Fuel Gauges Boogered

[athensrep]

How’s everybody doing?

‘88 HJ75 with dual tanks. About a year ago, my rear tank gauge decided that registering at 1/4 tank was good enough. Filled it up to see if a difference was to be made and no change. About a month or so later, my main tank decided to follow suit and started always registering 1/4 full. Checked grounds and all looked good. I’m not sure that bad senders would do this and why both would crap the bed in tandem, but maybe. I looked and couldn’t find anyone with this issue. Maybe the experts here will chime in?

Thanks in advance.

 

[coldtaco]

if they are original they could both failed. maybe the pickup filter came loose and is rolling around inside and jambed the sender?

 

[Billyfj7312ht]

If you only fill to 1/4 or 1/2 a tank on a regular basis the variable resisters in the sender unit can scale over a bit and not read properly until they are cleaned. When the fuel empties out and reaches 1/4 of a tank does the gauge then move slowly to empty? If so, I would say the float is getting stuck on something and will only go to 1/4. Mine was doing the same (only one long range tank) and when I removed the sender the float had a shiny patch on one side so it was getting caught on an internal baffle. I was lucky enough to have 2 positions drilled in the top of the tank sender collar, so tuned it to the other position which turned it 1/4 of a turn and fixed the problem.

 

[athensrep]

If you only fill to 1/4 or 1/2 a tank on a regular basis the variable resisters in the sender unit can scale over a bit and not read properly until they are cleaned. When the fuel empties out and reaches 1/4 of a tank does the gauge then move slowly to empty? If so, I would say the float is getting stuck on something and will only go to 1/4. Mine was doing the same (only one long range tank) and when I removed the sender the float had a shiny patch on one side so it was getting caught on an internal baffle. I was lucky enough to have 2 positions drilled in the top of the tank sender collar, so tuned it to the other position which turned it 1/4 of a turn and fixed the problem.

Yes, once the tank reaches the appropriate 1/4 full, it tends to work basically as normal. Getting hung up makes sense. I keep the tanks filled but don’t drive this as much as I should so may be getting corroded/gummed up? I’ve never dropped a tank in one of these as I can’t get to the top side even if it had access.

 

[coldtaco]

you should be able to access the level from the top, there should be a round cover you remove to access it.

 

[TreadingLight]

Ute or troopy? On my 90 troopy there is an access port for the front tank but not the rear - has to be dropped.

It does kinda sound like the issue is in the senders but you can confirm pretty easily by finding the signal wires going to the gauge and temporarily grounding them.

Both wires (one for each sender) should be yellow with a red stripe. On the 1990+ 75 series you can pick them up from a connector on the LH side of the engine near the firewall.

It is safer to ground them through a test light but if you don't have one you can ground them (one at a time) directly if you have an assistant watching the gauges inside the vehicle.

You don't want to directly ground the gauges for more than a second or so because the needle will move quickly and go off the scale leading to damage.

If you can observe the gauges moving correctly you know it is time to investigate the senders.

 

[athensrep]

Thanks - all good advice and I’ll give this a go next and report back. It’s a troopy with a floor and cabinetry so access is out of the question from the top.