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Discussion Starter · #1 ·
Now I know that this isn't about a Wrangler, but i still gotta ask just in case any one may know what ime going thru... so here it goes. Not new to Jeeps and definitely not new to the 4.0. I currently have a '94 YJ and a '98 XJ that are daily drivers for myself and the wife. I acquired a '93 ZJ Grand Cherokee -4.0HO, QuadraTrack(full time 4wd), Auto tranny, last week for free:cheers2:, that has a history of starting issues:thumbdown:. Between myself and the PO we've swapped out plugs, wires, distributor, Neutral Safety Switch, coil, also have all maintenance records going back to 95.(and let me tell you he treated this thing like a baby doll) at 200K it has had fluids changed like clockwork and so far as i can tell only had the starter and battery replaced under the hood. (PO was a maintenance chief for 35 years with the Army... so to say he took care of his baby is an understatement.)
Long story short, I've been thru this thing with a multimeter a dozen ways this week. I don't think that the factory anti-theft system has anything to do with it (only vehicle I've ever had with it) but I've got spark and fuel, she will crank smooth for about three seconds then will drag for one, then back to cranking smooth.

I've already killed one battery attempting to figure this out, now working on the Red Top out of my YJ.
Like i said before I'm not new to the 4.0, but this is the only auto trans I've ever owned. So my thoughts at this point are either its a bad Crankshaft Position sensor or a bad PCM? What would be the best way to test these?

Any ideas are appreciated, and thanks in advance...
 

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Id just replace the crank sensor. It's cheap enough. I tried testing sensors and all before with a no-start issue and the new sensor tested the same as the old one. The new sensor worked though once I swapped it in.

Also, not sure on that model, but I'd look into the cam position sensor as well. Had one go bad on my old XJ. It was located inside the distributor. Fuel pump relay? Fuel pump? Fuel pressure regulator?
 

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Discussion Starter · #3 ·
Cam position sensor is the same, dist, fuel pump, relay have all been swapped... I've got a crank sensor, just have to swap it out... Only thing else I can think of is the pcm,
 

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Discussion Starter · #4 ·
Ok so over the weekend I swapped out the PCM, CPS, and every relay I could find... No change whatsoever. Guess I'm gonna rip out the 4.0 and go with a 350 short block or a 4bt Cummings and turn it into a toy.. Any other ideas
 

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You say you have spark and fuel, have you checked compression and timing?
 
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