Not getting air?
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Not getting air?
1994 corvette won’t start. It has spark and fuel, but I can only get it to run if I pull the fuel rails off and let the injectors spray in. It clearly needs the air so something is choking it out. Any ideas, I tried the tps and it’s fine. I took the iac out and it will barely even run without it so it’s like it still needs more air. The car has a 306 comp cams roller but it ran on the stock tune regardless.
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Team Owner
Joined: Aug 2004
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From: Park City Utah
Pressure is good.
Have you confirmed your ignition timing? Have you confirmed that the harmonic damper hasn't slipped, thus, f'ing up your efforts to correctly set the timing?
.
Have you confirmed your ignition timing? Have you confirmed that the harmonic damper hasn't slipped, thus, f'ing up your efforts to correctly set the timing?
.
Last edited by Tom400CFI; Sep 29, 2021 at 08:02 PM.
Thread Starter
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you can’t check the timing on an lt1 the harmonic balancer isn’t keyed or have any timing marks. I don’t see anyway that could affect the engine
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Exhaust system open? If air can't get out, it can't get in.
Many, many moons ago I was reinstalling the head on a 6 cyl diesel engine in a 50' sailboat. My "helper" made a new exhaust flange gasket and installed it. This gasket is about 3" square, a 3/8" bolt hole in each corner, and a 2" hole in the middle. I did everything else including the cam (overhead) and injection pump timing. It would start, but not stay running. I rechecked the timing a half dozen times. About 4 hours later I still hadn't figured it out, and I know this particular engine type very well. We went to dinner, and when I got back I sat there and made it "do it" over and over. When "what it was" finally came to me, I was pretty pissed at myself for taking so long to figure out the cause.
My "helper" hadn't put the middle 2" hole in the gasket. That was 1990. I haven't allowed anyone to "help" me since.
Many, many moons ago I was reinstalling the head on a 6 cyl diesel engine in a 50' sailboat. My "helper" made a new exhaust flange gasket and installed it. This gasket is about 3" square, a 3/8" bolt hole in each corner, and a 2" hole in the middle. I did everything else including the cam (overhead) and injection pump timing. It would start, but not stay running. I rechecked the timing a half dozen times. About 4 hours later I still hadn't figured it out, and I know this particular engine type very well. We went to dinner, and when I got back I sat there and made it "do it" over and over. When "what it was" finally came to me, I was pretty pissed at myself for taking so long to figure out the cause.
My "helper" hadn't put the middle 2" hole in the gasket. That was 1990. I haven't allowed anyone to "help" me since.
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Thread Starter
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Team Owner
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From: Park City Utah
Just to be clear, your unbolting the fuel rail, lifting up the rail/injector assy, yet "aiming" it so the injectors are (mostly?) firing into the injector holes in the runners....and in that condition, it starts and runs?
If all that is true, can you introduce a vacuum leak (pull the boost line off?) and will it run that way?
Backfiring through the intake is a sign of a too-lean a/f ratio or improper timing. So it's hard to comprehend that if opening the throttle causes backfiring through the intake, introducing a vacuum leak works better. (?)
If all that is true, can you introduce a vacuum leak (pull the boost line off?) and will it run that way?
Backfiring through the intake is a sign of a too-lean a/f ratio or improper timing. So it's hard to comprehend that if opening the throttle causes backfiring through the intake, introducing a vacuum leak works better. (?)
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Just to be clear, your unbolting the fuel rail, lifting up the rail/injector assy, yet "aiming" it so the injectors are (mostly?) firing into the injector holes in the runners....and in that condition, it starts and runs?
If all that is true, can you introduce a vacuum leak (pull the boost line off?) and will it run that way?
Backfiring through the intake is a sign of a too-lean a/f ratio or improper timing. So it's hard to comprehend that if opening the throttle causes backfiring through the intake, introducing a vacuum leak works better. (?)
If all that is true, can you introduce a vacuum leak (pull the boost line off?) and will it run that way?
Backfiring through the intake is a sign of a too-lean a/f ratio or improper timing. So it's hard to comprehend that if opening the throttle causes backfiring through the intake, introducing a vacuum leak works better. (?)
Drifting
Joined: Jan 2021
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From: Northern California
So I'm not buying that the engine isn't getting enough air. If the intake tract is not blocked, and the throttle body is not all effed up, and the air filter / MAF / other intake elements are good, then how can the engine be starving for air that lifting the injectors out of the bore helps bring enough air in?
I am wondering if it's really something more like A/ the PCM is controlling a very rich mixture which won't run without additional intake air, and B/ when you provide that additional air through the open injector ports it brings the mixture closer to right?
If that's the case, that PCM/ECM should be throwing some codes....
I am wondering if it's really something more like A/ the PCM is controlling a very rich mixture which won't run without additional intake air, and B/ when you provide that additional air through the open injector ports it brings the mixture closer to right?
If that's the case, that PCM/ECM should be throwing some codes....
Team Owner
Joined: Aug 2004
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From: Park City Utah
Yeah...this story doesn't make a lot of sense. I think we're missing something from the details. 8 injector holes would make for a tremendous vacuum leak. Thing should be revving about 4 or 5 grand.
Is it totally flooded? Thus "requiring" a massive vacuum leak? Have you tried starting it at WOT?
Is it totally flooded? Thus "requiring" a massive vacuum leak? Have you tried starting it at WOT?
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The car won’t start at WOT but I’ve attached a video. In the video the injectors are sitting just up from the seats. The car starts and sucks the injectors back in and the engine and kills the engine. It won’t start no matter what with the injectors in unless you create a massive vacuum leak like removing the iac valve. And yes I’ve replaced the iac valve.
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