Hard cold starting

[82DMC12]

Hey guys,

After my frame-off, everything is working great and I have a short punch list of items that still need to be addressed. One issue my car has had for quite some time is hard cold-starting. When I say cold starting, I just mean the car has been sitting for a couple days. It could be 50F in the garage and it will take 4 to 5 seconds of steady cranking to get the engine to fire. Once it fires, it runs and it runs very well.

Stuff I have already checked:


confirmed the ignition resistor relay is working and passing +12 to the grid during cranking and stopping once the key is back to RUN.
Spark plugs checked and look 100% perfect, gapped correctly 0.026
New OEM coil wired correctly, new plug wires
Cold start valve confirmed firing into a jar upon cold start
TTS is not blown out and measures correctly with meter
I have two ISM's, both work the same and behave the same. Currently have an NOS black painted Volvo motor in. I was hoping that would help but it did not.
Lambda circuit is working and behaves as expect with open loop to closed loop change over and CO is set correctly
Timing is exactly correct with no advance at idle
I have McKeen's RPM relay which primes the fuel system when the key is turned to RUN. I know this is working because if the the car has been sitting and cold, the air flap moves freely. If I turn the key to run, wait a couple seconds, then turn the key to off, the air plate now has the expected resistance so I know there is fuel up to the distributor.
Throttle is correctly set and the car runs and idles perfectly under all conditions
New Eagle Premier starter installed


It just takes too long to start when cold, in my opinion.

Any other thoughts and things I should check or try?

[Helirich]

One thing you probably know, but I will mention anyways. When you go to start the car, you should turn the key on and wait for a few seconds while the fuel pump brings it up to pressure. Then turn to start. This is true for most, if not all, fuel injected cars. My wife is famous for turning the key right from off to start and wonders why it takes so much cranking. The cranking takes some power from the fuel pump right when it?s trying to get the system up to pressure. It?s not going to start until the pressure is up. There?s no reason to be putting the strain on the starter while the fuel pump is working.

[Bitsyncmaster]

You have done everything I would do. Only thing I can think of is your injectors are leaking so the lines get dry but even then I think the cold start valve firing should at least give you some sign of it firing.

[82DMC12]

One thing you probably know, but I will mention anyways. When you go to start the car, you should turn the key on and wait for a few seconds while the fuel pump brings it up to pressure. Then turn to start. This is true for most, if not all, fuel injected cars. My wife is famous for turning the key right from off to start and wonders why it takes so much cranking. The cranking takes some power from the fuel pump right when it?s trying to get the system up to pressure. It?s not going to start until the pressure is up. There?s no reason to be putting the strain on the starter while the fuel pump is working.

Good thought, in fact I already do that. The McKeen relay will prime for a couple seconds and then stop. My habit is to get in the car, confirm I'm in Neutral (manual trans), turn the key to RUN, I can hear the fuel pump prime and then after a couple of seconds it will stop. Then I turn the key to Start and hold it until it the engine fires. The starter is doing its thing, and if you have ever heard the Premier starter, it spins faster than the old PR starter did.

I have to assume it's a fueling problem because if it were spark, it wouldn't start at all, and I did confirm with a test light that the grid is only getting +12 when the key is on START. I believe that is correct. I'm talking about the left wire on the grid.

Note that on a warm start or hot start, the car starts instantaneously.

[82DMC12]

As you can see, the spark plugs look great so I think my mixture and timing is on the nose.

69617

[82DMC12]

You have done everything I would do. Only thing I can think of is your injectors are leaking so the lines get dry but even then I think the cold start valve firing should at least give you some sign of it firing.

Theoretically possible, however I did do a jar test last fall and they all seemed to be behaving properly. No drips or any of that. Might be worth another look just for the heck of it.

[David T]

It takes a while for the fuel pump to get up enough pressure to operate the fuel injectors. The Cold Start Valve (CSV) doesn't require as much pressure so it can squirt as soon as any pressure gets built up. The motor should be able to start on just the CSV and by the time it stops squirting there is supposed to be enough pressure for the main fuel injectors to run the motor. One quick test you could do is, when it is cold, take the CSV out and while you are trying to start the motor, make sure the CSV is squirting. It only squirts a) when you are cranking, b) only for less than a minute, c) only when cold.
Other systems to check are the vacuum advance, the thermal valve, and the heated air intake. The CPR acts like a choke, making the A/F ratio richer so you could check the pressures and the vacuum hoses to it.

