Hello folks,

I've just picked up a 1991 F150 (straight 6) with a flatbed on the back. 85K original miles on it.. Dual tanks... Neither fuel pump appears to be running or pressurizing the fuel line.

The truck has sat in the previous owner's yard for the last 6 years, and now - well - we had it towed to get it out of his yard - and into mine. (My brother owns a tow-truck - so no cost to me for that service)

I have seen a few other threads (ie: https://www.ford-trucks.com/forums/1...fuel-pump.html ) about the EEC computer going out, and checking other components first, etc... So - that said - here's what I've got...

Please let me know what else I need to test/try that I have yet to do... (or if I just need to replace the computer)

(All this is with the tank selector on the front tank - but we have tried both tanks)

• The inertia switch does receive power. (Lights a test lamp for a second when the key is turned). Tested the switch out of the circuit for continuity,and it's working (0 ohms across the terminals when in normal running connected mode)
• Fuel Pump Relay works (since it's sending power out to the inertia switch) (and clicks when the key is turned)
• The Check Engine light DOES light up when the key is turned - so I presume the ECC computer IS getting power from the EEC Power relay (is this a correct presumption?)
• We have a fuel pressure gauge connected to the rail - and at no time does the gauge read higher than 0 psi
• I tried jumpering pins 2 to 6 of the EEC test harness - and no change happened (no running of the fuel pump)
• I *DID* pull the EEC computer in order to do a visual inspection of the board. There were no *obvious* damaged or burned capacitors or chips... I know - that does not mean that the board is good - it just means there's not a visually noticeable damaged component of the circuit. Since there was no obvious damage- - I put is back in (for now).

What else am I missing that can be easily tested next? We have purchased a new fuel pump - and need to unbolt and lift away the flatbed to access the tanks - but would we be wasting our time - and just need to replace the EEC ? Or could both fuel pumps indeed be bad?


Rex S.
Harmony Hollow Apiary
1991 F150 Straight 6

 

Check the plug at the sending unit for power and ground if it's there then it's the fuel pump. Don't over think it, I just had to put a pump in my fornt tank and my back tank pump has never worked since iv owned the truck

 

Will do. I picked up Chilton and Haynes manuals for it today at Half-Priced Books - so will check for power, etc at the pump side of things in the next day or two. (The wiring harness at the tanks is a 4-wire connector).

 

Good news... It was a rusted pump (for the front tank). The previous owner had drained the tanks - and the pump had rusted (and fuel-level sending unit was practically non-existent with rust & corrosion). When I changed it out - I felt a LOT of scale in the tank walls as well - so this winter I can change out the tank(s) for a clean fuel system.

With the pump replaced - it runs well... Now for title, insurance, & inspection.

 

Nice good work. Got any pics

 

Here's the truck.... I accessed the fuel tank/pump by unbolting the toolbox below the flatbed directly behind the drivers seat.


1991 Flatbed F150 - (Yes - the hood is popped up, and does lower correctly).




Old rusted out fuel pump.

 

Not a bad looking rig. Safe to say that the sending unit didn't work lol