Erratic Fuel Gauge (2 Viewers)

[ccasteel]

I filled my tank earlier this week, so I know it's full. The fuel gauge had not been working lately after getting the 40 running after about 3 years in storage. When driving to lunch today the gauge was slowly moving from full to empty and back again. Sometimes settling in at half. Do you think I'm looking at a sending unit problem or gauge problem?

 

[sogafarm]

You can take out the sending unit, keep it plugged in and manually move the float arm to test it.

 

[Pighead]

Do you think I'm looking at a sending unit problem or gauge problem?

Or a wiring problem...

 

[charliemeyer007]

Some years power is like 7 VDC from the amp meter.
Clean the inside of your electrical connector at the tank and make sure the ground is good too.
Mine read F for a very long time, 1/2 and E are correct. Odometer is a better gas gauge for me unless its the stop watch for like low range low.

 

[45Dougal]

What year?
You can easily unhook the wire from the sender and measure resistance (later models) to see if its consistent with fuel level.
You can also short the same wire to ground (preferably via a bulb) to test the gauge.

 

[45Dougal]

Some years power is like 7 VDC from the amp meter.
Clean the inside of your electrical connector at the tank and make sure the ground is good too.
Mine read F for a very long time, 1/2 and E are correct. Odometer is a better gas gauge for me unless its the stop watch for like low range low.

I keep a couple of feet of string with a large Nut on the end in the truck. Lower it into the filler neck until it stops, then pull it out and see how much is wet.
Never failed yet.

 

[ccasteel]

It's a 1978. I'm holding off digging in as it's become a daily driver since my wife hit a deer with her Highlander. Hoping to get that back before the end of December. Then I have more time to pull it apart and let it sit. Thanks for all the advice.

 

[Grayscale]

What year?
You can easily unhook the wire from the sender and measure resistance (later models) to see if its consistent with fuel level.
You can also short the same wire to ground (preferably via a bulb) to test the gauge.

Isn't the 3.4W bulb, wired in sequence, is what the FSM calls for?
PDF pg. 326 / 412
"75 and 77 Chassis and Body Repair Manual"

Land Cruiser Factory Service Manuals (FSMs)

Factory service manuals (FSMs) for your Toyota Land Cruiser ! From the 1950s to the present!

www.cruisercult.com

 

[45Dougal]

Isn't the 3.4W bulb, wired in sequence, is what the FSM calls for?
PDF pg. 326 / 412
"75 and 77 Chassis and Body Repair Manual"

Land Cruiser Factory Service Manuals (FSMs)

Factory service manuals (FSMs) for your Toyota Land Cruiser ! From the 1950s to the present!

www.cruisercult.com

Yes exactly.
But you can also just flash it directly to ground for a few seconds to see if the needle will move (without burning it out).
My fuel tank is under the seats, so I can very easily do this test in 2 mins.