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Please Advise: Sending unit slapping around in my tank like a maraca

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cbez Cole B
Fallbrook, California, USA   USA
I narrowed it down thanks to the previous thread. I believe it is definitely the float. When I shake the car with the filler cap open I hear metal on metal.

I filled it up and one bounce inside = 5 or 6 knocks. Which I think can only be the float bouncing around on the end of the sending unit arm.

When I got the car, I had no gas gauge reading as the old sending unit (also brass) was full of gas. Replaced it and my gauge worked again but it was off, a full tank would read half and about 4 gallons left would read empty.

I tested the gauge by shorting the wires and it went to full. Manually extending the arm of the sending unit to max also makes the gauge read full.

According to the diagram in my Hayne's manual everything is set up right. The sending unit matches the one in the diagram so I assume it is stock.

Do they rattle around inside all the time and you just generally don't hear it with a plastic float? Or is something wrong with mine? I hear the knocking at basically all fuel levels not just at full or empty.

Hoping someone who knows more about the inside of the gas tanks or the brass float conversion can shed some light on my issue. And if you can help me get an accurate gauge reading that would be the cherry on top.



1971 Triumph Spitfire MK 4



Edited 1 time(s). Last edit at 2017-11-08 11:12 PM by cbez.

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Tonyfixit Avatar
Tonyfixit Tony M
Duncan, British Columbia, Canada   CAN
Strange that it should hit at all fuel levels.

The OE plastic float had a rubber 'O' ring around it to soften bumping. You might try that.

Doug in Vegas Avatar
Doug in Vegas Douglas D
Las Vegas, Nevada, USA   USA
Pulling the tank is not that much of a chore.

Turning it over and shaking it out is easier than turning the whole car over even though you will find more change.

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cbez Cole B
Fallbrook, California, USA   USA
Found another thread where some other people had an issue and no one really seemed to have a resolution. Bending the arm away was suggested? I'm not really sure what the inside of the tank looks like so I'm leery of going crazy on the sending unit.



1971 Triumph Spitfire MK 4

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, British Columbia, Canada   CAN
I replaced my original sending unit this last spring. The new unit needed some modification to work correctly. I still have to work on it to get the tank read fully full when it is full.

However, the sending unit metal case has Tabs that stop the wire arm's travel at the extreme range of it's swing.

I assume this would mean the arms float should NOT hit the top or bottom of the tank, as the tabs should prevent the float ever moving that far.

When I re-adjust my sender, the wire on the float arm will have to be shortened and re-bent so that the arm can then rotate more toward the Full tab stop when the tank is full.
But if I do that the wire would also need to be bent down so the float reaches near the botton of the tank when Empty.

Roy Avatar
Roy roy o
Marietta, GA, USA   USA
I needed to bend the float arm away from the rear of the tank to stop rattling . Easy to see when sender is removed from tank- arm should not be in line with mounting surface.

colodad Avatar
colodad Silver Member Calvin Williams
Grand Junction, Colorado, USA   USA
In reply to # 1496843 by cbez I narrowed it down thanks to the previous thread. I believe it is definitely the float. When I shake the car with the filler cap open I hear metal on metal.

I filled it up and one bounce inside = 5 or 6 knocks. Which I think can only be the float bouncing around on the end of the sending unit arm.

Do they rattle around inside all the time and you just generally don't hear it with a plastic float? Or is something wrong with mine? I hear the knocking at basically all fuel levels not just at full or empty.

Hoping someone who knows more about the inside of the gas tanks or the brass float conversion can shed some light on my issue. And if you can help me get an accurate gauge reading that would be the cherry on top.

If your hearing it with the filler cap open, at all fuel levels could be it's the float's arm hitting the fuel pickup tube, not the float hitting the side of the tank.
You could measure from the side of the tank to the tube, and to the float's arm from the sender's mounting plate. compare the measurements.

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Attachments:
cwIMG_5993 fuel pickup tube.jpg    16.2 KB
cwIMG_5993 fuel pickup tube.jpg

cwIMG_6340 old sender unit.jpg    26.1 KB
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and this arm goes behind the fuel pickup tube.jpg    31.6 KB
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cbez Cole B
Fallbrook, California, USA   USA
ok I THINK I got it. When I reinstalled my sending unit I blindly followed the diagram instead of common sense.

So I had bad fuel level readings and I think it was letting the float go too far to the right, which was contacting the baffle.



1971 Triumph Spitfire MK 4

Yellowhawk Valley Avatar
walla walla, washington, USA   USA
1969 Triumph Spitfire "Walla Walla"
1969 Triumph Spitfire "Portland"
1972 Triumph Spitfire MkIV "Spokane"
1975 Triumph Spitfire 1500 "Dayton"    & more
Great. We will keep our fingers crossed and wait for the absence of maraca's when you are driving next time.

Dan

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colodad Avatar
colodad Silver Member Calvin Williams
Grand Junction, Colorado, USA   USA
did you turn the float on the arm ?


Attachments:
cwIMG_6343 old sender unit float mounted wrong direction.jpg    31.7 KB
cwIMG_6343 old sender unit float mounted wrong direction.jpg

cwIMG_6344 behind fuel pickup tube, float mounted wrong direction.jpg    44.9 KB
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cbez Cole B
Fallbrook, California, USA   USA
Yeah I have it facing back towards the rear.

One issue might be the stock one mounts in the middle while the brass one mounts on the end.

I still had some bopping today but my fuel tank is full so maybe it's hitting the top.

My gas gauge is 10% off accurate now instead of 50% though so getting closer...



1971 Triumph Spitfire MK 4



Edited 1 time(s). Last edit at 2017-11-17 11:59 AM by cbez.

Yellowhawk Valley Avatar
walla walla, washington, USA   USA
1969 Triumph Spitfire "Walla Walla"
1969 Triumph Spitfire "Portland"
1972 Triumph Spitfire MkIV "Spokane"
1975 Triumph Spitfire 1500 "Dayton"    & more
Quote: One issue might be the stock one mounts in the middle while the brass one mounts on the end.

As close as the originals are to the sides I think that would be a good guess.
Dan

luckygalnj Avatar
luckygalnj Silver Member Martha S
Cherry Hill, NJ, USA   USA
I have same issue "Maracas" but only when tank is not full up. Have not attempted to address as I thought it would involve pulling the tank? But from pics above it's just the fuel cap collar that your remove to gain access? Forgive my ignorance - learning what I can.

cbez Cole B
Fallbrook, California, USA   USA
In reply to # 1498438 by luckygalnj I have same issue "Maracas" but only when tank is not full up. Have not attempted to address as I thought it would involve pulling the tank? But from pics above it's just the fuel cap collar that your remove to gain access? Forgive my ignorance - learning what I can.

Sending unit pulls out the back from the trunk. Safe to pull it around 25% of a tank.



1971 Triumph Spitfire MK 4

Doug in Vegas Avatar
Doug in Vegas Douglas D
Las Vegas, Nevada, USA   USA
An earlier post on another thread demonstrated the very interesting observation that the Spitfire's tank height in inches is nearly the same as it's capacity in gallons.

This means at 1 inch per gallon folks with sending unit issues can get by with a dipstick notched in inches.

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