[76TA462]

Before I dig too deep, I am wondering if anyone has ever had a fuel sender problem, and what was done to correct it. My car is a 1976 Trans Am. I converted to an EFI and am using an EFI style tank with in tank pump. All good except the fuel gauge showed a quarter tank less than what is in tank. I filled the tank several times and way past after the pump clicked off, to make sure. Everything was checked out by Aeromotive, and the guts re-installed by them and still the same. So, the problem seems to be in my car. Wires to the tank, as far as I can see them, contacts, etc. are all good. Before I go too deep into this, any ideas would be appreciated. I also have a spare combo fuel gauge, voltmeter off an old parts car if that makes any sense to use. Thanks for any help.

[JLMounce]

Which sender do you have specifically? Is it a float type sender on a wire?

Many of the float type aftermarket senders are pretty crappy. There's also an inherent issue with the F-Body tanks in that they are very shallow. Most are so shallow that the amount of swing that you can get on the floats makes them inaccurate.

In my instance, mine worked okay for about a week and a half, then just stopped showing anything other than about a 1/4 tank of fuel. My guess is that the float filled with gasoline and no longer actually floats.

Anyhow, considering that in order to really diagnose this you're doing to have to drop the tank and test the sender out of the tank to verify if it's a sender issue or a wiring issue, I would opt for one of the available floatless sending units. Get the proper length unit for your tanks (Likely 6"), test it in the car before dropping it in the tank, then when it most likely checks out, drop it in and button everything back up.

[Tom Vaught]

Originally Posted by JLMounce

Many of the float type aftermarket senders are pretty crappy. There's also an inherent issue with the F-Body tanks in that they are very shallow. Most are so shallow that the amount of swing that you can get on the floats makes them inaccurate.

Anyhow, considering that in order to really diagnose this you're doing to have to drop the tank and test the sender out of the tank to verify if it's a sender issue or a wiring issue, I would opt for one of the available floatless sending units. Get the proper length unit for your tanks (Likely 6"), test it in the car before dropping it in the tank, then when it most likely checks out, drop it in and button everything back up.

Believe both of the senders use a Float system. How about we call it a external float system or a internal float (in a tube) system?
The Tube system floats seem to work well if you get the right length one.

Tom V.

[Formulajones]

Like JLmounce said, it's going to depend on which sender you're using. Just as he said, I haven't had any luck with the aftermarket "ball on a stick" senders, they just seem to be crap these days. I've pulled them out and tested, and they coincide with the gauge out of the tank, but in operation it's a different story. No idea what Aeromotive is using for senders, I use Tanks Inc. EFI stuff.

I've started using what Tanks Inc calls a floatless sender. A ball in a tube that is much more stable and accurate. Very happy with results.

["QUICK-SILVER"]

With the tank full of gas, un-plug the sending unit wire and do a ohm test from tank wire to ground. Should be really close to 90 ohms.

0 (zero) ohms to 90 ohms is what the fuel guage reads from the tanks sending unit. 0 (zero) ohms is empty and 90 ohms is full.

Most wiring problems (high resistance) make the guage read more fuel instead of less fuel.

Doing the math, 67.5 ohms would be 3/4ths tank. If your sending unit tests near that with a full tank... Your gauge and wires are fine.

Clay