Fuel Gauge FUBAR

Hello all. I own a 99 4wd 2.7 liter and a few weeks ago I noticed my fuel gauge was stuck above full. I've been through several tanks of fuel since and the gauge hasn't moved at all. I replaced the fuel sending unit ($$$) and same result. All fuses check ok. I'm thinking of tearing into the dash to get at the gauge but was hoping someone may have been down this road before and might have some advice. Is there a way to test the gauge without pulling the dash apart? Fingers crossed...

 

You don’t have to pull the dash apart to remove the instrument cluster. It should take you 15-30 minutes max.

It’s like 10 screws, a few bolts, and the connectors.

 

Thanks!

 

Most all gas gauges are set up so that the sending unit connects the gauge wire to ground when full and has high resistance between the wire and ground when empty. Chevy is the exception. When you disconnect the sending unit on a Chevy, it goes way past full. I don’t know which way your Taco is, but if I was to guess, I would guess that the gauge wire is shorted to ground somewhere.

 

The next step is to test the resistance on the fuel gauge test points with a millimeter against the FSM specifications. I have a parts instrument cluster for sale if you need a new gas gauge.

 

Thanks. Testing the fuel gauge test points sounds technical. Probably needs to go to a shop then...?

 

Visually inspect the wiring under the truck. Look for a possible place where the wiring is cut by sharp metal or melted to the exhaust.

 

Thanks. Going to do this today.

 

No. Not at all. Put a multimeter into the Ohm Meter mode, usually denoted by the Omega symbol. Depending on what the FSM says, set it to the correct range based on the correct resistance range as per the specs in the manual.

A 5 minute video on using a multimeter is all you need to understand how to use it.

 

Thanks. I have a multi-meter and have used it some. Where are the test points?

 

Would this cause it to stay above full even when the ignition is off?

 

You need to find yourself a copy of the factory service manual, there should be a website stickied to the top of this forum

 

Again, I am going to generalize here. Some gas gauges stay at the last reading when you turn the key off and some go to empty. I’m not familiar with what 1st gens do. If they normally go to empty when key is off, then you have a stuck gauge. If they normally stay at the last reading, then it’s totally feasible that the gauge wire is shorted to ground.

 

I am sure he meant Multi Meter Mot Millimeter

Simple to test the old sending unit.

If electrical is not your thing get help

 

if you do a search on GOOGLE or TW with your year/make/model/issue you'd probably find out the troubleshooting process for ur truck

 

Yeah I’m on mobile. Sorry.

 

The plot thickens. I took the bed off and tested the sending unit and all connections at the electrical plug into it. All good. I traced the wires from the sending unit along the frame rail and into the cab. All factory bundled with no signs of a short. Then I checked under the carpet and up under the steering column. Looks factory with the factory wrapping still on it. One thing that I don't get is when I pulled the plug off of the sending unit I used a test light and found no wire was hot with the ignition on...That doesn't seem right.

 

As for your test light test, the gauge doesn’t flow enough current to light the test light. That’s no surprise. Also, if the wire is shorted to ground, you’re definitely not going to get any voltage at the sending unit. If you unplug the sending unit, does the gauge stay on F? Try grounding the sending unit wire and see if the gauge changes. From this point, I’m thinking you need to pull the instrument cluster. If you can depin the sending unit wire and power up the gauge, that should tell you something.

 

Yes, the gauge stayed pegged at above full even when I disconnected the sending unit. I also disconnected and reconnected the battery. I’m beginning to think the problem is the gauge…Thank you

 

Another test you could do is unplug the instrument cluster and unplug the sending unit. Take your multimeter and measure resistance from the sending unit wire to ground. If theres continuity, it would appear that theres a hidden short to ground.