TJ 2.5l hard start

[Captain]

Posted this on CO 4x4 and I'm not getting any response so I thought I'd try the experts. I have a 2000 TJ 2.5l 5 speed, 137k miles. It's always (at least for the last ten years or so) had a weird starting issue. In the summer only, it almost never starts on the first try. No matter how long you crank it, it won't even catch. Next try, it fires right up. I investigated a bit at the time this began, but never worried about it because it always started reliably. As the weather warmed up again this spring, it started doing it again (doesn't do it in cold temps) but then got worse, to the point of taking 4-5 tries to start it, sometimes catching and stalling. Strong smell of unburned fuel when it finally catches, and low power at RPMs below 2500. I figured it was time to do plugs, wires, cap and rotor (about 4 years and 35k miles since the last ones) so I do that (Champion RC12ECC, gapped to .035"). This didn't seem to change anything. What should I check next? I don't want to throw parts randomly at it, are there some tests I can do to narrow it down? What are the symptoms of a bad coil? Bad fuel pump? What do you think?

[transplant87]

i would start at checking the fuel filter and u might have an issue with your injectors flooding out the cylinders[i ran into this issue when i was working in a shop]if i think of anything else i post it up

[Brad]

Check your plugs after the first crank, see if they are wet. I would bet (given the strong fuel odor) you are missing spark.

[Captain]

Thanks guys! Sorry I haven't responded, I'm a teacher and school ends next week so it's nuts right now. Gotta get this fixed though, the wife is threatening to boycott the TJ and take the Volvo to Moab when we go next week. Um, no. I'm going to try pulling a plug after the first crank and I'll let you know what I find. I don't have $91 to drop on a new CPS, but I wasn't sure exactly what you meant when you wrote (in the link below, post #3) "Turn on your key and if your gauges now work, the sensor is bad." My gauges work fine right now, is that an XJ thing? I'll pull the plug on it tomorrow and see if it affects my gauges. I checked in my FSM and it talks about using a scan tool to see if the sensor is good, I don't have a scan tool, and it's not throwing any codes (as far as I know anyway - the check engine light has not come on). Don't places like Autozone scan codes for free? Would this be something they would/could test?

Brody previously posted:

[Robert B]

okay ima spit ball what i know about fuel injection here.................

okay only in warmer temps it does it and usually after the first try will fire...... (fuel pump will run for a few secs then shut off if no fire) do your fuel injectors happen to have any type of rubber in or around them???? i know its cold that usualy causes problems with rubber stuff but it almost sounds like the pressure that is left over when the truck is shut off is causing the fuel to go past the injectors and flood the cylinders..............which is where on some motors cranking it with no extra fuel pressure will evacuate the cylinders and then when you try the second time it is not flooded and can fire right up......... maybe not rubber on second thought but while it shrinks with cold it also expands with heat so still might be that ...........also if the fuel in the motor didnt stay in liquid form but went to a gas cause the heat BUT was trapped in the cylinder it would also probly cause this or something like it cause then there is too much fuel to air ratio and it wont burn either or at least wont do the explosive burn that is needed .............. if anyone has any modifications to this let me know since i know the simpler carb and TBI stuff beter and the new things with electronics in everything make it harder to fix problems


you could try an experiment............ if ur truck has a fuel pump fuse remove it before turning the truck off and let the truck die by it self and see if it will start first time after that (no left over fuel pressure) ..the pressure does normally dissipate to somewhere in a few hours but this should show if it is leaking into the cylinder and flooding it ..........


just a thought ...a big thought but a thought

[Captain]

I like big thoughts myself.

I got in there this morning and tried a couple things. First start attempt, pulled two plugs, both were dry. Backed out the PCM screws, no difference. Unplugged the CPS plug, no start at all. Plugged it back in, still sputters to life after 3-4 attempts. I'm beginning to suspect it's a fuel issue now based on the dry plugs, what do you think?

When the problem first occurred a long time ago, I was suspecting the valve that held pressure in the fuel rail. The schraeder valve still pissed fuel quite a bit but I never put a gauge on it...

