Intermittent morning no start

I've been "fixing" this problem on my wife's Daily Driver for several months now. 98 XJ 4.0 with close to 200,000 miles on it. It's been a good vehicle and we intend to drive it for as long as we can. At this point I am at a loss and looks more likely. Any suggestions are welcome.

Here is the write up of what is happening.

Since she drives it I don't usually get to see it in failure mode. Only seems to happen in the morning. She gets up and goes to work before I do. She'll crank it over several times and it won't catch. Turns over fine. After the crank it kind of half heartedly stumbles and coughs. Eventually she will get tired of trying and take my car while grumbling about my repair skills...

Thought it might be the CPS at this stage of the jeeps like so I replaced it with an OEM. Spark seemed weak and coil values were low so I replaced the coil. And the Cam position sensor. Rotor and dist cap were replaced a few years ago so they should be good.

Two weeks of functional jeep then it happened again so I bought a fuel pressure gauge. Hooked it up and tried it. Just cranked for several tries but the pressure was @50. Hooked up a spark tester to one of the cylinders and at first it didn't seem to spark but the connections may have been loose.
Does the half hearted stumble and tried to start. Cranked it again and a white cloud of smoke/vapor came out of the air cleaner intake. Then it started and ran just fine. Good spark on the tester and good fuel pressure at the rail.

It will probably run just fine untill my wife tried to use it! :lol:

Turned off the jeep and I left the gauge on the rail- in 40min it was at 35 psi. 4 hours it was at 15psi. Is this a sign of the Fuel check valve going bad like is mentioned below? Really hoping to confirm this before dropping the tank and replacing another unneeded part!

http://www.naxja.org/forum/showthread.php?t=1119238&highlight=fuel+pump+check+valve


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No suggestions guys? Am I headed in the right direction?

Basic question or not enough info to give advise? No one has had their XJ stumble at cold startup and backfire out of the aircleaner? Is the Fuel pressure loss I noted an issue or is that normal?

Have I hit the end of s knowledge? :scared:

I could really use some help before I drop the tank, replace the FP and have this STILL continue to be a problem. Any help, guesses, or moral support is welcome!

Your fuel pressure is holding fine. It appears your pump is fine.

You can determine if it is fuel related by waiting until this happens and squirt some ether down the throttle body while cranking. If it fires but you have pressure at the rail, you are having an injector drive problem.

I would start by doing the old standby, clean all the grounds on the motor. If that does not fix it, get a NOID light and verify the drive for each injector.

Start there and report back.

old_man said:

Your fuel pressure is holding fine. It appears your pump is fine.

You can determine if it is fuel related by waiting until this happens and squirt some ether down the throttle body while cranking. If it fires but you have pressure at the rail, you are having an injector drive problem.

I would start by doing the old standby, clean all the grounds on the motor. If that does not fix it, get a NOID light and verify the drive for each injector.

Start there and report back.

Click to expand...

Thanks Tom,

I appreciate the confirmation that the pump is not the culprit. Glad not to drop the tank. My wife never lets it get lower than a half a tank.

I'll get the NOID (need one anyway) and report the findings!

Harbor Freight sells them for around $30 with the discount. You might be able to grab one from Autozone with a deposit you get back when you return it.

From what you describe, it seems like you are probably losing injector drive (fuel). If there is no code, then it might be connection related back in the harness, but think about it. It should still start and run (rough) if you lose 2 cylinders at once. That means that two opens would have to happen simultaneously multiple times. Not likely. That is why I mentioned cleaning up the grounds, since it can cause multiple failure modes.

old_man said:

Harbor Freight sells them for around $30 with the discount. You might be able to grab one from Autozone with a deposit you get back when you return it.

From what you describe, it seems like you are probably losing injector drive (fuel). If there is no code, then it might be connection related back in the harness, but think about it. It should still start and run (rough) if you lose 2 cylinders at once. That means that two opens would have to happen simultaneously multiple times. Not likely. That is why I mentioned cleaning up the grounds, since it can cause multiple failure modes.

Click to expand...

There was a P0320 code but I thought that might have been from the testing I did when I installed the OEM CPS. I cleared that with my reader and it has not come back.

I'll clean the grounds asap. The one to the rear of the engine near the CSP was pretty gunky.

Finally got to work on the grounds last night. Cleaned and dielectric greased them both and it started right up.

This morning... same cranking no start with a coughing at the end of the crank attempt. Beginning to suspect the IAC as I was able to get it to start holding down the pedal while cranking.

Drove fine once it started. Very weird. I hate electrical problems!

I did pick up the NOID light so if troubleshooting the IAC doesn't pan out then I'll move to that.

Check/replace the ASD relay. It is supposed to keep the power live for a second after you turn off the key. During that time, the ECU is supposed to set the IAC to the position for startup. If it doesn't get the IAC set, things don't fire up well the next time you try to start.

If fuel psi is fine also check or replace TPS.

A bad CPS is known for those symptoms.

Digger87xj said:

A bad CPS is known for those symptoms.

Click to expand...

I thought so too! Unfortunately it is a new OEM from the dealer. Harness to it seem OK as well.

I appreciate all the help. Here is a recap of replaced parts and actions for easy reference.

Replaced:
CPS
Cam Position sensor
Coil
Fuel Pump relay
Wires/plugs/rotor- replaced within 15000 miles

Fuel pressure 49#
Spark to plugs is good
Engine Grounds cleaned and greased

I have a ASD relay in hand. IAC can't be gotten from Advance till July 9th! So time to check the other parts houses or order it from Rock A.

Oh, and when I drove it to work and back last night one of the rear drum brake cylinders blew out spewing brake fluid everywhere. So I have got that going for me! :lol: I think the rears are original so it's about time. Guess it will get a little TLC before getting it back on the road. It deserves it. It has be a good vehicle.