90' XJ Won't start

Jerms · Dec 27, 2004

Hi,

My Dad owns a 90' xj 4.0, aw4, 242, that won't start. when we bought it it had a bad computer that caused it not run very well. it has pulled this no start trick on me once bfore but after i let it sit it fired right up. here is what i know.

It does NOT have spark.
It does have fuel preasure.
It cranks pletny fast. (enough to build 60 PSI oil preasure)
It has never started well when it was cold (20 and down)

what i would like to know from any one who knows, is how can i tell if this jeep has eaten another computer. Is there away to see if it has an injector pulse with out specail tools, and what would cause a no spark condition. these are the parts that i can think of that are possible causes can someone tell me if any of these parts would cause this and if so what would be most likely, Ingnition module, Coil, CPS, Sync Sensor, Computer.

Thanks for any help

Jerms
Thanks

old_man · Dec 27, 2004

Sounds like the classic crank shaft position sensor failure. If you do a search on this site for CPS, you will find a ton of posts.

Cliff · Dec 27, 2004

cps would also be my first tought

Zoro · Dec 27, 2004

Are you sure that all of your wires and plugs are hooked up correctly?

hillbilly_jeeper · Dec 27, 2004

knowing xj's with 4.0's, probably a crank sensor. those buggers can cause all sorts of no-start or randome dying problems!! got mine for $45 from napa, so not real bad. a bit of a pain to change, but not terrable.

Dragon_Fly · Dec 27, 2004

What about his NSS? Maybe just needs to service it?

Caleb · Dec 27, 2004

Dragon_Fly said:
What about his NSS? Maybe just needs to service it?

Not the NSS if it was, it would keep the motor from cranking as that is what the NSS does. It would NOT cause it not to get spark!

As others have said, check the Crank Position Sensor, if that doesnt do it, also check the Cam Position Sensor in the distributor!

TUFFXJ · Dec 27, 2004

Jerms said:
Hi,

My Dad owns a 90' xj 4.0, aw4, 242, that won't start. when we bought it it had a bad computer that caused it not run very well. it has pulled this no start trick on me once bfore but after i let it sit it fired right up. here is what i know.

It does NOT have spark.
It does have fuel preasure.
It cranks pletny fast. (enough to build 60 PSI oil preasure)
It has never started well when it was cold (20 and down)

what i would like to know from any one who knows, is how can i tell if this jeep has eaten another computer. Is there away to see if it has an injector pulse with out specail tools, and what would cause a no spark condition. these are the parts that i can think of that are possible causes can someone tell me if any of these parts would cause this and if so what would be most likely, Ingnition module, Coil, CPS, Sync Sensor, Computer.

Thanks for any help

Jerms
Thanks

Agreed sounds like the CPS... Try disconnecting and reconnecting the wire. It runs down the Driver side rear of the valve cover should be a wonder plug right about the same level as the intake/exhaust it is a 2 wire connect and attaches to the bellhouseing at about 1 o'clock looking at it from the front

ren · Dec 27, 2004

I agree, the cps is a good candidate, but on my 90 limited, it turned out to be the wiring harnes. go figure. BTW, I learned this the fun way, stick and auto harnesses are different, worst part was the plugs on the computer. (if it does it again, i think i will drop the computer out to change the wires. took about 20 mins. to do.

Jerms · Dec 27, 2004

Thanks for all of the help it was the CPS. I replaced it and the idle air motor too so that maybe it will start better when it is cold. so far it is running very well. again thanks for all of the help.

Jerms

90' XJ Won't start

Jerms

NAXJA Forum User

old_man

NAXJA Forum User

Cliff

NAXJA Forum User

Zoro

NAXJA Forum User

hillbilly_jeeper

NAXJA Member #1081

Dragon_Fly

NAXJA Forum User

Caleb

NAXJA Forum User

TUFFXJ

NAXJA Forum User

ren

NAXJA Forum User

Jerms

NAXJA Forum User

Similar threads