Heat Soaked LS1 with Surge Tank Vapor Locking
09-30-2012, 08:10 PM
#1
TECH Apprentice
Thread Starter
Heat Soaked LS1 with Surge Tank Vapor Locking Just checking to see if I am the only one having this issue. It is unlikely electrical as it comes and goes, plus feels like vapor lock.
I run a mild turbocharged LS1 powered Holden Commodore (an Australian GTO with 4 doors). I kept the factory in-tank pump and added a surge tank with a Bosch 044.
When car has been driven around town and got up to full temp then is shut down, like all cars it will heat soak a while. Then when later restarted sometimes I have had it stumble and even die suddenly when driven again - but not usually straight away - it might take 1-2 miles of city driving then suddenly it happens.
It only happens randomly - but when it does , usually it has idled around ok but as soon as I gave it any sudden throttle (more than 1/3 throttle at a guess) and it has reheated back to operating temps - it is like vapor lock - just vapor in the fuel lines and it runs like **** until I can stab the pedal enough times to get cold fuel back up there.
What we think is happening is that the heat soak on shut down is enough to turn the sitting line fuel to vapor. Then when re-starting the fuel pressure pumps enough fresh fuel in to run ok except there is still gas in there that takes time to work itself out. If there is a sudden throttle opening, or just a clump of gas vapor goes in randomly then the engine wants to die. It can be tricky trying to flick neutral while driving so I can dance on the pedal several times trying to get keep the old girl alive and still keep up with traffic - trickier still trying that in gear with 550hp lol.
A return line would fix this obviously, but there are down sides to them (heating the tank fuel being an obvious one). Has anyone else encountered this problem and how did you fix it?
Help appreciated.
I run a mild turbocharged LS1 powered Holden Commodore (an Australian GTO with 4 doors). I kept the factory in-tank pump and added a surge tank with a Bosch 044.
When car has been driven around town and got up to full temp then is shut down, like all cars it will heat soak a while. Then when later restarted sometimes I have had it stumble and even die suddenly when driven again - but not usually straight away - it might take 1-2 miles of city driving then suddenly it happens.
It only happens randomly - but when it does , usually it has idled around ok but as soon as I gave it any sudden throttle (more than 1/3 throttle at a guess) and it has reheated back to operating temps - it is like vapor lock - just vapor in the fuel lines and it runs like **** until I can stab the pedal enough times to get cold fuel back up there.
What we think is happening is that the heat soak on shut down is enough to turn the sitting line fuel to vapor. Then when re-starting the fuel pressure pumps enough fresh fuel in to run ok except there is still gas in there that takes time to work itself out. If there is a sudden throttle opening, or just a clump of gas vapor goes in randomly then the engine wants to die. It can be tricky trying to flick neutral while driving so I can dance on the pedal several times trying to get keep the old girl alive and still keep up with traffic - trickier still trying that in gear with 550hp lol.
A return line would fix this obviously, but there are down sides to them (heating the tank fuel being an obvious one). Has anyone else encountered this problem and how did you fix it?
Help appreciated.
10-01-2012, 07:34 PM
#3
TECH Apprentice
Thread Starter
Normally the car runs perfect.
The only thing we can think of is vapor lock from fuel trapped in the fuel rail going back to the surge tank after shut down (i.e. fuel pressure released from pump turning off would mean fuel runs back into surge tank). The evaporated fuel has no where to vent so turns to pockets of vapor that can stumble the engine until cleared... but only sometimes
If true - perhaps a one way valve?
