My Libby let me down on Wednesday morning: I hopped into it for my morning commute and it cranked fine, but wouldn't start. It ran fine the night before. No CEL or other obvious issues, although I don't have a scanner. Fuel pump primes (at least it whirs) when the key is turned to the on position. I replaced the crank-position sensor -- since it was cheap and easy it was the first item on my "low-hanging fruit" list. It just cranks and cranks and seems to cough a little every couple revolutions.

I'm not sure how to check for spark w/ the coil-on-plug setup. I need to go rent/buy a fuel pressure tester, with 85K miles it's conceivable that I've got a clogged fuel filter or weak fuel pump.

Any suggestions on how to attack the diagnosis? I'm not really sure how to proceed.

Thanks,

Brian

I'd start with the filter,but it sounds like you're not getting spark.
I've got a CRD,so can't tell you how to check spark.
Mabe TJKJ will chime in and help out.He'll know.

_________________
Bub
06 Inop Edition CRD Silver
06 Inop Edition CRD Green

Thanks KJ 119. Looks like my problem was neither fuel nor spark, but air. After the fuel pressure checked out I was playing and got the rig to cough and sputter by playing with the throttle while cranking -- I could get it to run by using my foot to set idle speed, but if I let off it'd sputter and die. So the IAC was the immediate suspect, especially when I realized that it wanted to idle at 600 RPM regardless of engine temp. I took off the intake ducting, removed the IAC, and used carb cleaner to remove a whole bunch of varnish and gunk from around the butterfly and IAC passage and pintle.

That didn't seem to solve the problem immediately, but after a ride around the neighborhood and the morning commute to work today, it seems that the IAC has unstuck itself. The idle speed now flares up to about 1500 at start-up, immediately dropping down to a temperature appropriate speed between 1000 and 600 RPM. So, I'm *assuming* the IAC was gunked up badly enough that couldn't do its job and over-choked the engine.

Anyway, I'm happy to have the Jeep back on the road for basically the cost of a can of carb cleaner and some shop rags.

Thanks for lending a hand!