gp_cj-7

I've got an 87 F-150 with the EFI 4.9L L6. It will start fine and run for about 2 minutes but then the gas pedal does the opposite of reving the engine and stalls it out when pressed. It will rev back up when the pedal is let-off but only briefly and then stalls. After 5 minutes of sitting it does exactly the same thing again.

Here's the whole story of what I've checked: My gas pedal became non-responsive while driving down the highway. I replaced the fuel filter and it did no good. My mechanic tested the fuel pressure and diagnosed it as a bad electric fuel pump (the one outside of the tank). I replaced the fuel pump and was still having the same problem. I then replaced all 6 spark plugs and the ignition coil, no luck. I then replaced the throttle position sensor and changed the air filter, no change. I thought it might be the catalytic converter since it would stall out after warming up. After removing both cats it does the same thing. I'm running out of things to check or replace, any ideas?

ymeski56

Low pressure in tank pump that feeds the hi pressure external pump?

gp_cj-7

I guess its possible, but it has 2 fuel tanks and does the same thing no matter which tank is engaged. Plus, I don't think it would run perfect for 2 minutes and then suddenly lose fuel pressure.

ymeski56

"Perfect for 2 minutes" at Idle.

gp_cj-7

I can rev the engine for 2 minutes. I was holding it at 2000 rpms last time.

ymeski56

So you have to determine the fuel pressure drop's out when it die's. To rule that out or confirm we're still dealing w/ a fuel delivery problem.