[82DMC12]

It takes a while for the fuel pump to get up enough pressure to operate the fuel injectors. The Cold Start Valve (CSV) doesn't require as much pressure so it can squirt as soon as any pressure gets built up. The motor should be able to start on just the CSV and by the time it stops squirting there is supposed to be enough pressure for the main fuel injectors to run the motor. One quick test you could do is, when it is cold, take the CSV out and while you are trying to start the motor, make sure the CSV is squirting. It only squirts a) when you are cranking, b) only for less than a minute, c) only when cold.
Other systems to check are the vacuum advance, the thermal valve, and the heated air intake. The CPR acts like a choke, making the A/F ratio richer so you could check the pressures and the vacuum hoses to it.

I'm sure the thermal vacuum switch is working normally and I have no ignition advance at idle. I actually replaced the thermal switch last year and I know the vacuum hoses are routed correctly.

The CSV will only fire while the key is set to START and the engine cranking, correct? I know the CSV will eventually stop due to the TTS heating up. My CSV is indeed firing while I try to start cold (confirmed by pulling it out and putting it in a jar, and then cranking with the coil wire off). Seems strange that I can confirm it is firing but doesn't seem to "do the trick". It appears some versions of K-Jet allow the CSV to spray for varying lengths of time depending on ambient temp but looks like the DeLorean is a fixed time only cut short by the TTS. Maybe my CSV is not firing long enough due to something wrong with the heating element in my TTS, cutting it off far too early?

[Bitsyncmaster]

I'm sure the thermal vacuum switch is working normally and I have no ignition advance at idle. I actually replaced the thermal switch last year and I know the vacuum hoses are routed correctly.

The CSV will only fire while the key is set to START and the engine cranking, correct? I know the CSV will eventually stop due to the TTS heating up. My CSV is indeed firing while I try to start cold (confirmed by pulling it out and putting it in a jar, and then cranking with the coil wire off). Seems strange that I can confirm it is firing but doesn't seem to "do the trick". It appears some versions of K-Jet allow the CSV to spray for varying lengths of time depending on ambient temp but looks like the DeLorean is a fixed time only cut short by the TTS. Maybe my CSV is not firing long enough due to something wrong with the heating element in my TTS, cutting it off far too early?

CSV can only fire when cranking. If the thermal time switch times out or engine temp above 95 deg. then it will not fire even cranking.

[Ron]

Spraying some starting fluid in it might tell you if it wants more fuel.

[Rich]

Spraying some starting fluid in it might tell you if it wants more fuel.

+1 on this recommended test.

There may be a difference between the CSV spraying and the CSV spraying *enough* to do the job.

If it starts fast with starting fluid that tells you that the charge needs to be richer than your current CSV setup is capable of providing.

[82DMC12]

+1 on this recommended test.

There may be a difference between the CSV spraying and the CSV spraying *enough* to do the job.

If it starts fast with starting fluid that tells you that the charge needs to be richer than your current CSV setup is capable of providing.

OK Cool, I can try this out. Embarrassing point - I have never used starting fluid before. Would I be actively spraying it into the air meter under the flap while someone else is cranking?

[David T]

OK Cool, I can try this out. Embarrassing point - I have never used starting fluid before. Would I be actively spraying it into the air meter under the flap while someone else is cranking?


Yes, but DON'T OVERDO IT! Too much and you can destroy the motor's internals. Just need some small, short squirts. Do it in a well ventilated area like outside. If you breath too much of it, for people it is STOPPING FLUID.

[82DMC12]

Yes, but DON'T OVERDO IT! Too much and you can destroy the motor's internals. Just need some small, short squirts. Do it in a well ventilated area like outside. If you breath too much of it, for people it is STOPPING FLUID.

Yikes. Maybe I'll set something up where I can squirt it down the cold start tube, if I can seal it off relatively well so it's not a big vacuum leak (or else the test will be moot).

[cbateman]

Yikes. Maybe I'll set something up where I can squirt it down the cold start tube, if I can seal it off relatively well so it's not a big vacuum leak (or else the test will be moot).

Any update on this? Did the starting fluid do the trick?

[82DMC12]

Any update on this? Did the starting fluid do the trick?

Sorry, just saw this. I never did try the starting fluid, but I did later learn the PPR o-ring on the tip of the regulator had a small cut in it which eventually caused some minor hot start problems. I didn't find out about this until the next summer. I fixed that with a new set of o-rings from PJ Grady and that solved most of my issue. I also adjusted the throttle linkage again , turned out I was able to open the throttle about an extra 3/4 of a turn before it affected hot RPM's so perhaps a combination of throttle adjustment and fixing the o-ring made the difference.

Funny thing is sometimes if the car sits for two weeks, it fires up immediately, sometimes if it sits for 4 days it takes a few revolutions to fire. Who knows!

I did determine that priming the pump before cranking makes ZERO difference though. Seems like it's better to just hit the key straight up.