Fuel injector or O-ring leak?? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 06-22-2013, 12:47 PM   #1
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Default Fuel injector or O-ring leak??

Greetings, GM 3400 wont hold fuel pressure, leaks down within a minute or two with pressure gauge attached, smell gas hard warm start, will crank a dozen times to fire, smoke like a flooded engine occasionally, recent high rev at start cold etc. Changed FPR with no change. Planning on tearing it down, will start with and O-Ring kit. Can a bad O-ring cause gas to flood engine? Mechanic seems to think it is a bad OR , said he would replace them and if still leaking would clean them?? Didn't sound right as he didn't even mention a new injector. So I figured I would do it lest he have the vehicle for days. I assume I will need a new gasket for the plenum? Will check for presurised leak once I pull the fuel rail, assuming this will indicate a partially stuck injector. I am assuming it is a partially stuck injector as it runs fine and idles fine, start good when cold "rich mixture" Does this sound like I'm on the right track? Never worked on injectors but it looks like something I can do if my back holds out Any info would be much appreciated.
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Old 06-22-2013, 02:58 PM   #2
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If it is a bad O-Ring, it will usually leak externally. If he is talking about the injector o-rings, those will either leak fuel externally also, or cause a vacuum leak. The only thing that can cause fuel to flood the engine are the injectors or the regulator, which you just replaced. The computer can also command too much fuel, but it should also hold fuel pressure with the engine not running.
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Old 06-22-2013, 03:09 PM   #3
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I would suggest having the car scanned for any possible codes. Even pending codes won't trip a light, but it will give us somewhere to start.
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Old 06-22-2013, 03:46 PM   #4
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Thanks guys, Thats kind of what I figured, that the internal leak was probably an injector. The mechanic wanted to work on it at night, probably after work moonlighting but I wondered how he would get parts after hours, he seemed convinced I just needed Orings. So glad I checked with you guys to confirm. I have scanned it with a cheap hand held and no codes , just know I have a flood condition and it will need tearing down, pretty sure I can find which ones are leaking at that point. I will change all o-rings while I'm in there. I will let you all know what I find, Thanks again.
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Old 06-22-2013, 03:59 PM   #5
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Take a can of carb cleaner and spray it around the injectors with the car running. If the engine changes idle, then you found a leak.
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Old 06-22-2013, 04:09 PM   #6
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Thanks Mike , I will try that in a minute, but that would only indicate an external leak, right,? it wouldn't tell me whats going on at the bottom end. Any idea on the kind of O-rings to buy and gasket?

I see you are from NY. I am from the Utica area actually Remsen , moved to Michigan about 30 years ago.
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Old 06-22-2013, 04:24 PM   #7
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Ok sprayed wd arond all injectore, no change in idle. Got a code though, 0102-Mass or volumn air flow circuit low imput. Any ideas on that one, Thanks
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Old 06-22-2013, 04:45 PM   #8
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Checked voltage at MAF sensor, over 12 Volts. Need a scan tool to check its operation. would a parts store do that?,Could that cause a the gas problems I am having, I mean except for the pressure drop.? thanks
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Old 06-22-2013, 05:23 PM   #9
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If the voltage at the MAF sensor is 12v, then that is fine. The sensor needs 12v to operate. It then sends a signal to the PCM telling it how much air is coming in. More than likely, you need a new MAF sensor. Once that is replaced, use your scanner to reset the PCM and restart all diagnostics.

I believe once the MAF is replaced, your issues should go away.
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Old 06-22-2013, 10:50 PM   #10
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My plan is to use a cleaner on the MAF to see if that helps first. But I still have the leak down issue to deal with, the gas is going somewhere, Thanks again
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