454 vs 350 injector bowl

Discussion in 'Engine & Performance' started by Overthedge21, Apr 20, 2017.

  1. Overthedge21

    Overthedge21 Junior Member

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    I found that my injector bowl was cracked on my 87 TBI 350. A friend had a TBI off an 88 454 TBI. The injector bowls were the same size and my injectors fit into it, but it needed a taller gasket/spacer between the base of the bowls and the throttle body. It now leaks gas profusely from somewhere, and I don't know why. So my question is are they interchangeable like that and I screwed up and made a leak, or is it leaking for a reason? On a similar note, my gas tank is for some reason not venting pressure, so much so that it literally flooded my crankcase with gas so I have to clean that all out too. Anybody know why my tank won't vent pressure?
     
  2. 1987 GMC Jimmy

    1987 GMC Jimmy Full Access Member

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    Did you replace the entire injector pod and FPR assembly, undo the little bolts, stick your 350 injectors in it, and bolt it back together? If so, I would guess that the fuel pressure regulator diaphragm and/or a gasket around the back of that injector assembly is busted and allowing fuel to pour out and you simply need to get you a little TBI rebuild kit. It's cheap and easy. I hope that I understand the situation because that's a logical approach in my mind. As far as the flooding goes, are you sure you're not dumping fuel down the intake because of the same potential leak in the injector assembly? The easiest way to diagnose a venting problem is to simply remove the fuel cap and see if things get better. The fuel cap could be bad, and there's also the purge valve and a filter on the underside of the charcoal canister to check. Besides the one vacuum line going to the TBI, that's it. Evaporative emissions problems can cause rough running and pungent gasoline smells either at the fuel tank or canister, but I've never heard of them causing flooding before.
     
  3. Overthedge21

    Overthedge21 Junior Member

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    I used the 454 bowls and put in my injectors, and put the top from my 350 on it. That top has a new fpr, and the gasket on it didn't leak before as it too was new
     
    Last edited: Apr 21, 2017
  4. yevgenievich

    yevgenievich Full Access Member

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    Double check on that fpr gasket if you had the fpr out. Very easy for it to twist a bit and cause a leak when installing. I even had one that took months before it started leaking. But it should be pretty obvious of the leak with just watching the tbi unit while someones primes the fuel pump. Or use the fuel pump test connector on the firewall
     
  5. Overthedge21

    Overthedge21 Junior Member

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    The injector tower was open and apart when it has flooded, I had left it apart for two days while I got a new gasket for one of the injectors. It was pouring out and flooded everything because the top was literally wide open
     
  6. 1987 GMC Jimmy

    1987 GMC Jimmy Full Access Member

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    I'm afraid I don't understand. Are you saying that it flooded with the injectors taken apart, or did you figure out why it did it in the first place?
     
  7. Overthedge21

    Overthedge21 Junior Member

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    I know why it flooded but I do not know why it happened. The tank built pressure while it sat for those two days, and instead of venting this pressure, the expanding gasses forced fuel up through the pump and fuel lines and out the injector feed in the bowl tower. And since the top was off of the tower and the injectors were out of it, it was wide open as gas pouerd from it into the throttle bores for god knows how long before I finally came home and found it. My only idea on that is a bad gas cap, because when I noticed the leak I immediately opened the gas cap. Upon doing this, a ton of pressure hissed out of the filler neck and lo and behold, the gas stopped flowing from the injector tower. I know it pushed out a lot, as two cylinders poured fuel out when the plugs were removed, and the oil is thin as all hell, so there's plenty of gas in the oil too.
     
  8. 1987 GMC Jimmy

    1987 GMC Jimmy Full Access Member

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    I gotcha now. Sorry about that. It may time to replace the gas cap, like you said, and the filter at the bottom of the charcoal canister is only like three bucks. That maybe worth changing at the same time, too. I got mine at NAPA, but O'Reilly's should have them, too. It should be able to breathe at the tank and canister for sure then. As far as the leak goes, I do think something's fishy with a seal or diaphragm.
     
    Last edited: Apr 21, 2017
  9. Overthedge21

    Overthedge21 Junior Member

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    Turns out the feed line for the fuel HS a bag gasket ring on it, a new one seems to have stopped the leak. Now all that's left is flinching and replacing the oil. What drained out was like water, so that leak must have been going on for at least a full day of non stop pouring
     
  10. 1987 GMC Jimmy

    1987 GMC Jimmy Full Access Member

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    Jeez, that sounds bad. Glad you were able to find the leak.
     
  11. 1987 GMC Jimmy

    1987 GMC Jimmy Full Access Member

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    Were you able to get the fuel cap and that canister filter?
     
  12. Overthedge21

    Overthedge21 Junior Member

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    Not yet, I'm gonna do the oil change tomorrow and make sure I've got it running right first. I don't have a lot of money right now sadly so I gotta go one step at a time
     
  13. 1987 GMC Jimmy

    1987 GMC Jimmy Full Access Member

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    Ahh, I gotcha. I feel you there. I tiptoe around expenses as much as I can, too.
     

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