M923A1 losing prime

[aheilmann68]

I know this is an old post but it relates to a question I have. Does anyone know how the tank in the A0/A1 trucks are layed out? I put a fuel pump to push fuel to the ip and its working great with the exception of being under load and taking tight turns. What I think is happening and how I am working through this is that there is much more fuel being returned to the tank at higher rpms as the fuel lift pump is able to flow full bore. The return line just dumps into the top of the tank and lets the fuel fall causing air bubbles to be entrained in the fuel. The lift tube is in the same baffle compartment as the return and I end up sucking air causing a stall (iv git my purge procedure down pat and a lift pump is great in purging). I have extended the return line down into the bottom of the tank and was going to modify the pickup tube but I noticed that it slided into a guide at the bottom of the tank. Does anyone have an idea of the inside of the tank and how it is laid out? I have over 3/4 of a tank now so I have a while until I can drain it and use a scope to look inside. I was also thinking of adding a new fuel port so I can draw fuel level with my pump vs drawing up, then down into the pump.

 

[M35A2-AZ]

The tank just has two baffles in it, if that is what your asking?
I would not think the air bubbles would be a problem with more then 10-15 gals. in the tank.
You maybe getting air in some other place.

 

[aheilmann68]

Where are the two baffles? I found one approximately 3 inches to the front (cab) of the pickup and returns. The pickup tube feels like it slides in a section in the tank at the last inch of the pickup. I think I'm getting an air bubble in the pickup due to you can here the pump loose suction and prime. There also ends up being a fair amount of air when this occurs (happened 3 times)

 

[M35A2-AZ]

There is one at the other end also, I think!
I still think you have an air leak in the fuel line some place.

 

[allie]

M931 fuel tank leaks only after driving it. Im thinking theres a crack that upon vibration it opens. if i clean tank off it stays dry as soon as i drive it it begins to leak
any suggestions?

 

[painter paul]

I believe I would try a thin bead of clear fuel tank repair stuff on it if you can find the crack.

 

[allie]

Thanks for the reply I found problem The platform on top of pass side fuel tank was rubbing on a fuel line it ate through it so fuel was sweating out and dripping down fuel tank i cut bad part out and used 3/8 rubber hose with some hose clamps all is well now!

 

[M35A2-AZ]

Thanks for the reply I found problem The platform on top of pass side fuel tank was rubbing on a fuel line it ate through it so fuel was sweating out and dripping down fuel tank i cut bad part out and used 3/8 rubber hose with some hose clamps all is well now!

My m929 did the same thing on the right side, The top plate rubbed a hole in the line.