98 cherokee 4.0L Won't Run - HELP NEEDED

[stamptrain2]

The other day I went to use this vehicle and it started fine but died about ten seconds later. It cranked OK but would not fire. I can hear the fuel pump buzz when the key is turned on so I am assuming fuel pressure is OK. I pulled a plug but no spark. The next day it did the same thing, started and died after a few seconds. Would appreciate some experienced help on troubleshooting this problem. Thanks in advance.
Richard in Vermont

[fredjacksonsan]

I'd suggest to start here:

http://www.automotiveforums.com/vbul...d.php?t=687635

Couple questions --


How many miles and is it auto or manual trans? My first thought (as usual) is that it could be the CPS (crankshaft position sensor), as your symptoms go along with that. Have you had any other symptoms, like an engine miss here and there, or if auto trans, mis-shifting? Any coolant use?

[stamptrain2]

Miles is about 131K, automatic and no other symptoms leading up to this problem(no misfiring and no coolant issues). I did check the troubleshooting list first thing but thought I had better seek a pro's help before throwing parts at it. Many thanks for your reply. Is there anyway to test the CPS and where is it located? Should this car have a trouble code if the CPS is the problem?

Originally Posted by fredjacksonsan

I'd suggest to start here:

http://www.automotiveforums.com/vbul...d.php?t=687635

Couple questions --


How many miles and is it auto or manual trans? My first thought (as usual) is that it could be the CPS (crankshaft position sensor), as your symptoms go along with that. Have you had any other symptoms, like an engine miss here and there, or if auto trans, mis-shifting? Any coolant use?

[stamptrain2]

I'm still trying to figure this one out. It will start and run for only a few seconds then it dies and usually won't restart for a while. I've tried unpluging the crank sensor plug and re-plugging but that didn't help.

Questions:
1) Where is the socket located to read fault codes?
2) Would reading the codes pin-point the problem?
3) On a '98, how do I do the "self test method"?
4) When measuring the CPS output voltage, which of the three pins are used to make this measuremtent?

Any help is gratefully accepted.

[Saudade]

If your MIL is lit, you need to pull the codes first. The connector in just under the dash near the steering column. You need a code reader. If you don't have access to one, typically your local autoparts store will read codes for you. MAKE SURE YOU WRITE DOWN THE EXACT CODES! (Yes I'm shouting). The codes may or may not pinpoint the exact problem but will point you in the right direction.

If your self-test refers to the key-click method, forget it. It's not a reliable method on your model year.

[jdl]

The data link connector should be under the dash left of steering column. To check for codes, at the least, you need an obd2 code reader. My info didn't show an mil method. The three wires at the crank sensor are ref voltage, about 5 volts--ground--signal. The siganl wire is on and off pulse.

[fredjacksonsan]

If it's a late 98 build, it may have the diagnostics of a 99. Try turning the key on/off/on/off/on in 5 seconds. If you have the 99 type diagnostics, you'll get codes flashing in the odometer. If not, you'll need the scan tool mentioned earlier.

It does sound like the CPS to me.