Trying to figure out my gas gauge issues. I started out by testing the gauge by grounding out the sender wire and the gauge shoots to full. I checked my sending unit and found it was shot. I replaced the sending unit with a new one from DC. I tested the range and it is 10-73 ohms. I currently have a near full tank of gas and the sender is putting out 14 ohms. So when I first turn on the ignition the needle on the gauge starts to rise for a few seconds then it gets to between 1/4 and 1/2 tank and then the needle falls to below E where it stays. I have checked connections on the cluster and at the sender. Is my gauge shot or is there a ghost in the machine?

 

Do you have a good ground?

 

I believe so...

 

Have you checked the float in the gas tank? Sounds like it has a hole in itand is full of fuel. Pull it out, shake it, if any fluid in it, replace it.

 

Sender and float is new. Sender is putting out 14 ohms, which is proper for a near full tank. 10 ohms is full, 73 ohms is empty.

 

May be the voltage regulator. Behind the speedo bezel. It should drop the voltage to Fuel and Temp gauges to around five volts or thereabouts.

But you should test the sending unit itself before installation, make sure it pegs the gauge to Full and Empty at the limits of travel. Fine calibration is adjusted by means of a set screw on the float arm attachment point.

 

New floats are faulty also. It's a quick check at least rule it out. I've bought new parts that didn't work.

 

I was wondering about the voltage regulator as well, but my temp gauge works fine. Sending unit was tested with an ohm meter before install and was fine. Not sure why the gauge starts to rise and then falls back to E. I will test further tomorrow.

 

Thanks for the input guys. So here is a short video of how the gas gauge reacts when I first turn on the key.


I tested the voltage at the sender and it goes to 12+ volts at first and then drops to 0. I now think that the Instrument Cluster Voltage Regulator may be suspect as well as grounding issues. I will order a new ICVR and report back after repairs are made.

 

Measure the output before replacement, you mentioned the Temp gauge works OK? All it is, a bimetallic strip that heats up and breaks contact, so it's a pulsed voltage drop, sort of off/on. They are (slightly) adjustable, even. Sort of pricey for what they are too.

 

For reference, I received today in the mail and installed a Dennis Carpenter Gas Tank Sending Unit (made in China, C1TZ-9275-K). The Ohms/Resistance was close enough to spec for me (readings on my multimeter were 13-73). Gauge read 3/4 tank which is about right. Need to run it down to E and experiment with adding 5 gallon increments to see how close it is to accurate out in the field...

Float included is plastic, not brass. A little put off by that, but I still have the original brass one....

The constant voltage regulator also regulates voltage for the Temp and Oil gauges, and you said your Temp gauge works fine, so not yet convinced your CV regulator is the issue...

 

hot from sender to guage might be pinched (i.e partial short/high resistance short, ect), run a test wire from sending unit to guage to see if symptoms change.

 

just flushed tank on truck the other day, and put a cork on sending arm for the float that was missing on the arm, while adding fuel, gas level gauge deflection from E started at about 2 gallons, i.e to say when that guage says dead empty, there is still 2 gallons in the tank

 

If they made the float out of the right type of plastic it should be fine. If not then you will know soon enough. It most likely is of the right material and if the manufacturing process used turned out a properly designed and formed float then it is prefurable to a brass float. Brass floats use solder to seal them up and the brass it's self can corrode. I don't know about your state but here in Washington it is required to have atleast 10% ethanol in the fuel. This attracts moisture and both the alcohol and water are corrosive to metals. The right plastics are impervious to damage. You should get decades of use out of it if it does not give you trouble in the first few weeks. Good luck, dts.

 

That sounds like an easy enough test to try. I will receive the new ICVR today and will install it this weekend. Should have it working soon unless the gas gauge itself is shot.