Most likely cause of fuel gauge being inaccurate?

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MrJLR

MrJLR

Built, not bought
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When I fill my tank, it only goes to 3/4 and empty is just above 1/4.
Sending unit?

Kinda sucks not knowing where yer fuel level is!!!!!

Any ideas? Seen this before?

Thanks!



:burnout:
 
Has the fuel gauge sending unit been replaced recently with an aftermarket one? Do a search here and you will find numerous discussions on that topic with opinions on good vs. bad ones, as well as interesting methods to calibrate one by adding in additional resistors. I'm equally interested because it looks like I'm about to have to change one out soon.
 
I just went through this and it is frustrating. I first verified that my gauge was still working correctly using a home made tester that shows full, 1/2 and empty. Next I verified a good ground at the sender. Then I traced the gauge wire back to the dash. There was a connector behind the kickpanel that needed cleaned.Finally I checked the ground at the dash. The nuts had worked loose over the years so I tightened them down.

My gauge is now pretty close whereas before on a full tank it showed about 3/4. It was probably a combo of everything I checked but the ground being clean and tight is a must.
 
'74 Sport said:
Has the fuel gauge sending unit been replaced recently with an aftermarket one? .
Click to expand...

This seems to be a common problem

There are many pitfalls

Bad connections in the system, how old are these girls, again?

Inaccurate IVR unit

Inaccurate gauge unit

"In general" sender problems, old, rusty, chinese, ..... ... . . .. . . . .. . .

There was a discussion some time ago, someone is making a guage calibration device you can install inline for about 40 bucks


This

http://technoversions.com/MeterMatchHome.html

which came from here

http://www.forabodiesonly.com/mopar/showthread.php?t=275117

and another thread related

http://www.forabodiesonly.com/mopar/showthread.php?t=264543
 
Vast majority of electrical issues in these older vehicles is poor connections. Majority of those are in the daisy chain of parts and hardware that create a ground path.
Your search here will find a lot of posts about inaccurate aftermarket senders. What's missing from those is details about what the gauge was doing or not doing with the original sender. It boils down to owners assuming or guessing where he fault is and/or which part is easiest to replace. Fuel gauge wrong ? Sender R&R is easier that inst' panel/gauge R&R.
Fuel filter appears empty ? Must be a bad fuel pump.
After their hale mary attempt at cure fell short is where their internet posts begin.
Like someone else said, dig deep enough in your own car and you will find the root of the problem. Good hunting.
 
RedFish said:
Vast majority of electrical issues in these older vehicles is poor connections. Majority of those are in the daisy chain of parts and hardware that create a ground path.
Your search here will find a lot of posts about inaccurate aftermarket senders. What's missing from those is details about what the gauge was doing or not doing with the original sender. It boils down to owners assuming or guessing where he fault is and/or which part is easiest to replace. Fuel gauge wrong ? Sender R&R is easier that inst' panel/gauge R&R.
Fuel filter appears empty ? Must be a bad fuel pump.
After their hale mary attempt at cure fell short is where their internet posts begin.
Like someone else said, dig deep enough in your own car and you will find the root of the problem. Good hunting.
Click to expand...


Ugh.....sounds like fun!
One day I'll pull the entire interior before paint and in putting it back together hopefully find the issue.....

I ran it to empty the other day so I knew where empty was. I had 3 gallons of gas in the trunk - but it ran out in front of my house and I coasted in my driveway! Sucked up some crap from the bottom of the tank and clogged the fuel filter. .....
I replaced the filter and tossed an extra in the trunk...running great again now.
I guess a new tank is also on my "someday" list!


:burnout:
 
The fuel sender is just a old fashion re-o-stat.They can be adjusted by removing the tin cover, but most likely the resistance coil needs cleaned.Yep these girls are showing their age. The after market replacements should be checked before installing and matched to the gauge.Connect a jumper wire at the sender wire at the tank,a 12gauge wire about 8 feet long to reach the driver compartment.Connect the wire to the sender terminal with the unit in your hand and with another jumper wire ground the sender to the body.There you can check it with the key on,move the float arm to half tank and see what the gauge reads, check at full and at empty. You can adjust the re-o-stat sweep(if needed) before installing it in the tank. Just a thought.
 
Darter6 said:
The fuel sender is just a old fashion re-o-stat.They can be adjusted by removing the tin cover, but most likely the resistance coil needs cleaned.Yep these girls are showing their age. The after market replacements should be checked before installing and matched to the gauge.Connect a jumper wire at the sender wire at the tank,a 12gauge wire about 8 feet long to reach the driver compartment.Connect the wire to the sender terminal with the unit in your hand and with another jumper wire ground the sender to the body.There you can check it with the key on,move the float arm to half tank and see what the gauge reads, check at full and at empty. You can adjust the re-o-stat sweep(if needed) before installing it in the tank. Just a thought.
Click to expand...

You don't need to go to all that trouble, LOL. You can check it with these fancy new things known as an "ohmmeter"
 
Do both if you are having trouble; the ohmmeter checks the sender by itself, and the coordinated test will check them together with the limiter.
 
You mentioned you sucked in some crap from your tank. I'd say it's time to drop the tank and either clean it out or replace it. Make sure you have a pickup screen on the pickup tube too. If you have not replaced the instrument voltage regulator you may want to make the effort to do so cause it will fail.
 
I've got a cure for ya; keep your tank full like your supposed to.

If you want to know the secret:

#1 Fill it up AND a spare 5 gallon can.
#2 Take note of the odometer.
#3 Take a trip on the highway.
#4 Run out of gas.
#5 Take note of the odometer. That's how many miles you can float on a tank, freeway.
#6 Fill it up with 5 gallon spare, then drive to a filling station, re-fill and drive home.

If you really want to be a pimp, do this in stop and go: daily grind, this is your city mileage.

Even when new these gauges are ballpark at best. Don't trust them.



Also, consider a wideband o2 sensor so the A/F ratio is correct.
 
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