Hey!

Unfortunately, i’m having a tough time getting my Zj started. Replaced the engine 200 miles ago with a junkyard donor, it has run incredibly strong until a bolt made it into cylinder #8 [img]data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7[/img] I was a able to salvage things using a donor piston out of my old 5.2 as well as new rings and a hone. It’s back together and i am now trying to get it started, but it doesn’t want to run.

Here’s what’s happening

From what i’ve concluded it’s a timing issue, it backfires and fights the starter, very obviously not firing at the correct time.
With no fuel, pump relay removed, it spins over just fine.

I’ve confirmed plug wires are routed correctly, rotor and cap are new, cam sensor is facing correct direction, and i replaced the crank position sensor as well.

It’s really stumping me as i thought it was going to be the crank sensor. While repairing the cylinder i did break my TPS, i replaced it with a new one, as im trying to think of all variables, could a TPS affect timing ?

Any advice is appreciated!

 

To add, I have an aluminum plenum plate with a new gasket about 200 miles ago. I’m thinking maybe a vacuum leak on my china wall?

 

Did you remove the distributor during your repair process? If so, when it was re-installed, it likely threw off your timing if it wasn't re-installed in the exact orientation as it was removed. The distributor controls the firing and the fuel sync for the injectors.

 

didn’t touch the distributor, it’s set up the same since i had it running well.

 

i did have a bad ground connection on my battery when i went to first fire. I thought i had a bad starter which was sucking all my power, i would turn the ignition and it wouldn’t turn over, interior and gauge lights would dim, and the door ringer sounded weird. In one of my attempts trying to start it the negative post made a visible arc, after replacing it would turn over fine.
Just trying to think of all variables, could a bad ground have messed up my PCM ?

 

Video

 

Didn't see a link to a video. Have you connected an OBD2 scanner to the truck? Getting any pending or stored codes on the scanner?

 

Struggling to upload my video, it might take me a bit. It is a obd1 vehicle, 95 jeep, although it’s not showing and CEL.

 

This is with the fuel relay pulled in an attempt to not foul the plugs, trying to run off carb cleaner(ik)
But we have good oil pressure