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Thread: leaking injector to "fuel"lock while cranking --> Is my S50 Fried?

  1. #1
    Join Date
    Oct 2008
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    Chicoutimi, Quebec, Canada
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    E30S50

    Unhappy leaking injector to "fuel"lock while cranking --> Is my S50 Fried?

    Hi All,
    Been working on my swap for a while and finally came to the point I could start it! Cranked and started! But then came the problem. The injector on first front cylinder was leaking. So when I started it for the second time it made a very bad noise that is really hard to describe and I immediately stopped cranking... (could be the starter pinion and ring gear...). cranked another time and same noise. When I got out of the car there was a lot of fuel on the ground, under the open headers.

    After removing all plug, found out that the first one was soaked with fuel. Turned the engine by hand, put plugs back in and cranked. It fired and the idle sounded normal... When I stopped it, I heard the leaking sound and could easily tell that it was coming from the first injector. that was confirming my diagnostic...

    Ok now, Sending the 6 injectors to get them cleaned and flow benched. Will drop the brand new oil due to possible fuel contamination. I was scared about internal damage so I bought a compression gage and tested the 3 first cylinders (Was short on time last evening)

    cyl #1 145psi
    cyl #2 203psi
    cyl #3 195psi

    There is definitely something wrong with the cylinder #1. 145 psi seems high for a bent valve... Is the starter strong enough to bend a rod? Can it just be that the fuel soaked the cylinder and temporarily decrease the sealing capacity of the rings? Could the unlubricated ring scratched the cylinder?

    This is where I'm standing presently... being not very happy and full of question. I think I'm going to get it going (still have to install shifter, driving shaft, exhaust, front brake) and run a bit with it and see how it is running... and retest the compression after a little while...
    what do you think?
    Thanks!
    E30 S52

  2. #2
    Join Date
    Jan 2007
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    A leaking fuel injector wouldn't bend a valve.
    You could bend a rod if the injector was leaking in the cylinder and you hydro locked the engine which i doubt happened.
    A flooded combustion chamber would not decrease comp numbers, besides...
    The fact that you had fuel on the ground and intake manifold probably means the injector was leaking at one of the two oring locations, probably at the rail, and the fuel injector is not bad.

    Your noise is probably not related to your fuel injection system.
    Last edited by conway; 09-18-2014 at 04:50 AM.

  3. #3
    Join Date
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    If you are saying the fuel was out of the open manifold, then it may very well have hydro locked, but if it was idling or less you are probably ok. If the cylinder is washed down witht fuel then it certainly CAN lower compression. Pull all the plugs, pour a half teaspoon of oil in the cylinder and retry compression test. Also if the injector is leaking that bad, you should be able to pull the rail plugged in and see it

  4. #4
    Join Date
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    Chicoutimi, Quebec, Canada
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    E30S50
    Quote Originally Posted by conway View Post
    A leaking fuel injector wouldn't bend a valve.
    You could bend a rod if the injector was leaking in the cylinder and you hydro locked the engine which i doubt happened.
    A flooded combustion chamber would not decrease comp numbers, besides...
    The fact that you had fuel on the ground and intake manifold probably means the injector was leaking at one of the two oring locations, probably at the rail, and the fuel injector is not bad.

    Your noise is probably not related to your fuel injection system.
    The injector was clearly leaking by the injection point itself. The fuel got out of the exhaust manifold. The exhaust it not yet installed. I have one bad injector. The motor nearly hydro locked while cranking with the starter and the fuel escaped by the exhaust. Could have generated a nice fire...


    I think the noise came from the starter pinion rocking on the flywheel ring gear due to near hydro lock situation.

    - - - Updated - - -

    Quote Originally Posted by Sstamand87 View Post
    If you are saying the fuel was out of the open manifold, then it may very well have hydro locked, but if it was idling or less you are probably ok. If the cylinder is washed down witht fuel then it certainly CAN lower compression. Pull all the plugs, pour a half teaspoon of oil in the cylinder and retry compression test. Also if the injector is leaking that bad, you should be able to pull the rail plugged in and see it
    The injector are already pulled and sent out for rebuild + bench test.

    In the cylinder one, I had put some storage oil before doing the compression test... But not that much. Also, since the engine is standing at an angle, not sure about the fact that the ring would get lubricated all around.

    One more information, prior to this start, the engine had not ran for over four years... The ring may be stuck...
    E30 S52

  5. #5
    Join Date
    Oct 2008
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    Leaking injector replaced and engine seems to be running strong!
    E30 S52

  6. #6
    Join Date
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    Did you ever get the low compression figured out?

  7. #7
    Join Date
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    Quote Originally Posted by weedshoes View Post
    Did you ever get the low compression figured out?
    Flooding the cylinder chamber with fuel will cause low compression numbers. I've dealt with this several times when performing compression tests.

    Not sure what the above poster was talking about because what he said isn't necessarily true.

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