I just replaced my motor and clutch in my heep, its a 95 xj manual trans, I can start it and drive it for a mile or 2 but then it putts and shuts off then I won't get any spark but occasionally I'll get a spark but still won't start, after a bit it'll start and drive for another mile or 2 and does it again... What can it be

 

1. Refresh all engine grounds. Grounds can be responsible for many gremlins, especially in vehicles with the engine swapped.

2. The "crankshaft position sensor" is a primary suspect. When they fail, you will not have spark and you will not have fuel going TO the fuel injectors.

3. Try testing your ignition coil for primary and secondary resistances when it won't start. Coil is a possibility, but the crank sensor is higher on the suspect list.

 

Crank sensor is newer I replaced that maybe 6 months ago, but grounds can cause it to run then pretty much stall out? I know 1 ground is on the fuel rail that was originally on the block, I'll put that where it was when I get home

 

All good info to check. Completely agree with CPS; could just have a bad one.

My Ranger had the the 2.9L V6 and on hot days, the coil would heat up and quit working. Leave you stranded until it cooled and worked fine until it heated up. Problem was that was operating temp and it didn't throw a code. Took me forever to figure it out.

 

That might your problem right there.

 

It's a short shoelace looking ground that originally went from the firewall to the valve cover, what is that a ground to? Does anyone know? Or would it run like that because its on the fuel rail?

 

*Where did you buy your crank sensor from? Aftermarket crank sensors are "hit and miss" with a lot of miss. I use only Mopar crank sensors.

*It wouldn't hurt to get a fuel pressure gauge on the rail and watch it and see if you can recreate your symptom in the driveway while you watch the rail.

*Definitely fix that ground wire and any other ground issues. Start with the one on the back corner of the head, and where it attaches to the firewall, as it deteriorates over time and is an area that makes it susceptible to damage. Best to replace that woven cable with a #4 or #2 gauge cable. You can attach the one end to the intake manifold if you would like. Next go over to the engine dipstick tube stud. Remove the nut and clean the wire ends and scrape the block until shiny at the stud. Reattach tightly. If you are so inclined, add at least a #6 cable from the negative terminal of your battery to one of the bolts on your radiator support.

 

Ok not getting spark from the coil... What all can it be, crank sensor, coil, what else? It will randomly catch for a bit but then die

 

Cam Shaft Position sensor? does that year have the coil pack rail or a distributor ?
was it timed out correctly with the cam pos sensor when you made the switch that could cause all sorts of issues
just make sure its mopar all that other off brand stuff is a little shaky when it comes down to it.

 

It's a distributer, and I am not sure where the cam sensor is though