• Hi Guest!
    If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Fuel tank sending unit

Share this page

bugedd

bugedd

Jedi Knight
Country flag
Offline
My next project is to replace the sending unit for the fuel gauge, and was wondering what is better. The ebay ones "with dual brushes" or Moss?
 
Word to the wise. I dropped the tank to check inside of tank after fuel pump crapped out. Inside of tank looked clean but fuel gauge would not work after removing and reinstalling. All grounds nad power were good and double checked with VOM meter. After lots of head scratching ordered new MOSS Dual Brush Unit. Lots of plactic but appears to be well constructed. Replaced sender and suddenly realized the orientation of the float arm on the old unit was pointing awfully close to the pickup hose in the fuel tank. Is it indeed possible to orient the Float Arm so it interferes with free movement of the float caused by interference with fuel pickup hose in there? I'm thinking now the dumb current owner(DCO) of Bugssy screwed up and bought a Fuel Sender assembly he didn't need. Oh and when Bugsy's fuel gauge reads empty there are still close to 2 gallons in the tank.
 
I guess I should discuss my problem rather than assume its a bad sender. The tank was replaced my the stupid previous owner, and he said the sending unit was replaced as well. But the fuel gauge was incorrect, so I bought a correct one and had Palo Alto speedo rebuild it. Well, it jumps around and when the tank is full, its just wigs out and goes all over the place. So I put a stick in my gas filler to know how much gas I have :smile: I assume its grounded well at the gauge. I read there is supposed to be a ground at the sending unit. I assume its just the tank grounding to the body.
Am I missing anything here? should I check anything else?
 
I would keep the orginal sender if at all possible. I haven't seen a new one that is accurate. Your original should be the old style 0-70ohm sender if its your bugeye in the picture. Lots of times those senders get a little play in the wiper arm and at the top when full, when it hits the stop, it lifts the wiper off of the wire resistor that it wipes on. When that happens it goes from full 0 ohms to empty 70ohms every time it wiggles around. You might be able to fix that with a small tweak with some pliers or something to get rid of that play. If you get one of the new senders, it might be worth your while to calibrate it with the gauge. Yours will be the 12v gauge and the not the 10v type on later models that were 0 ohms when empty and 270 when full(hope I got that right).
 
regularman said:
Lots of times those senders get a little play in the wiper arm and at the top when full, when it hits the stop, it lifts the wiper off of the wire resistor that it wipes on. When that happens it goes from full 0 ohms to empty 70ohms every time it wiggles around.
Click to expand...
Funny, that describes exactly what mine is doing. I really need to drop the tank and fix that.
 
Jim_Gruber said:
Oh and when Bugsy's fuel gauge reads empty there are still close to 2 gallons in the tank.
Click to expand...

we need to swap senders - mine is empty at 1/4 tank showing - should pretty much even out.
 
Just discovered my latest acquisition is empty at 1/8. On my way to the gas station at the time. Started cutting out and I knew what the trouble was. Waggled the wheel and got enough to get the speed up so that when it died I coasted into the station! All the while wife is giving me glaring looks and complaining about having to push my british obsession's!!

Keeps life interesting!!

Kurt.
 
Kim adjusted my sending unit a few years back. Works great now and has about 2 gal at empty.

Thanks Kim.
 
Interesting, that sounds like what mine is doing. I am almost out of gas (I think), so I should be able to drop the tank soon.
 
jlaird said:
Kim adjusted my sending unit a few years back. Works great now and has about 2 gal at empty.

Thanks Kim.
Click to expand...

Jack (and Kim) I understood that my showing 1/4 tank at empty was because the arm had to be bent like a toilet float. Is this not the case?
 
I think I will let Kim answer that JP. Far as I am concerned he is the expert.
 
Well, the arm could be bent but it made out of pretty good spring metal on the old ones at least. The only way to be sure of a fuel gauges accuracy is to calibrate the sender and gauge together. For my tank I put a known quantity of fuel in the tank and adjusted the gauge. I put in one gallon and at that point I set the gauge for empty. I know this is accurate because the wife and I took a trip and ended in no gas land with 1/4 tank and we had to take it down to just below empty and it had about .7 gallons left according to the fill up(I was nervous though and don't like playing it that close). What you don't want is a gauge telling you that you have some fuel left when you don't. When I did other people's senders and gauges, I tried to leave a reserve of some kind but I did not have a tank to use for better accuracy.
 
And how do you adjust the gauge when you have your known amount of fuel in the tank?
 
bugedd said:
And how do you adjust the gauge when you have your known amount of fuel in the tank?
Click to expand...

yes please and FWIW mine is a new sender in a new tank on a '76
 
bugedd said:
And how do you adjust the gauge when you have your known amount of fuel in the tank?
Click to expand...
On yours, assuming it is the stock gauge for a bugeye. There are two screws on the back of the gauge that you loosen and move that move the coils and affect the deflection of the needle. One affects the empty area and the other the full area. They interact with each other and you have to have the patience of Job when setting it. There will be no perfect "sweet spot" and so you have to get as close as you can to right. I try to make it as right as possible at the empty area first and then worry about the half and full.
The reason being is that a gauge saying you have 7/8 of a tank when it is full, is not near as bad as a gauge saying you have 1/8 of a tank and you at bone dry.
 
JPSmit said:
bugedd said:
And how do you adjust the gauge when you have your known amount of fuel in the tank?
Click to expand...

yes please and FWIW mine is a new sender in a new tank on a '76
Click to expand...
ok, yours won't be like the bugeye one. 76, hmmn, that is a rubber bumpered one. I have not physically had my hands on one of them but as I recall it is the 3rd kind.
OK, apologies, my mind is skipping around today.
First type. Bugeye(and lots of other brit cars)- somewhere in the mid 60s, 12v type.
60s-before rubber bumpers 10v with voltage stabilizer.
rubber bumpered 12v.
I don't know exact dates, but I have a 76 junker that I got for free and have been waiting on a title for for 3 years. With no luck. I need to go get all the usable parts out of it.
I had dreams of making it an alternate fuel car. I am not going to do anything without some papers to say its mine.
Anyways, there is more than likely some adjustments on the back of the gauge. There is even a chance that yours is the 10v type and has the voltage stabilizer. If its the later model than that, then it might not be adjustable. I just don't know.
 
I took it apart today and to my suprise, found that I had almost a full tank! Thank goodness I had my jack under the tank to remove it! My gauge had been reading 1/8 of a tank. I took the sender out and found that the float was full of gas. Hmm, that makes sense for the empty reading. Then I ran the float arm up and down to check ohms and it read 7-96 ohms, rather than 0-70. And I got random spikes of 200+ ohms as it went through the readings, which is why it had the crazy spikes to full. I took off the cover to the resistor unit and was disgusted with how poorly it was wound. Never have I seen something so poor. So I ordered a new Moss part hoping it will be better than the piece of junk the previous owner put on there.
Anyhow, hopefully by Sunday it will be back together and I will have a clue on how much fuel I have.
 
bugedd said:
Anyhow, hopefully by Sunday it will be back together and I will have a clue on how much fuel I have.
Click to expand...

You have almost a full tank :whistle:
 
I have experienced three fuel sending unit float failures in the last two years. All three were plastic floats. All three were filled with fuel. Two of the three were relatively new units. I suspect that our modern fuel supply (ethanol) is the culprit.
I have since changed out the floats to a brass float readily available at your local Ford dealer or on line at several sources. The Ford No. is COAZ-9202-B and fits various Fords from the 70's. I believe there is a GM and MOPAR version as well. It might be the same float. So far, all gauges are working properly.
 
Back
Top