Not getting gas to the carb on my 84 F-250 w/ 460 and 105k miles
(on chassis).
Had intermittent stalling and finally complete failure.
No noise coming from in-tank pumps, so it "smells" like
something in the electrical dept.
Tank selector switch clicks back and forth; fuse OK.

Is there a relay or inertia switch somewhere in the system on
these older trucks?

(I see in a recent post the culprit was the ignition switch, but
engine cranks over just fine)

Any suggestions?
Thanks,
Robb

 

Yes there is, there are two relays, one oil pressure switch and one inertia switch on the toe board passenger side.
Here is a diagram of your system.

http://i54.photobucket.com/albums/g91/subford/Fuel/1983FuelElCT-1.gif

 

Thanks very much, Bill. I will check out these items, too.
Amazing how complex the electrical circuits are, even in
these older trucks!!

 

Bill (Subford):

I was able to trace most of the wiring down and determine if they have juice.
All seems to be OK except for the brown wire running from the tank pump to
the selector relay (brown wire on right side of your great diagram). Testing
it at the left side firewall shows no power. I need to test all the way back to
the tank pump, but am not sure where the relay is (Assuming its not in selector valve itself).
Also, is the ignition switch harness exposed at the bottom of the column to
test those posts?

Thanks, again, in advance,
Robb

 

If you have selected the rear tank and the Brown wire is not hot then either the relay is missing or power is not being feed to the relay.
You need to find the relays and then check them out while it is running or short the plug on the oil pressure switch to test it.
I am not sure what wires you are looking for at the bottom of the column.
The Relays would be in the engine compartment and the inertia switch in the cab.

 

I had the exact problem on my '83 f250. It was indeed the transfer relay completely full of corrosion. It is located on, or near the firewall beside the power brake booster.

-doug

 

Thank you, gentlemen. I appreciate the help.

Will see if I can get this problem resolved next week when I get back
into town.

Robb

 

There seems to be a lot of this going around ...

Thanks for posting the wiring diagram Bill. Lots easier to read than the one in my Haynes manual.

Coming back from a 2000 mile trip to southern Colorado this month I encountered fuel problems about 150 miles from home down in southern Minnesota. Clyde just seemed to run out of gas with fuel showing in both tanks. I clipped a jumper between the + battery post and the "crank to start" citcuit that runs from the starter solenoid across the radiator support (something you other sufferers might want to try) the fuel pump hummed to life and I drove her home normally, tank changes ect., thinking it was the oil pressure switch that had failed.

Hooking the pressure sensor switch up to an air pressure regulator it turns on promptly at ~10 psi and off below that. Doesn't seem to be a problem. Jumping the pressure switch changes nothing. I have power on both sides of the inertia switch and to the pressure switch.

Cleaned up that relay corrosion a couple years ago when I had fuel pump problems. It was very bad! Another thing for sufferers to check out. Swapped the relays (both relatively new ... I understand they seem to have a high failure rate though) to no effect. The wiring diagram for the relays seems to be a problem since using a continuity testor I can't seem to tell which terminals are the actuators and which are switched. Anyone have a terminal diagram for those? There is information available on the net for changing over to Bosch relays but I haven't gotten to that point just yet.

Tank switching and pumps seem to operate properly when "jumpered" so I've ruled out everything downstream of the power supply circuitry like the dash switch, tank selector valve on the frame and the pumps.

 

Maybe you could draw the relay wiring.
Does the relay look like this?

 

Oooooohh!!! You're GOOD!

EXACTLY what I'd been looking for!

There are two relays mounted together in the same area below the booster. Do you know what the other one operates? Looking at the whole truck schematic singling out the second one seemed to be harder than I thought.

It's my day off today and I WILL be spending some time with this.

Thank you!

 

The two relays are the "Tank Selector Relay" & "The Fuel Pump Cutoff Relay". Look at the Diagram link I posted in Post #2 above.

 

Aaaaaaaaaaaahhhhhhhhh ha! [speaker slaps forhead with palm of right hand]

I had in my head that that was something other than fuel system and the relay for tank switching was on the frame. It all makes more sense now.

Checked the relays again with the testor after I knew what I was looking for ... thanks again ... and found what I thought was a bad relay. Tore it apart and it was pretty heavily corroded I know I've replaced both of them but these have a reputation for failure and I guess mine failed.

Called my Parts Department buddy at the dealership I worked at and had him order a couple for me. Because I'm "still family", having worked there for more than ten years, I still get a healthy discount on both parts and labor so I take advantage of it.

Installed the new relay with a jumper on the already proven pressure switch and the relays clicked and the fuel pump started hummin'. I will now carry an extra relay as I already carry an extra fuel pump.

Thanks to Bill and all the other contributors! I hope the others on this thread can report similar results.