Help with Diagnosing Fuel Gauge/Sender - MF20

Clarkbug · Apr 11, 2023

Hello everyone.

Wanted to get a little help for a troubleshooting process, and not sure where to start. I have a MF20 with the Perkins gas engine. The fuel gauge doesn't work, and hasn't since AI bought it. Originally the sender wire wasn't connected, and it looks like sealer was painted over the entire area where the sender is, presumably due to a leak. I recently cleaned up the connections and re attached the wiring, but no use.

Where do I start with the electrical troubleshooting to see if I have a bad sender, a bad gauge, or both? I have a test light and a multimeter, but not anything more advanced. My understanding is that the resistance change form the sender is what moves the needle, but beyond that I'm a little fuzzy.

Any tips or places to start?

used red MN · Apr 11, 2023

Either use a jumper to ground the sender wire or
remove it from the terminal and short it to a good
ground. You did not report the gauge read full when
disconnected so grounding it with the key on should
make it read full. If it responds in this manner it is very
likely your tank sender is bad. When you get it out if
the float is brass float it in some water. If it sinks the
float may be the problem and can be replaced. If the
gauge did not respond to the grounded lead then it is
not being powered properly, the connections on it are
bad or the gauge has failed.

This post was edited by used red MN on 04/11/2023 at 08:27 am.

Clarkbug · Apr 11, 2023

Thanks Red. The gauge always reads empty, has with or without the wire connected. I'll try your troubleshooting steps and will see if the needle moves.

Is there a way to see if both items are bad? I have read on some other threads that they need to be matched as far as the output/range? I mostly would want to buy a matched set if I need both, or understand the range of whatever the working part that's left is.

Thanks!

47fivewindow · Apr 11, 2023

make sure the tank is grounded before you take anything apart.

Jim.ME · Apr 11, 2023

(quoted from post at 11:42:01 04/11/23)
Thanks Red. The gauge always reads empty, has with or without the wire connected. I'll try your troubleshooting steps and will see if the needle moves.

Is there a way to see if both items are bad? I have read on some other threads that they need to be matched as far as the output/range? I mostly would want to buy a matched set if I need both, or understand the range of whatever the working part that's left is.

Thanks!

First, Does the gauge have power on the terminal that does not go to the sender, when the engine is running?

Next use a jumper wire to ground the sender terminal of the gauge and see if the gauge moves. If it does then it should work if you ground the wire at the sender. You may need to go to a known ground as sometimes the tanks lose ground preventing the system from working. The sender can be checked with an ohmmeter by removing it and measuring the resistance between the sender terminal and the sender mounting flange. It should change as you move the float. And yes, the resistance range of the gauge and sender must match to read properly.

Clarkbug · Apr 12, 2023

Thanks again for the tips Jim. Hopefully I can get a bit of time this weekend to do some troubleshooting.

Clarkbug · Apr 14, 2023

Well, did a little checking today. I have power at the positive lead to my gauge, but no movement when I ground out the other post. I went straight from that post to the negative terminal on the battery, so figure that's a pretty safe bet. Sounds to me like I need a new gauge.

One other thing I found was after working the tractor hard and shutting it down, I heard a hissing noise. It was blowing from my fuel tank around the fuel sender. I had just bought a new fuel cap that says it is vented, but clearly that vent isn't working. Not sure if there is a way to fix it, but may just be buying a new cap.

Thanks for the assistance thus far....more to come.

Clarkbug · Apr 29, 2023

Thought I would post an update. Bought a new sender and gauge. Turns out it was a Sparex S.61429. Original MF gauge was a Stewart Warner 821478, which judging by the amount of rust in it that came out is definitely bad. Hooked up two wires on the new gauge (even though it has a separate attachment for ground) and it looks like my old sender is doing something!

With the key on it goes to half a tank, so that's exciting. Not sure if it's accurate or not, but it's better than where I was.

There is a leak around my sender, and looks like someone put some sort of sealer all over the area there, so I may be able to get away with just a new thicker gasket on the old sender, but not sure. I'll need to figure out how to get the old screws out since they are all filled with sealer. Is there any sort of sealant you can suggest if I need more than just a gasket?

Help with Diagnosing Fuel Gauge/Sender - MF20

Clarkbug

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used red MN

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Clarkbug

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47fivewindow

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Jim.ME

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Clarkbug

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Clarkbug

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Clarkbug

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