LT-4 stops Vapor Lock
Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 2,526
Likes: 104
From: Stafford Va
LT-4 stops Vapor Lock
Well I finally go my 64GSR with a cammed Lt-4 on the road and the car has quit on me twice. First was leaving a car show where the car sat for 5 hrs, 5 minutes down the road and died. I pulled off the road waited 5 minutes and good to go, I repeated that this weekend after about 1/2 hr of driving. I have a fuel safe fuel cell with the vent as high as the filer neck and a vented cap with access to the cap for fuel on the outside of the car body ( top right side of the rear panel) and the return line hose is as big as the fuel line. Fuel pressure good with key on and running. I also thought fuel injected motors really do not get vapor locks?? Any thoughts?
Last edited by vstol; May 18, 2010 at 06:43 PM.
Race Director
Joined: Apr 2003
Posts: 17,700
Likes: 1,667
From: moraga ca
You're right. Fuel injected cars with 40 psi fuel pressure do not get vapor lock. It is near impossible for fuel to vaporize within the fuel line with this amount of pressure unless the fuel line is touching a header pipe which I am sure it's not. Might be the ignition module which can go out when hot.
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
Vapor lock is the perculating of fuel in a fuel line due to excessive heat and the gas boils and turns to vapor. The vapor then pushes the liquid fuel back with the vapor pressure so it doesn't run. If the car isn't heat soaked, it's not vapor lock.
1. If you have a liquid fuel return line back to the tank, there should be no vapor lock.
2. I bet you have a vacuum created by the using of the fuel, and not enough fuel or air returning to the tank to balance the negative pressure.
3.I would try driving it with the gas tank cap removed or open and taped in position on the car so that it doesn't let in dirt, but vents.
It might be that the vent you have is not enough.
1. If you have a liquid fuel return line back to the tank, there should be no vapor lock.
2. I bet you have a vacuum created by the using of the fuel, and not enough fuel or air returning to the tank to balance the negative pressure.
3.I would try driving it with the gas tank cap removed or open and taped in position on the car so that it doesn't let in dirt, but vents.
It might be that the vent you have is not enough.
