GT1975

I have a stock 99 XJ. Auto, 4x4, 125K. Issues started months ago. Started dying randomly at 45-60 mph. Had to wait 10-15min to restart. Seems to have good FP. Will eventually restart and no issues for days, weeks. Some mornings it wont start. Replace dist., all seemed good. Went weeks with no issues. Problems again. No start after a baseball game. No FP, good spark. Eventually lit off and got me halfway home, died. No start. Good FP, good spark. So far.....new (mopar) CPS, new battery, new ign coil, new distributor/ PU coil. All connectors seem good. Good grounds. No CEL or codes in history. Cant find any bad spots in wiring. Runs great, when it runs. Becoming very unreliable. ECM? O2? Please, in need of your wisdom.

jordan96xj

How have you been confirming good/bad fuel pressure?

If you are in a position where you -know- you have good fuel pressure, and spark is present, then the next thing to check is fuel injector pulse using a noid light or high speed test lamp. (Google for more information if necessary).

moparado

Based on that one statement alone, looks to me it could be an intermittent fuel pressure related issue.
Before diving into a fuel pump replacement, i'd swap or replace the relay with another one and change not just check the fuse.
Also might want to check the fuel pump wiring/connectors.

Over time, the internal fuse links can develop hair line stress cracks causing intermittent problems.

GT1975

Thank you for the ideas. To answer 1 question, I did not check the fuel pressure with a gauge, only by bleeding off the Schrader valve at the test port. As far as the relays girl, I've swap them around multiple times. I am 95% sure that the relay is not the culprit here. I didn't think about the fuel pump, but it runs so fantastic more times than not. I was worried that it might be the ECM, because the times I do appear to have spark and fuel pressure, the injectors must not be firing. I do need to get a noid light to check injector pulse. I've read posts were the front oxygen sensor is an issue, but I don't see that causing any no start symptoms. So I had the wife Bring the truck so I could strap it and yank it home. No start, so he proceeded to go down the road and I tried turning the key three or 4 miles into our tow, and it fired up. I drove it the remaining 10 miles home with no issues whatsoever. It has started every attempt since then. It makes it really hard to diagnose an issue with everything working. As much as I love this jeep, part of me wants to burn it to the ground I get so frustrated

GT1975

Sorry about the typos, the talk to text feature on this phone does not pick up my redneck accent well.