boost leak at injector insulator

Posted by DroppedMitsu, Apr 14, 2010
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  1. DroppedMitsu

    DroppedMitsu Proven Member

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    Vacaville, California
    I have a boost leak at my fuel injector at the lower insulators/seals where they go into the head and I can't get rid of it. I installed some aftermarket seals that I bought from napa and they leaked, then I bought some OEM ones from JNZ and they also leak when doing a b.l.t. When putting both the aft. and OEM seals they were loose fitting around the injector pintle caps, stock 450 btw. What can I do to get rid of this leak, I made sure to be careful when putting them in? Thanks for any help
    Last edited: Apr 15, 2010
    #1
  2. cdm_sd02

    cdm_sd02 Supporting VIP

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    Sounds like they are not the right seals for the Job. Are they fitting tight to the fuel rail?
    Are you smelling/seeing any gas on that side of the head
    #2
  3. DroppedMitsu

    DroppedMitsu Proven Member

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    Vacaville, California
    They don't seal on the fuel rail, they seal in the head as I'm talking about the lower insulators. I tried both aftermarket and oem and neither really fit snug around the injector nor the head really
    #3
  4. ramsack

    ramsack Banned Member

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    West Lawn, Pennsylvania
    do your injectors have good pintle caps?
    #4
  5. BigBeans

    BigBeans Proven Member

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    I am in, Rhode_Island
    Do you have the right spacers between the fuel rail and where it bolts up to the head?
    #5
  6. SpawnedX

    SpawnedX Banned Member

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    West Warwick, Rhode_Island
    Edit: Nevermind, just re-read.

    Can you take one of the injectors out and take some close-ups of the lower injector with the seals on?
    #6
  7. DroppedMitsu

    DroppedMitsu Proven Member

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    Vacaville, California
    Not sure on the pintle caps, they look decent, no defects or anything. I have aft replacements if need be but I don't know how they come off the injectors or anything.

    Yes I have the black plastic spacers that go between fuel rail and head.

    Heres a pic of the injector and seal, I tried as hard as I could to get a clear close up but my POS camera wont do any better.

    Attached Files:

    #7
  8. SpawnedX

    SpawnedX Banned Member

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    West Warwick, Rhode_Island
    Where is your o-ring?
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  9. rza808

    rza808 Proven Member

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    what o ring? is there a o ring at the bottom seal? if there is im missing it to!! pics of o ring please!!!
    #9
  10. SpawnedX

    SpawnedX Banned Member

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    West Warwick, Rhode_Island
    Not by the seal, the picture is blurry and not of his entire injector. I am just wondering where the o-ring on the fuel rail side is.

    The picture of that seal isn't going to help us much.

    If the o-ring at the top of the injector is torn or not there, then the injector won't sit snug and straight in the head with the seal, even a little amount of space is enough to cause his problem.

    Are you getting this leak on all injectors or just one?
    #10
  11. DroppedMitsu

    DroppedMitsu Proven Member

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    Vacaville, California
    Yes, the o-ring is at the top of the injector where it goes in the fuel rail, as well as that other little rubber piece that is up there between the rail and injector. They are all brand new, every o-ring/seal on all four injectors is new, and I am having this problem on all 4 injectors. They are not sealing at the bottom insulators. sorry about the pic, as I said, thats the best I can do.
    #11
  12. SpawnedX

    SpawnedX Banned Member

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    If these are new seals and you are positive these are Mitsu 450's, then I can only think you have the wrong spacers or you aren't tightening the rails down. Inspect the area where the injectors go into the head for cracks.
    #12
  13. DroppedMitsu

    DroppedMitsu Proven Member

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    Vacaville, California
    Almost positve they are mitsu 450's as there are two blue and two black like every other first gen manual tranny 4g63t, and the car that I got the engine out of was practically all stock, didn't look like they had ever changed anything besides maybe belts and oil. I am definitely tightening the fuel rail enough and pretty positive the rail spacers are original stock spacers.

