All right, another fuel gauge question.

Fuel gauge reads empty all the time. Rear tank nearly full @ 22 ohms. Front tank nearly empty @ 133 ohms.

Gauge will drift up to about 1/3 when ignition is off. When it is on it pulls down to empty.

Pulled connector from selector switch. Yellow wire from instruments has ~11.5 volts open circuit. Connect it to either tank and gauge pulls to empty. Leave circuit open and gauge drifts toward 1/3. It should peg out but at no point does it move upward on its own power. Just the same drift as with key off.

I presume this means the gauge itself is no good, if so, how much needs to be replaced to fix it?

Thanks

 

On this era truck if the circuit is open it will read full. If it is shorted it will read empty.
Fuel Level Sender & Gauge Wiring for '92-96 Broncos ('87-96 F-series & Bronco similar)
IF THE IMAGE IS TOO SMALL, click it.

Sender Range: 160 (full) - 16 (empty) Ohms
A gauge that pegs past full indicates an open circuit on the Y/W wire (broken wire; unplugged connector; corroded terminal; varnished sender; F-series - selector switch or connector faults).
A gauge that pegs past empty indicates a short to ground on the Y/W wire (pinched to the frame, body, or dash supports), OR a sunken float.

 

Wire is not grounded, ohms out good to both tanks reading from the gauge.

Tore apart the cluster this morning. Found some poor connections but not the cause of the problem. Soldered the fuel gauge tangs to the PCB (see them and you will know what I mean)

Removed the gauge itself and hooked it up with alligator clips to the vehicle wiring. Same behavior. Squeezed the gauge with my fingers and it began to read correctly. Put it all back together and it is still broken except after driving a bumpy road it began to work, first time in a long time.

Ordered a new gauge pair (comes with oil also) so we will see when it arrives. Obsolete from Ford, had to dig pretty deep but I found 2 for sale.

I have seen very little reference to a bad gauge itself so it must not be a very common problem.

 

Got the new gauge pack/pod/pair finally. One of two I could find in the whole country. Obsolete from Ford although I am sure there are plenty of good junkyard units because nobody else seems to have this problem.

Easy to replace, just pull a couple layers of dash including the clear plastic screen, unplug the old ones and plug in the new ones.

The new gauge moves a lot quicker/less damped than the old one. Now I get to watch the fuel slosh around as I go on hills and corners.

 

OK, my turn. Very similar issue on an 1989 F350 460 w/manual. Rear tank was removed by PO and those hoses are well wrapped in plastic.

Issue began with gauge getting stuck at about half full. I had just filled the truck a day or two before and hadn't driven it very much since. So it should be at Full or close for sure.

So once it started misbehaving I was watching it more. It didn't change much going up & down hills, around corners, etc. I started using the truck more frequently specifically to see what might be going on with the gauge. Eventually it began moving - but it fluctuated wildly between Full and 3/8 or less. Not momentary fluctuations mind you - it would move and stay in that area. Then it would do it again and land on a different fill level. I knew I had used a fair bit of gas by then and went to the station to fill up.

What was REALLY odd happened next. The pump at the station kept burping and popping off the auto-fill latch. Strange, I thought, but it must be the station tank in the ground was getting really low since it can make the pumps do that. I had only put in about 2 gallons or so - it couldn't be full yet.

So I kept squeezing more fuel into the truck, and then it squirted gas back out. (!?!??! WTH?) Thankfully I was fueling by hand and it was negligible but it was definitely acting "full"

I figured something inside was getting stuck in a "high fuel level" position or a valve door was stuck shut. There was no way the truck was full. I tried once more just for a split second - same deal. It was stuck.

I needed to keep using the truck, so I started keeping a 5 gallon can full of gas in the truck just to be on the safe side while using it. Same problem persisted - gas gauge acting very funny. I put more mileage on doing cross-town deliveries etc. When I was almost done, I stopped for gas again.

It started to behave the same way - not letting me put gas into the truck. So I pumped for a couple seconds at a time, and repeated that about 10 times on purpose. Then tried again. I think I finally opened something up or otherwise freed its movement inside the tank, because it then took nearly a full tank.

Clearly something is goofy. What is it?

 

About 20 years ago I had to take a gas tank out of a 1989ish E-350 van which was full of fuel (of course) and it had some plastic ping pong ball thingy at the end of the filler, either to prevent theft or rollover protection or something, so maybe that was stuck, if you've got one.