Greetings! I have not been able to solve this problem and could use some pointers.

2000 XJ, 4.0l, engine and related components are unmodified. 185k miles.

Classic no-start, crank position sensor or camshaft position sensor failure symptoms with the P0340 code.

Initial symptom: Oil Pressure Reading dropped to zero while driving. I thought little of this because the oil pressure sensor has failed before and it did not impact drivability. I parked the Jeep and after it no longer started. No codes at this time. I replaced the oil pressure sensor because I was concerned it might be preventing start. Anyway, no dice, so I called a tow truck.

At home, I retested and got the cam sensor code mentioned above. I checked engine bay fused and swapped relays. No problem suspected with them. Fuel pump makes normal fuel pump noise when key is turned. I plugged in a spare ecu to see if that might have failed. No change, so reconnected the original. I then replaced the camshaft position sensor - no change. Same after replacing the crank position sensor. Pulled crank sensor read as open between all pins. Installed new sensor read 4M Ohms between one two pins. The the cam position sensors read similarly to each other.

Last thing, the cam position synchronizer doesn’t move when the engine is turned over. Should it move?

I haven’t checked the fuel system, but this definitely seems like an electrical/sensor related problem to me.

It ran fine up until it failed to start.

Any recommendations or next-steps are appreciated. Thanks!

 

Check for fuel pressure on the rail. Don't assume.

CPS does not move (not that you can see anyway).

Probe the gray wires of CPS and CKS to see if you're getting a 5 volt signal during cranking (this won't work if it actually starts cause a DVM can't read the signal fast enough)(course if it starts I guess the problem is solved). Check signal at sensors and at CPU (could have fried wire somewhere)(speaking of which check for any fried wires down there by the CPS connector).

 

Then I think you're looking to see if the oil pump shaft snapped.

 

Now I see (says the blind man). Yank this out. Something on it's busted:

 

Pull the valve cover and see if all the valves are working (broken cam, timing chain, timing gear).

 

OK that's all I got.

 

"Pulse ring."

 

You could mark the position of the CPS before you yank it out, but at this point it probably won't help (although it can't hurt). And you may (probably) need a DRB tool or an oscilloscope to sync CPS/CKS.

 

Thanks. The cam position synchronizer doesn’t move when the engine turns over and I’m pretty sure it should rotate in sync with the engine. I’ll pull it tomorrow. I’m not 100% certain how everything mates together, but if there is a problem I’ll pull the oil pan and check the oil pump as well.

Whatever failed didn’t prevent the Jeep from running and didn’t introduce any abnormal noise or vibration that I could sense. Fortunately I only drove it a few miles. I believe I installed a high flow oil pump in 2015 or so. If it’s bad I’m going with a normal one, as close to oem as possible.

 

Page 8D-16 should tell you what you need to know:

https://cdn.xjjeeps.com/pdf/en-us/20...ice-manual.pdf

 

Syncing CPS/CKS not a big deal, if it comes to that:

Bad:



Good:

 

That right there is the problem and would also explain the oil pressure dropping to 0.

 

I got $10 on the roll pin that holds the gear on the shaft. The real question though, is why did THAT break? Those roll pins aren't easy to snap!

Also, you definitely ran without oil pressure if the roll pin snapped. This is why it's always good to trust your indications.

 

I know that this probably will seem to simple but have you checked verified all fluid levels?
im just going out on a limb and guessing oil dropped level far enough or oil pump seized.

 

Then again maybe the retainer keep came loose.
Have you checked mega fuse?