Fuel tank pressure issue even with relief valves installed.

[†3AD† S.T.A.R.S. Delta 7]

I'm running a twin Small engine setup with two medium pumps to pump fuel out of the same fuel tank. I am running into negative pressure problems inside the fuel tank running these engines. I have installed up to three gas relief valves inside the fuel tank leading to ports on the outside of the aircraft. Would it be necessary to install an air pump to pressurize my fuel tank? And if so will I need to install a secondary pump inside my fuel tank to create negative pressure to refill my tanks?

[Captain]

You should not need a pump for the fuel. The engine will pump the fuel itself.

[†3AD† S.T.A.R.S. Delta 7]

Those Small engines don't have enough power to fly my aircraft unless I had medium pumps for the air intake and pumps for the fuel.

[†3AD† S.T.A.R.S. Delta 7]

Noone told me this but I had to add liquid relief valves to my fuel intakes due to the fact my gas relief port was allowing air to suck into the fuel lines.