How do you test the fuel gauge on a 77 F 250

 

Ground it out, if needle pegs full it's good.

 

X2. Get under the truck and unplug the wire that goes to the sending unit. With the ignition "on" ground the wire. The gauge should swing all the way over to "full". If it does, either the sending unit is bad or the sending unit has a bad ground connection. You'll see a second wire for the sending unit, this short wire connects to the crossmember right in front of the tank, this is the ground. Take the screw that connects it to the frame out and try cleaning the contact area and reinstall.
If you ground the wire and the gauge doesn't move then either the gauge is bad, there's a problem with the wiring or the IPVR (instrument panel voltage regulator) is bad.

 

I'm assuming this should be the same setup on my 79' F350. I have the same issue, gauge appears to not be working.

How do you get to the IPVR?

 

The set up is the same.
The IPVR is on the backside of the instrument cluster. To get to it you remove the cluster. Its attached by a single screw and has a plug that looks like a 9V battery connection.

 

Thanks Mike!

What is the easiest way to remove the instrument cluster?

Do I need to remove the dash cover? Does that just pop up?

 

Just a side note, 99.99% of fuel gauge problems have to do with a bad sending unit or a bad ground out at the tank. It's very rare to have to replace the gauge or the regulator.

You don't need to remove the dash pad to take the cluster out. The dash pad is attached by several hex nuts along the bottom of the top-side of the dash; they're not easily accessed.

You have to take the dash bezel off; which means removing the wiper and headlight *****. The wiper **** is held on by a small tab behind the **** that gets bent forward, allowing the **** to come off. The headlight **** is removed by disconnecting the negative battery cable (to kill the headlights with the switch ON), turning the headlight switch ON, reaching up underneath to press a small button on top of the switch, holding the button and pulling the headlight **** shaft out. Then you can remove the screws that hold on the dash bezel - with it partway out you'll need to reove the "wiper/lights" light on the back of the bezel.

There are screws that hold the cluster in - you'll need to remove the speedometer cable and electrical connector. I might have missed something - others can fill in.

Again though, I wouldn't start here because they are very rarely ever the problem. You should eliminate the likely and obvious sources first per the instructions in this thread, and yes it's the same setup as your F350.

 

X2. If the other gauge(s) are okay the IPVR is working.

 

So the guage is working.

Now I need to get a sending unit.

Any suggestions on where they may be available? It is the front gas tank on my 79' F350.

 

Fuel gauge sender
D9TZ-9275-A
Fits:
78/79 F150-350 regular cab 4WD
use with plastic midship tank
Green Sales, Cincinnati, OH has 2 (800) 543-4959
Prepare yourself for some sticker shock, last list price was $122.03, dealer cost $73.22.
I'm not sure whether these are still available aftermarket or not.

 

thats one part that no one seems to make "after market" is for the front tank tons for the broncos,and all f series with the rear tanks even then with a jbg new sending unit,wireing/ground/gauge teasting good it still reads wrong next time i will use a marine unit w gauge seen them before on these trucks need some work to mounht the senders but they work good

 

Thanks Mike!

I found one on LMC for a 3rd that price. Seems fishy to me.

Anyone tried the LMC sending unit for front tanks?

 

• Months ago my gas gauge stopped working after I had excess pressure built up in my tank. I figure it messed up the sending unit so I dropped the tank and changed it. The gauge started working “sort of”. It would go to full and stay there for about 30 miles then would drop down quickly and show empty after about 60. I figure I had a bad ground and I knew that one of the posts in the fuel gauge itself was loose so I put in a new gauge. It had no effect. So I pulled the ground wire back at the sending unit and cleaned a lot of grime off the frame and reinstalled the wire. When I turned on the key to check it I think I heard a strange noise and the gauge did respond at all and now the temp gauge isn’t responding either. I know they are on the same circuit board but so is the rest of the dash cluster Any ideas?

 

When the ICVR (Instrument Cluster Voltage Regulator) fails, it affects the fuel, temperature and oil pressure gauge (if present).

Oil pressure and amp gauges were an option, so not all trucks have them.

 

ICVR seems likely to me. I’ve ordered a new one. Thanks