73 duster - gas gauge not working

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plyduster73

plyduster73

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History - the gas gauge worked when I first got the car running about 6 yrs ago.

After the initial restart the car has been sitting in a garage for past 3 yrs not running, while I was at callege.
The car has a new motor now and is running great but now the gas gauge is not working.

I have not looked at anything, so where is best place to start.

Is it in the dash or could the unit be clogged up in the tank, I put a new tank on the car 6yrs back.

The 3yr old gas that sat in the tank was not gelled and burned fine.

Any direction would be great.

Thanks
 
Check your ground strap back by the tank. There is a strap that straddles the rubber line from sending unit to fuel line.
 
Ground the sender unit wire to the body, turn on the key and it should go all the way up.
If it does, then the sender in the tank is bad or not grounded.
This is an easy way to get started on the diagnostics.
 
TrailBeast said:
Ground the sender unit wire to the body, turn on the key and it should go all the way up.
If it does, then the sender in the tank is bad or not grounded.
This is an easy way to get started on the diagnostics.
Click to expand...

I started to type that, but went with the easy check first, lol.

If you do this don't leave the key on long, just long enough to see if the gauge moves.
 
Alright fellas I got under the car this weekend to look at the sending unit.

Im far from a mechanic, so I don't assume much when working on my car.

This is what I got...

This is on the front of the tank ( encase the orientation is questionable)

The small wire is what sends the shows on the dash right?
I couldn't see where the rubber hose in the background went to.
But I should look on the rubber wire in the foreground to ground it out?
 

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That rusty clip you see on the supply tubing is probably the problem.
There should be a small strip on it connecting to the fuel line
On the other end of the rubber fuel line. Basically you have a metallic
Sending unit and a metallic fuel line with a piece of rubber hose connecting
them so the little rusty ground strap is what completes the ground circuit.
The wire with the 90deg. Elbow going through the trunk gose directly
the gas gauge if you ground it you should see your gauge go to full when
You turn on the key
 
So the little rusty piece should not the connected to any thing else?

When you say..

"There should be a small strip on it connecting to the fuel line"

You mean a portion of the strap should be rust free and making good contact with the metal fuel line its clamped to?

So what I am grounding out is that fuel line, and if the gauge works then that little rusty piece needs to be replaced or cleaned.

So just clean off a place on the frame and get a small wire with clamps and put one end on the line and one end on the frame?

Just assume I have absolutely no knowledge and lets run from there :violent1:
 
That clip you see should have a strap and another end just like what's in the picture. It goes from where you see it to the metal supply line on the other end of the rubber section. If that piece is missing, broken or doesn't have a good ground, that could be your issue.

This is what it looks like.
 

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The rusty clip is supposed to have a strap on it that goes to a ground (usually to the steel line up farther past the rubber part of the line where it is steel again)

The green arrow shows the part of the sender that should be grounded to the body or where the line is steel again somehow (even with a hose clamp and a wire if need be)

The red arrow points at the part that pulls off.
This is the sender wire that makes the guage move, and if grounded to the body, the guage should go to full.
If it does, then the sender in the tank is at fault, or the ground strap isn't making a good connection.

The strap for the rusty clip may be behind the rubber so we can't see it, but is supposed to follow the rubber line up to where it is steel again, and have the same clip type end on it.

If the rusty ground strap is all there, then you might just wiggle it at both ends where it is on the steel line and the guage may work again.

Overlapping info :)
 

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Y'all are great.
Now the work day needs to be over ASAP so I can go home and fix it.

Thanks for the guidance.
 
I cleaned the original grounding strap and the gas lines to where I could see nice shinny metal, the gas hand never moved.

I tried grounding it to other places under the car with new clean wire and still nothing.

I had a mechanic try to ground it also and never got the hand to move.

I also unplugged and looked at the electrical plug on the sending unit. The threaded part coming out of the unit is clean but the rubber cap appears a little black on the inside.

Since the hand never moved, has this turned into an electrical issue or will a new sending unit still cure the problem? :banghead:
 
next check would be the voltage limiter and the plug on the back of your dash and also check the pins and be careful you dont break the pins off when removing the plug
 
plyduster73 said:
I cleaned the original grounding strap and the gas lines to where I could see nice shinny metal, the gas hand never moved.

I tried grounding it to other places under the car with new clean wire and still nothing.

I had a mechanic try to ground it also and never got the hand to move.

I also unplugged and looked at the electrical plug on the sending unit. The threaded part coming out of the unit is clean but the rubber cap appears a little black on the inside.

