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Posted By: chanceafrica fuel gauge issues. - October 12th 2014 12:21 am
Ive swapped out my fuel sending unit and my gauge reads 3/4 tank when full and when its at E it probably has around a quarter tank left. ive checked the gauge before installation and it has an ohm rating of 10/75 full/empty. the guy i spoke with at spectra(manufacturer) insists that is the proper specs for a stock 77dodge b200 fuel gauge. my van is a "factory custom" but all the pictures of 77 dodges seem to have this same fuel gauge. what are some causes of my improper reading do you think? should i check the lead from the unit to the gauge and see if there is an improper resistance reading due to wire breakage/corrosion at connections? has anybody had this same issue? the sending unit i put in looks like it has calibration tabs on the float arm closest to the unit, to change where the arm stops at full and empty. the guy at spectra says the unit does not come with calibration capabilities and i should not mess with the tabs , as they will not change the resistance reading. thanks for any insight on this issue. also tank is a stock 22gallon i think. i replaced the sending unit ground and sanded the chasis where it connects, next i need to check at the gauge to see if im losing resistance along the run, but not sure how to check it unless its completely full or empty.
Posted By: DesertRat Re: fuel gauge issues. - October 12th 2014 11:55 pm
The gauge is probably toast, mine was stuck on full and everything checked out fine. Stock gauge was part of the cluster so I used a blank gauge recess on my dash and just bought an aftermarket gauge and flush mounted it. I guess if you really like the stock one you could check with a speedo shop, I would think they would be able to repair it.

Good luck
Posted By: chanceafrica Re: fuel gauge issues. - October 13th 2014 11:05 pm
mine is operating somewhat as i suggested in my previous post. i just checked the ohms on all the lines and it seems im losing resistance at the dash circuit board. im losing a small amount at the quick connector and once it reaches the gauge lead its losing almost half.

so at my sending unit the ohms reading is about 25.5 then at the quick connector its about 23 ish then once it travels through the post and copper ribbon its at about 13. i sanded the post the quick connector attaches to and still losing resistance. so the copper ribbon theoretically makes sense to me, but i am more familiar with wiring. is there something im not considering that is specific to the ribbon? by ribbon im reffering to the flat copper tracks on the gauge "circuit board" that sends the signal to the gauges. also i havent taken the gauge out and checked it beyond the "circuit board"
Posted By: chanceafrica Re: fuel gauge issues. - October 29th 2014 8:53 pm
not that anyone seems to be paying attention to this, but after roughing up the connections in the dash, my gauge now reads to full. but still only seems to have the range of a half tank. so at half a tank my gauge reads empty,and at 3/4 tank,gauge reads half.

sure its better than nothing, but i want to understand how this works and why its malfunctioning.
yeah its an old vehicle, but its meant to operate a certain way and when you diagnose a specific issue with a part, replace the part with an aftermarket part that is setup to the original specs, why wouldnt this be functioning correctly,besides losing resistance in the lead, which i seem to have corrected.
Posted By: Reed Re: fuel gauge issues. - October 29th 2014 9:15 pm
http://www.allpar.com/history/mopar/electrical.html

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

http://www.allpar.com/history/mopar/electrical2.html

I highly recommend yo get a copy of the factory service manual for your van. It will walk you through how to truly diagnose and trouble shoot every system on your van. Your problem could be a faulty dash gauge, a faulty instrument panel voltage regulator, a faulty sending unit, a bad ground on the sending unit, and/or bad wiring.
Posted By: HonestRansy Re: fuel gauge issues. - October 29th 2014 9:35 pm
I have not had to troubleshoot fuel gauges before but I am electrical. So, did the fuel gauge ever work? If so, at what point did it not work? Maybe after changing fuel sending unit? Your sending unit probably has three wires going to it. I think that one is a ground and probably goes to the frame near the tank (it does on the 1980's Dodge pickups) . I would definitely check this. One is positive 12V. The other wire has a lesser voltage after the varying resistance of the sending unit in the tank. The connections to the tank/tank harness are known problem areas on all vehicles that have the tank outside the cabin area. I would check these connections. Next, check your wire that is the positive 12V and ensure that you do have 12V with the Ignition on. Next, if possible, jumper 12V from a known good source (the battery positive terminal) to the 12V that goes to the sending unit. Make sure to not backfeed onto the vehicle harness wire that goes to the front of the vehicle. See if this makes any difference.
Posted By: Reed Re: fuel gauge issues. - October 29th 2014 9:55 pm
Dodge sending units have a ground strap that bolts to the frame and then clips to the fuel line on the sending unit and the sending unit wire. Only two wires- ground and output (input, really) to/from the dash. The sending unit itself is a variable resistor attached to the float arm that changes the resistance to complete the gauge level circuit. (+) comes from the battery, to the gauge, to the sending unit, through the variable resistor, then back out through the ground strap to the frame to complete the circuit.
Posted By: Mogs Re: fuel gauge issues. - April 22nd 2019 9:05 pm
Originally Posted by chanceafrica
Ive swapped out my fuel sending unit and my gauge reads 3/4 tank when full and when its at E it probably has around a quarter tank left. ive checked the gauge before installation and it has an ohm rating of 10/75 full/empty. the guy i spoke with at spectra(manufacturer) insists that is the proper specs for a stock 77dodge b200 fuel gauge. my van is a "factory custom" but all the pictures of 77 dodges seem to have this same fuel gauge. what are some causes of my improper reading do you think? should i check the lead from the unit to the gauge and see if there is an improper resistance reading due to wire breakage/corrosion at connections? has anybody had this same issue? the sending unit i put in looks like it has calibration tabs on the float arm closest to the unit, to change where the arm stops at full and empty. the guy at spectra says the unit does not come with calibration capabilities and i should not mess with the tabs , as they will not change the resistance reading. thanks for any insight on this issue. also tank is a stock 22gallon i think. i replaced the sending unit ground and sanded the chasis where it connects, next i need to check at the gauge to see if im losing resistance along the run, but not sure how to check it unless its completely full or empty.



