Fuel Gauge

[RPMLegends18]

Well I did some looking into this before I am posting this question but I cant figure it out. The full ohm is 10 and empty is 73...Maybe I have the tester set to the wrong setting, I can never figure those damn things out anyways. Well when I put the positive lead of the volt tester to the lead off the sending unit and then the negative to the steel fuel line (which I cleaned all the gunk off and it was shinning) the volt meter read .89 ohms... So I may not have the knob set to the correct spot on the tester. But this is what is happening, the gas gauge does not work. I did the test and took the lead wire and grounded it out (not to long because I heard that could damage the gauge) and the needle went to full, unhooked it and straight back down. So I was reading around and read that there is suppose to be a ground strap off the sending unit bypassing the rubber line and then clipped onto the steel line on the chassis, my car is missing that. So I took a jumper wire cleaned off both the line and the sending unit hooked it up and tired to see if it worked. The needle barelyyyy moved, I mean hardly any. So I dont know if the tank is empty...it may be, or if the sending unit has gone to the way side. I kinda want to pull it out and check it but looking at some of the pictures of sending units that have come out of these cars I dont want to take it out and it be...well something wrong with it where I cant put it back in, I dont have any cash right now to buy a new one. So whats the best way to check and see if the unit is bad or good without taking it out...I probably need to be schooled on how to use a damn volt gauge...

Thanks,
Ryan

 

[cudajim]

You have your volts and ohms terminology a bit backwards. You read voltage with a voltmeter and resistance (in ohms) with an ohmmeter.

The sending unit inside the gas tank is simply a variable resistor with one end tied to ground and the other being the wiper which moves up and down. To test it properly take it out of the tank and put it on your bench. Next use your ohmmeter, not your voltmeter, and touch the 2 leads together to prove the meter is working. The meter should show close to zero ohms. Next attach the ground (black) lead to ground on the sensor and the other red lead to the output terminal. Now read the meter and it should vary as you move the float up and down. If it does not your sensor is bad (which is likely). Sometimes you can gently bend the wiper arm to make better contact to the resistor and fix it but most likely you'll have to replace it.

When you put the sensor back into the tank be sure to use the ground strap and install it properly so that the sensor gets a good ground. Good Luck.

 

[RPMLegends18]

cudajim,
We have one of those volt/ohmmeter testers, wheres its got the knob were you can select which one. If this is the ohm symbol Ω then I had the tester set to that but I dont remember the first setting when it read .89. I changed it later that day to the 20k I believe and it read 66.873 then I changed it to the 2k and it read 67. So I figured it was close to empty. So I drove it down to the gas station and it only took five gallons before spewing out the filler. Maybe its just the sending unit

 

[RedFish]

If you want to take the sender out and play with it you will need a nearly empty tank and a new seal. Reused seals leak.
My advise is just keep the tank filled until you can buy a new sender.

 

[cudajim]

You're right about the Ohm symbol on the meter. Basically your fuel circuit is a simple series circuit. If you do not have the ground strap properly connected it will never work because you have an open circuit. The wire from the gauge needs to find a path to ground through the variable resistor (the sending unit). Let us know what you find.

 

[69B-Cuda]

Trip odometer reset every time you fill up and a 2 gallon "reserve" in the trunk...always gets you home or to a gas station!

If the gauge checks out and the sender unit checks out, it could be a bad connection or break in the wire somewhere along the way...