Hello, I have a 86 F250 4x4 diesel that the fuel guges work, kinda, but the indication is way off. It tends to display empty before I even get to 1/2. I currently have the tank switch disconnected and direct wired the front tank. If I ground through a test light, it reads 1/2. The reference from the guage pulses the light, is this normal? I run a lot of distance, so it really is not pleasant not having the guages working right. I just recently purchased this truck, so I don't know a history on it. Any help would be greatly appreciated, Thanks!

 

This is a common problem on these trucks. Do a search and you'll find tons of info. I believe it should pulse the light, if I remember correctly. If you have a trip odometer, I would just use that as your reference (much more trustworthy than a gauge!).

 

You will have to go to the top of the tank, and find the fuel guage wire. With the truck key on, ground the wire. The guage should go to full. Then take the wire off and let it hang in the air. The guage should go to empty. If it passes this test, then your sending unit in the tank is bad.

 

I'm currently running direct at the tank switch connector. I wasn't sure that grounding the gauge was the way to go, will go ahead and try that. They work kind of, just lie to me. Unfortunately, I do not have a trip odometer, would love to have one, I haven't seen one on that year as yet. I grew up on my dad's 84 extended cab, and believe it or not, his sender outlasted the tank. We never changed the senders on his truck, and it is approaching 300,000 well abused miles. It was bought new in 84, and still is operational, even with his lack of maintenance. I do track mileage, but there is always that time that something has changed, and I get burned for it. I just got this truck about a week ago, for a very nice price, I might add, even though I have to fix a couple things, so I am learning it's behaviors as yet. But I couldn't argue with $1850 for a fresh rebuilt 6.9 4 speed 4x4 with minimal rust on cab and clip, and the box is repairable, and does it's job without any repair. I needed a truck that could handle a trailer and do it's normal work as well. Sure I'd love to have the newer stronger diesels, but I grew up with a 6.9, so I have no problems running them now. Thanks for the advice!!!!

 

Just a side note. You can get a variable resistor, jumper any gauge to the resistor, twisting the **** in either direction and the gauge should move top to bottom. A bad gauge may get stuck.

 

It might even be your voltage regulator for the guages behind the guage cluster them selves on top of the instrument panle above the speedometer as far as a trip milage odemeter if you have a local junk yard that you can acess and go look around id go there i got a tach and trip milage odemeter for my 84 F250 with a 460 out of a bronco there the same thing for a diesel to the speedometer that is the tach wont work in the diesel but ford dose make a tach for the diesels i have seen them and a guy in town here has one with one a 86 extended cab all you need off the junk yard bronco or if you can find a junk yard diesel in there with that set up be even better but all youd need is the speedometer and the out lens as it has the button to reset the miles but becareful some are junk i had got one and it was 10 MPH off when i was doing 65 was really doing 75 but i cuaght that fat with the help of the tach and knowing what it should of been at so i got anohter one along with the tachs for spares as well also if you want id look on ebay last few weeks ive seen 2 insrument clusters for diesels with the tach set up there worth having plus they look cool good luck with your truck