1. #1
    Join Date
    Dec 2006
    Location
    San José, Costa Rica
    Posts
    1,693

    Engine fails ONLY in hot weather

    Guys,

    I am new to this site (as of today), but I would like to ask you all a question; I live in FL, and my YJ S 2.5L 4 cylinder Jeep ussually works fine. But on the hotter days, after is has run for some time, it starts to fail, as in no ignition (like it's not taking in gas or something).

    My first thought was that it was something wrong with the ignition, but I changed EVERYTHING (rotor, distributor cap, cables, coil and plugs). Then I changed the Fuel filter and SURPRISE! I dont think the previous owner ever changed it (the Jeep had 109K miles on it). The thing was FILLED with a mud-like substance. I replaced the filter, and cleaned the injectors and rails (used a cleaning product and then actually took out the injectors and rail and cleaned it out). By the way, the rail and injectors were also dirty as hell... But they are all now clean.

    The Jeep actually stopped giving me any problems for about a month, but yesterday it started again. Any ideas on what it could be? The 94 YJ 2.5L does not have an ignition module (you have to change the entire computer, and that's about $500, so I dont want to go in that direction if I dont have to), so changing it is not a possible solution. Could it be that my fuel system is still filled with dirt? If so, what would you guys recomend? Re-cleaning the rail and injectors, and cleaning the fuel tank?

    Any ideas welcomed...

    Felipe

  2. #2

    Re: Engine fails ONLY in hot weather

    If you had that much dirt in the rest of the system, its very possible that the tank had a bunch in it also. If thats the case you could've just sucked a bunch of new dirt into your nice clean fuel system, causing the same problem.

  3. Re: Engine fails ONLY in hot weather

    It's hard to say what the problem is, but I would say that throwing parts at it is not the solution. If you had ample dirt in the fuel filter and did not clean the tank, then it is possible that there is still dirt in the tank. However, this should have nothing to do with the temperature. I would suspect that you may have a vapor lock issue or fuel pump issue. Can you hear the fuel pump running when the problem occurs. It may only cycle for a few seconds when you hit the switch, but you should still be able to hear it. Does your fuel rail have a schrader valve to check the fuel pressure? You should be able to put a gauge on it to check the pressure next time the problem occurs.
    One other rare problem to check...look at the gas cap and see if the spring vent is working properly. I had that happen to me once before. The spring broke and the gas tank would get a vacuum. It never stalled the engine, but would cause the gas tank to "thump" as the vacuum occurred. It eventually worked a crack in the tank before I figured out what the problem was.
    Safety yellow and Handicap blue CJ with 5.3 Vortec/TH400/Tons/Atlas/Roks/Locks and Airshocks.
    1622 Miles from Moab.

  4. #4

    Re: Engine fails ONLY in hot weather

    Ahh... good call rooster, didnt think about the temp aspect.

  5. #5

    Re: Engine fails ONLY in hot weather

    If you are suspicious of dirt in the system, check your fuel filter again. It should be tell you if you have a problem.

  6. #6
    Join Date
    Feb 2004
    Location
    I'm here just for TwistedCopper!
    Posts
    5,098

    Re: Engine fails ONLY in hot weather

    Despite the temp factor here, with as much dirt as you mentioned in the filter and injectors, I'd still drop the tank and clean it thoroughly. It can't hurt.

  7. #7
    Join Date
    Dec 2006
    Location
    San José, Costa Rica
    Posts
    1,693

    Re: Engine fails ONLY in hot weather

    Green, Sparky, Jay,

    I agree with all of you. I think I will get the tank cleaned this weekend... Even if it is not all that dirty, it cannot hurt to get it cleaned. Might take advantage of the fact that I will have the tank down and check the fuel pump (the pump is one of the suspects at this time; it could be affected by the heat, especially if it is all dirty and stuff).

    Rooster,

    Thanks for the advice; before the problem went away, I checked for gas tank vacuum (opening the gas tank to check if there was any pressure built up in there), but that does not seem to be the problem. But I do suspect the fuel pump, as I already mentioned. Runing it in the amount of dirt that I found in the fuel filter could not have been good for it, right? Also, I understand that the YJ have an additional filter inside the tank which HAS to be ruined based on what I found on the in-line filter (I think I'll replace it if I can, but I am not sure if the YJ do have it or not).

    As for the parts, I changed the plugs, wires, rotor and dist. cap because of maintenance when I got the Jeep (I had no way of knowing when they were last changed, so I always prefer safe over sorry). The distributor I may have not needed to change, but I wanted a slightly more powerful one anyway for improved combustion, so the problem was actually only part of the reason I changed it.

    In any case, looks like I will be busy this weekend with the Jeep wiring my KC Daylighters (I installed them last weekend, but did not have time to get them wired), installing my new hard top and droping the fuel tank! Thanks to all for your comments!

    Felipe

    PS: Any other ideas still welcome!

  8. #8
    Join Date
    Mar 2006
    Location
    Denver, Colorado
    Posts
    312

    Re: Engine fails ONLY in hot weather

    I had the same problem in Moab this summer. The temp at noon was near 112 degrees and my 89 YJ 4banger would die. Turned out to be a fuel pump going out. The plastic with in it heated up and expanded so it wouldnt send fuel to the motor but the return line worked somehow, so the fuel got hotter and hotter not letting the pump cool off.

    Welcome to Jeepz

  9. #9
    Join Date
    Feb 2004
    Location
    I'm here just for TwistedCopper!
    Posts
    5,098

    Re: Engine fails ONLY in hot weather

    I believe you'll find a pre-filter in the tank at the fuel pump pick-up. It's a small nylon "sock" that fits over the end of the pick-up. If you decide to replace the fuel pump, be sure the one you buy comes with the "sock", as some brands don't have it. That's what I ran into when I changed mine out a few months ago, but fortunately I realized it before I left the parts store. I'd have been PO'd if I'd driven the 30 miles back home before finding out it didn't have it!

  10. #10
    Join Date
    Dec 2006
    Location
    San José, Costa Rica
    Posts
    1,693

    Re: Engine fails ONLY in hot weather

    Where's a good place to get a new fuel pump? Any recommendations?

  11. #11
    Join Date
    Feb 2004
    Location
    I'm here just for TwistedCopper!
    Posts
    5,098

    Re: Engine fails ONLY in hot weather

    Quote Originally Posted by jfrabat View Post
    Where's a good place to get a new fuel pump? Any recommendations?
    I get most of my stuff at Advance Auto Parts....good prices and they have pretty much everything in stock, unlike Pep Boys, Auto Zone, and some of the others......

Posting Permissions

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

Log in

Log in