Need to know what size Gas tanks forward and rear are on my 1990 Ford F350

maybe someone stuffed a rag in the hose when the tank wasn't in use. stick something in it to check for blockage

try replaceing the solinoid that lets you switch tanks

REAR MOUNTED TANK 133 INCH WHEELBASE 19 GALLON 19 GALLON TANK

negative back pressure/ low pressure

do you need an engine wiring diagram?.....need to know engine size then ill send ya what i have,[email protected]

check the fuel filter, then the fuel pump's there is also a cross over valve on the drivers side frame rail that controles witch tank u are getting gas from

When you switch tanks can you see what the correct amount of gas is in the that forward tank? Can you verify that the fuel-pump inside the forward tank is coming on? A common problem for fords are the selector switch units. But you want to make sure you narrow it down enough so you don't buy the wrong part. Let me know how it is going.

yes, diesel is "dirty" compared to gas

The input lead to the sending unit should read 8 Ohms if good. If not replace the sending unit or live with it for they are expensive if purchased new

If you just filled up you could have some bad gas.Hope this helps.Good luck.