Bad fuel sending unit???

[jeepnsam]

Gas Tank:

Skyline
Model: 47689-00
Gallons: 31
Measurements: 26" W x 42" L x 8" D

So I filled the tank until gas came out of the vent line, make
sure to let it settle then topped it off. Checked my gas gauge and it was pegged at 1/4.
Ran the river for the day and gas gauge never went about 1/4.

Noticed the gas gauge needle started to bounce around between E and 1/4 so I figured
I'm getting low.

Stopped at the fuel station and topped of the tank. Only 10 gallons went in, which means I had 20 gallons left over.

Pulled the fuel sending unit today (see picture below) and it moves freely. Put a tape measure down the sending unit hole (8 inches high tank) and 4 inches of fuel left over. So I've got 15 or so gallons left in there.

Knowing what came out is not always what SHOULD be in there, I figured I would ask the "smart ones" which one should replace this old unit?

6"-12" Electric Sending Unit - Moeller
12"-24" Electric Sending Unit - Moeller

Does this sound like the sending unit or the gauge is bad??


WHAT CAME OUT:

 

[Mountaineer67]

Re: Bad fuel sending unit???

I just replaced mine. Less is more. I would opt for the 6-12 because it just means you'll have to cut less of it off. Oh... READ the directions. I didn't went through 2 of them before I got it right.

I had the same question (gague or sending unit). Here's what they told me: check/jiggle/clean the connectors on the beck of the gague, but replacing the sending unit is usually easier to get to and cheaper, so they suggested I do that first. In MY case, it worked (well, it worked the second time...).

 

[franktrav]

Re: Bad fuel sending unit???

check voltage on lead coming from sending unit. it should increase and decrease as the float lever moves up and down respectivly.if it does than the unit is working unless the float lever is binding keeping it from moving up and down with the fuel level. if no binding and voltage readings are good then it is probably the guage

 

[CheeseCutter]

Re: Bad fuel sending unit???

Test the sender with an ohm meter. The resistance should be about 240 ohms for a full tank, and about 30 ohm when empty. There should be a smooth transition between those readings as you move the sender from full to empty. If the sender checks out, looks like the guage would be bad.

 

[Pez Vela]

Re: Bad fuel sending unit???

Test the sender with an ohm meter. The resistance should be about 240 ohms for a full tank, and about 30 ohm when empty. There should be a smooth transition between those readings as you move the sender from full to empty. If the sender checks out, looks like the guage would be bad.

... or it could simply be poor wiring connections. Hook the (+) and (-) leads back up to the sender while it is out of the tank. Move the float up and down and see what your gauge does. Along with CheeseCutter's recommendation, this should tell you what you need to know.

 

[jeepnsam]

Re: Bad fuel sending unit???

WTH???

Read the updates this morning, wired the + and - leads to the sender...turned the switch on and the darn thing reads FULL. Held it straight and moved the arm very slowly..and the gas gauge followed.

Guess i'll clean all the connections, put her back in and test it out on the lake this Sunday.

 

[Silvertip]

Re: Bad fuel sending unit???

Some incorrect advice here. DO NOT replace the sender first. DO NOT replace the gauge second or first. DO NOT measure voltage at the sender and 240 ohms FULL and 30 ohms EMPTY is NOT correct. Always diagnose the problem and then repair or replace as necessary.

1) Turn the key on (RUN position).
2) Short the "S" (sender) terminal on the gauge to ground. The needle should peg full indicating the gauge is OK. If it doesn't, use a voltmeter to verify the gauge has +12 volts and ground. The gauge is very rarely the issue.
3) If the gauge is fine, now move to the sender. Disconnect the send wire from the sender.
4) Using an ohm meter, measure the sender resistance to ground. If you have even a rough idea of how much fuel is in the tank, the resistance readings will be 33 ohms full, 109 about 1/2 full and 240 ohms empty (in other words just opposite of what was suggested earlier). The readings can be slightly different but not drastically.
5) If a problem is determined, remove the sender and check the float arm for freedom of movement. Use the ohm meter again to verify resistance readings empty to full.
6) Replace the sender if necessary.
All of this requires that all connections are clean and tight.

Here is a diagram of the fuel gauge circuit.

 

[jeepnsam]

Re: Bad fuel sending unit???

WELL!!! the verdict is in!

All I had to do was adjust the swing arm to 1/2 since I have 4" of gas in an 8" deep tank. Everything else checked