transmission rebuilt...now not starting

i have a 1991 4.0l 4wd auto

i took my jeep to a transmission shop to get the trans rebuilt (water got into the system and ruined the paper clutch)

i get a call saying that they cant get it to start...(it always took a few seconds of cranking to start) i tell them to turn the key on and off a few times then start cranking

i get another call from them saying that they still cant get it started...so now they want me to there and show them how...so i do that and i cant get it started

any ideas why its not starting...they said that theres a spark, i can smell fuel coming from the exhaust, the engine sounds like its almost its going to start but doesnt...the only thing i could think of was that they didnt put the cps back with the correct screws, but they said that they did

any clues...tia

SirFrack said:

i have a 1991 4.0l 4wd auto
...the only thing i could think of was that they didnt put the cps back with the correct screws, but they said that they did

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It certainly sounds like the CPS isn't working, either because the mechanics didn't install it properly or because they've damaged the sensor itself. The sensor is very sensitive so it doesn't take much abuse to render it useless.

Dr. Dyno said:

It certainly sounds like the CPS isn't working, either because the mechanics didn't install it properly or because they've damaged the sensor itself. The sensor is very sensitive so it doesn't take much abuse to render it useless.

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Hmmm, the CPS operates not only the ignition but also tells the system when to fire the injectors as far as I know. If the CPS was bad not only would there be no spark but there should also be no injectors operating or am I wrong.
Could the NSS be the culprit ? I have never had an auto so have no idea what a bad NSS acts like, does a bad one allow the engine to turn over but not start or does it prevent the starter ckt from engaging ?
Could they have crimped something when they were pulling/putting the tranny or did they not get that far yet ?

the rebuilt trans is already in and theyre trying to start my jeep to see if the trans is operating properly

SirFrack said:

the rebuilt trans is already in and theyre trying to start my jeep to see if the trans is operating properly

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I would put good odds they missed a connector somwhere or pulled one out that was not supposed to come out. Again the only thing thats I *know* for sure is back there is the NSS but I don't know what the results are if it's not plugged in right or not plugged in at all.

Since it's much easier for them to switch the CPS to the rebuilt trans while both trans are out of the jeep I'd bet they disconnected the CPS plug and maybe didn't re-seat it properly when they re-installed, could be that unplugging and replugging firmly is all that's needed. I think the NSS will disable cranking totally as it would move the vehicle if in gear, so shouldn't be that. Otherwise I can't think what they could have touched that would cause a no start but getting gas and spark.

Also, another thing to check for, there are two small lugs with thin wires that ground to the block where your negative cable bolts down. I know for a fact that if both of those are off you will get crank but no start with no spark or fuel. You may even hear chattering relays, as those wires are grounds for the ecu and without them connected you have the mother of all ground loops. My point is that these wires break out of a harness at the firewall and it's entirely possible that if the motor is dropped far enough back (to help stab the tranny back on) that one or both of these wires could break off as the harness does not give them a whole lot of give. Just something to check.


HTH,

Mark

RichP said:

Hmmm, the CPS operates not only the ignition but also tells the system when to fire the injectors as far as I know. If the CPS was bad not only would there be no spark but there should also be no injectors operating or am I wrong.

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The timing of the injector pulse is determined by the cam position sensor (or pick up) in the distributor.
If the crank position sensor goes, there's no spark. If the cam position sensor goes, there's no fuel. Either way, the engine won't start.
The NSS prevents you from starting the vehicle if the tranny shifter is in any other position than Park or Neutral. Even if it's disconnected from the wiring harness, the engine should still start unless the engine's computer has been programmed to prevent it if the NSS fails.

If the NSS is bad or disconnected the XJ wont start. When I rebuilt mine I tested the idea. Not saying that all XJ's should work this way tho. Maybe mine is funky.

Actually I rebuilt it and then it crapped out a month or so later and was worn too far for a rebuild so was replaced. Same signs both time.

Before rebuilding: Wouldn't start unless you pressed on the shifter a certain way.

Pulled: Wouldn't start

Fixed: YEAH!!!!

Sarge

It pretty much has to be the NSS or the CPS, and if they pulled the tranny they had opportunity to muck up either or both.

Assuming they put the linkage pack and adjusted it correctly (which may be a big assumption), my guess is that they left the CPS on the bellhousing when they pulled the tranny, and mashed it against the ring gear when they reinstalled the tranny. My vote goes to CPS.

Bottom line is, it isn't your problem, it's their problem. If they can't fix it, it is THEIR responsibility to flatbed it to a Jeep dealer and let the dealer diagnose and repair whatever the shop messed up. If they don't see it that way, call whatever agency in your state licenses repair shops.

If NSS is bad or disconnected it will prevent engine from cranking, don't think that is your problem, sounds like CPS.