1987 F150 losing fuel pump power
 

I have a 1987 F150 4X4. It starts fine and will drive for about a mile. The motor will begin to sound like it is coughing and then it will stall. A mechanic looked at it and stated the main fuel rail pump was losing power. He throw up his hands.

He tried changing the fuel pressure regulator, rerouting the power, and checking the ground. This is very frustrating. Any help will be greatly appreciated.

Does it do it when its hot, cold, all the time? Does it do it if you put the engine under load, or will it do it just sitting idling? Is it intermittent or does it do it every time you try to run it? Will it restart after a few seconds without cycling the key (turn it off, then back on), If you cycle the key does it restart?

Given the info you have provided so far, I would be inclined to suspect maybe a bad fuel filter (never hurts to change this when diagnosing any fuel system problem, they are cheap and relatively easy to change, you will likely need a fuel line disconnect tool, also inexpensive, just don't cut the plastic fuel lines) or maybe the pump itself is weak and can't keep up with the EFI system pressure demands, ooorrr it could be a bad fuel system relay being effected by heat.
If it isn't one of these and If you are fairly mechanically inclined and have access to the needed tools and reference materials you could try some or all of these test diagnostic steps before you start throwing more parts at it. some things may be in different spots then specified.

Get a fuel pressure gauge & leave it connected while you drive. Don't let it distract you from watching where you're going, but try to notice what it does just before & during the stall.

https://www.supermotors.net/getfile/...ssuregauge.jpg

The connector on that style of hi-pressure pump is known to loosen, but it's easy to repair. There's a molded hard plastic connector near the pump clipped to the frame rail - that's NOT the one. Follow those wires down to the pump, where they go into a rubber boot. Slide the boot up to access the terminals. Pull one off at a time, crimp it slightly tighter with pliers, & put it back. Reinstalling the boot is a challenge, but it's doable.

'87 fuel lines use hairpin clips, which can be removed with a flathead screwdriver or hook probe - no special tools required, other than at the fuel rail.

try the map sensor. my 88 f150 with the 302 would start chugging then stall. would crank right back up and then do it againshould be on the left side of the firewall up top under hood.

How about a weak/ worn out Fuel Pump Relay?

Attachment 37343

I am chasing an electrical problem with mine and having a hard time with it. I really wouldnt know but by your earlier discription, mine was doing that before and it was the map sensor.

I have a 87 ford f150 with no power to the fuel pumps. Do you know where the fuel pumps get powered from ?

The tank select switch, which gets power from the inertia switch, which gets power from the FP relay, which gets power from a fusible link wire. But the FP relay only comes on for ~1sec after turning the key to RUN unless you install a jumper wire (just for testing). Read this caption:

https://www.supermotors.net/getfile/.../dlc-eeciv.jpg