Help 6.2 with air leak

[jackfisherman]

I have spent a considerable amount of time trying to locate an air leak but with no luck. Put 8 psi air into tank but no fuel weeping out of any lines. In the morning the FM80 is 1/2 full of air. New lift pump 6 months ago. No air from clear hose at injector pump. Any suggestions on what else to try would be appreciated.

[britannic]

Are you getting any running/starting symptoms? If not, it could be just fuel contraction due to the overnight cool down releasing entrained air. To ensure the IP doesn't lose it's prime, fit the anti-drainback return line check valve to the pump and the updated ventless check valved lift pump.

[jackfisherman]

Thanks for the reply. Yes, I get a hard start in the morning or if it sits more than 4 hours. I have a couple bad glows but have been plugging it in overnight so that should cure the heat problem. I also applied 12V to cold start soleniod just to make sure that's ok. I wonder if I pickup a bad lift pump. Was thinking of changing it out but don't really want to mess with it if I don't have to. Will fuel cool down attribute to that much air in the FM80 overnight? Can an injector be leaking air all the way up to the FM80. Or would I see air in the clear line attached from the pump to fuel return. Also, no leaks at the filter base.

[britannic]

Yes, fuel can cool down enough to create a vacuum and release the entrained air collected from filling and sloshing in the tank, however, you have way more than normal if it's causing starting problems. There was also an issue with drainback, that GM took care of by fitting an anti-drainback check valve in the IP and the using vent-free check valves in the lift pump.

Unfortunately the FM80 is notorious for leaking through the draincocks and also through the restriction sensor (if fitted). I switched over to the FM100 that was fitted to the 6.5L and didn't hace any more air leak problems afterward.

[jackfisherman]

I will check with GCL (the company who rebuilt my injection pump) to see if they installed an anti drain back valve. It is a recent rebuild,(2002) so shouldn't it have the latest and greatest parts? I will tackle the lift pump once it warms; up just to be sure. Good day.

[britannic]

It's quite easy to tell: look at the injection pump check valve, it will have the normal hex flats on the bottom and another one near the top, showing its a 2 part component with the anti-drain back installed.

Have you confirmed for certain that your FM80 isn't leaking air or fuel?

[jackfisherman]

I don't think my FM80 is leaking because when I put air to the tank there was no seeping at the base. I left 8 psi on it for about 1 hour. Please describe the check valve at IP. Do I have to open it up to see? Or is it located in the fitting which the return hose attaches to? Thanks Brit.

[britannic]

Try 10psi in the tank and BTW, the return fitting is the check valve, the anti-drainback version will have 2 hex nut surfaces on it.

[jackfisherman]

Try 10psi in the tank and BTW, the return fitting is the check valve, the anti-drainback version will have 2 hex nut surfaces on it.

I have 10psi in the tank now and its been 2 hours and no leaks. Return fitting is a normal nut similiar to any 6 sided nut but a little thicker. It looks excactly like the one in my Haynes manual. Did not see any hex nut surface but not sure.

[jackfisherman]

Thanks Brit for your help. This is the last time I post on this forum. Will use other sites to get my questions answered and save my money come renewal. You guys sure blew it when you forgot to make server backups.

[arveetek]

Whoa! What was that all about? Are you blaming the posters themselves for the unfortunate loss of threads that occurred a while back? That's not very cool.

Why the sudden attitude?

Casey

[Peter J. Bierman]

Did we say something wrong :eek: :( ??!?

Peter

[britannic]

You have the standard check valve, the upgraded GM part # is: 10149645 and the updated lift pump # is: 25116503 which has ventless check valves.


Originally posted by jackfisherman:
Try 10psi in the tank and BTW, the return fitting is the check valve, the anti-drainback version will have 2 hex nut surfaces on it.

I have 10psi in the tank now and its been 2 hours and no leaks. Return fitting is a normal nut similiar to any 6 sided nut but a little thicker. It looks excactly like the one in my Haynes manual. Did not see any hex nut surface but not sure.