I have an 84 f-250 6.9l.

<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>

The fuel tank selector switch got to where I was having to switch it a few times to get it to switch. Now it is stuck on the front tank and wont switch to the rear. I’ve got 12V at the plug going to the back of the switch but don’t know how to test the other three wires, one of which goes to ground.

<o></o>

Is there a relay? (My manual doesn’t have this circuit.)

Is the switch a common problem?

How can I test it?

 

84-86 is the same so you don't have an electronic solenoid like the 83 and before does which I wrote out below. Our tank solenoids are done by pressure from the intank pumps.

Does your gas gauge swap when you switch tanks? If not, then your switch is likely bad. If it does switch, then your in tank pump is probably bad.

To check switch though......

Yellow/White wire comes from gauge and goes to switch to feed either Yellow/light blue for rear tank or Dark Blue/Yellow for front tank.

Pink/Black comes from intertia switch to feed pumps selected at switch by either Brown/White wire for rear tank or Red wire for front tank.


================================================




EDIT - Brain Fart, I wrote this for an 83 instead of an 84 but will leave this part here for anyone else that has an 83 and wants to troubleshoot............



According to my diagram for an 83,

The Brown and White is what switches the valve assembly so it goes to the actual valve assembly. It gets it's power from the Red wire on the other side of the switch.

Red should be the same as Brown/White when on Back tank and open circuit when on front tank.

Yellow and white goes to your gas gauge and gets it's feed either from Yellow and light Blue when on rear tank or Dark Blue and Yellow when on the front tank.

My diagram shows no grounds at switch. All grounds are at the units themselves elsewhere such as Fuel gauge, sending units and tank selector solenoid etc.

I am using my Haynes for this reference.

Good Luck,

Lee

 

I have checked my switch and it's ok. My wife reminded me that we were on the side of the road for this before. They remember that stuff! Seems like I was taking off the switching block / valve to look at it and she called out to tell me it switched. Maybe I've got a bad conection at the valve, dunno.

What does this mean?

No, the gauge doesn't switch, and if it does the same as before this means the tanks don't switch over either. But I've taken the switch out of the dash and it seems to be functioning.

Four wires / terminals, red=12V, orange=open, brown white=open, black=ground.

When on the front tank, orange & red are closed and brown & black are closed. When on the rear tank, red & brown white are closed and black and orange are closed.

The brown and orange both ohm out like they goe to a coil, but I'm not sure whats at the other end yet.

Is, there a relay in the circiut?

 

1. There shouldn't be ANY electrical connections at the switching solenoid on an 84 truck so you must have an older setup or something according to my book. Maybe someone else with an 84 can chime in as I have an 86 and my setup is per the manual. ( I too have troubleshot this on my own truck)


2. As I said in #1, there isn't supposed to be anything electrical on the 84-86 trucks. The switch in the dash turns off and on the in tank fuel pumps and the pressure is "felt" at the switching solenoid to rotate the switch the feed from the correct tanks. It all just kind of swivels freely in there with no pressure at all and whatever tank has the pressure coming out moves the solenoid to the correct position. When I had problems, my front tank pump died and I was feeding off of both tanks as the switch just kind of flopped back and forth. Before that, I had a bad hose from my rear tank and I couldn't get anything at all out of it and could only run from the front tank. You have to have good fuel pressure from the tank to get the solenoid to switch in the later trucks and there shouldn't be any wires at the actual solenoid.


3. If the fuel gauges aren't switching, then I would have to suspect the switch. Maybe the contacts are dirty and making enough of a connection to ohm out OK but not enough to carry the required current?? That is a weird one. Not sure. WIsh I could see it myself.

4. It isn't looking like your wires are matching either of my diagrams for 83 or 84-86. I show no ground and I show Pink/Black where you have an Orange it appears to me. This makes it hard for me to figure out.

5. My book shows no relays. Hot power to the inertia/rollover switch, to the dash switch then straight to the fuel pumps on 84-86 trucks and to the switching solenoid on older trucks.

Sorry I couldn't be of more help.


====================

OK, Edit again - I screwed up. On the Diesel, they do have a black wire on this switch that is not on a Gas model.

Give me a second and I will try to decipher all this

 

OK, I am getting waaay confused here as my diagram has switches all over depending on engines and other variables. I don't see a 6.5L at all so here is the 7.5L diesel combo as best as I can tell. PArdon the drawing but I am no Microsoft Paint expert and my computer with a scanner is down right now.......