Hudy

Another point to add: the gauge cluster voltmeter has always read low. Typically around 13 when running, and sometimes as low as 12 with the headlights on and fans on high. Voltage at the battery remains at ~14.

Same readings. I did “refresh” the connectors while it’s out. Also cleaned grounds in the engine bay. In my case, I have both ground terminals from the cab AND the (-) battery terminal all grounding at the dip stick stud. I do have extra ground wires at the rear of the intake manifold and also at the battery.

Which connector would you recommend probing?

Yes. The .7 ACV is when hot.

I had posted about this some time ago, but I’m starting a new thread as that one evolved into a fuel pressure issue. 5 years with this truck, and this is still a mystery. Now I’m determined to get this solved. If my MJ is HOT, that’s to say I’ve driven it and brought it up to temp, it doesn’t like to restart. I’ll have to give it 3 or 4 cranking attempts before it will start. By this I mean I’ll crank the starter for 3 or 4 seconds, stop and repeat this 3 or 4 times before it starts. If I allow the truck to cool all the way down, or if it’s a morning start, it fires right up. Every time. 1. I have great fuel pressure and it holds fuel pressure. 2. I have spark during this no-start period. I’m determining that with an in-line spark tester. 3. I would THINK the injectors are working as I can smell fuel when the truck finally starts up. 4. CPS values are where they should be determined by cruiser54’s guide. (Right around .7 ACV) 5. I’ve added multiple additional ground points. OHMs from the TPS to battery are around .05 6. Coil and relay contacts were cleaned. I have not tested compression but if this was an issue, I’d think id have this symptom all the time. Am I missing something? Is it possible I have spark but it’s not sufficient for running conditions? And if so why would heat affect this? Do sensor values control fuel in some way versus spark?

They're rock solid! --- So here is the 7 month update (and mostly everything's happened in the past month or so): I decided its time to show the MJ some more love. I had a cap on it (I use the truck for a side contracting business), but the cap was leaking and more hassle to use then it was worth. The truck was hesitating to start, and other little things were making it a drag to use almost daily. Off the cap came. I bought a backrack for it (the rear window guard) and a toolbox to store my tools. I've been super happy with the size as its just big enough to store all my junk but not so big that I can't use the bed anymore. And some mechanical things: New fuel pump (and the story behind that HERE) New starter (and the story behind that HERE) Headlight Wiring harness (after repeated posts from Pete helping me out and not being able to ignore his signature) Newer style mirrors Door Locks ... yeah, pretty neat to have And some photos to show where we are today:

And grind it will. I have a feeling it will get better as the starter’s gears wear in. Or explode.

I came to this realization a few months ago. Did some rust repair on my DD, sprayed it with primer (with my own conclusion of “good enough”) and a week later there was surface rust showing through. Only then did I look into it and realize that stuff draws moisture in. All this time I’ve just been making things worse... anyway, yeah: primer and paint.

I added a wire to the starter solenoid to bypass the ignition switch as I thought this might be the culprit. Unfortunately I still had the noise At this point I can’t imagine what else it could be then the flywheel?

Agreed. To me it seems like the flywheel has an edge worn on the teeth that’s “catching” the starter and stopping it from fully releasing. Absolutely nothing I can do short of filing each tooth straight or replacing it, which will have to wait for the BA to AX swap.

I pulled the dust cover back and put my inspection camera in there. Youtube this time for the video.

Tight as can be. Is it possible the flywheel was replaced at one point with a different tooth count? Did this change at any point across the years? Are they different for the BA10 and AX15?

I picked up another starter (Reman this Time) and installed. Same sound. Reinstalled the new starter. Cleaned all terminals. Ran a new starter wire. Same sound. The sound its making is the exact same sound it makes if you try to crank the starter with the motor running.

Flywheel photo attached. I didn’t have any shins on the old one, and through all of my 4.0s have never shimmed before. Is the MJ different? The bolts seem right to me... it’s definitely tight and didn’t crossthread.

I feel like a regular in MJ tech Threw a new starter in tonight. I had an old ACDelco reman starter making a ton of noise. Part of that noise was a grind towards the end of the crank. New ACDELCO starter came in. Replaced it. Grind still present. But the starter motor is much quieter! The old one had some SERIOUS play in it. I attached a video. And listening to it now on the video you can barely hear it 39EAC4F6-C499-4187-9998-5136125E421B.MOV

Haha! Not knowing any better I would probably have done the same thing. I wouldn’t be surprised if my filter was bogging the pressure down and if your pump had a good clog. Good news is the fuel filter probably picked up whatever went through anyway. I’ll be putting a new starter in tomorrow night along with checking compression and hopefully with all that I’ll be in better shape. I wouldn’t hesitate to replace that pump in your shoes. Cheers brother!

Yeah... alignment is a real struggle. Its a tight fit! In the long run I'm glad I did drop the tank because I found a good amount of rust on top of it; itll have to be replaced when I replace the bed. Ill be driving it daily for the next few weeks to confirm this is dealt with. I feel fairly good about it.

Alright! New pump is in. Priming at 39, running at 31. Holding pressure. Still not priming every time though. When it doesn’t prime it takes a little longer to start. Relay problem? Ive had several hot starts and it’s starting in a reasonable amount of time. No gas plume. I did drop the tank and it took forever. I think it could reasonably be done in the truck. I used a carter pump. It was not a perfect fit and took some finagling to get it to work. The screen on the old pump was completely clogged. Photos attached. I’ll post an update if anything changes. I do have to mention that the AZ pressure gauge I used initially no longer works, so perhaps my initial readings weren’t right.

Hoping this link works for those of you outside of Facebook. The post from Plymouth Township (PA) Police reads: Chief Lawrence rode into the Plymouth Township Police Department in 1987 in this very truck. Now, as he rides away for the last time as our Chief, we wish him the best of luck in all of his endeavours (especially in making it home in that truck!). Congratulations Chief Lawrence. You will be missed.

Yep, same gas plume here. Hoping to see the pump sometime next week. In the mean time I’ll be running the tank down. Good call on the ground suggestion, thanks Pete.

Yeah, agreed. New pump is ordered. I’ll shoot an update when it’s in.

Holy cow. Wouldn’t I be having more issues with it this low? I guess I’m in the market for a new pump.

And back with more... The priming issue is still hit and miss. The hesitation to start occurs when there is no prime. I do have spark - thanks Pete - neat tool.

A few interesting points: 1: I pulled the fuel rail and the injectors are not leaking, so that’s out (I think?) 2: My fuel pump wasn’t always priming. More often then not, I cycle the key and it stays at 0. If I attempt to start it jumps up. 3: Briefly during testing It was starting but then dying. I remembered there is a white resistor next to the airbox. Cleaned, and now it is priming every time. Is there a way to rule out the pressure regulator leaking down?

Okay, fuel pressure gauge is connected. Prime is 14psi then drops to 12psi. Running at 8psi. Shut it off it drops to 6psi, and it is at 0 at one minute and 30 seconds.