wagoneer880

Hello to All,

I have a 2000 XJ with 156K that was working properly until yesterday, I got home and it was running fine, then I was goin to the store and it would not start, checked spark, fuel pressure, battery etc, everything was fine. I have read many posts about the cps going bad and since I had a spare I changed it, still the Jeep didn't start.

Not sure why but I decided to put a splash of gas down the throle body and it started right up and ran without any issues but as soon as I turn it off it would not start again unless I put a little gas in the throle body, while running I then checked all the injectors and all were working.

Can this be the ECM gone bad?

Any suggestions would be greatly appreciated.

Thanks,
Jimmy

RTorrez1

You said you checked the fuel pressure. How did you check it? Did you use a mechanical pressure gauge on the fuel rail? if not that will be the only way to know if you have the correct amount of fuel pressure.

macgyver35

My guess would be TPS or Idle Air Controller took a dive on you.

Just so we're clear,when you put a little gas in the TB and it starts, can you leave it running for several minutes, or just until that gas runs out?

If it's several minutes, I would suspect that some signal from the TPS or IAC is not being sent to the computer.

Radi

Just for giggles, try turning the key to "on", wait 5 seconds...then off again. Repeat once more, then try to start. See if anything changes.

wagoneer880

The fuel pressure was checked with a mechanical gauge on the fuel rail.

When I put gas in the TB and it starts it runs for as long as I let it run, it doesn't miss fire, it runs smooth like it usually runs.

I'll try turning the key on and off as Raddi suggested and see what happens.

Thanks,
Jimmy

VTJeep

Will it crank but not catch? Weird issue.. Maybe get a code reader on there (even w/o cel) to see if anything has stored? It's not the ignition itself probably.. Loose or poorly connected wires for power, ground or relay?

Edit- this doesn't seem like an ECM thing.. Yet..

porphyry

I'm with an above poster on this one. Buy a fuel pressure gauge and check pressure at the rail. At idle for my 96 XJ 4.0L HO, fuel pressure at the rail should be 49psi, +/- 2psi (338 kPa). I've had fuel filters get clogged, drop pressure 5-10+ psi @fuel rail and my XJ started doing some weird stuff. Look there first.

If that checks out, buy a set of Noid Lights. Hook one up to an injector clip and make sure you have pulse. If you have pulse, you should be good, but if you don't, look at your Crankshaft Position Sensor (CKP) first.

The problem with the CKP is that sometimes the flywheel scrapes it. Even just a little scraping can cause a CKP to go on its downward spiral. Any problems with your CKP, and it won't produce a 5 volt current to send to the PCM (Powertrain Control Module, or ECU), which tells your computer to fire your injectors. Often, the wiring harness on the wiring loom side can go bad. Check to see that the metal connectors on the inside of the harness are firmly in place and go right to the end of the harness.

Once that's done and you're still having problems, check secondary spark at the coil. Get a spark plug tester and hook it up to one of your spark plug wires. Don't have spark there? Take the plug wire off the center post on your distributor: the lead from the coil that energizes the distributor. Hook the tester up to that and check for spark. If you still don't have spark, it's most likely your coil. If you have spark there, but none to the spark plugs, then check your cap and rotor, and replace as needed.

Also, check all the free stuff: your engine grounds. Pull the bolts, sand 'em down real nice and replace. That's a great place to start before you do any of the above. That would be the first thing I would do. Then try swapping out a known good relay with your ASD (auto shutdown) relay. It could be your ASD system.

It is rarely, if ever your PCM or ECU. However, there are ways to test that, as well.

One last thing...check your vacumn lines. Make sure there are no holes. As for TPS and IAC, backprobe them to make sure that they are in good working order before you replace them. It will save you a bunch of money. Good luck, and let us know what it was!!

wagoneer880

After going back and checking all the ground wires, fuses, TPS, changed the ASD relay, cleaned the IAC valve, still would not start unless I pour a little gas down the TB.

After running it for a while I did noticed that the battery was not being charged, checked the alternator and it was not charging so I figured maybe the voltage regulator inside had gone bad. I took the alternator to a trusted local shop and had it rebuilt.

Completely charged the battery and installed the freshly rebuilt alternator, pour a little gas in the TB and started it again like before, checked again, and again the alternator was not charging the battery.

At this point I feel it has to be the ECM not sending signals, now I have two separate issues.

Ended up taking it to the dealer, I'm still baffled and probably broke by the end of the week.

I'll update once I get it back.

Thanks to everyone for the time and effort in giving me ideas in how to get my girl going again.

Jimmy

porphyry

Your wiring could be bad. I would double check that first. Good luck, man.

jblack'00xj

In for results.

Sorry for thread jack: I woke up this morning with the same issues. Drove over to my aunts, came later today to get the XJ. Wont crank. Battery has charge, all fuses are checked. At first I could crank motor but it wouldnt turn over. However if I depressed the gas pedal I could get the motor running. Only when I released the pedal, to allow the vehicle to idle, it would choke out and cut off. After an hour on the charger, NOW the vehicle wont crank. The starter sputters and all my lights flicker, WHILE THE CHARGER/STARTER is hooked up?

Am I looking at simply a new alternator/battery or something more like CKP?

-Jon

porphyry

You should check and clean your grounds first. Unbolt, remove and clean your throttle body. Please elaborate some more about your problem. That would help.

wagoneer880

After all, here are the final results on the problems I was having.

Internal short in PCM that prevented output to the ASD relay, had to replace and reprogram PCM and the relay. (Chrysler Reman PCM). $567.00 less 10% disct.

Also replaced the battery cables, charging issues resolved, although my cables appeared to be good they were not

Thanks to everyone for their suggestions.

A little expensive but my girl is back running smooth!!!

Jimmy

H Man

FWIW...as much as we like to make our own repairs on our Jeeps, and there's great satisfaction in doing so, with all the computer controllers and sensors that they have, taking it to the dealership can sometimes be your best option. Back in the day, if you had spark, fuel, and air, the engine would run. Those days are long gone though.

Glad to hear you got your rig all dialed in!