Thread: Weird no start problem

Page 1 of 2 12 LastLast
Results 1 to 25 of 29
  1. #1 Weird no start problem 
    Member
    Join Date
    Mar 2011
    Location
    Bakersfield Ca
    Posts
    132
    Rep Power
    54
    Lately the my 93 5.2 has been leaving Me stranded every now and than. I thought it was a coil problem, cause when I switch the coil it would fire right( I carry 3 coils with me) up. I have spark good fuel psi when it runs. I just decided to check fuel psi under a no start condition, and the FP fires up and the jeep starts and fuel psi drops to zero. Up till this last two days I had checked/ replaced all fuses and relays. The CPS was 6mon old, but I changed yesterday to a Mopar unit. The VSS is grounded at the door. Any ideas? I've been reading no start treads for a week now!
    Last edited by firehawkclone; 09-16-2017 at 06:38 AM.
    Reply With Quote  
     

  2. #2 Re: Weird no start problem 
    Senior Member Lifetime Supporter
    Grand Slam West Planner
    jsteves's Avatar
    Join Date
    Jul 2004
    Location
    Fort Fun
    Posts
    2,388
    Rep Power
    111
    Fuel pump relay.
    04 Dub -- Longarms, JK44, 9" ARB's etc.
    68 Super Wagoneer - Resto Project
    93 ZJ: longarms, 231D, 35's, 44/Hi 9", ARB's, etc. -- Sold
    Reply With Quote  
     

  3. #3 Re: Weird no start problem 
    Member
    Join Date
    Mar 2011
    Location
    Bakersfield Ca
    Posts
    132
    Rep Power
    54
    Quote Originally Posted by jsteves View Post
    Fuel pump relay.
    I changed it out atleast four different times with known working and new relays.

    The previous owner just replace the FP before I bought the jeep. Though that means not a damn thing when it's a Chinese part. The jeep is starting up, half the time it runs a bit ruff with good fuel psi than smooths out. Other times starts up with no problems at all.
    Reply With Quote  
     

  4. #4 Re: Weird no start problem 
    Member
    Join Date
    Dec 2011
    Location
    Ohio
    Posts
    167
    Rep Power
    51
    security system issue maybe?
    Reply With Quote  
     

  5. #5 Re: Weird no start problem 
    Member
    Join Date
    Mar 2011
    Location
    Bakersfield Ca
    Posts
    132
    Rep Power
    54
    Quote Originally Posted by tjswj View Post
    security system issue maybe?
    That's what I started thinking too. I have the prl/yel wire grounded now, and pulled the VSS relay while the truck was running.

    I may have to drive it around and wait for another no start situation.
    Reply With Quote  
     

  6. #6 Re: Weird no start problem 
    Member
    Join Date
    Dec 2011
    Location
    Ohio
    Posts
    167
    Rep Power
    51
    Im pretty sure that the vss kills the injector pulse, but it may control the fuel pump as well. While its happening, try locking and unlocking the passenger door or the hatch with the key.
    Reply With Quote  
     

  7. #7 Re: Weird no start problem 
    My avatar isn't animated Lifetime Supporter SirFuego's Avatar
    Join Date
    Nov 2006
    Location
    Elma, NY (near Buffalo)
    Posts
    2,765
    Rep Power
    144
    Quote Originally Posted by jsteves View Post
    Fuel pump relay.
    A bad ASD relay will exhibit the same no start symptoms. My Jeep cut out on an obstacle at Rausch Creek and wouldn't start again. My fuel pump wasn't turning on, so I tinkered with the fuel pump relay and was probing for voltages everywhere in the fuel system (which quickly ruled out a bad fuel pump since it wasn't getting any voltage to turn on) until I read about the Auto Shutdown relay in the FSM (little tip for those with smartphones -- get a PDF of the FSM and put it on your phone...). It's been a while, but I THINK I used the A/C relay in its place -- my A/C hadn't worked for years, so I didn't care. Once I replaced that I was gold -- or so I thought.

    The Jeep would run rough after that and would occassionally cut out. After it was running for a while, it seemed to run fine. Then the next day my Optima started to boil due to it overcharging (the ECU controls the voltage in a 93-95 5.2L). Afterwards, I couldn't even get it to start with a fresh battery. Finally my buddy gave me a junkyard ECU to try and she fired right up and has run fine ever since (this was a few years ago).

    My final verdict on the situation was that the voltage control from the ECU was the root cause of my ASD relay and battery failure.

