Gas guage problems..

[doublearrow]

I thought I remembered seeing a thread on troubleshooting gas guage problems, but cant seem to find it so I thought I'd run my question by ya'll.
I have a 1987 silverado and the gas gauge shows 1/4 to 3/8 full when the tank is completely full. This is for both tanks. When it shows empty the tank is empty. Any idea where to start? Thanks for any help. Ryan

[tucsonjwt]

This topic has a lot of discussion here, but it all boils down to:

Check the grounds from the sending units.
Check the selector switch.
Check the fuel gauge.

If your gauge reads identically on both tanks, then I say go for the gauge. My take - remove/replace the gauge without getting dirty (takes about 20 minutes to check) - cost about $50-$60. Assuming you don't find any loose wires under the truck, this is the way I would go.

[RandyP]

Sounds like a good time to replace the sending unit to me. Your truck will probably thank you for the new pickup filter in the tank anyways. Just my .03 though (inflation).

[Duct Tape Racing]

Originally Posted by RandyP

Just my .03 though (inflation).

hahahahah

Yea id start with the sending unit/ wiring of it. Its all about trouble shooting

[doublearrow]

Sending unit is what I'm afraid of lol. Lots of money to be spent on those. Thanks for the help guys, hopefully next weekend I can start trouble shooting.

[wyattglock]

Unfortunately that is more than likely the problem. The good thing, you should be able to take the bed off with a hoist and save the trouble of dropping the tanks. Highly recommended and also allows you to work comfortably!

[tucsonjwt]

Both sending units go bad at the same time? If so, maybe it is the gauge. If you can get your hands on a known working gauge to temporarily replace yours, that will save you the hassle of dropping the tanks (assuming the sending units are OK.) Of course, check the grounds on the sending units first.
Aftermarket Spectra brand sending units are about $40-$50 each, but they cause the gas gauge needle to bounce on acceleration, stopping, turns, etc. AC Delco gauges don't do that, but they are about $140-$160 each.

[old Rusty C10]

check the grounds before you do anything those are the usual culprits on stuff like that

[hatzie]

Originally Posted by tucsonjwt

Both sending units go bad at the same time? If so, maybe it is the gauge. If you can get your hands on a known working gauge to temporarily replace yours, that will save you the hassle of dropping the tanks (assuming the sending units are OK.) Of course, check the grounds on the sending units first.
Aftermarket Spectra brand sending units are about $40-$50 each, but they cause the gas gauge needle to bounce on acceleration, stopping, turns, etc. AC Delco gauges don't do that, but they are about $140-$160 each.

There are a bunch of circuits for adding hysteresis to automotive fuel gauge senders and I guarantee they don't cost $100. Google "anti slosh circuit".

[tucsonjwt]

Originally Posted by hatzie

There are a bunch of circuits for adding hysteresis to automotive fuel gauge senders and I guarantee they don't cost $100. Google "anti slosh circuit".

Can you tell us which brands of sending units less than $100 do not cause the gas gauge to bounce?

[hatzie]

Originally Posted by tucsonjwt

Can you tell us which brands of sending units less than $100 do not cause the gas gauge to bounce?

I think you mis-understood my post. For less than $10 in parts from Radio Shack you can add enough hysteresis (electronic damping) to the sender signal that the gauge doesn't jump around with the cheap senders.

Here's a link to some discussion on an electronics board about building a simple anti-slosh circuit for a 1960's Italian car. http://www.discovercircuits.com/ubbt...er=6590&page=1

I would guess GM used mechanical damping on the actual movement of the sender arm. F*&d used a simple circuit on the gauge panel with cheaper senders.