Hello folks,

long time no work on truck. Life has been too busy/side more important projects.

The truck: 83 f250 with 460.

symptoms: doesn't start, seems to be a lack of fuel delivery. No Fuel pump noise at all when I turn the key. Parked on a hill facing down.

The Pump used to buzz when I started truck up, but nothing now (for almost a year now. again, haven't done much on the truck in a long time).

Replaced the fuel relay a while ago, didn't make a difference. Don't have a fuel pump on engine. Replaced carb (although a friend of mine who is a mechanic says it's not the correct one although I swear it was one that someone here said would work). The fuel problem preceded the carb though.

Anywho, after taking some advice i removed the front tank figuring it was the pump. I also had some other tank related fixing i needed to do, so it's not like I did something extra here.

The electric connections ON the pump itself are spotless, no corrosion whatsoever. I haven't looked at the plug itself (thats next on my check list) because when I finished working on the tank, it was dark and I was hungry.

I bench tested the front tank puel pump, and low and behold, it works. I don't know if that means anything (like it should), but it works. It didn't spit any gas out of the hoses though.

What I don't know is if the dual tank switch is crap and could that cause this (pump not working, no start)?

In the past when the truck was running, I would switch between tanks the gas gauge would show a difference in fuel in the tanks.

The truck IS 30 years old, so anything could crap out anytime it feels like it. Could a bum switch make it so the fuel pump doesn't work at all?

 

If your selector valve is bad it won't switch over when you move the dash switch.
The tank reading won't change because the gauge wiring goes through the selector.

 

Ok, the gauge does show difference in the tanks.

After I removed the front tank, bench tested it (it worked), I checked the plug for power. I turned the key on, turn the switch to front tank, and checked the plug.

My multimeter showed I had fluctuating power. What could that be caused by?

 

Damned if I know, but you seem to have the same problem (fluctuating power) as Opossum.
You might want to check his threads.
You're both up in the PNW.

https://www.ford-trucks.com/forums/1...-handling.html

https://www.ford-trucks.com/forums/1...umps-quit.html

 

thanks!

Actually, I had come across those posts via searching after I posted my last pot. I had just tried the fusible jump suggestion, but didn't see anything that looked right.

Im gonna try the inertia switch jump, but I'm fairly certain the IS is fine. But who knows, I thought the fuel pump had died but I got it humming perfectly fine by bench testing it.

As much as it will make me look like a goober, I really wish this was a simple quick easy fix, so I can sell the truck faster (I need the $$ more than i need a 2nd vehicle).


reread the thread you linked:

AAAAh..starter RELAY...dur...back to the truck I g

 

Looked at the starter relay, didn't really see any blue wires, but there are 2 fusible links. Not sure which one is for which. One is dark green, the other is yellow.

 

I figured out what line went to the Fuel Pump relay (or whatever it's called, it's a yellow line). I tried to jump it, and it didn't seem to do anything.

If I disconnect the line from the battery to the starter relay, there a noise near the carb, and the relays click. I have power TO the relay, I know that much.

I switched the relays (the new one and the old one) and it didn't make a difference.

Keys were in the correct position too.

 

Just because you hear the relay "click" doesn't mean there is power going to (or through) the relay.
Pump power is provided by one circuit, relay pulldown by another.
'Subford' says the diagram I linked in the other thread is correct for 1983, so it *should* reflect your wiring.

 

Thanks, I'll recheck again. (the issue I have is that the person who owned it before me obviously did some re-wiring, so it doesn't look exactly the same)

if it's the link in this post : https://www.ford-trucks.com/forums/1...l#post12307537

I can't seem to get it to work.

wait, all the sudden I can get it to work.

 

This diagram shows the selector switch getting power in start or run from the #15 fuse.



When 'front' is selected the selector relay closes, and switches to the front tank. (rear is default)
The inertia switch provides pump power to the safety relay at all times.
The oil pressure switch closes the safety relay and sends pump power to the selector relay.
When the starter relay (solenoid) closes, it provides power to the selector relay by way of the pink/black 'bypass' wire spliced between the safety relay and the selector relay.

With the key off, do you have power at the yellow wire of the safety relay?

 

I'll have to re-check that in a bit, but right now i'm not sure. I think it had power regardless though (if you're talking about the relay? thats the only yellow one I can think of right now).

A friend of mine thinks that the inconsistent power @ the fuel pump could be a grounding issue. I think I saw it once in a manual. either that or it was for my volvo)

 

I just replaced the pump in the middle tank as they call it. My problem was the truck would starve for fuel at higher rpms. When i pulled the pump out I put it in a bucket with a little gas in the bottom. The pump will not run until you crank the motor, I assume because it needs oil pressure. Anyways my pump ran fine but it was squirting fuel out of the bottom of the pump. I guess a seal went bad or something. Put a new pump in and it runs like a champ again. This is on my 84 f350 with a 460.