Since the hand never moved, has this turned into an electrical issue or will a new sending unit still cure the problem? :banghead:
Click to expand...

YOU NEED TO unhook the sender wire. Stick a screw, clip lead, etc in there and ground it. Then go turn the key to "run" for a short time and watch the fuel gauge
 
You can go in the trunk and shove a shirt pin through that wires casing and ground the pin easier than crawling under the car again. With a little more effort you could remove the left kick panel and find that wire in the rear harness connector. Separate the connector, Use a multi-meter to check for a pulsing approx. 5 volts coming through the gauge at switch on and check for somewhere between 73 and 10 ohms resistance through the sender. I don't like to work hard if I can work smart instead.
 
Bad Sport said:
He musta missed that part, lol.
Click to expand...

Yup.

I keep trynnna preach to think of this stuff AS A SYSTEM. Troubleshoot by keeping in mind "the box" and what's "in" that box, and what "comes into" and "goes out" of the box. "End to end."

1---Does the TEMPERATURE gauge work OK? You sure? If it does, this indicates that the cluster voltage limiter is getting power and working OK. From the limiter power goes to the temp gauge, fuel gauge, and oil gauge if equipped.

2--So your circuit path is---------

Voltage limiter-------fuel gauge-----harness wiring------sender------ground

and all the connections in between

=============================================================

So the first order of business is to SPLIT the problem. Eliminate what you can "as the problem" so that you know where to head.

By grounding the sender wire and looking for gauge movement...........even if it's not accurate............ you at least know the wire is good all the way from the trunk to the cluster an gauge, and if the gauge moves, you know the gauge "can do something" and is getting power from the key through the voltage limiter

THIS ONE simple test can immediately point you either to concentrate on the tank, or "what's up front"
 
Not to put a fly in the ointment, but when I pulled my '75 Duster apart..my connection looked ezactly like the one shown in message #5 and it did not have a ground strap, etc...and I have put it back together the same way.

Could the no ground strap be a change and it being grounded in a different way ?

Just a thought...

Ian.
 
grassy said:
Not to put a fly in the ointment, but when I pulled my '75 Duster apart..my connection looked ezactly like the one shown in message #5 and it did not have a ground strap, etc...and I have put it back together the same way.

Could the no ground strap be a change and it being grounded in a different way ?

Just a thought...

Ian.
Click to expand...

The sender can get it's ground through the tank to the body, but it can also easily move and loose that ground.
The ground strap is insurance.
 
I got under the dash this weekend, it is all very clean no with no rust and good connections.

Everything in the dash is working, speedometer, temp, alternator. That's all the gauges I have.

I had a mechanic put a thermal gun on the motor to check the accuracy of the temp gauge and it is dead on.

"YOU NEED TO unhook the sender wire. Stick a screw, clip lead, etc in there and ground it. Then go turn the key to "run" for a short time and watch the fuel gauge"

Im to dumb with electricity to know if that is a joke or serious, or what that will tell me :violent1:

So if the other gauges are accurate and working then the voltage limiter is fine and the temp gauge is fine so its down to the gas gauge its self, the harness, or the sending unit? It has a good ground connection now.
 
TrailBeast said:
The sender can get it's ground through the tank to the body, but it can also easily move and loose that ground.
The ground strap is insurance.
Click to expand...

Thanks. I have painted everything...wonder if mine will work again. Running a ground strap sounds like insurance to me. Thanks.

BTW, Great thread
 
Yea im learning a lot from this, its just frustrating as hell
 
plyduster73 said:
"YOU NEED TO unhook the sender wire. Stick a screw, clip lead, etc in there and ground it. Then go turn the key to "run" for a short time and watch the fuel gauge"

I'mto dumb with electricity to know if that is a joke or serious, or what that will tell me.
Click to expand...

A couple of us mentioned this. Take the wire off of the sending unit and ground that wire to a good ground. Turn your key on and see if the gauge goes up, but don't leave the key on any longer than needed to observe the gauge movement. IF the gauge moves, usually spikes to full, then you have a ground issue at the tank. IF the gauge moves that tells you the wire to the gauge and the gauge itself is good.

No, it's not a joke.
 
Ok, I understand what yall are getting at now.

Ill check tonight, thanks
 
So I took the electrical plug off the tank, put a screw in it and ground it to the brake line. See photo.

The gauge moved all the way to full!

While I was under the car and had a good grounding position, I took the clamp and hooked it to the tank and reconnected the electrical plug to the tank also...nothing happened this time.

Also on a side not the electrical plug was wet with gas, so im assuming the rubber seal is rotted?

So with this info I am assuming that the sending unit is bad?
 

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