vacuum leaks should be corrected because any vacuum leak will interfere with the fueling system. There are so many things that work together and have to be working properly in order for good reliable starting and running. Ignition, fuel, vacuum lines, a few electrical switches, and mechanical adjustments like the throttle.



Sent from my Pixel 6a using Tapatalk

[Magnus86]

Ah thank you.
Well i did notice that the oil cap itself isn?t sealed very well as the O-Ring seems to be worn. When the cap is fully closed i can jiggle it around a bit. Is a vacuum leak there also a problem?

Regarding the Vacuum i did a first check:
There is this one ?closing valve? (don?t know the english word) that goes inside the WUR. I removed this one (rubber hoses pretty stiff) and sucked on the vacuum side of the hose, the black side of the valve. I noticed that it didn?t really holds the vacuum. There is some Vacuum but it slowly gets loose. When i close the other side of the hose (white part of the valve) with my finger and i suck on the black?s side hose i could feel that i got some vacuum on my finger building up. I don?t know if this piece needs to be completely tight? I also tried it the other way: Put the black side of the hose inside a jar of water and blew inside the hose on the white side. I could easily see bubbles coming out of the hose on the black side. I?m not sure if this thing needs to be a 100% tight:

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Another test i did today:
I checked the control pressure, so i opened the valve to the WUR and let the fuel pump prime. With the fuel pump priming i got about 13PSI:

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Right after i turn of the fuel pump the pressure goes up to roughly 23PSI:

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Aaand after about an hour i got 20PSI:

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This is how my fuel gauge is hooked up for the control pressure test:

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All those tests are with a cold and not running engine as i still wait for my new fuel lines.
Are those values i got for rest pressure good?

Oh and i tried again pushing the air plate down while having a good rest pressure. The pressure didn?t change in any way after i pushed the plate down.

[Magnus86]

Hey guys,

as i'm still waiting i did another test today with the rest pressure.
Strangely, today my primary pressure wasn't at 70 PSI but more around 60-65PSI. I couldn't find any leaks in my pressure-gauge hoses. What could be the problem when on some day the primary pressure is at 70 PSI and on another day it's just 60PSI?

As i said i replaced the O-Rings of the pressure valve inside the fuel distributor..is there something i can mess up here?
Furthermore the pressure dropped way faster than a few days ago. Starting at 60PSI the pressure dropped down to 15PSI in just 1 hour and 30 minutes.

A few things i noticed:
My fuel pump was a bit wet on top of it's head, since the car hasn't been driven for quite some days it seems like it's slightly leaking. I let the fuel pump prime but didn't see anything. I think one of the new copper washers isn't tightened enough. Can someone tell me whats the correct torque for the fuel pump banjo bolt?

But as far as i understand, the (sometimes) slightly leaking fuel pump would not be a problem for the rest pressure as the fuel accumulator and the pressure valve in the distributor should stop the fuel from returning to the fuel pump right?

Another question:
As mentioned earlier it seems like one of my fuel lines is leaking. Strangely this doesn't happen all the time and sometimes the line is completely "dry". Of course i'll replace the fuel lines anyways. I heard that a leaking fuel line to the injectors could cause a pressure loss. But how is that possible? As far as i understood, when the fuel pump is off with rest pressure and the plunger is in it's resting position, it closes all the fuel injector lines and thus, a leaking injector or fuel line wouldn't cause a drop in rest pressure. Or am i getting something wrong here?

I thought about this because i had one injector removed to get it cleaned or replaced (bad spray pattern) and even though the fuel line with the missing injector was completely "open", there was no drop in fuel pressure and no fuel coming out of the fuel line (of course as long as i didn't push the air flap), even with 40 PSI rest pressure.


Another thought i had:
Could a clogged fuel filter (the one next to the fuel accumulator) cause my cold/hot start problems?
But with a clogged fuel lifter there should be a problem with the running engine or driving around as well?
That's not the case, as soon as the engine runs everything is fine.

Thanks a lot :)

[Bitsyncmaster]

Your original type fuel pump the banjo fitting is after the check valve. So yes a leak at the banjo would reduce rest pressure time but not affect primary pressure tests.

[Magnus86]

Hello there,

so i finally got my new fuel lines mounted and replaced one injector that had a pretty bad spray pattern. Before i mounted the injectors back into the intake i put them into the jars with the new fuel lines to verify that they are all spraying (jumpered rpm relay and push down the air plate). Everything works fine there.

But i still get the problem with starting issues and slowly i'm running out of ideas.

One thing i noticed with my hot start issue..maybe some of you have an idea what could be the problem here:
When i crank the hot engine after a few minutes of sitting most of the time it won't start. I noticed that i have pretty good pressure on the air plate and my gauge is reading 40-45psi rest pressure (valve to the WUR opened for the gauge). So what i did was i unplugged one of the injectors, put it inside a jar and let the engine crank. There was no fuel in the jar after cranking, so the injector wasn't spraying even though my gauge showed good rest pressure. I then jumpered the rpm relay to have the fuel pump running all the time and i cranked the engine again. And still..no fuel coming out of the injector.
After that i slightly pushed on the air metering plate while the pump was still running and the injector was spraying. So as a next step i cranked the engine (RPM Relay in place again) and let a friend of mine slightly push down the air metering plate and the engine fired up. It seems like cranking the hot engine doesn't pull down the air metering plate enough to get the injectors to open?
What does the air metering plate should look like when cranking on a hot engine?
Could this be caused by a vacuum leak or maybe the starter is not turning the engine fast enough for enough air to be sucked in?

I removed the fuel distributor to sort out a stuck plunger. I cleaned it with some acetone and put it back in. To me it looks okay (see video below)?


https://www.youtube.com/watch?v=5zMFPdoP2AY

The other thing is that sometimes i completely loose Pressure on the air plate while my gauge still shows some good pressure.
What could be the problem here? Will check the accumulator in the next days and see if there's any fuel coming out of the rear end of the accumulator.

Thanks a lot in advance

[Bitsyncmaster]

Maybe you have weak vacuum due to a leaky valve or piston rings. Can you do a compression check?

[Ron]

With the fuel pump priming i got about 13PSI...
Right after i turn of the fuel pump the pressure goes up to roughly 23PSI:


The other thing is that sometimes i completely loose Pressure on the air plate while my gauge still shows some good pressure.

None of the above makes sense to me -- Seems you are doing something wrong.


Oh and i tried again pushing the air plate down while having a good rest pressure. The pressure didn?t change in any way after i pushed the plate down.You must of missed post 10 -- Good rest pressure is ~45 psi. Since the injectors open at 50-60 psi they wouldn't spray and lower the pressure. Normal.


What does the air metering plate should look like when cranking on a hot engine?
It will barely pulse up and down, less than 1/4", iirc.