[Hypoid]

I'm reluctant to do a web diagnosis, because there is too much basic stuff that needs to be covered. So much in fact, there are entire books on the subject.

Since I'm not well versed on the engine management system used in your Jeep, all I can suggest is to try your local library for good reference material.

The quick and dirty test for a weak fuel pump is to cyle the key from off, to run, three or four times, without cranking the engine. If the engine starts after priming the fuel system, you have a weak pump or bad check valve (commonly, inside the pump).

I think you local auto parts should have a fuel pressure tester in their loan-a-tool program.

Good luck!

[Captain]

Yeah, I've tried the on/of/on/off thing both when it first started years ago and again a couple times yesterday, it doesn't change anything. :(

I read in my FSM that the CPS and corresponding flywheel notches are for regulating spark timing by energizing the coil. Fuel injector commands apparently come from a tone ring on the distributor shaft. Anyone ever hear of those going bad? Since I seem to have spark (although not sure it's at the right time), I'm thinking maybe it's more fuel-related now. Is there any way to check to see if the plugs are actually firing during those first crankings? I thought I remembered years ago that a timing light used the current from a plug wire to light. Would that show me if the plugs were firing during cranking?

[Hypoid]

Captain previously posted:

[Captain]

Hypoid previously posted:

[Hypoid]

Captain previously posted:

[Captain]

OK, pretty sure it's the pump now. Got a fuel pressure gauge, turned on the key without starting it, no pressure at the fuel rail. Cranked a few times, no pressure still. Once it coughed to life, the gauge moved slowly up to 32psi. Ran weak (as I have experienced the last few weeks) until I gave it a little gas, then it jumped up to 48 psi (should be 49 psi +/- 2 psi). Once I shut off the engine, fuel pressure dropped immediately to zero. So I'm thinking the pump is on its way out and the check valve that holds pressure in the rail (part of the regulator, I believe) isn't working so the pump has to build pressure every time it starts. Am I thinking about this correctly?

[Robert B]

Captain previously posted:

[Hypoid]

Captain previously posted:

[94ToyBear]

i Agree with This !


If you have a few extra bucks, it may be worthwhile to replace the CPS just to eliminate it from the equation. It has a wire plug, two bolts, is a bit hard to reach, but only takes 30 minutes maximum with no special tools. The other thing you may want to do, again to eliminate it from the equation, it to remove the ECM cover screws and install shorter screws.[/QUOTE]

[94ToyBear]

Google Image Result for http://www.4x4xplor.com/images/cps/DSC02130.jpg


Google Image Result for http://i.ebayimg.com/00/s/MTA4MFgxMDAw/%24(KGrHqNHJCcE7y%2B!J0uMBPENqp(6,w~~60_12.JPG


I would just shot gun the CPS. this sound like a cps problem to me. it might be 91 bucks but i could be your 2 bolts and a plug fix.

[Captain]

Hypoid previously posted:

[Captain]

Hey, guess what? It was the CPS. I dropped it off at 4WD Extreme this morning and Greg (great guy, BTW) said the pump was OK but the CPS was bad. I didn't get a chance to quiz him why I got the fuel pressure readings I did, but I'll ask him tomorrow. The Jeep's still there because I had him check out my front end (yes, it needs everything - ball joints, TREs, track bar, and (ugh) steering box. No wonder my death wobble was coming back, I kinda saw all that coming. Looks like I've got some projects this summer.

But the kicker was that exhaust manifold leak - I broke an exhaust manifold bolt (guess which one? Yup, you're right, the one practically tucked into the effing firewall) many years ago. You could always hear it (more so on cold mornings), but this winter it got worse. Turns out the manifold cracked, so I've got to replace that now as well (starting to get fumes). :( That's what I get for putting it off for six or seven years I guess. Tomorrow I find out if he can do it without pulling the engine to get at the busted stud...

[Popsgarage]

Replace it with one of these.

http://lgcdn.jeep4x4center.com/media...ARMOR_6000.jpg

Or even better, one of these.

http://www.racepages.com/brand/banks/headers.html