Fuel Leak Back

[JLMounce]

On my 1969 Firebird, I've always had issues with the fuel returning to the tank quickly and leaving me in a situation of not being able to get the car started again after short periods of non-use. After this happens, by the time cranking has produced fuel to the carb, the high compression 455 has eaten up all the juice in the battery and there's nothing left to fire the motor.

Is this fairly normal to see all the fuel exit the system within a couple days? To the point that the only way I can realistically get the car to start is to squirt some fuel in the carb enough to fire the motor temporarily and get fuel up to the carb. That's fine right now with the car still being worked on. Once finished though I don't want to have to do that every time I want to take it out on a weekend.

The engine is a Pontiac 455 with an early performer intake (P4B) and a 700cfm Edelbrock performer that is out of the box. I'll be replacing that with a carter 9800S that I have and will be rebuilding. But for now I just need to figure out this leak back issue.

This car did have AC on it from the factory, so it has the 3/8" feed lines and a 1/4" return line.

Any insight would be greatly appreciated. Thanks!

[rohrt]

Many over on the Performance Years site use a pusher pump at the Tank. You can plumb in a one way valve to allow you to use the pusher pump momentarily to feed the carb only and also use it as a back up in case the mechanical pump fails. Others just use the a pusher pump without a mechanical pump. You can search the archives and find a good deal of info on pumps to use and drawing on how to plumb it all.



I have a 68 bird 455. Its a PITA to start as well if it hasn't run for a couple days. I don't think mine is draining all the way back to the tank but still takes a fair amount of cranking and foot pumping to start. Its a common problem and with todays gas it evaporates and boils much easier then it use to.

[JLMounce]

Many over on the Performance Years site use a pusher pump at the Tank. You can plumb in a one way valve to allow you to use the pusher pump momentarily to feed the carb only and also use it as a back up in case the mechanical pump fails. Others just use the a pusher pump without a mechanical pump. You can search the archives and find a good deal of info on pumps to use and drawing on how to plumb it all.

I have a 68 bird 455. Its a PITA to start as well if it hasn't run for a couple days. I don't think mine is draining all the way back to the tank but still takes a fair amount of cranking and foot pumping to start. Its a common problem and with todays gas it evaporates and boils much easier then it use to.

Here's something to add to the mystery. I went out on lunch and pulled the dip stick. Definitely fuel in the oil, which sucks for obvious reasons.

The car has been sitting in storage for the past couple years. I wonder if it's possible that I've got a couple issues. Possibly a ruptured diaphragm in the mechanical pump and a carb that is leaking it's bowl into the engine after it's off.

What are your thoughts on that?

[rohrt]

In most cases if you have gas in the oil you either have a ruptured fuel pump that is leaking gas in or a huge amount of gas getting by the rings. In any case I think your heading down the right direction. I would start with a new fuel pump and see what happens.