89 XJ won't start

Hello all,

I have a really strange problem that seems to defy all logic. I recently bought an 89 xj 4.0 liter. The guy sold it to me for a song because it had starting issues. They day i went to pick it up and trailor it home the darn thing actually started and ran for about a minute. It just flat-out-stalled and wouldn't restart. At the time i was actually smiling because i was sure it was the CPS. So we loaded it up on the trailor and brought it home. I did the quick ohm test and it was within tolerance but i replaced it anyway. The darn thing still wont start. NO SPARK AT ALL. It cranks but doesn't even try to start.

I'm going to list what i have checked and replaced.

CPS - replaced
CPS - hard wired to ECU - soldered and heat shrink
Coil - checked - good
Coil - ground - good
Ignition Control Module - Replaced
Cam Position Sensor - Checked Ground - good
Cam Position Sensor - Checked Continuity to ECU both wires - good
Cam Position Sensor has 5volt fluctuation when cranked - measured at distributor and computer.
Cap and Rotor and wires - Replaced
Ground Strap - Perfect
Grounds from diptstick location - all good
Fuel Pressure - ignition on - 40 lbs
Fuel Pressure - cranking - 40lbs
Fuel Pressure - running - not able to check YET
Fuel Pump Balist Resistor - Broke when checking connections - replaced
The previous owner replaced the ECU - has remanufactered - brand new like the guy just replaced it.

I'm completely baffled. I have another xj but its a 91 so i cant just swap the ECU to check.

I'm kind of curious if anyone knows what the signal coming out of D13 on the renix computer is supposed to look like. This is the wire that connects the ECU to the ICM.

Any help would be greatly appreciated.

Thanks
Larry

i am having the same exact issue at the moment with my 89 i am about to replace the fuel pump check yours and see if that might be the problem

Fuel pump is kicking out very well. I ended up replacing fuel system parts just for good measure. I'm at a complete stand still here. I've just about wore out my mutlimeter checking connections.

I have an 88 wagoneer Limited with the same F***** problem. it's driving me nuts. also replaced the ignition control module, Coil, Distributor Cap and Rotor, Cables and Spark plugs. Fuel pump, fuel filter, Pressure on rail is good, the darn thing turns but does not start, checked all the relays as well and cables, still no spark from coil.

Hmm, seems to be that more people are accumulating my problem these days. I'm in the same freakin boat as all you guys. Exactly.

From the renix manual, heres what the ECM needs to see in order to start-except for the cam sensor it will still start without it, though performance will suffer noticably.
Coolant Temp sensor
Manifold Air temp
TPS
Starter relay
Engine speed sensor (CPS)
Sync Signal Generator (Cam sens)
Battery Voltage

And to how these sensors must be responding, I don't know. With the coolant temp harness disconnected it says the ECM assumes coolant temp at 176. Doesn't say about anything else.

And an engine crank signal? I assume that comes from the ignition switch to the ECM.

And you hardwired the CPS to D1 and C1 of the harness connector at the ECM?

How would these temp sensors affect spark? And the TPS? Would that effect spark? My main key right now is that lack of spark.

Hey! I had the same problem along with a rich running condition. I ended up replacing and checking just about everything you did including the computer and the Ignition Control module. It's under the coil and I'm not real sure if there's a way to check it but a buddy of mine had a spare laying around from another XJ. Mine ended up just being the computer so see if you can get your hands on someone's spare.

Dane

Have you disconnected your Ecu and left it out for a few, then reconnected it? I was at the same spot you are just 2 weeks ago, checked everything. i was seriously about to give up. and that trick fired it right up.
By the way, i have an 89 aswell

Nobody's checking the MAP on the firewall? Having had problems with other Chryco MAP's, and owning a RENIX, I understand how indestructable it seems to be.

Still, it's another sensor input that can be lacking data to crank.