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Thread: STFT and blow injector seal

  1. #1
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    STFT and blow injector seal

    Would blowing out an injector seal or seals cause the STFT to change this much and go lean from one drive this morning. The two other drives around town during lunch. I mean if it did would it kind be like a whole in the cylinder wall since it's Direct Injection?

    As you can see 10-15-19 1 the STFT look pretty good to me. Then 10-15-19 2 and 10-15-19 3 they are +7 or higher.


    I've been struggling with my HPFP after doing a TSP 32% over fuel lobe. After failing two fuel pumps I switch to the LS7 lash cap instead of the comp cam lash cap TSP supplies with there kit.



    After removing the injectors, I've had trouble using the seal tool you can buy on Amazon to slide the new seals over the injectors. It wants to stretch the new seal out to much. And I think they'll not seat properly. I found this out this first time I failed the HPFP. I used it again but this time I let the injectors sit over night and the seals seem to shrink back. But it does sound like the shrank back enough.10-15-19 1.hpl10-15-19 2.hpl10-15-19 3.hpl

  2. #2
    Are you using the seal resizer after seal installation? Like GM tool # EN-49245

  3. #3
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    Sure didn?t and now I realize my mistake

  4. #4
    Advanced Tuner IARLLC's Avatar
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    Yep. The seal has to get back down to size or it will be damaged on installation. Initially you will hear a light ticking sound but as the seal burns you lose compression and exhaust out around the injector tip. I have seen people let it go to the point that the plastic of the injector body started to melt. Fortunately we got to it before the upper O-ring lost integrity and began to spray fuel at a few thousand psi. No joke man. It can get ugly fast.

  5. #5
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    Looks like I popped the seal on number 8. These DI seals are such a pain in the ass to get them to slide into the hole correctly.

    I can?t get the pic to down load from my phone.

  6. #6
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    Quote Originally Posted by Kyle_Customizer View Post
    Are you using the seal resizer after seal installation? Like GM tool # EN-49245
    I have the resizer but it doesn't seem to do much in terms of sizing it down. I ended up sticking them in the freezer for a few min to try and get them to tighten up around the tip after using the resizer. Either way I've been riding around on them for about 10,000 miles now without any issues so maybe it was a success?



    EDIT: I just remembered they sent me a revised resizer months after I bought the first one from freedomracing.com so maybe there was an issue with the 1st part number.
    Last edited by us3rname; 10-17-2019 at 07:37 AM.

  7. #7
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    I ended up doing it this way. They are much better but still not perfect. I saw another video where a guy heated them up to get them to shrink down

    https://youtu.be/htLtikGBjFA

  8. #8
    Advanced Tuner IARLLC's Avatar
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    Good find. Of course you don't have to buy the tool GM uses. I use the tapered plastic tip from a gasket sealant. I cut off the tip that is used to expand the seal onto the injector. I make sure it is very smooth first. Then I squeeze the seals into the openings in the injector. Then I use the inside of the larger part (of the gasket sealer tip) to smoothly/carefully crush the seal into its place. Best to do them one at a time so that you don't have to back the "sizer" over one.

    At first I measured good used seals, still on the injector and made sure not to crush the new seals smaller than them. Then over time I just got used to it.

  9. #9
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    I fired it up tonight and let it idol for about 10 mins until the temp got up to 140 or so. It sounded fine, so I think I got the seals back in right. But we will see, last time I thought I had them in there right until one let go. At least I know this time if my STFT % get way off or start showing lean real bad. I know what to look for.

    I also notice that when the seal lets go. You get a strong smell of gas fumes in the cad. I didn’t notice any fumes while it idoled