I have a 1973 dodge dart 4door with the 225 slant 6. Recently my fuel gauge stopped working. First I thought it might be the float so I replaced that and it still would not work. I researched a little and found out there is a resistor behind the gauges so I replaced that as well and it still will not work. It is grounded I bolted a wire to the frame so I know it's grounded. When I test it the gauge spikes. So I don't know what else to do at this point. Does anyone have any tips or tricks to try?

 

well its not the gauge
do you have a ground that's suppose to be grounding the float/pickup
is your tank grounded?
or the new float is bad you need to test it also.

 

Yes it's grounded to we're the original strap wire is placed, there is also another ground strap to be safe, it's from the fuel line directly to the sender. How could I test the gauge to make sure it doesn't need replaced?

 

If remove the wire from the sending unit and install a test light to it (make sure the test light has a good ground) with the key on the test light should pulse and the gauge should go to full. If that happens then everything is good from the tank to the gauge. Then I would take a corner of the tank look for the seam and drill a hole to the outside of the seam and install a ground wire to the body/frame of the car. If that doesnt fix it the sending unit is bad. You say you replaced the float? Was it the float or the sending unit because the float is just the part that floats. (A brass cylindrical barrel looking thing)

 

I replaced the float and the sending unit, with a new one. When I get off work here soon ill go home and try that test light and let ya know what happens. Thanks

 

Instead of thinking of this as "a gauge" and "a float," you need to start thinking of the SYSTEM. This IS a "system."

You have power from the ignition feeds

THE PC BOARD CONNECTOR. Now this may be OK if the temp gauge works OK

From there we go (not to "a resistor") but to the instrument regulator/ limiter.

Again if the temp gauge seems OK, THAT device is probably OK, but evidently you've replaced it.

From the limiter/ regulator, power goes to the GAUGE POWER STUD. This stud/ fake nut can be loose corroded

Through the GAUGE. The gauge itself could have failed

Out the SENDER STUD on the gauge. This is the second stud and fake nut, once again, could be loose/ corroded.

From there it goes to the KICK PANEL REAR HARNESS CONNECTOR. This is the tail/ turn signal connector down in the left kick panel just before the rear harness goes to the rear, and this connector could be corroded

Then we end up back at the tank and the WIRE CONNECTOR at the tank could be broken inside the molded connector.

1---If your temp gauge seems normal, this (at least temporarily) eliminates the power to the board, the instrument limiter/ regulator

2--Clip the sender wire to ground back at the gauge, turn on the key no longer than necessary, and the gauge should head to full.

3--If not, find the terminal in the kick panel connector and ground that. If the gauge does not deflect AND THE TEMP gauge is working normally, it's time to pull the cluster.

4--If and when you get any reading on the gauge you can check it's accuracy by buying some resistors. The original test set resistances from Mopar were:

L = 73.7 Ohms (empty)
M = 23.0 Ohms (1/2)
H = 10.2 Ohms (full)

You can buy resistors at Radio Shack and install in place of the sender to test. If nothing else, buy 4 100 ohm and put them in parallel, which will give you 25 ohms, and should show very close to 1/2 full.

 

Wow way to put it into easy term for the guy. I am born and bred on mopars and work for chrysler for 40 years as a master tech and the way you discribed all that will have him pulling his hair out. Basicly if there is power at the wire that hooks to the sending unit. As I discribed before then every thing foreward to the gauge is OK. The sending unitis a ground on a rheostat switch the closer the source gets to the ground feed the the greater the resistance, and the higher the gauge reads.Right ??? It was all good stuff that you said but very complexed for someone not in the field or just learning.

 

I don't know how this is complex, but "having power" at the sender wire proves nothing----------

the gauge limiter could still be intermittent/ bad/ out of calibration

the gauge itself could be bad

the nuts on the gauge could be making poor connections.

There could still be a bad connection in the sender wire. It takes almost ZERO current to deflect even an analog voltmeter, less to show a reading on a digi meter. It doesn't take much more to light a test lamp. CURRENT is what must go through the circuit in order to show up a bad connection. This is why you use a resistance at the sender to check it.

This is a simple series circuit

Ignition switch---pc board connector--voltage limiter--gauge connections--sender wire--kick panel connector--to sender connector--through sender--to ground.

 

ok so today I went out to work on trying to solve the problem. when i started the car it was on empty I went and filled the car. on my way home i noticed the gas gauge was on full for about 10miles. When pulled in the drive it stayed at full so i proceded to shut the car off and waited till it went to empty. I then started the car up again and it went up to full then it slowly goes down to empty again? Does this rule anything out? Does this mean my gas gauge is working?