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Thread: Has anyone did a fuel injector upgrade 1992 Yj 4.0

  1. #1
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    Has anyone did a fuel injector upgrade 1992 Yj 4.0

    The old dog is gettin' a bit hard to start, I've replaced the fuel pump in the tank and added a new fuel regulator. I am going to replace the injectors but figured there must be a popular upgrade since 1992, has anyone did an upgrade and if so what do you recommend ?

    Thanks

  2. #2
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    Re: Has anyone did a fuel injector upgrade 1992 Yj 4.0

    I'm guessing that the crank-to-start times are growing longer... If that's the case, it's likely the result of a lack of fuel pressure being retained in the rail, when the engine is off, which is caused by the check valve in the injector rail sticking partially open and allowing the fuel rail pressure to bleed off back into the tank. When this happens, the result is a delay in getting sufficient fuel pressure to atomize the fuel, until the fuel pump has the chance to rebuild the line pressure.

    A simple way to confirm this is the case is: When starting, turn the ignition to the ON (but not crank) position for 2-3 seconds (allowoing the fuel pump to begin pressurizing hte fuel system), followed by switching the ignition off, and repeating the ignition on (but not cranking) twice more, and then on the third time try cranking to start. If it starts quickly following the third fuel pump cycle, you can be reasonably sure that the fuel delivery system and all fuel injectors are fine. And you can also be reasonably sure that the root cause is the aforementioned check valve in the fuel rail, which is supposed to keep pressure in the rail when the ignition is off, to allow for quick starts.

    Correcting this, is not inexpensive, as it requires replacing the fuel rail, as the check valve is integral to the rail.

    Hope this helps...
    Working for a living is highly over-rated...

  3. #3
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    Re: Has anyone did a fuel injector upgrade 1992 Yj 4.0

    Gave that a shot, but it did not make a difference. The injectors have never been changed, so I am going to replace them and will replace the fuel rail at the same time. I'm just not sure which injectors would be the best to go with. Trying to ready for the Cleator run this Saturday, thanks for the help.

  4. #4

    Re: Has anyone did a fuel injector upgrade 1992 Yj 4.0

    Is your fuel pump relay good. Key on can you hear the fuel pump run for a couple seconds? Long or extended crank can be the result of bad relay, having to crank until oil pressure comes up to tun on the fuel pump. Listen at the fuel filler with cap off while someone turns ign. switch to on.
    I used to worry about rich and skinny
    til I wound up poor and fat
    KE7VKY

  5. #5

    Re: Has anyone did a fuel injector upgrade 1992 Yj 4.0

    Although I have never done it, there is apparently a way to test the resistance on each injector. I can't imagine that they have all gone bad at once.

  6. #6
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    Re: Has anyone did a fuel injector upgrade 1992 Yj 4.0

    Dont know if they used the same style injectors, but on the early XJ's you could swap in stock mustang 5.0 injectors. You could get a full set of 8 that have been tested for the same price of 2 OEM Jeep injectors used.
    2013 JKU RUBICON 10TH ANNIVERSARY EDITION: Wife's DD
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  7. #7

    Re: Has anyone did a fuel injector upgrade 1992 Yj 4.0

    Change out the injectors, 1 or more could be leaking internally after so many miles and use and I am sure there dirty as well, several companies out there where you can get rebuilt injectors, cleaned with new parts and matched flowed for $100-200 bucks a set.

  8. #8
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    Re: Has anyone did a fuel injector upgrade 1992 Yj 4.0

    I would start with a compression test.

    That being said, I'm gong to follow this since I've probably got old tired injectors as well.
    Non-College Educated Working Class White Deplorable....

  9. #9
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    Re: Has anyone did a fuel injector upgrade 1992 Yj 4.0

    Are we sure it's fuel? My YJ used to be slow to fire up until I replaced the starter and then it would fire up pretty fast.
    93' 2.5L YJ 8.8 4.88 33's E-Locker & LSD

    WTB- co2 handle/valve guard for 5# tank.

  10. #10

    Re: Has anyone did a fuel injector upgrade 1992 Yj 4.0

    Agree, it could be a bunch of things but since we don't have the vehicle to diag, the original poster should do a complete diag. before changing parts.

  11. #11
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    Re: Has anyone did a fuel injector upgrade 1992 Yj 4.0

    Haven't seen anyone mention the fuel filter. It's located inside the frame rail in front of the rear fender opening on the driver side (I think).

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