    So a bad ECU can cause some weird symptoms when its on its way out -- running rough, blowing out relays, etc. FWIW, any 93-95 5.2L ZJ ECU should work.
    Last edited by SirFuego; 06-20-2012 at 11:04 AM.
    Quote Originally Posted by SB406
    I think that's your signature move.
    "The Former"- Lay Jeep against obstacle in trail. Mat gas pedal. Form Jeep to the shape of obstacle.
    Robot
    Reply With Quote  
     

  8. #8 Re: Weird no start problem 
    Member
    Join Date
    Dec 2011
    Location
    Ohio
    Posts
    167
    Rep Power
    51
    this ^ is very true as well. For me at least, it seems even more common in the 5.2L's. Within the last year ive probably had 5 5.2L zj's come in with bad pcm's.
    Reply With Quote  
     

  9. #9 Re: Weird no start problem 
    Member
    Join Date
    Mar 2011
    Location
    Bakersfield Ca
    Posts
    132
    Rep Power
    54
    I've changed the ASD relay. But I will try another. The ECU is a new Mopar performance unit. I still have the oem ECM that I could put back in.
    Reply With Quote  
     

  10. #10 Re: Weird no start problem 
    Member
    Join Date
    Mar 2011
    Location
    Bakersfield Ca
    Posts
    132
    Rep Power
    54
    Fuel pump relay had no change on the problem. I didn't get a chance to switch out the ECU yet.

    It starts on the 2nd or 3rd try(never has on the first try) when it does it's stumbling barely running, than steadily gets better and runs just fine.
    Reply With Quote  
     

  11. #11 Re: Weird no start problem 
    Member
    Join Date
    Mar 2011
    Location
    Bakersfield Ca
    Posts
    132
    Rep Power
    54
    Can a TPS cause this. Mine says Holly on it. I couldn't fine anything on Holly's site or a quick google search.
    Reply With Quote  
     

  12. #12 Re: Weird no start problem 
    Member
    Join Date
    Mar 2011
    Location
    Bakersfield Ca
    Posts
    132
    Rep Power
    54
    It started running perfect again. I replaced the iac, but I ended up putting the old one back on because the new Autozone one was bad. After searching a bit more, realized the Holley TB is stock. I read a "no start" tread somewhere that a tps could cause a hard to start when cold. I think it was when it was cold. Been reading alot of treads. Anyway I went ahead and replaced the Holly tps. The jeep had been starting up pretty good lately. I have replaced the CPS and TPS at this point. And reset the Mopar performance ECU.

    I drove it around town for a few days, and it started up everytime. I'm still a bit nervous about taking it out in the woods. Im carrying most of the major sensors with me. And may try to sneak a back up Alt and fuel pump in the jeep, for the trips to nowhere.

    Thx for the help guys
    Reply With Quote  
     

  13. #13 Re: Weird no start problem 
    Member
    Join Date
    Mar 2011
    Location
    Bakersfield Ca
    Posts
    132
    Rep Power
    54
    It left me stranded three times yesterday on the trail. Back to the drawing board.
    Reply With Quote  
     

  14. #14 Re: Weird no start problem 
    Member
    Join Date
    Mar 2011
    Location
    Bakersfield Ca
    Posts
    132
    Rep Power
    54
    Well I have never found what causes this no start problem. Most of the time it's while on the trail, but does it around town to. It runs 200-210 around town with the AC going. I was starting to lean towards vapor lock issue, but this is so rare of a problem in an EFI system.

    Currently it's a no start. Which is nice because now I'm hoping to find what's causing it. But it will fire up knowing my luck. This is the only problem I have with the ZJ now days. But it's enough to start thinking about a JK, which will suck cause I can't do half the stuff I do now without worrying about hurting it.
    Reply With Quote  
     

  15. #15 Re: Weird no start problem 
    Member
    Join Date
    Mar 2011
    Location
    Bakersfield Ca
    Posts
    132
    Rep Power
    54
    No fuel pressure! I hope it's not a cps. I just put a mopar cps in a few months ago. All oem security has been bypassed.

    Drinking beer is more fun than tracking this down right now.
    Reply With Quote  
     

  16. #16 Re: Weird no start problem 
    Senior Member AgitatedPancake's Avatar
    Join Date
    Feb 2006
    Location
    Sac, California
    Posts
    3,391
    Rep Power
    143
    when you cycle the key to the "run" position you should be able to hear the fuel pump whirr in the tank for about 2 seconds. Just to verify that the fuel pump is or is not getting power
    The Blue Submarine
    2001 Grand Cherokee (WJ) 4.7

    Life’s journey is not to arrive at the grave safely, in a
    Well preserved body, but rather to skid in sideways,
    Totally worn out, shouting “HOLY SHIT, WHAT A
    RIDE!”
    Reply With Quote  
     

