1985 F350 Fuel cut off switch issues
 

On my F350 460cid 4 bbl carb. the fuel cut off switch button is poped up. I pressed it down to reset it and nothing happened. It still stayed in the upright position. I know very little about wireing, I can kind of read a diagram just enought to get my self in trouble. When I was under the truck following the fuel lines back and the wires, I noticed that some hilljack decided to splice in to the wires to the conjunction box where the fuel lines go. There is return and feed lines going to front tank and another set to the rear tank and another set going to the engine. Well the wires that were spliced in to were just stripped back and wrapped around with another wire for the trailer breaks/lights. I have gotten rid of the wires they put on there and the factory wires are still good. When I switch the tank slector from front to rear I can here something clicking under the hood (guessing its a relay or something). I also do not hear the pumps running either front or rear. So any help with this would be greatly appreciated.

Also the fuses in the fuse block were all good non of them had been blown

The "conjunction box" under the drivers side mounted to the inside of the frame rail is the "Fuel pump selector switch." Someone boogered mine up too, but its fixed now. The power for the fuel pumps goes through this, so if the wiring is wrong.... the pumps might not be getting juice.

Do you have or have access to a test light?

How far is the fuel reset button sticking out? It may not actually be tripped.

Another thing to check is the "Low Engine Oil Fuel Shut Off." It is a sensor just below the oil pressure sensor between the motor and the firewall (under where the EGR valve is). Mine is bad and I had to unplug it and "jumper" the plug in with a piece of wire.


Yes, the clicking is the relay on the driver side inner fender well. Normal.

Sorry for the bad picture Here is a picture of the sensor. Its the black thing pointing towards the firewall under the silver cylinder (oil pressure sending unit)

http://i650.photobucket.com/albums/u...-16-05_150.jpg

And here is a picture of how I have mine jumpered. This end plugs into the above picture.

http://i650.photobucket.com/albums/u...-39-52_173.jpg


You might want to try this regardless just to be sure this is not killing your power. Then once you get it running (if this is not the problem) you can re-connect it to see if your sensor is bad or not.

Awesome, I'll try the jumper wire on the oil sending unit when I get home frome work. And I do have a test light.

The switch under the dash is out all the way I do believe but then again I dont know how far it really comes out.
And the egr plate isnt hooked up anymore some one slapped a 4bbl holly carb on there so I dont know it that has anything todo with it either, what I did to get it to run was hooked a electric fuel pump up to the fuel line going to the carb and hooked the wires right to the battery. Only so I could get it homeso I know it does run by rigging that up. But I will try thr jumper when I get home. Thanks again

I am not really sure how far the reset button sticks up when it is tripped, but I know mine is down and I can still push it in about 1/8" or so.

Do you know if the fuel pumps actually work? Does the fuel gauge on the dash work properly? Test light in the three prong outlet right at the pumps will tell you that. With a good ground, one prong should light up (thats the power to the pump), one prong should flash (thats the gauge sending wire), and one should not light up (ground).

Yes the fuel gauge does work, I have about 1/4 tankin the front and the rear is empty. Thats the other thing is I dont actually know if they work or not I was told when it got parked bout 6 months ago it ran just fine, well Ive heard that a number of times. Im gonna be optimistic about it and say they do work but not right now bc of that cut off switch or the low oil sending unit.

This might help too...

http://i650.photobucket.com/albums/u...ingdiagram.gif

I tried the jumper wire and still nothing.... I traced the wires over to the brain box and found a 4 wire connector that 2 of the 4 prongs blink with a test light and the other 2 stay lit up, with the key on the on positio.

Brain box? You shouldn't have a brain box on an 85 460, it's straight forward carburetor and Dura Spark II ignition. The ones that blink should be the fuel gauge wires, pre-89 trucks use a regulated 5v supply that is generally done by a heated thermal regulator which will "pulse" whenever the ignition is on. The gauges are a bimettalic heated system. This is the reason for the slow, pulsing response when first turned on. The ones that are staying lit up are probably the wires for the tank selector valve motor.

The brain box im talking bout is just a gray box on the driver side wheel well... I did get under there and pulled the plug to.the tank slector, out of the 5 wires got one to blink one to stay on and the other 3 didnt do anything, im guessing on is ground and the other 2 are for the rear tank when its switched over to the rear. My only guess right now is its that stupid cut off switch under the dash

Pull the plug and bypass it, it may just be gone with age. The gray box is your ignition system, no "brain", it should have two plugs, 2 wires and 4 wires and has nothing to do with fuel delivery. Try cleaning the wires at the plug so you can see the colors, you only need to find one to figure out which is which from the diagram. I would bet the one that blinks is yellow with a white stripe and would be pin #4. the one that is on should be either #1 or #2. You probably need to locate the tank selector relay as it is what controls which pump is on. If you take the blue fusible link from the small pin on the starter relay and jump it to 12v it takes the inertia switch and the fuel pump cutoff realy out of the circuit. If you can get either or both pumps running that way you at least know they work and can start back from there.

Ill give that a try. I did pull the cut off switch off and ran a jumper on it and still nothing but I did use a testlight with is disconnected and key on got one to light up other nothing, pluged it back in tested again and both terminals lit up. I donno I hate wiring, ill try what you posted and if that doesnt work im just going to take it some where or have someone that knows something about wiring come over and help my dumb @$$ out.

Don't feel bad, a lot of very good mechanics are scared to death of wiring and generally can't diagnose it. I got real good at it working on British cars (Joe Lucas, Prince of Darkness).

Lol thanks for the help and words of wisdom!