Sputtered and died

99 4.0 167000 - modified - weekend warrior
As it is winter I have been working on my junk. The only one thing that I have done that could be causing die is replace alternator, tho directly after replacement drove for hours with no hesitation or sputtering.

Fast forward 3 days and I decide to take my jeep to a company event. I leave the drive way with a half a tank of gas, drive about a mile and sitting at a stop light and the jeep starts running very rough. I chalk it up to just sitting to much and isn't warmed up yet, so I give it a little gas at the green light and try and clear it out, what ever it is.

I stop in front of my coworkers house and let it idle while I type a few emails. 10 minutes later we pull away, running like crap I pull up to a stop sign. I put it in neutral and rev the engine, put it in drive and it dies. I let it sit then put the gas pedal all the way to the floor and cranked it fired and I revd the engine, it stayed running. Let it idle for a minute then put it in drive, it died. Cranked for a few minutes and got it to fire up, revd to 3k and it just died no sputter or anything. After that all I could get it to do was pop a little in the intake.

What I did:
Switched relays around- then put new ones in
Checked fuses
Unplugged cps and plugged back in
Unplugged all sensors on intake
Checked volts on batteries (dual batteries)
Checked coil wires and dist. Cap
Ran a scanner on it...no codes.

Towed it home and has not been able to start it since.

ALL sensor have been replaced in the engine in the last 2-/+ years. Everything is pretty much brand new, granted some sensors were not bought from the dealer. Like the CPS.

The current fuel pump is about the same (2 years) replacement schedule as the sensors, but it's from NAPA and was in the $100-200 range. With that being said after work today I grabbed a fuel pressure gauge as I had my wife prime the fuel rail while I had my ear on the tank because I couldn't hear it from the cab, which was odd.....

When I put the gauge on, the jeep had been sitting for a full day.
I primed the rail, gauge was at 10
Hit the key again -35
Again - 40 - leaked down to 10 instantly
injectors are also about 2years old

Kept up like that for about a dozen primes. Safe to assume I should just buy the Bosch fuel pump and be done with it?

Cheers,

Cheap parts are cheap for a reason. Just because they are newer doesn't mean they are any good.

Bosch or genuine Jeep are the only fuel pumps to buy, unless you enjoy changing fuel pumps every 18 months.

Test the CPS, consider buying a genuine Jeep CPS.

agreed and noted. cant find a dealer for the bosch pump, rock auto, advanced, amazon... is it discontinued?

Alright. Replaced the fuel pump with mopar, holds 45-49psi strong. Still no start- switched out IAC- tried another PCM- jumped the battery- tested the cps- had resistance replaced with mopar still just cranks.... Going to let it sit after all the cranking unplugged the battery to let it reset.

Anything else I am not thinking of?

Get back to basics. What component are you missing. Fuel or spark. Injector pulse is another possibility.

On the 99, there are a few quick and dirty tests to perform.

1. Pull a plug, keep it attached to the plug wire. Place the plug electrode near a good engine ground. Have a buddy crank the engine while you watch. You are looking for a strong, BLUE, snapping spark. Yellow/orange/white indicates a weak spark which may not be strong enough to start the engine (ignition coil is primary suspect for weak spark)

2. If spark is good (and only if) then put a small splash of gas into the throttle body. If the engine starts and runs for a few seconds, you have identified a fuel delivery issue.

3. If the above do not yield any clues, you need to verify that you are getting a pulse from the computer to fire the fuel injectors. Use a noid light for that.

Good luck and report back what you find!

After tons of tracing and research, I was able to narrow it down to the ignition coil itself, also replaced ~2 years ago. Fired up and running great! I think the lesson I learned here, buy quality parts, the new "cheap" parts only made diagnosing my problem harder.