Fuel sender resistance values?

[Spittybug]

My fuel gauge has been showing progressively lower and lower over time despite gas in the tank. For example, I filled up today and it shows less than 1/4. I did the jumper test and confirmed the gauge itself is good (bottoms out and peaks out when jumpered and when disconnected) and the low light comes on too. I removed the sender; original plastic. The float in it moves freely. No "gel" or decomposed gaskets like others have described. Basically in excellent shape. I put the ohmmeter across the pins and got a low of ~5 and a high of ~110. It seemed fairly linear in between, but sometimes the values jumped around before settling. The pins were all sandpapered and all put back together again. Same result.

Does anyone have the specs for the resistance across this rheostat? I hate the fact that DMCH wants $150 for a new one; especially since it is such a simple thing.... anyone know of a crossover?

Thanks.

[mburshtain]

I was experiencing a similar issue and after opening it and cleaning it well (with WD40) it started performing well. As you may expect from old plastic, you have to be extremely gentle taking it apart.


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[Spittybug]

I was experiencing a similar issue and after opening it and cleaning it well (with WD40) it started performing well. As you may expect from old plastic, you have to be extremely gentle taking it apart.


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How does it come apart?

[mburshtain]

How does it come apart?

Please take a look at this page - http://dmctalk.org/showthread.php?8538-Fuel-sender-options/page2
Pull the filter out and you should see a small nut. Once you remove it you can pull the plastic piece and access the float.

[mburshtain]

http://uploads.tapatalk-cdn.com/20160516/20a0d66257c08501e946021709410905.jpg


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[Bitsyncmaster]

FYI: the gauge reads full (centered on the 4/4 mark) with 83 ohms to ground on the sender pin. I did that test at 14 volts but as I said, very little change with 12 volts. Zero ohms moves it to empty.

I posted this on this:

http://dmctoday.com/showthread.php?908-Wanted-Fuel-Pump-Sender-and-Fuel-Pump-Boot&p=37840&highlight=fuel+sender#post37840

[Spittybug]

Thanks.. . I know what I'm doing tomorrow!

[Spittybug]

That was straightforward enough. Just not sure if it worked! I made the copper rod down the center nice and smooth, cleaned contacts, tried to smooth the walls of the float with very fine sandpaper, cleaned the thing thoroughly and tested. Works great simply attached to ohmmeter. When put back into the car however, the fuel gauge only goes up to about 1/4. I'm going to drive it and bump it around since I believe the float has lost some of its buoyancy over time and tends to hang up when rising in the tube. Either that or the center hole is a little sloppier than when new and allows the float to get a little crooked in the tube, binding it a bit. If this still doesn't work after the drive I think the next step will be to shave the diameter of the float a bit.....

[dn010]

That was straightforward enough. Just not sure if it worked! I made the copper rod down the center nice and smooth, cleaned contacts, tried to smooth the walls of the float with very fine sandpaper, cleaned the thing thoroughly and tested. Works great simply attached to ohmmeter. When put back into the car however, the fuel gauge only goes up to about 1/4. I'm going to drive it and bump it around since I believe the float has lost some of its buoyancy over time and tends to hang up when rising in the tube. Either that or the center hole is a little sloppier than when new and allows the float to get a little crooked in the tube, binding it a bit. If this still doesn't work after the drive I think the next step will be to shave the diameter of the float a bit.....

Stupid question but did you test it out of the tank to see how the gauge reacts? My original sender lacked the outer plastic tube, maybe the float getting stuck is the reason why. I may still have it laying around somewhere if you want it for parts...

[Bitsyncmaster]

That was straightforward enough. Just not sure if it worked! I made the copper rod down the center nice and smooth, cleaned contacts, tried to smooth the walls of the float with very fine sandpaper, cleaned the thing thoroughly and tested. Works great simply attached to ohmmeter. When put back into the car however, the fuel gauge only goes up to about 1/4. I'm going to drive it and bump it around since I believe the float has lost some of its buoyancy over time and tends to hang up when rising in the tube. Either that or the center hole is a little sloppier than when new and allows the float to get a little crooked in the tube, binding it a bit. If this still doesn't work after the drive I think the next step will be to shave the diameter of the float a bit.....

It may be your fuel gauge. The gauge uses two coils so as to stay accurate with voltage changes. I was surprised at the power required to run the fuel gauge.

[Bitsyncmaster]

Your fuel gauge powers one coil with 12 volts and ground and the other coil is powered with 12 volts and the sender is it's ground. So a bad connection of the fuel gauge 12 volt or ground pins could cause your problems. Or it could be the gauge itself.

[Spittybug]

Grrrr... doesn't go up much past 1/4. Will yank again and check to see if I can get good readings on gauge by keeping it connected and moving the float up and down by tilting. I should have done that as a check in the first place, but I though the jumper test ruled out the gauge being bad....... I'm not truly comprehending exactly what benefit the tube provides in any case....

[Bitsyncmaster]

I have a spare gauge and can do some testing if you can determine what you can test. I don't really want to sell my spare gauge which I bought to someday make a circuit to drive the fuel gauge from different senders (those all in one fuel pumps).

[Spittybug]

The problem has been proven to be that my float does not float anymore. When I manually move the float my gauge in the car reads perfectly. I've already found the replacement online in parts for sale Section. Thanks for the advice Dave.

[dn010]

If you want to save a few bucks or if you want to make one out of 2 senders so you have a spare, I will send you my old junk plastic one if you want it, provided I didn't throw it away already.