Brad.208

Hey folks,

. Been lurking for the last month reading everything I can since I bought a basket case 2000 XJ. It's a non runner with a '98 engine that never got running after the swap. I buttoned up a bunch of stuff and still haven't got it running aside from once (fluke, super rough for a couple seconds and died).

I have a P0340 that comes on after about 4-10 seconds of cranking and an intermittent P1391 that sometimes kicks on. I checked all the circuits for the sensors and everything checks out on the multimeter for connections. I've been through a heap of parts store sensors and a bunch of junk yard ones too since the dealers don't carry these any longer. Some of the parts came out of wrecked rigs so I'd have to think they were good sensors to get to the crash site...

Long story but here's the takeaway, it acts like it's out of time and throws those codes. Is it probably a computer at this point or should I do the Mopar sensors first?

lawsoncl

It's almost never Lupus the computer.

Brad.208

Thank you! I am starting to feel pretty insecure in my diagnostic ability, but I think I can be sure after digging through the whole harness that it's one if the three components.

Found some stuff over on TJ Forum with similar issues, they've been liking NAPA/Echlin sensors and I can get those local so I'm going to try new ckp and cmp tomorrow first thing. Will report back.

tjwalker

When you have both of those specific codes together (rather than just the P1391 alone), a primary suspect would be the camshaft position sensor. I'd start by concentrating on that circuit. By circuit, that means not only the sensor, but connector and wiring and the computer, (especially with an engine swap) although I agree with Lawson that the computer is the least likely.

Keep us updated!

Brad.208

Went to NAPA and got both sensors this morning. So I tried just the cam sensor and it threw a 1391 pretty much immediately, didn't even have time to throw 0340. Swapped the crank sensor too, and after a starter-slaying long crank time with lots of backfiring I got it started a couple times. Here are the details.
-tachometer is bouncing in the 4k-6k range, erratically.
-car won't idle by itself
-lots of gas smell and rich smoke, maybe from cranking so long/soaking cylinders in gas
So I want to get it to start and then maybe start moving the whole synchronized assembly around till it will stay running, I think. Thoughts?

Brad.208

Update - after those couple times I can't get it started again. The synchronizer was in pretty rough shape so I got a new one from NAPA, sounds better but doesn't affect the no start. If I play with the synchronizer position a little I can make it better like it wants to go, hit a couple times, then eventually it'll backfire and give up. Same codes. So with a half dozen each cam and crank sensors and three synchronizers, the parts cannon is running out of ammo.

the cam sensor functions fine with a voltage test and intermittent cranking. Crank sensor reads OL one way and like 500k ohm the other way, but the one I tried this morning from JY reads like 5M ohm and didn't even try to start so I don't know how much is enough. Kind of down to a bad tone ring on the flexplate, or back to bad ecm... it's outside the box time.

Brad.208

Scanner Danner turned me on to this idea of having a flex plate that's got a low spot in the tone ring and I got to looking. Guys have issues from time to time with the weaker aftermarket sensors tripping over inconsistencies in the tone ring, so I could be having that issue. Might be better to get a good flexplate than keep looking for a ckp seeing as the last six (used OEM and new aftermarket including echlin) were not strong enough.

Another thought: I've heard of a few guys that got flex plates with windows in the wrong spots before. That would probably cause what I'm experiencing too. And I don't know anything about this particular flexplate or even for sure what year the engine was so its plausible.

so does anybody feel like getting a pic of the underside of the flexplate at tdc 1 so I can compare window positions? My inspection plate is already off anyway...

Dave51

IMO you should get an entry level oscilloscope to confirm the sync as well as checking the COPs and injectors.

Brad.208

I hear that, thanks for the response. I'm looking into it because that's gonna be the best way to confirm if I'm getting a drop out from being out of true or flat out misaligned.

Dave51

Yep. My Hantek was less than 100 bucks on Amazon. Accessories like the current clamp and an attenuator add a little.

Dave51

BTW which parts are 1998 and which ones are 2000? Is the ECU from the 2000?

Dave51

And you're sure the synchronizer assembly is installed correctly?

Brad.208

Ecu is 2000. Engine is 98, with a synchronizer in the distributor hole. Harness is original to the car and the exhaust manifold is 2000 but idk what else on the engine is what year.
Yeah it's aligned properly as far as I know, I've wiggled it back and forth a few degrees trying to find a happy place but it went in with the holes lined up on TDC 1. Even tried it backwards once for kicks in case I lost my mind.

O-scope should be here today, I'm hoping that will shed enough light to get us up and running.

One final detail: the harmonic balancer has orange paint pen marking the timing mark. There's also a few little orange dots on timing cover around 10 o'clock, so 60 degrees off TDC or so. Weird right? And the PO expressed that it was timing he couldn't figure out... maybe he was on to something I haven't seen yet. No orange paint on the actual 0* mark FWIW

Dave51

You mean like the cam was changed and put in wrong? Or the timing chain is worn and/or jumped (rare but it can happen)? Did you check the compression at some point?

Brad.208

Honestly, your guess is as good as mine on that rabbit hole. I verified that the piston is actually at top dead center within a degree or so of the 0* mark so that's good... Guess I should check compression to verify cam timing huh. Good one.