Fuel Gauge Issues

dieseldazzle · Nov 17, 2014

So I installed a new sending unit in my 67 charger and the gauge stays buried on empty. It did read 1/4 once then back to empty.

When Im under the car and have the lead off of the sending unit what should I look for on my volt/ohm meter?

Whats the troubleshooting steps to test the actual gauge in the dash?

Pops1967GTX · Nov 17, 2014

Did you replace or is it missing the ground strap, about 6" long, that clips onto the fuel hose line for ground.... gauge will not working if loose or missing....quick test...... disconnect the gauge sender wire at the tank, & ground the lead... turn the key to "run" & see if the gauge reads full...If full reading you have a sender ng...If NO.... problem in wire to gauge or gauge cluster limiter...check cluster for loose screw & grounds...

http://www.moparfins.com/repairs/fuel_gauge_repair/fuel_gauge_repair.htm

http://www.chargersourceguide.com/voltagelimiter.html

dieseldazzle · Nov 17, 2014

Ok will do.

gibber · Nov 18, 2014

The 5V voltage limiter on our Chargers is located in the fuel gauge. Those points have a shelf life, and most of the 66/67 Charger instrument clusters I get in for repair (about 90 percent actually) have the nichrome wire inside the gauge cooked from the points sticking. Remedy is a rebuild of the gauge plus taking the points out and putting an IVR-3 solid state voltage limiter from Real Time Engineering on the back, no more limiter issues...so even if the grounding of the sender moves the gauge towards full, the likelihood of that gauge not reading accurately is very high...

The only way to test the gauge itself is to hook it up with a 5V input on one post and a known resistance on the other post, 9.6 ohms, FULL, 23 ohms, 1/2 tank, 73 ohms, Empty...

Mark

dieseldazzle · Nov 25, 2014

gibber said:
The 5V voltage limiter on our Chargers is located in the fuel gauge. Those points have a shelf life, and most of the 66/67 Charger instrument clusters I get in for repair (about 90 percent actually) have the nichrome wire inside the gauge cooked from the points sticking. Remedy is a rebuild of the gauge plus taking the points out and putting an IVR-3 solid state voltage limiter from Real Time Engineering on the back, no more limiter issues...so even if the grounding of the sender moves the gauge towards full, the likelihood of that gauge not reading accurately is very high...

The only way to test the gauge itself is to hook it up with a 5V input on one post and a known resistance on the other post, 9.6 ohms, FULL, 23 ohms, 1/2 tank, 73 ohms, Empty...

Mark

Uhmmmm I guess Ill be sending it out to you then?? lol

nm9stheham · Nov 25, 2014

All correct above on the gauge testing. But before sending it off:

With the key in RUN, put your voltmeter on the wire coming to the sender, with it disconnected from the sender, and see if you get a pulsed voltage back there. It is even easier to use a test light; if the limiter is working properly, then you will see a pulse of light about once per second. You should also run this test at the temp sensor wire; but fuel and temp work off of the same limiter.

If you see no pulses, then the limiter is dead. (And if the limiter is dead, the temp gauge wil not work either.) You can find new form-fit-function solid state replacements on-line from RTE.

If the pulses are there, and if the temp gauge rards about normal, make sure you have a good ground from the sender ring to chassis; an alligator clip jumper will make a good temp jumper.

If good ground and limiter pulses show up, then the fuel guage is the issue.

BTW, did you verify that the new fuel sender is a 10-80 ohm range sender or thereabouts?

dieseldazzle · Nov 25, 2014

nm9stheham said:
All correct above on the gauge testing. But before sending it off:

With the key in RUN, put your voltmeter on the wire coming to the sender, with it disconnected from the sender, and see if you get a pulsed voltage back there. It is even easier to use a test light; if the limiter is working properly, then you will see a pulse of light about once per second. You should also run this test at the temp sensor wire; but fuel and temp work off of the same limiter.

If you see no pulses, then the limiter is dead. (And if the limiter is dead, the temp gauge wil not work either.) You can find new form-fit-function solid state replacements on-line from RTE.

If the pulses are there, and if the temp gauge rards about normal, make sure you have a good ground from the sender ring to chassis; an alligator clip jumper will make a good temp jumper.

If good ground and limiter pulses show up, then the fuel guage is the issue.

BTW, did you verify that the new fuel sender is a 10-80 ohm range sender or thereabouts?

Thanks. I will climb under the car the next time I get to storage and check into it. Until then Im workin 12 days straight.

gibber · Nov 26, 2014

That internal sending unit in our fuel gauges is 50's technology at best (using points with a bimetal strip). I would say in the over 120 of these 66/67 Charger instrument clusters I have repaired/restored, less than 5 percent have not had the nichrome wire on those points charred to some degree. I still think it was a good idea back in the day, and was fairly accurate using those points from the factory. We just now have the benefit of much better technology in voltage limiters available (Real Time Engineering IVR-3) Happy Thanksgiving everyone!

Mark

wannadrag · Nov 26, 2014

Welcome to the world of garbage chinkish fuel senders.They are all crap and most guys just deal with it.I have one new one here that reads empty all the time,have another in my Barracuda that with 15 gals in the tank it reads 1/4 and the last 5 gals takes it to full.The easiest way to check the gauge is turn the key on and quickly ground the sender wire,if the gauge goes to full it good.

dieseldazzle · Nov 9, 2015

So now I'm not getting voltage on the blue wire into the sending unit so I traced it back to the kick panel and still nothing. So I checked the temp sensor and it is pulsing voltage there. Pull the cluster and look at the back of the gauge??

