Vapor locking issues
Thread Starter
Pro
Joined: Nov 2008
Posts: 543
Likes: 24
From: Riverside CA
Vapor locking issues
Today, went out (about 102 out) had it SMOG'd and notice it was hot, real hot over 240.
Took it on the road and I noticed it started vapor locking - what's up with that? Is there supposed to be a sheild by the filter?
Any other ideas?
Eric
Took it on the road and I noticed it started vapor locking - what's up with that? Is there supposed to be a sheild by the filter?
Any other ideas?
Eric
Race Director
Joined: Oct 2005
Posts: 11,770
Likes: 175
From: Rolla Missouri
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Are you running a carb on the C4?
I didn't think you could have vapor lock with the stock fuel injection system, since it's under so much pressure.
You might possibly have a fuel injector issue.
I didn't think you could have vapor lock with the stock fuel injection system, since it's under so much pressure.
You might possibly have a fuel injector issue.
Instructor
Joined: Sep 2007
Posts: 249
Likes: 0
From: Abilene Texas
Sure it can. My wife's 87 vert was doing it every l the fuel cap now and then. You could pull the fuel cap and get a huge suction. The vent in the cap would stop up, replaced the gas cap and no more problem.
Drifting
Joined: Aug 2004
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Team Owner
Joined: Mar 2001
Posts: 54,124
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From: Cincinnati, Oh USA
Vapor lock comes from gasoline so hot it boils and makes high pressure vapor in the fuel system such that no liquid gasoline gets to the intake system. If you had SUCTION, then you did not have vapor lock.
Drifting
Joined: Jan 2007
Posts: 1,908
Likes: 3
From: Supreme Soviet Peace-Loving Pipple's Kollektive of Seattle Wa
eric, what year is your C4? my '84 uses 14psi for injectors, but after sitting for 1/2 hour it will stumble on restart for a couple of minutes untill cooler gas comes into the lines, then it's ok. later tpi has a higher pressure. anyone think either of us has true vapor lock?
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Team Owner
Joined: Aug 2004
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From: Park City Utah
Folks, RollaMo-LT4 is right. You can't get vapor lock on a EFI system.
The WORST gasoline under 45 PSI pressure boils at 266* F While it's possible for the fuel rail to reach that temp (though not likely), as soon as you start the fuel pump, and gasoline starts circulating through the rails...FROM THE TANK, and back to tank, that possibility is over.
The pump is sitting in gasoline, IN THE TANK. How hot does the tank get? Maybe as high as 120*F on a hot summer day? Sorry, but "Vapor Lock" is not happening. The problem is caused by some other, explainable issue like a bad pump, clogged filter, etc.
A "Couple minutes"?? No. It takes about 5 seconds for fuel to make it to the Throttle bodies once you turn the key on. In fact, key on, the pump runs (primes) for ~2-3 seconds. That alone is nearly enough. By the time the starter cranks the motor a turn or two, cool gas from the tank , is at the injectors, and already circulating back to tank.
As for if I think you have vapro lock, no. You have a different issue.
The WORST gasoline under 45 PSI pressure boils at 266* F While it's possible for the fuel rail to reach that temp (though not likely), as soon as you start the fuel pump, and gasoline starts circulating through the rails...FROM THE TANK, and back to tank, that possibility is over.
The pump is sitting in gasoline, IN THE TANK. How hot does the tank get? Maybe as high as 120*F on a hot summer day? Sorry, but "Vapor Lock" is not happening. The problem is caused by some other, explainable issue like a bad pump, clogged filter, etc.
As for if I think you have vapro lock, no. You have a different issue.
Last edited by Tom400CFI; Sep 24, 2009 at 03:02 PM.
Drifting
Joined: Jan 2007
Posts: 1,908
Likes: 3
From: Supreme Soviet Peace-Loving Pipple's Kollektive of Seattle Wa
Folks, RollaMo-LT4 is right. You can't get vapor lock on a EFI system.
The WORST gasoline under 45 PSI pressure boils at 266* F While it's possible for the fuel rail to reach that temp (though not likely), as soon as you start the fuel pump, and gasoline starts circulating through the rails...FROM THE TANK, and back to tank, that possibility is over.
The pump is sitting in gasoline, IN THE TANK. How hot does the tank get? Maybe as high as 120*F on a hot summer day? Sorry, but "Vapor Lock" is not happening. The problem is caused by some other, explainable issue like a bad pump, clogged filter, etc.
A "Couple minutes"?? No. It takes about 5 seconds for fuel to make it to the Throttle bodies once you turn the key on. In fact, key on, the pump runs (primes) for ~2-3 seconds. That alone is nearly enough. By the time the starter cranks the motor a turn or two, cool gas from the tank , is at the injectors, and already circulating back to tank.
As for if I think you have vapro lock, no. You have a different issue.
The WORST gasoline under 45 PSI pressure boils at 266* F While it's possible for the fuel rail to reach that temp (though not likely), as soon as you start the fuel pump, and gasoline starts circulating through the rails...FROM THE TANK, and back to tank, that possibility is over.
The pump is sitting in gasoline, IN THE TANK. How hot does the tank get? Maybe as high as 120*F on a hot summer day? Sorry, but "Vapor Lock" is not happening. The problem is caused by some other, explainable issue like a bad pump, clogged filter, etc.
A "Couple minutes"?? No. It takes about 5 seconds for fuel to make it to the Throttle bodies once you turn the key on. In fact, key on, the pump runs (primes) for ~2-3 seconds. That alone is nearly enough. By the time the starter cranks the motor a turn or two, cool gas from the tank , is at the injectors, and already circulating back to tank.
As for if I think you have vapro lock, no. You have a different issue.
Team Owner
Joined: Aug 2004
Posts: 21,543
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From: Park City Utah
CFI's are known for having questionable pumps. Throw a gauge on there, and check it; at idle and under load. Spec is 9-13 PSI. What ever you see KOEO, you should also see at WOT. If the pressure drops at any time, under any condition, you have a problem w/your fuel delivery system (filter, pump, screen, as you stated).
Last edited by Tom400CFI; Sep 24, 2009 at 04:59 PM.
Drifting
Joined: Jan 2007
Posts: 1,908
Likes: 3
From: Supreme Soviet Peace-Loving Pipple's Kollektive of Seattle Wa
CFI's are known for having questionable pumps. Throw a gauge on there, and check it; at idle and under load. Spec is 9-13 PSI. What ever you see KOEO, you should also see at WOT. If the pressure drops at any time, under any condition, you have a problem w/your fuel delivery system (filter, pump, screen, as you stated).
