Just looking to see if anyone could ID the four terminals of the wiring harness pigtail for a 1986 f350 fuel pump. It's a single tank, electric fuel pump feeding a 460 carbed motor. It is the low pressure in-tank pump which is followed by a crappy Mr. Gasket 12S electric fuel pump.

The reason I am asking is that the in-tank pump doesn't seem to be running with the key on, and when I probe it with the key on I only have one of the terminals showing hot (the second from the left if looking at it plugged in).

Would guess that one is for power to the pump, one is ground, and one is for the sending unit/fuel gauge. Clueless on the fourth.

No idea on colors as they are all the color of crud.

 

IIRC the fourth connector is unused.

Black=ground
Yellow(/white?) is the dash gauge sender signal
The other is for the pump power.

 

Single tank 460?
Is this a C&C?

You won't have power with the key on and the engine not running.
These trucks provide power with the key in the 'start' position but require the oil pressure safety switch to close to ground on the pull down side of the fuel pump relay while running.

Jumper the safety switch and check again for power (or just listen for the relay to click closed)

 

It's a rollback tow truck, hence only the single tank. (At least that's how it came when I got it. Would be hard to fit another tank back there with the hydraulics.)

My question stems from the fact that I can't get the darn thing running. It was sitting for a while, and when I went to start it, it ran for about 10 minutes and died (no fuel). Replaced the high pressure pump (12in away from the tank and below the tank), ran for 10 minutes died again. Replaced the high pressure pump again, ran for 10 minutes and died again.

Was thinking maybe the high pressure pump is priming itself (enough to power 10 minutes), and maybe the in-tank pump isn't pushing enough fuel to keep it running. Most everything else is new - relay, inertia, in-tank pump.

I've seen posts from others who have had a similar problem, but never seen a resolution. Could be just the high-pressure pump, but the fact that I am about to put on my 4th pump this week leads me to believe/hope that at least one of them had to be good.

 

So it is a cab and chassis truck.
If you replaced the sender i have to assume the 'sock' is not packed full of gunk from sitting.
Try jumpering the oil pressure switch, or just ground the pulldown side of the relay.
10 minutes is about enough time for the engine to warm up and "lose pressure".
Could be a faulty switch.

You say "high pressure pump".
What kind of return regulator are you using?
Electric pumps do NOT like to be deadheaded and will fail pretty quickly without fuel flowing to cool them.

 

Started a new thread with more/better detail. Any help would be greatly appreciated as I am totally stumped.

 

One has a 1986 Ford E-350 Cutaway, running a 460 cu. in. 7.5 Liter 4-Barrel Carburetor, for a 27 Foot RV that has been plagued with fuel pump and sender malfunction issues for four years. Finally, found the problem - power to the Electric Fuel Pump Relay, Passes Through the Oil Pressure Sender Unit on the Rear of the Block, and that had an Intermittent Connection. Hope this Helps.

The Electric Fuel Pump Wiring is: Red/Brown Stripe = Power to fuel pump; Orange/Yellow Stripe = Fuel Gage Sender; Black = Ground.

By: schroll, david clarence.

 

David Clarence, you rock!!!

Reps given, thank you for your participation here... 7 posts total....