  17. #17 Re: Weird no start problem 
    Member
    Join Date
    Mar 2011
    Location
    Bakersfield Ca
    Posts
    132
    Rep Power
    54
    Yeah nothing from the pump. I have a fuel pressure gauge on the rail, not even a blip on it. I have a new fuel pump assembly that I pluged in and not a thing. No power at the FP harness. So it's back to checking the oem alarm and CPS again.
    Reply With Quote  
     

  18. #18 Re: Weird no start problem 
    Member
    Join Date
    Mar 2011
    Location
    Bakersfield Ca
    Posts
    132
    Rep Power
    54
    Ruled our cam sensor, doubled check alarm bypass, and ECM. Starting CPS. It tries to fire with just a little carb cleaner.
    Reply With Quote  
     

  19. #19 Re: Weird no start problem 
    Member
    Join Date
    Mar 2011
    Location
    Bakersfield Ca
    Posts
    132
    Rep Power
    54
    Not the CPS. I have no power at the chassis fuel pump harness. I have power on fuel pump relay pins 30 85 86 w/o the relay in ign on. I've swapped the relay and fuse countless times. My Chilton's says there is another relay in this circuit. It's a ballast resistor bypass relay. The is also a ballast resistor in this circuit.

    Anybody with a FSM that could confirm this? Or have an idea what else I can test. At this point I'm assuming the relay is is working, and am going to start tracing the org/blk wire back from the fuel pump
    Reply With Quote  
     

  20. #20 Re: Weird no start problem 
    Member
    Join Date
    Mar 2011
    Location
    Bakersfield Ca
    Posts
    132
    Rep Power
    54
    Question, what's the lite blue wire in the drivers side kick panel.

    Edit: after reading this post, it's not much to go on is it.

    This wire appears to be factory taped in a bundle. If I had to guess what it is, I would say its for a trailer brake controller.
    Last edited by firehawkclone; 09-17-2012 at 10:44 AM.
    Reply With Quote  
     

  21. #21 Re: Weird no start problem 
    Member
    Join Date
    Mar 2011
    Location
    Bakersfield Ca
    Posts
    132
    Rep Power
    54
    No power all the way to pin 87 of the fuel pump relay. Which is the org/blk power wire for the fuel pump. So power to one of the other 3 pins is preventing the relay from closing. Now I just have to figure out which one it is.

    Relay pin 85 pink wire goes to pin 51 on the PCM and pin 85 of the ASD relay.
    Relay pin 86 blu/red wire is pin 9(ign) PCM goes to just about every sensor there is.
    Relay pin 30 red wire is power in.
    Reply With Quote  
     

  22. #22 Re: Weird no start problem 
    Member
    Join Date
    Mar 2011
    Location
    Bakersfield Ca
    Posts
    132
    Rep Power
    54
    It has a code 42 now. FP & ASD relay no voltage at controller. I'm assuming the controller is the PCM.
    Reply With Quote  
     

  23. #23 Re: Weird no start problem 
    Member
    Join Date
    Mar 2011
    Location
    Bakersfield Ca
    Posts
    132
    Rep Power
    54
    No codes. I must of done something to set that one off. I'm slowly going through test in the FSM. So far Notting!
    Reply With Quote  
     

  24. #24 Re: Weird no start problem 
    Junior Member
    Join Date
    May 2011
    Location
    Tacoma WA.
    Posts
    1
    Rep Power
    0
    check the fuses mine died on me my o2 wires melted on the exaust end shorted out and blew a 30amp fuse in the pannel by the battery

    when i have problems with my alarm the pump will still prime, the jeep would start and run like crap for like 3 secounds then die when the fuel bleads off.
    it primes but when you start it the pump wont run
    it does it when the battery is almost dead or i disconect the battery.
    i have to put the key in the door and unlock it for it to start
    Reply With Quote  
     

  25. #25 Re: Weird no start problem 
    Member
    Join Date
    Mar 2011
    Location
    Bakersfield Ca
    Posts
    132
    Rep Power
    54
    I found the problem(I hope)! The next time I read something, read all the way through. I had grounded out the purple/yellow wire, but didn't cut the wire. Epic fail! I still couldn't get the AZ fuel pump to prime by jumping it directly to power. But the new Crown fuel pump would. So it was replaced also. The old one also had some o-ring pushed out on the bottom.

    I hope this solves it. But it has started fine before for weeks, than acted up. So I'll find out so enough.

    Im still unclear what side to ground. I've seen the door side and the chassis side grounded in treads. I have the door side grounded in the kick panel.

    Thx guys
    Reply With Quote  
     

Page 1 of 2 12 LastLast
Thread Information
Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •