For the past year or so, my jeep (1992 XJ 4.0) will struggle to start in the morning or after sitting for ~8 hours. Generally, it cranks for a moment then turns over, and then immediately dies. I usually have to repeat this about 4 times before it will stay running. once its going it runs very well, and will fire back up with no issue as long as I don't leave it for more than 7 or 8 hours. I have also found that if the weather is hot enough it starts easier sometimes not needing to be cranked over several times, but still not reliably on the first try.
I have read other forums with issues similar to mine and I believe I have tried most potential solutions that were suggested, although those forums did not detail the exact symptoms I'm experiencing.
I don't think its a fuel pressure issue, as my fuel pump is new as well the FPR. I also tested with a gauge and got a healthy 31 psi, only dropping 5psi after 2 hours.
Starter and battery are new also. I have also replaced the spark plugs, plug wires, and distributor cap while chasing down another issue but did not see a change in my cold start issue.
Please give me any advice you have, as I am out of ideas at this point. Thanks.

 

Next time you start cold, disconnect the coolant temp sensor in the thermostat. Fuel mixture is largely regulated by temp. Cold is rich and hot is lean. If your sensor is sending a warm or hot temp signal it will cut back fuel making it difficult to start cold. No signal sends a rich mixture. If it starts easy then change it out. You will set a check engine light and code ...don't remember how to reset on OBD1 ...might reset on next start with normal config

 

Thanks, I will try this in the morning and post an update.

 

I did not notice any change in the way it started after disconnecting the coolant temp sensor. Turned over after cranking for about 8 seconds then died. Repeated 3 times before it idled correctly and stayed running.

 

Things I have replaced this year with no change in starting issue:
New injectors,
New fuel pump,
New throttle position sensor,
New idle air control,
New throttle body,
New starter
Checked vacuum tube to fpr,
Spark plugs,
New distributor cap,
New spark plug cables,
New fuel pressure regulator,
New battery and ground cable
New Crankshaft position sensor

 

A list like that is always helpful to post straight up-
saves a few scenarios.
There are still a few to go. CPS, coil, relay circuits, etc to name a few.

Does it die like you switching off the key or does it stumble and die?

And before anything else: when did you last cleaned up all your grounds?

 

I would describe it as more of a stumble, it does happen rather quickly though.

 

Ok
-You didnt yet reply to the ground question
- Plus what brand CPS?
- just checking: you don't have an engine immobiliser feature do you? I think no.

Can you try this for the next time it dies after it runs:
leave the key in the run position
remove the starter relay
jump terminals 30 and 78
tell me what happens

 

My battery ground is good, I will test the other ground points tomorrow after work.
The CPS is Duralast (SU368)
I do not have an immobiliser.
I'm going to try what you said to in the morning, I just looked at the starter relay and I see the 30 pin and the 87 pin, which I'm assuming you meant rather than 78? I will let you know how it goes.

 

Yep meant 87. Down Under we sometimes swab numbers to make it more confusing for eachother.

(Take them apart and clean up the ground points (7) to get that out of the equation. Its likely not the issue, but bad grounds make for a wide variety of symptoms. Plus its good maintenance)

Let me know how you go with jumping the starter relay and we can go from there. You will need to be willing to do a bit of diagnostics after all the parts replacement festivities....usually its the other way 'round.

 

I went to start up the jeep this morning and it failed the first try as usual, I then bypassed the relay as you described and it fired right up! But I think I will need to test that on a few more cold starts before I know the relay is the issue for certain. I think tomorrow I will turn the key half way to prime the FP then go straight to jumping the relay and see if it fires up first try that way. I also still plan to test my grounds this evening.

 

OK
what that would tell, is that the path FROM the switch side onwards is working as it should. Next thing is to check the things to the coil side but we'll get there.

You can also swap the relay with a similar one in the meantime, to see if it's just the relay itself. Like the fan or horn relay (not sure if they're the same for your year as the starter relay)

And re the grounds: take them apart, clean the mating surfaces up and snug back. Makes for good maintenance and taking it out of the equation.

 

Jumped the starter relay again this morning and it fired up really well. I swapped the relay with a matching one I borrowed from another car so I can see how that does tomorrow.
I tested all the grounds last night for continuity and they all look good. Went ahead and ground down the paint and cleaned up the contacts to be certain.

 

Sounds good-

And physically cleaning up the grounds like you did is the way to go. Measuring continuity on them is only partially helpfull (but we all do it

Let us know how you go

 

So there's no improvement with the swapped starter relay after all. I think that my starter itself is working as it should at this point because it's cranks over just fine but of course dies after that. What else can I look into?