3.4L Issues - FirebirdV6.com/CamaroV6.com Message Board


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3.4L Issues

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  • 3.4L Issues

    First this is not trying to say stay away from a 3.4L I love my engine. This IS a warning for an issue to watch for.

    OK. Back in Aug some of you will remember I posted a thread about my engine running like $%^$ and flooding the #5 cylinder over and over. Well in the end it cost me a motor. I continued to have the same issue on the new engine and for the life of me could not figure out where the issue was.I had the fuel pump replaced and swapped out the fuel pressure reg with a spare I had floating around but that still did not help. I was not getting consistent fuel pressure but there was no leaking under or in the car.

    Two garages and 3 months went by without an answer or a running bird. Over the last few weeks I have been given wonderful help from the members of this forum and a few good friends one of which worked for GM about when the L32 was in use.

    Turns out I had a few problems stacked that made it look like I just needed to trash the car.
    1. the fuel pressure regs I had where both bad in different ways.
    2. The hose from walbro would not hold a seal on the fuel bucket

    Fairly strait forward yes but what caused my old engine to blow up?
    Turns out on my original engine the pressure reg developed a hole in the diaphram and would leak fuel into the vacuum system. not a big deal but the vacuum port is in the back of the manifold sitting on a cross tube that is for keeping the pressure even on both sides of the manifold. All fine and dandy but GM put a drain port from that cross tube strait to the #5 runner so all the fuel that was supposed to go back the return line would just go to that cylinder. This also explained why if the car sat more than about 14-18 hrs it would hydro lock. As the feel line would depressurize it would vent through the ripped diaphram and into the engine.

    So to sum this up:
    1. check your pressure regs often and replace if you think its damaged ( It may not show a loss of fuel pressure)
    2. If you see this issue of just the #5 cylinder flooding, its probably the reg leaking
    3. DON'T USE the line that comes with a walbro just get some fuel line from a local parts house and a set of good clamps

  • #2
    Re: 3.4L Issues

    I never had an issue like this with my 3.4. Not to say it doesn't happen I'll just rain some goodness on the engine. I had a 3.4 that ran like a champ for 40k(160k total before I totaled the car) had a walboro pump. The car routinely sat in the cold for awkward amounts of time, like a week or two, then I would drive it after not touching a thing.

    Thanks for sharing the issue though I'm sure it will stop at least some one from just junking their entire car at some point.


    • #3
      Re: 3.4L Issues

      Oh yea the engine is great its just that this seems to be one of the few ways the engine can kill it self so I figured I would put it up


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