Thread: Fuel Sender 101
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Old 06-27-2012, 03:10 AM
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mtajpa mtajpa is offline
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Join Date: Feb 2009
Boat: MC 1999 Maristar 230 sport
Location: Southwest
Posts: 731
Fuel Sender 101

My fuel gauge on my 99 Maristar 230 quit working so I decided to post my method for testing and replacement. When the key is turned on the gauge pegs and then returns to the empty position. This is with the key on and appx half a tank of fuel.


The sending unit I have is a 2 wire unit. It is basically an adjustable resistor that is activated by the fuel level. Some have a float others has an electronic sender. The fuel position on the guage should read full when the sender is at 33 ohms and empty when sender is at 240 ohms. Half s tank will be indicated at appx 100 ohms. The factory sender had adjustable trim pots to fine tune the sender to the gauge.

I am not 100%sure but I think this procedure will work with the 3 wire sender also as the 3 wire unit has a positive connection also.


First we will disconnect the sender from the harness. Then I got some resistors from Radio Shack 2 ea 100 ohm and a 33 ohm. I placed these in series to test the gauge. Should read 233 but this is close enough. Kind of a cheapo meter.



Next I connected some test leads to the harness leading to the fuel gauge. This is the part that was previously disconnected. One side goes to the sender and the other to the gauge.


At the other end of the test leads I connected the resistors and observed the gauge. With the key on I then placed the test lead across the 33 ohm resistor and the gauge reads full.

Then moved the leads to the 100 ohm resistor. This gave me a half tank reading.


Then the last test with the resistors is using the 2 100’s and the 33 in series for a total of 233 ohms. This gave me an empty reading.

This verifies the gauge operation to be correct for the 33-240 ohm sender.

I then moved to the sender to see what kind of ohm reading I was getting. It was reading 320 ohm across the black(gnd) to Pink (sender) leads. Since the sender should only read 240 ohms when empty then this means the sender is faulty.


For this next step be sure to have your ignition off and disconnect or turn OFF you batteries. Make sure you have a fire extinguisher at the ready.

I then removed the sender by removing the 5 screws and pulling the sender up and out of the tank. Have a rag handy to catch any fuel leaking off the sender.

Once the sender is removed the fuel tank the tank will be exposed to the elements place a rag or something to keep things from falling into it.

My sender looks like this it is 10 inches in length.


My tank is a 65 gallon with a depth of 11 inches at the sender location. If your are not sure of your depth then get a wooden yardstick and insert it into the tank at the sender hole. Your sender should be 1 inch less than the tank depth.

I ordered a replacement from SkiDim. It isn’t exactly the same but will work as electrically it has the same value of 33 ohm when full and 240 ohms when empty. The one I took out did not have an external float.


TO BE CONTINUED ON NEXT THREAD WITH MORE PICTURES

disreguard pictures below they are the same as the ones used between text couldn't figure ho to get rid of them.
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99 MariStar 230 Sport LTR 330

Last edited by mtajpa; 06-27-2012 at 07:57 PM.
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