81 f250 fuel gauge not working. The person who had it before me did some pretty crappy work. So i went back over it today. Now i pulled the fuel sending unit to see if it was moving and it was. Its a new unit by the way. Its a single tank setup. But was set up for 2. But again the guy before me removed it. I was just looking over everything and i found another connector with 2 wires. The original one i was using had 3 wires going into it.
so what could it be ? Just the gauge ? Is it hard to wire in a aftermarket one ?

 

Ok the truck HAD? 2 tanks but now has 1?
What happened to the tank switch on the dash?
What happened to the duel take switching valve on the frame rail?
What tank do you still have installed in the truck?
Did you check the sender with an ohm meter to see if it was working?

With that information maybe we can help you a little easier on what to look for and do?
Dave ----

 

Still has the tank switch in dash. I dont k ow about the tank switch on frame. And its the rear tank that is on there now. I have to test the sending unit tomorrow

 

What happens if you flip the dash switch does the gauge do anything?
That switch on the dash is to switch ports on the valve and senders in the tanks.
If the wiring is good from gauge to the dash switch to the switch valve one of the wires should blink if you use a test light on the wire.
That blinking wire needs to go to the sender in the tank and sender needs a good ground.
As a fast test to see if that blinking wire moves the gauge ground it and see if the gauge moves.
DO NOT ground wire too long as you can hurt the gauge.
Dave ----

 

Ill have to switch the dash switch and see what happens

 

If I under stand how it works is from the IVR thru the fuel (oil & temp) gauge(s), thru the dash switch, thru the switching valve on the frame then out to what ever tank sender was picked by the dash switch.


The IVR sends a pulse of volts to maintain the (think) 5 volts and why when checking with a test light you will see it blinking.


I think there is only 1 wire from the dash switch to the switching valve where it splits going to each tank sender.
Wait depending on year & valve there could be 2 wires, 1 from each tank to the dash switch where it then goes to 1 wire to the gauge. Think that is how my 81 is as the switching valve does not have any wires to it.


I do know the wire to the sender should blink when using a test light.
Dave -----

 

Being the truck is so early, it probably did not have the motorized 6 port valve on the frame that switches the sending units. The sending unit switching was done with the dash switch. Only the trucks with a fuel return system had the 6 port valve and that did the sending unit switching on those trucks down on the frame.

He probably had the simple 3 port valve on the frame that only switched the fluid lines from tank to tank. The dash switch should be double pole, one side sends power to the switching valve on the frame, the other side switches the sending units.

 

Yea when I got thinking how my 81 was setup and not knowing his year without going to first post I added the second part of the switch doing the gauge switching.


So it could be the switch is on the wrong tank or be a bad dash switch not sending power to any wire/tank or bad gauge not sending power to the switch.
I would flip the switch and see what happens. If nothing then use a test light on the wires at the senders and if nothing work my way back to the switch/gauge.
Dave ----

 

Which is why I usually do not chime in when people won't take the time to put the specifics about their truck in their signature. I cannot keep the info in my head, and can't spend the time going back to another post to find it.

But, hoping the OP will this time, I'll agree that the first test should be to put a test light on the sender wire. If that doesn't work, flip the switch and try again. If there no pulse then we've cut the suspects in half.

 

I have found if they check in on a phone the sig does not show up so he may have it but posted this on his phone.
Dave ----

 

I finally had to wire around my dash switch in my old 1980. There for awhile I could flip it up and down rapidly and it would work for a few months. In then got to where it would not work at all, the dash switch finally went bad and I could not get it working again.

 

Dave - If you use your phone you have the choice of using the mobile view of the site or the full view. The mobile view is what doesn't show the sig. The full view does show the sig. So it is up to the user which way he/she wants to post.

Personally, I will not use the mobile view, for a number of reasons, and the signature is one of them. And, I won't go looking for a poster's information. If they don't provide it I will move on. Their call.

 

I know of the mobile or desktop view but only found out a few weeks ago.
On other sites the desktop view is funky and why I don't use it.
If I ask for information when on my phone I will use desktop view.
Dave - - - -