Thread: 95 ZJ 4.0 Fuel Issue

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  1. #1 95 ZJ 4.0 Fuel Issue 
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    I've had Jolene for about a year now, and on Tuesday the fuel pump went (tried to start, no dice. Sprayed starting fluid, ran like trash, but she started). I got a Carter fuel pump and installed it today, along with a new fuel filter, put 5 gal of fuel in her. Battery lost some charge due to trying to start, so it will need to be charged. When I go to crank her, she doesn't chooch, connected fuel pressure test gauge. On first key ON (not starting) I get between 10 and 20 PSI), on second key ON (no starting) she bumps up to 38 PSI. I am out of ideas and was hoping someone could shed some light or provide something I haven't thought of. Pressure bleeds down to 36 after about 10 seconds.
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  2. #2 Re: 95 ZJ 4.0 Fuel Issue 
    Senior Member Ken L's Avatar
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    What did your fuel filter look like when you changed it? Is it possible that there is a bunch more crud in the tank that plugged the new one?
    Ken L
    '96 ZJ with stuff
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  3. #3 Re: 95 ZJ 4.0 Fuel Issue 
    Senior Member DJJordache's Avatar
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    I6 or V8?
    what year?
    93' ZJ 4.7L STROKER, Clayton LONGARMS, 4wd conversion, 231 SYE, HPD30, 8.8, BFG 35's, 2000 manifold & injectors, Hesco fpr, Port & polish, LS1 valves, WJ Steering/brakes, KOR SliderZ & steering box brace, Clayton TB bracket and my custom trackbar, Crane ignition, B&M cooler, Tom Woods, etc....
    Quote Originally Posted by Krash80 View Post
    We're all insane here...
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  4. #4 Re: 95 ZJ 4.0 Fuel Issue 
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    In the title my man, 95 4.0. Let me update you.

    Determined that it was the ASD relay shutting off power to the coil and injectors. I would get power to the injectors for 2 seconds on key "ON" and then it would cut out. I have no CEL when I turn the key to on, it has always been kind of faint since I got the car, but now its completely gone. Checked the cam sensor, it was ok. Got a new crank sensor, but haven't installed it yet. I was redoing a few grounds and the battery terminal when I noticed that the injector coil had a crack in it, so I replaced that. Bought a new PCM, since the whole "no CEL" thing made me think it was that. Installed it, but no dice. Now I have no power to the injectors at all, ASD relay still clicks, but no power to the injectors at anytime after key "ON" with either PCM. Checked fuses, nothing is blown.


    ***EDIT***
    Wonky ground for circuit Z12, the black/tan wire that grounds out on the ignition coil bracket. Tightened her up and the PCM turns on, but still hits my ASD relay, so back to square one. Just spent the better part of an hour removing a crank sensor with 22 years of crust on it. Tomorrow I'm going to try to use my circuit tester as a makeshift CEL with the pinout on the PCM to see if it's the light or crusty dash gauge connector

    Some backstory if it helps:
    A few months ago I had an issue with my speedo reading the wrong speed, after about 5 seconds it would start reading normally, eventually that problem went away. A month after that, I had an issue with the seatbelt light coming on randomly, even if the seatbelt was connected. The light would come on at startup, but it didn't matter if I didn't have my seatbelt on, it would go away. I've also gotten an error code for the o2 sensor a few times, and a 12 error code, even if I hadn't disconnected the battery in the past 50 startups.
    Last edited by porridge8712; 07-09-2017 at 04:18 AM.
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  5. #5 Re: 95 ZJ 4.0 Fuel Issue 
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    ********UPDATE********

    Well, a lot has transpired since 4:18 AM (after taking off the CKP) Installed new CKP (from NAPA, although they provided no spacer with the sensor. I would think for $84 you'd throw in a $.0001 piece of cardboard, but I digress.), connected my jump box (battery was LOWWWW) and braced for the worst. I was pleasantly surprised to hear the sound of that Magnaflow I installed last summer, SHE CHOOCHES!! I was prepared to have to quit my 2nd job (with a baby on the way) and rack up 20k miles on my wife's Mazda, but as of right now I'm golden! CEL comes on, as faint as ever, but there. A few funny moments, I forgot to hook up the vacuum hose for my brake booster, that was exciting! (I disconnected it trying to see if there was some way in god's green earth I'd be able to reach the CKP from the topside), noticed she ran pretty rough when I first started her up, chalked it up to a new PCM until I noticed my CEL on. I had forgotten to reconnect a fuel injector. With the new coil, CKP, and fuel pump, I hope she gives me another 150K of enjoyment. Now to the laundry list of other things I have to do to this girl....
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  6. #6 Re: 95 ZJ 4.0 Fuel Issue 
    Senior Member Ken L's Avatar
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    Glad you had a successful outcome and thanks for closing the loop on your issue for us. It helps to build on the tech in the site.....
    Ken L
    '96 ZJ with stuff
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