Another fuel gauge issue....

[superbee70]

Well, I searched the forums for tips on tracking down why my fuel gauge doesn't work, I found some useful info, but still don't haver a working gauge.

Steps taken:

Note, temp and amp gauge work, non rallye dash

Installed new voltage limiter.
Verified voltage level at back of gas gauge
Verified all circuit board traces are good
Checked all nuts on back of circuit boards for firm contact
Grounded sending unit wire (gas gauge went to full)
Removed and inspected sending unit, replaced (sock and float NFG)

Gauge now moves (it didn't before) but only to just below "E"

Questions:

Have I missed something?
Could the gauge still be wonky?
Is the sending unit compatible? (bought from NAPA, says its for 68-73 Dart)

Thanks Guys...

Will

 

[Steve68]

the grounding on the sending unit at the tank can trip you up also. the unit is grounded using the metal fuel line, but this assumes that the fuel line is also solidly connected to a ground. There is a clip type strap that bridges the rubber section between the sending unit an fuel line. You can check to see if ground is a problem by measuring for voltage between teh line on the sending unit and a good ground point on the chassis. Shouldn't be any voltage if you have a good ground.

 

[superbee70]

Grounded the sender to the chassis to make sure, no change.

So I am officially stumped, only possible explanation I see, is the sending unit I bought is not working properly.

 

[doktor_x]

It may be worth pulling the sender out and checking resistance as the float arm is moved. If nothing else, you'd have an idea of what it isn't.

 

[superbee70]

The tank is about half, I am getting a reading of 50 ohms at the sender, pretty sure its ok. But I have not ruled that out yet, think it might be worth a try.

 

[doktor_x]

The tank is about half, I am getting a reading of 50 ohms at the sender, pretty sure its ok. But I have not ruled that out yet, think it might be worth a try.

What's the resistance reading at the gauge?

 

[superbee70]

What's the resistance reading at the gauge?

Would that be obtained by going across the two connectors or from one connector to ground?

 

[RedFish]

With the gauge disconnected from the printed circuit board. resistance across the gauge should be 20 ohms -0 \+2 .

""Grounded sending unit wire (gas gauge went to full)""

While that is a common test proceedure it should be a very brief test condition controlled by the ignition switch. Prolonged zero resistance can destroy a working gauge. Hope this helps.

 

[doktor_x]

Would that be obtained by going across the two connectors or from one connector to ground?

My aim on this is to check for either an open circuit or abnormally high resistance between the pigtail at the sender and the gauge.

With the gauge disconnected from the printed circuit board. resistance across the gauge should be 20 ohms -0 \+2 .

""Grounded sending unit wire (gas gauge went to full)""

While that is a common test proceedure it should be a very brief test condition controlled by the ignition switch. Prolonged zero resistance can destroy a working gauge. Hope this helps.

Good call. I hadn't thought of testing the gauge itself. :thumbrig:

 

[superbee70]

16 ohms at the gauge, a workable reading.

 

[superbee70]

Well, all voltages, resistances and grounds were verified. I was left with nothing else but try another gas gauge, low and behold problem solved, confirmed by swapping back in old gauge, so I am pretty sure it was the cause. (or an electrical gremlin?)

I don't know what to say.....but I now have a working gas gauge...thanks, all for your input!

Will