Fuel gauge problem

[macawpat]

I just picked up a 1976 Dodge M880. I would like to start restoring it and use as daily driver also. I am having an issue with the fuel gauge though. When I turn the key it comes up to the empty position, I turn it off and it returns to the bottom of the gauge. I pulled the relay from the back of the gauge and am getting power there on both sides of the gauge board where it plugs into. I am not getting power to the sending unit. I cleaned the ground wire on the sending unit and still nothing registering on the gauge. I am wondering if the relay on the back of the gauge may be bad but not sure how to check it and cant find one at the auto parts store. Any help would be greatly appreciated. I am really looking forward to this project but not if I keep running out of gas. Thanks All, Pat

 

[popacom]

Its been a minute on this one, but the item you are referring to on the back of the guage unit I think
is actually a voltage regulator and not a relay. I would take a resistance reading from the wire at the guage which feeds back to the sending unit in the tank to chassis grd,note that reading and then add a few gallons of fuel,take
another reading and compare the readings. If the sending unit is working then you should see a change in resistance reading after adding the fuel. If that proves out then you have it isolated to the cluster and then
its a matter of sorting out which component is at fault on the cluster or if you have a power issue. Hope this makes it an easy fix.

Thanks popacom / Bill Kagin III in Ky.

 

[macawpat]

Well I just had the whole dash apart and I have all the wires going into the gauge panel thru a round series of pins which connect the gauges thru a for lack of a better term computer tape. I unpluged the connecting harness and took a file to clean out all the connections and still have no fuel reading and also lost the oil pressure and water temp. I am sure I have all the wires pushed back on the pins and there is only one way it can fit back on. I will have to tear it down again tomorrow and chech that too. I also found out the ampmeter works and that you have to be really really carefull not to toutch any metal when moving it around (OUCH). Thanks very much on your suggestion. Pat

 

[AN/ARC186]

The best way to clean the connections on the ribbon cable is with a pencil eraser. the copper is very thin and using a file can damage them.
You can buy contact cleaner from electronic stores, in a pinch radio shack sells tv tuner cleaner/lube spray. this works as well.
Once you get everything back together, disconnect the lead from the sender at the tank. attach a long jumper that reaches the cab(so you can see the gauge) switch on ignition, touch the wire to a good ground point and see if the gauge reacts. If it does then your gauge is ok and you have a bad sender.

 

[papakb]

Pat,

The fact that the gauge moves at all is an indication that power is getting to it. On my crew cab the sending unit float had pinholed and never lifted with the fuel level and the reading always stayed at empty. If you can get to the wire on the sending unit, momentarily ground it and see if the gauge goes to maximum. If it does then your problem is with the sending unit itself. I have also seen the wire to the wiper in the tank break and do the same thing. I believe the resistance of the sending unit is around 100 ohms. If you need a replacement float I have them and can send you one.

Kurt

 

[MWMULES]

Welcome to the "WTF is with my Dodge dashboard club"! I have 3 of the M880 series and each has their own dash problems. This link explains what is going on Catalog and this is what other members have tried http://www.steelsoldiers.com/m880/27435-77-m886-alt-gauge-meltdown.html Thanks to skajm for the link

 

[macawpat]

I put a tester on the power wire to see if there was power even getting to it and found that there is no power getting to the sending unit. I think it may be somewhere in the dash. I tested the wire going to the sending unit at the dash and get no power althouth when I pull the voltage regulator from the back of the fuel gauge and test there I do get power on both sides. Could it be the voltage regulator ? If so is there a way to test that or is it possibly something else. Thank you all for being so helpfull and patient. Pat

 

[macawpat]

Thank you so much papakb. You absoutly nailed it. It turned out to be the float just like you said. Put the one you sent me in and it is working fantastic. Problem solved and wont have to carry a gallon of gas around with me anymore. Thats one less thing I will have to worry about. 1 problem down about 100 to go. Thanks again to all who helped with this thread.