    I am starting to think these are not "OEM mitsu" seals as JNZ stated on their site since they came in a ziplock bag of four, and after looking at them closely they don't look like the stock ones that came out. The stock ones I pulled out fit way more snug around the injector then any of these new ones do, but they were just a little hard and would not seal at the head.
    #13
  14. ramsack

    ramsack Banned Member

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    they probably are oem, mitsu just doesn't sell a kit of them, so i'd imagine jnz just baggies them up. why would there be 2 blue and 2 black injectors? i've never seen a car come like that. it's possible 2 of them are 2g 450s and 2 are 1g 450s. what are the numbers and other identificatoin marks on the sides of the injectors? there should be 3 seals/o-rings per injector. i have gotten parts store insulators and haven't had any problems. the insulators don't seal on the sides, it is the fronts that seal, the injector pushing down.

    only things i could think of are:

    1. you aren't being careful putting the insulators into the head and they aren't seating right
    2. the injectors aren't correct (too short)
    3. the spacers are wrong
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  15. UofACATS

    UofACATS Proven Member

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    New isolators should fit very snugly. I agree with your suspicion they aren't oem pieces, at least not for the correct application.

    I just replaced mine, the fit *perfectly* and I even applied a very fine layer of oil to get them installed easier.
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  16. ramsack

    ramsack Banned Member

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    they don't need to be snug to seal. they seal by being squashed into the head when the fuel rail gets bolted in. mine aren't really tight by any means when the rail is unbolted and they hold at least 30 psi in a boost leak test.
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  17. DroppedMitsu

    DroppedMitsu Proven Member

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    Vacaville, California
    they are all blue mitsu 450's, sorry about that, I was thinking of the plugs for the injectors when I said two blue and two black.
    Thanks for the info on them seating on the faces and not the side, I was wondering that. Anyways I bought an injector seal kit first and put all new seals/o rings on them. Then the injector insulators still weren't sealing so I bought OEM ones from JNZ just to clarify. I have all 3 new seals on each injector, I am 100% sure on them sitting in there flush as well as the injectors sitting flush in them. Maybe a little bit of paint buildup on underside of rail where spacers meet is not letting it tighten down enough is only thing I can think of now?
    #17
  18. ramsack

    ramsack Banned Member

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    that's definitely possible. i really think it just has something to do with the way the rail is bolting down more than anything. try taking the spacers out and bolting it down carefully and then do a boost leak test on them and see if you can get it bolted down to the point where they won't leak. it could be an intake manifold gasket from the same areas too...
    #18
  19. DroppedMitsu

    DroppedMitsu Proven Member

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    Figured it out, just did a blt and its not leaking from them anymore from what I can tell, now just a small one on the throttle body gaskets. The problem wasn't the lower insulators, it was the upper insulators that are between the fuel injector and the rail. Turns out the aftmarket ones I put on from the kit were shorter then the originals that were on there therefore making the injectors "too short" and not allowing them to fully compress the lower insulator to make a seal. Thanks for the help guys, probably wouldn't have figured it out yet if not some of the info and advice given.
    #19
  20. pj91gsx

    pj91gsx Freelancer

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    Stuart, Virginia
    maybe you put the seals upside down just a thought. I always add rtv gasket maker to seal mine because ive never bought new ones yet but it always works for me with my old ones.
    #20
  21. ramsack

    ramsack Banned Member

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    those upper o-rings that space the injector don't have a set way of going on. in fact none of the 3 seals on the injector do. glad to see you got it working, now you just need throttle body shaft seals or wherever there its leaking from.
    #21
  22. DroppedMitsu

    DroppedMitsu Proven Member

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    Thanks for the help, its not the shaft seals, I replaced those also before the swap. Its the cheap throttle body gaskets that are leaking, should have that sealed up tomorrow hopefully.
    #22
  23. SpawnedX

    SpawnedX Banned Member

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    Glad to hear you got this resolved. I was actually discussing the issue over some beers with a few buddies before we went to work on a car. It had us all perplexed.
    #23

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