I have a 1988 F450 460v-8 EFI dual tanks [gas]. Recently mostly when vehicle is on an incline, the vehicle will not restart. It's not that the vehicle has been sitting, without running, but shut off with key and tried to restart with in 10 minutes. The Starter tries but the vehicle acts like it is not getting any fuel. I find when in this nonstart condition, if I let it roll to a more level spot, it will start. I figured it might be a fuel vapor issue, and replaced the original FORD gas caps, with non ford caps. For a while this worked fine, no stalling or issues with starting. In the last six months the intermittent starting and or stalling out began. I recently replaced the non Ford gas caps with new FORD caps for this era vehicle, and the truck would not start. I replaced one of these New gas caps and the truck would start, but stall out in 3-5 minutes. I replaced the other New Ford cap with the former non ford caps, the truck starts and continues to run. My concern is the stalling out and intermittent starting really have not been solved. I did replace the front gas tank pump, sending unit and float approximately 3 yrs ago and the truck was operating fine.

 

 

Sounds like the tank fuel pumps are not running and you are just running off the in line pump.

 

Subford, as I said this is an intermittent issue. 99% of the time the fuel issue isn't there. Sometimes its has occurred when driving down a steep grade, no acceleration needed down the grade, it will stall at the bottom of the grade, most other times, when parked for 10-15 minutes on an moderate incline. I don't drive the vehicle too far, up to 25miles at a time, and there has not been this issue when driving on grades, and reasonably flat surfaces. Therefore, wouldn't this mean the fuel pumps are working normally as these 25 + mile trips would use more than what is in the fuel lines. I don't know if this could help the issue, I am going to replace the frame rail/chasis mounted fuel filter.
I have checked the newly installed fuel relay with a meter, wires are all good and the relay seems ok.

 

Thank you Subford and My4Ford trucks, for the advice. I cannot say the issue is repaired, but not knowing the fuel filter on these trucks requires maintenance replacement, I tried that. The truck starts and thus far runs without stalling, and restarts on an incline. This is a great forum, I will be back.