'91 4.0 cranks but no start has fuel and spark

I consider myself (and my tech's) to be pretty good, but this one has us stumped.

1991 XJ 4.0/auto. A little history. The engine was replaced. One guy removed and disassembled, and basically set the re-man long block in place, then bailed. The rest of it was re-assembled by several backyard mechanic types, so who knows where the problem could be. It did run before the engine replacement. We found the main engine to body ground missing, and replaced it. The ground wires on pass. side of block were bolted to valve cover instead of the block, so we fixed those. We have good compression, meaning the timing chain was installed correctly. We have spark, we have correct fuel pressure to rail, we have injector pulse (noid) while cranking, but it doesn't even TRY to start. No hickup, no backfire, nothing. We have verified powers and grounds to the computer. I have tried a different computer. We have verified that it has the correct flexplate installed. We have verified that the distributor is installed correctly.

HELP??? hahaha Any other ideas?

Thanks

John

Hallo. 1 idea: ignitionswitch is not powering the ASDR relay, only when cranking.:dunno:

Sounds like you know what you're doing, but I'll throw out a couple of ideas anyway. You probably already looked at the plugs, they should be wet by now. Dry them out and try spray start. Maybe the gas is totally bad? It sounds like you already synced the distributor.

ok, this is dumb but did you re-install the rotor... don't ask, the wife still laughs at this one..

Firing TDC on exhaust stroke instead of compression stroke?

:eyes:

well from what you posted it sounds like you've concentrated on 2 out of the 3 components of what it takes to make an engine run....fire...fuel...and dont forget...Air. make sure your engine is able to breathe, otherwise she'll crank for days. Also, make sure you have spark in all cylinders. Good luck!!!

and i do believe that there is a ground wire attatched to the valve cover, should be back right side?

Sounds like the CPS sensor is working if you've got fuel. Did you swap over the flex plate from the old motor or did you install a new one? Is it a Renix setup or Chrysler electronics, as they are two different flexplates. The wrong flex plate will royally screw up the timing.

Do you have any spark? Plug wires in the right place?

Jeepcherokeeboy97 said:

....fire...fuel...and dont forget...Air.

Click to expand...

don't overlook "fire" as being at the right time-- pull the distributor and valve cover and reset cyl #1 at TDC of the compression stroke and then drop the dist. back in pointing to the #1 terminal. You can have good compression with a properly set timing chain but unless it's there when the spark gets there, it won't help much.

I agree that you should pull the plugs and clean/ dry them also, as a fuel soaked plug will give you fits.