I have been fighting this problem since Feb. I have an 89 f150 302 4x4 automatic duel fuel tanks. I have power to high pressure tank, but no power to in tank pumps. If I ground the test point I have power to all pumps. The problem seems to intermittent. I think I have it fixed and it eats the in tank pumps. They will not run when bench checked. Thought it was selector valve. Would pump form rear, but filled front tank and front tank would pump, go nowhere and burn up pump. Bought new in tank pumps worked on bench, put in truck and wen to put valve in. Turned key to verify front and rear lines, and no fuel. Bench checked pumps, nothing they will not turn. I verified all wiring in the engine compartment. Replaced all fuel pumps, and EEC and fuel pump relay. I am stuck and confused. What would cause the pumps to fry that quick? Would it be a direct short between the Inertia Switch and the pumps? If anyone has any ideas I would love some new advice. Many Thanks.

 

I was thinking, since the rear pumps have power when I ground the test point does that mean the EEC relay is not grounding the fuel pump relay? If that is the case would the high pressure pump still run, because it comes on without grounding test point.