66383charger · Nov 10, 2015

Pull both the wires off the gauge, put you meter on the ohms setting, mine meter has a 20, 200, and 2000 ohm range, use something around 200. Put your lead ends on the 5 volt terminal and the sender terminal, you should read 21 to 24 ohms. If not gauge is toast and send it to Mark.

Jeff

dieseldazzle · Nov 10, 2015

Took it all apart gauge must be toast it's like 225k ohms measuring across those two post my bi metallic strip looks charred but I guess I don't understand the functions because I get 5 volt pulses to the brown wire and all my other gauges along with my el lighting work flawlessly.

dieseldazzle · Nov 11, 2015

Isolated to faulty fuel gauge. Got the tank back in with new sender, verified empty full and half resistance good. Found that the sender can spin in the tabs because it's all aftermarket crap. Staked it in. Bought the new filler hose kit grommet and clamps from eBay worked great.

Gpuller · Nov 11, 2015

So your gauge is working now? Is it reading correctly at anything other than full and empty?
Where did you get your sender?
I ask because the new sender in my car is not accurate at anything other than full. Fill and drive 20 miles and the gauge reads 1/2 tank. When the needle is on empty the tank is just under 1/2 full.
Got mine from Van's auto, talked to them about it at a show and they said "Never had complaints, check your ground"

SwedCharger67 · Nov 11, 2015

It could actually be a grounding problem...based on your readings you have too much resistance in the sender circuit (or, the 5V average voltage is too low...but this should affect the temp and pressure gauge too).
Test with a separate grounding wire from the sender unit to battery ground.
You should also measure the actual resistance you have at nearly empty tank, it should be 73 Ohms something according to the source guide.

If the resistance is incorrect in your sender, it can fixed by a simple external resistor behind the dash.
I can help you with the details.

Dennis H · Nov 11, 2015

My gauge has not, does not, and will not ever work. Odometer.

Gpuller · Nov 11, 2015

SwedCharger67 said:
It could actually be a grounding problem...based on your readings you have too much resistance in the sender circuit (or, the 5V average voltage is too low...but this should affect the temp and pressure gauge too).
Test with a separate grounding wire from the sender unit to battery ground.
You should also measure the actual resistance you have at nearly empty tank, it should be 73 Ohms something according to the source guide.

If the resistance is incorrect in your sender, it can fixed by a simple external resistor behind the dash.
I can help you with the details.

The sender ohmed out correctly at full and empty in the middle is where it gets fuzzy. New ground strap plus extra ground at sender.

- - - Updated - - -

Dennis H said:
My gauge has not, does not, and will not ever work. Odometer.

Yep that's the way I do it even with a semi working fuel gauge.

SwedCharger67 · Nov 12, 2015

Gpuller said:
The sender ohmed out correctly at full and empty in the middle is where it gets fuzzy. New ground strap plus extra ground at sender.

Hmm, that's a difficult case then, Ohms are correct at top and bottom but not in the middle? Sounds like a manufacturing flaw?
I put my original sender in yesterday, a pity I didn't take any measurements. Due to special stuff with pump, filter etc. it's a bit difficult to take out again.

dieseldazzle · Nov 12, 2015

My sending unit is fine it ohms out great.

What the issue with the sending unit was that i didnt realize the indexing into the tank was off so it spun 90 degrees and was essentially sitting sideways. It did not leak out of the gasket area.

When I took it out to ohm it out I realized it had spun because its all cheap aftermarket crap and the tank receiver was larger than the tabs on the ebay special sending unit.

I fixed all that, marked the unit (indexed it with sharpee like a spark plug) then peened the tabs down on the sending unit retainer so it doesnt leak.

Bought the new fuel filler hose kit from Dantes. I didnt use the factory clamps, however. I opted for large band c clamps.

Also found my locking gas cap to be the non vented sort.

I ran an additional ground from the tank to the rear shock crossmember after cleaning it up with a wire wheel and no oxded it.

This is not a concourse car.

I then found that the brown wire on the back of the gauge is pulsing 5 volts so my other (temp and oil) gauges work along with my EL lighting and needles.

I found no voltage on the terminal that the dark blue wire, which runs down into the kick panel connector harness and then back to the sending unit. I supplied 5 volts by jumping the brown terminal over and then checked for voltage at the end of the wire under the car where the sending unit plug is. Everthing checked out great.

I am no considering my fuel gauge toast and will be sending it to gibber for rebuild and a limiter installed.

I removed the fuel gauge from the cluster. It is measuring 225K ohms across the terminals. Should be 20-25 evidently.

I pulled it apart and there is visible heat damage.

Pisses me off because last week before I found the sending unit ISSUE of it not being indexed correctly, I was getting 5 volts pulsing back at the tank.

I learned alot about the function and wiring within my cluster, however.

I will be rewarded with a great working fuel gauge and a non leaking tank HOPEFULLY.

I can also share my knowledge now.

Thanks everyone.

dieseldazzle · Dec 9, 2015

Got the repaired fuel gauge back from Gibber last week (thanks, great guy to deal with).

Ordered IV3 limiter from RT ENG ebay site.

Should be here today or tomorrow then Ill get it button backed up and should have a fully functional fuel gauge!!!

Fuel Gauge Issues

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