The fuel gauge in the crewcab is all twitchy. It twitches between the range of a 1/4 tank, but never the same distance. Seems to twitch about 1/8th of a tank on either side of the actual fuel tank reading.

The fuel gauge also twitches when you apply the brakes, turn on the lights, and hit the turn signals in either direction. I figure it has to be a ground issue. But I have cleaned and redone all the grounds. Even pulled the headlight switch to double check the ground on it. Checked the grounds up under the dash on the cad plated bracket. And even added a secondary ground from the motor to the firewall in the engine bay. I really can't figure out what is causing this problem.

This is the complete 93 wiring from my donor truck. Everything worked fine before I pulled it apart. I have tried to trace the wiring in the FSM, but it goes into so many splices I can't track down where the wiring goes.

Any thoughts?

 

Probably a failing connector crimp from corrosion. Have someone watch the gauge while you systematically molest the wiring.

Another common fault that often shows up as weird intermittent faults in sensor wiring is the damage caused by corrosive chemicals gaining entrance to the copper wire through probing pinholes.

Another common cause of this sort of thing is a bad solder connection on a printed circuit board. Under high magnification, it shows up as a barely visible dark ring in the solder puddle around a pin. Again, you should be able to track it down by molesting the suspected area while watching the gauge.

 

Probably not your issue, but on my Ramcharger, whoever restored it had the gauges out, and when they put the voltmeter and temp gauge back, they didn't have the screws holding the gauge to the housing tight.

Believe it or not, that was all it took to make them act sporadic.

I tightened the screws up so that the gauge was setting against the plastic, and haven't had a single floating gauge since.

 

Thanks for the advice.

I did have all the gauges out at one point. Maybe I did not get the fuel gauge to sit tight? I will pull the gauge cluster...again...and check the pin for the fuel gauge, and that it is sitting tight and clean against the connections in the gauge cluster that attach to the circuit board.

I did have to solder in 16" of wiring into the main chassis wiring. I did mechanical connector, then soldered each side of the but connector to the wiring, then di-electric grease and finally shrink tube to protect it all. I will go under and manipulate the wiring at the extension and see if anything changes.

 

OK I got it all figured out this evening.

I pulled the dash cluster and cleaned and inspected all the connections on the circuit board....everything looked good. Pulled the fuel gauge and re-installed. Tried it back in the truck...same thing, gauge pegging all over the place.

I decided to swap in a spare junkyard gauge cluster I had in my spare parts inventory. Fuel gauge worked perfectly. So I pulled everything again and swapped the working fuel gauge into the original cluster. Plugged it all back in and it works fine now.

So guess it turned out the gauge was the culprit. Sure glad I had that spare gauge cluster...made diagnosis so much easier...and repair that much quicker and cheaper.

 

Wow, glad you got it figured out, and I need to keep that one in the back of the old noggin.

Wonder if there is an internal ground in the gauge going south?

 

Moved the truck around this morning, and the gauge doesn't jump around like the other one did...but it does seem to swing a bit more then it should....IMO.

How much movement on the gauge should there be while the truck is in motion, going up hill and down? I'm seeing at least 1/4 tank worth of movement.

I'm concerned that there is another issue that might have fried the other gauge, and this one might go the same direction eventually too.

 

Not sure how much baffling you have in your tank, but without much, 1/4 tank isn't uncommon.

I wouldn't get too excited unless it starts doing it not moving.

 

When you rear end a dump truck because you were studying the fuel gauge instead of the road, it'll seem like the twitchy gauge was a small problem after all.

 

There is no unusual movement from the fuel gauge in mine, regardless of road conditions...Mark