The gas gauge on my '82 D150 has been acting goofy for the past few months, and I'm really not sure where to begin looking. (I'll admit; I haven't even torn into it yet, but I'm hoping to find most of my pitfalls before I begin.)

When you fill the tank up, it goes to F, no problems. It stays there until you burn about 4 gallons (20 gallon tank), and then starts varying gauge level w/ engine RPM, acting kinda like a tach. Finally, when you get it down another couple gallons (14 gallons left) it will read dead empty, and stay there until you run it out of gas (don't ask how I know).

Initially I assumed it was a bad gauge or sending unit, but the more I thought about it, that wouldn't explain the variance w/ engine speed. (or would it?) I have an aftermarket volt gauge, which reads a constant 14 volts. (stock ammeter has never worked).

Does it sound more like I'm chasing a sender/gauge problem or an instrument voltage regulator problem?

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Used to own:
'82 Dodge D150
Erson 270 Cam, O/S valves, mild port work, ~9.5:1 compression

Currently fighting with an '85 VW Cabriolet

My other passion

I had the exact problem on my 87 ramcharger. I installed a new sending unit because the old one rotted out. Once installed, the gas gauge started acting goofy. I pulled the tank again thinking I got a bad sending unit. I checked the operation of the sending unit, wire connections, wire resistance, & gauge voltage regulator. All checked out ok. As it turns out, I had a spare gas gauge and wired it up outside the gauge cluster and the problem went away. I say check the gas gauge first before pulling the gas tank.Could save yourself a ton of time & work. I learned the hard way.

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I just went through this on my Valiant. Go to the allpar.com site. They have a great article on this issue. Make sure your sending unit is grounded to the chassis with a wire from the fuel pipe going into the tank. Check the 5V voltage regulator located, in my case within the fuel gauge, or the external one mounted on back of the gauge cluster on later vehicles. If your temp. and alt. gauges work OK then the regulator is probably not the issue. Pull the sender back out and bend the tabs and remove the cover protecting the variable resistance wire and wiper. make sure the wiper makes good contact with the resistance wire and clean the resistance wire with a rag and simple green or similar. As you move the float lever up and down the resistance should vary between 10 and 80 ohms approximately.

The ground was my main problem. There was no wire on mine and I just assumed it got ground from the tank and strap. The gauge didn't work at all in my case.

I've seen some tank sender grounding schemes that use a wire and two clips to bypass the short rubber hose connecting the sender/gas outlet pipe to the car's metal fuel line. Theoretically this should work. I suppose it usually does for most folks, but I just don't trust it. Too many places for a loose contact or corrosion for my taste.

I spent my career building and fixing radio stations, and radio stations and cars certainly are different animals. That said, I have seen more intermittant and just plain wierd problems in both (and other electronic applications as well) fixed by just making sure the ground side of the circuit was complete, intact and solid.

When I install a gas tank sending unit, I run a 12 or 14 gauge green wire from the sender to the frame of the car, and I clean the connection points to shiny bare metal and apply some grease or non-hardening sealer to the joint to keep air and moisture from getting in and causing corrosion.

OVERKILL, you say??? DARN right, I reply! Overkill beats the snot out of no kill (or ever more frustratingly) INTERMITTANT kill.

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'64 Dart GT convertible, 64 Dart 170 2-door post sedan in faded blue and rust (the Az Dart) & a sixty THREE Dart 170 2-door post sedan in faded blue and rust. (future project)
Early Dart Disorder (EDD) is real, and I've got it!

Makes a whale of a lot of sense to me, especially since I just found a bad connection on mine.

I soldered a stranded 12 gauge wire to a small hose clamp and then tightly clamped it to the fuel tube coming out of the tank (part of the sending unit). I crimped on an eye to the other side and attached it to a bolt in the frame holding an axle snubber after cleaning mating surfaces. Yes, bad grounds will come back to HAUNT you.