91 4.0 won't start - What to try next?

[3XJFamily]

This problem started about a month ago, and was initially an occasional stall at idle - but restarted with no problem. Then, it would stall the first time or two when starting up but, would start and run with no problems. Now, it will start, stumble and stall then only crank unless I leave it sit for awhile - after which it will start then stumble and stall.

Within the last year, I have replaced: Fuel Pump, Filter, CPS, and done a tune up.

Within the last month, I've replaced MAP and IAC.

Last night I bypassed the Fuel Pump Ballast Resistor with no improvement. I can hear the Fuel Pump running, especially when the ignition is in the Start position. But, it seems like I have low pressure at the rail. I depressed the shrader valve, and only got a dribble of fuel. . . Fuel lines all look good and jeep is rust free. I'm guessing Fuel Pressure regulator?

Any idea how to test it? or a better guess?

 

[Kreutz]

Are you getting spark?

 

[3XJFamily]

Are you getting spark?

When I get home tonight, it will start and run for several seconds so, at least initially, it is getting spark. I can double check after it stalls and see. . .

 

[Kreutz]

The reason I was asking if you were getting spark, is because I was having the same problem a while back. It turned out to be the ignition module going bad. Sometimes it would start and other times it would just crank and crank. I replaced the distributor and it started right up. I thought that did it, then two days later it wouldn't start. Had autozone test the module for me and it failed 3 out of 4 times. Replaced the module and no plroblems since. Just a thought. I know it could be a number of different things. Good luck.

 

[Runnin'OnEmpty]

About the only way to test the FPR is with a gauge. You can take the vacuum line off, and see if raw fuel is inside the line. Usually when they fail, fuel will be sucked into the intake manifold through the vacuum line.

My guess is the same as Kreutz', a bad ignition control module.