1969 roadrunner gas gauge not working

[Blue-by-you2]

Hopefully someone can shed some light. Here's the details:
- first thing I did was install a new, good, ground to the sending unit, no change
- with tank almost full of gas and gauge reads lower than empty line, I read 18.2 ohms resistance that the sending unit is putting out
- when I ground gauge wire at sending unit gauge goes way past full
- the voltage reading from gauge wire at sending unit toggles from 0 to 5 volts, just like it should
Please help so you don't see me on the side of the road with my gas can!!!!!
Pete

 

[69 Runner]

I'm sure someone will chime in with the proper resistance for the sender, but assuming you have a good connection between the wire and the sender and assuming the sender is the correct resistance, (I know, a lot of "assuming" then I'd say there is a problem with the sender. Maybe the float has sprung a leak or fell off. I would probably pull the sender, then hook it to the wire and ground and MANUALLY move the arm and check the gauge.

 

[70BEE&500]

I too had the same problem. My gauge hung at 1/2 for years and it finally went to empty. I pulled the sending unit and found the brass float to have a hole in it (very small) and the sock/tube was 3/4 plugged. This would explain why the car would shut off above 85mph. I have ordered a new SS sending unit, gasket, ring, grommet, pad and j bolts from Vans Auto in WI. Sorry I don't have any #'s on readings.

 

[Meep-Meep]

Very common to have the float sink.

 

[70BEE&500]

Full should read around 9 +/- 1 ohms and empty around 79 +/- 12 ohms. This reading is what my manual says for a 70 Coronet. 18.2 would be on the full side. Sounds like the voltage limiter (regulator) is working correctly with 0-5volts. But why does it read below empty with a full tank? Do you have the sending unit grounded to the fuel line? Off the corner of the tank to the frame?
I hooked up my sending unit without any ground and the gauge pegged out (full) with 5-10 gal of gas. When I grounded it, the reading went to between empty and 1/4. Ohm #'s don't match my level either. It wa suggested that I bend the float rod to compensate. I am also thinking about getting a new voltage limiter (regulator) from Dash Worx ($50) to possibly solve/help with this problem. I hate electrical gremlins!

 

[jfritzel]

i have the same prob. my gas gauge worked fine a few weeks ago then it just stopped working and wont go above E. i checked the float in the tank and its working i checked the wire to the back of the tank and its all there. but on the back of my guage there is a silver regulator or something and is it possible thats why it stopped working?

 

[beezee]

Pete,Sound,s like you have a sending unit problem as you have tested the circuit and is responding.

 

[moparker]

Testing outside the car will work but, those little strands that the float arm will hit could be broken. When you move it up and down by hand it will be pressed right up against the strands and it will seem to work fine. When it has to float up and down on it's own it won't make contact. There is a place here in Ohio called S.U.R.R. They rebuit mine for my Scamp. The strange part that had me pulling my hair out was an after market one from the auto parts store would'nt work. s.u.r.r. probably has a web site. They are on S.Main st in Akron Ohio. Summit County. Good luck.

 

[T7RM21]

When I installed a new from Chrysler sending unit it would never read more than 1/2 full. I checked everything I could think of and everything seemed fine. Eventually, I pulled the cover off the new unit(careful bending the little tabs)and compared it to an old one I had laying around. There are significantly less copper(?) windings in the new unit as compared to the old ones so I cleaned up my original inspected the float for leaks and installed it. Reads much more accurately now. Might be the same issue you are having.

 

[67Coronet500]

Hey all, I have a 67 Coronet with a slant six with an A833 four speed, V-gate shifter and 8 3/4 rear-end. I have updated everything to V-8 strength as I kept breaking everything. I used to be a member of slantsix.com years ago I tried to log on today to look up my gauge issues and it doesn't even exist anymore. This site looks like it is just what I need.
With all that said, I have the exact same issue as the original question. I know my sending unit went out on me years ago. I finally replaced it with a new one from Yearone. I ohmed out the sending unit and the numbers look perfect. I grounded out the sending unit wire and the gauge pegs full (these tests show everything is fine). When installed the gauge stays at empty?????? I have grounded out the tank and the sending unit and still no change. I even had another instrument cluster from the rear-end donor car that I found years ago, same thing, gauge stays at empty. PLEASE HELP, it is driving me crazy. I was an electrician in the Navy and I now work at a Powerhouse, I am pretty technically inclined but I cannot figure this out!

 

[Budnicks]

Ground issues at the dash or sending unit, broken or ground out sending wire, faulty dash printed circuit board, bad voltage limiter {gauges only run on 5 vlts. not 12 vlts. except the Amp gauge is direct voltage from the Alternator}, maybe a bad gauge or need to be recalibrated... Is that the only gauge that isn't working ??, is the water temp acting up too ??, if so it's probably the voltage limiter or bad grounds &/or printed circuit board or bad ground strap at the fuel line to sending unit or corrosion messing stuff up... Look at the main bulkhead connections on the firewall, they are know for problems, check for corrosion & oxidation, then clean both sides with small brass wire brushes, pipe cleaners & electrical spray cleaner, then reassemble with some dielectric grease on every connection, not too much though, make sure to be very careful when you remove the plugs/connections on the bulkhead, be patient, they can easily break, they are probably brittle after all these years exposed to heat & moister

 

[Propwash]

One thing I noticed when recently rebuilding my rear harness, is when I ohms tested the wire running in that harness back to the fuel sending unit, the reading was bunk. Turns out the wiring was broke in half under the insulation in two spots. First thing I would identify is if you have a solid connection in between the sending unit and the guage itself. Heck, even run a jumper from the S.U. to troubleshoot it.

 

[67Coronet500]

fixed gauge issue.

Well it's official, I found the right website! Thank you for your tips guys. The problem was a continuity issue. I took the instrament panel apart and cleaned every connection I could. Not sure exactly where it was since I cleaned everything but it doesn't really matter, it works now! And my temperature gauge that has never worked since I have had the car (16 years) works now. Thanks again for your tips.

 

[Budnicks]

Voltage Limiter

It' good you found it... Usually when both the Fuel & Water Temp gauge qiut work together, it's the voltage limiter that is usually the main cause... Or sometimes the printed curcuit board... these examples are for a 68 Charger... It was probably corrosion or oxidation with in the many dash connections...