Another crank/no start. No spark to coil, new CPS... help!

[sweenepj]

Hi all, first post on Jeepz! I wasn't having any luck on another forum so hoping for some help.


I have a 1999 Jeep XJ and I have no spark from the coil. The coil is powered with the 12v wire, but the signal wire does nothing. I have checked the other end of the signal wire at the PCM side, A7, and there is no activity there either straight from the PCM (I put a test test light between A7 and positive battery terminal -- it does not flash when I crank the engine). I tested continuity on the wire, and it's good between the PCM side and the plug that attaches to the coil.


The ASD relay appears fine -- I have swapped relays around, no change. The fuel pump does run for 1-2 second when I turn the key to the ON position, and there is fuel pressure at the rail.


I installed a new OEM/Mopar CPS, and it tests good.


I have cleaned and re-set the fender and firewall grounds, and battery terminals.


I have wiggled and visually inspected every wire that I can find and looked for shorts or cracks although I have not removed anything from the looms yet. O2 sensors on the exhaust are relatively new and the wires are good.


I'm not sure what to do next. I'm guessing it's either something shorted in the wiring harness that is not visible, or maybe the PCM is just not working. Or maybe there's a sensor issue still. I have read a little about the camshaft position sensor, should I check that next?

After lots of research and testing I feel like I am at a dead end, looking for some help to avoid just randomly replacing sensors and pieces. And of course the jeep isn't throwing any codes :-(

 

[JPNinPA]

Just clarify the mopar part. CPS cam position sensor

Did you check the CKP crank position sensor. It is on the bell housing. New oem should have a paper gasket on it to set the spacing. This gasket gets scraped off in use as it is only there as a spacer.


And did you verify you have a good battery and good grounds. Bas grounds and/or weak battery has been linked to many issues.

Never look down on anyone unless you are helping them up - Jesse Jackson

 

[sweenepj]

Thanks for the reply!

When I said CPS I should have clarified, I replaced the crankshaft position sensor that lives on top of the bell housing. But I have not replaced the cam position sensor in the distributor. I've also seen this called the pickup coil.

I don't believe the crank position sensor had a paper gasket on it, at least nothing that I noticed. It is fixed-position, no adjustment that I can see. Here's the part: MOPAR 56027866AC

The battery is not very old, maybe 2 years, and I did clean the firewall and fender ground points as well as the battery terminals. I didn't clean up the grounds that attach below the coil, it's on my list to try.

 

[JPNinPA]

Engine ground too?


Never look down on anyone unless you are helping them up - Jesse Jackson

 

[sweenepj]

I think I got them all, I cleaned up the engine ground that goes from that valve cover bolt to the firewall. And also cleaned up the grounds that attach under the coil tonight. Still no luck. I did order a pickup coil, so I'll see what happens when that arrives.

 

[JPNinPA]

Dont you have a ground from battery to the engine block?
Ground from battery to distributor?
Check CPS sensor and connections.

Did you check all fuses and relays?



Never look down on anyone unless you are helping them up - Jesse Jackson

 

[sweenepj]

Yes, sorry, the direct ground from the negative battery terminal to the engine block is the one that mounts near the coil. So I did get both ends of that. I also checked every fuse in the engine bay and kick panel as well as relays. CPS sensor is testing good.

Could be there is something going on between the CPS pigtail and wherever it goes... I didn't trace the wires back to the PCM or anything. Is there a way to test the signal going to the CPS to make sure it's good? Is it just power and ground and the third wire is the signal wire?

I've read that the CPS and camshaft position sensor/pickup coil sometimes go bad in tandem, so I'm hoping when I get a new pickup coil (Monday) maybe that will have an effect.

 

[JPNinPA]

Where dies this issue stand?


Never look down on anyone unless you are helping them up - Jesse Jackson

 

[trails]

did you check for codes ?

does the CEL come on @3sec then go out everystart?

 

[sweenepj]

Sorry for going quiet for a few days, I was waiting for a chance to install the new pickup coil (Mopar 56041030)... and good news, the Jeep finally fired right up!

Thank you for the help and suggestions, I'm glad to finally be back on the road.