Same issue here. Dodge 77 b200 van.

I replaced an old sender with a sunk float for a new spectre part from rockauto for a 22 gal tank.

I tested both the old and new units outside of the tank: with the floats manipulated to full sweep, the dash guage read 3/4 with both units. I read that someone elses gauge also reads only 3/4 on a full tank, so I was willing to accept this as a quirk. (I'm in the UK so I just assumed it's a thing for them to never read over 3/4 -maybe they never did from factory?) So I assumed the new unit was calibrated the same as the old one.

I have to try hard to brim the tank, with the nozzle clicking off at the station. I can get the guage to read 3/4. But then with some driving it drops drastically! After 6 miles I'm at 1/2 and another 6 miles I'm at 1/4. I'm pretty sure when it hits E I've still got most of a tank left.

I have tested the guage by earthing the sending unit and witnessing the dash gauge peg to full.

Getting a 5v reading from the dash volt reg too.

Anyone throw any light on this or did chanceafrica find a solution or any information?

Thanks.
Posted By: DontComeKnocken Re: fuel gauge issues. - June 24th 2019 9:33 pm
Originally Posted by Mogs
Originally Posted by chanceafrica
Ive swapped out my fuel sending unit and my gauge reads 3/4 tank when full and when its at E it probably has around a quarter tank left. ive checked the gauge before installation and it has an ohm rating of 10/75 full/empty. the guy i spoke with at spectra(manufacturer) insists that is the proper specs for a stock 77dodge b200 fuel gauge. my van is a "factory custom" but all the pictures of 77 dodges seem to have this same fuel gauge. what are some causes of my improper reading do you think? should i check the lead from the unit to the gauge and see if there is an improper resistance reading due to wire breakage/corrosion at connections? has anybody had this same issue? the sending unit i put in looks like it has calibration tabs on the float arm closest to the unit, to change where the arm stops at full and empty. the guy at spectra says the unit does not come with calibration capabilities and i should not mess with the tabs , as they will not change the resistance reading. thanks for any insight on this issue. also tank is a stock 22gallon i think. i replaced the sending unit ground and sanded the chasis where it connects, next i need to check at the gauge to see if im losing resistance along the run, but not sure how to check it unless its completely full or empty.



Same issue here. Dodge 77 b200 van.

I replaced an old sender with a sunk float for a new spectre part from rockauto for a 22 gal tank.

I tested both the old and new units outside of the tank: with the floats manipulated to full sweep, the dash guage read 3/4 with both units. I read that someone elses gauge also reads only 3/4 on a full tank, so I was willing to accept this as a quirk. (I'm in the UK so I just assumed it's a thing for them to never read over 3/4 -maybe they never did from factory?) So I assumed the new unit was calibrated the same as the old one.

I have to try hard to brim the tank, with the nozzle clicking off at the station. I can get the guage to read 3/4. But then with some driving it drops drastically! After 6 miles I'm at 1/2 and another 6 miles I'm at 1/4. I'm pretty sure when it hits E I've still got most of a tank left.

I have tested the guage by earthing the sending unit and witnessing the dash gauge peg to full.

Getting a 5v reading from the dash volt reg too.

Anyone throw any light on this or did chanceafrica find a solution or any information?

Thanks.


My 82 B150 has always done the same thing since I bought it a few years ago. It shows somewhere around 3/4 when its full and when it shows empty, it only takes about 15 gallons. It might be something wrong with the gauge but it is always consistent so I've just used it as is. I also changed the gas tank because it was a bit rusty and smashed in (looks like someone backed over a big curb) and reused the fuel sending unit. Everything looked fine and it did the same thing.
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