1988 fuel guage - Tired of its lies

[PetroleumJunkie412]

So, my fuel gauge has never worked since I bought KaP.

I used to listen to its filthy lies, and refill my tank every time it would read empty. Turns out, it says it's running on fumes when there's about 10 gallons used out of the 18 gallon tank.

Tank and lift pump assembly are brand new. Pulled the pump a few months ago when I had the bed off and checked it out. Sending unit for the guage is spotless and brand new.

Guessing the issue with the gauge is somewhere else?

 

[fastpakr]

I'd still be inclined to blame the sending unit. The good news is that you're well practiced on the art of bed removal! Can you disconnect the harness going to the pump and sender without lifting the bed/dropping the tank?

 

[PetroleumJunkie412]

I'd still be inclined to blame the sending unit. The good news is that you're well practiced on the art of bed removal! Can you disconnect the harness going to the pump and sender without lifting the bed/dropping the tank?

Probably. Also just as easy for me to pull the bed tbh. Bolts are brand new and coated in anti seize, and have a forklift hanging around the current shop.

What's your thoughts on the cause??

 

[fastpakr]

Lots of aftermarket pumps have junk senders. The easy way that comes to mind for testing the sender would be to check the specs on the sender design. I'm sure the resistance for full vs empty are published. Create a matching resistance and hook it to the wiring to see how the gauge behaves. If it's correct, you know the wiring and gauge are good and the sender is faulty.

 

[PetroleumJunkie412]

Lots of aftermarket pumps have junk senders. The easy way that comes to mind for testing the sender would be to check the specs on the sender design. I'm sure the resistance for full vs empty are published. Create a matching resistance and hook it to the wiring to see how the gauge behaves. If it's correct, you know the wiring and gauge are good and the sender is faulty.

That's freaking brilliant.

Also, no chance it's the gauge itself?

 

[Curious Hound]

Always a chance. But less likely than the sender.

 

[fastpakr]

Could be, but if the gauge goes where it's supposed to when you apply the right resistance, you've eliminated it.

 

[Bird76Mojo]

I've noticed over the last 10 years or so that ALL aftermarket sending units seem to be off by a decent margin. It's like the aftermarket companies can't get their shit together on the correct ohm levels of the senders. The last 4 to 6 fuel pump assemblies I've replaced have all had the gauge read "off" quite a bit after swapping everything out. I've tried all brands from Advance Auto, Oreilly's, Napa, etc.. I'm starting to think the only way to get someone accurate will be to find an original Ford unit.

RockAuto lists the ohm levels of several of their units. At least they did the last time I looked.