Oil & Fuel Fuel gage not working

[PAB_OH]

I noticed the other day my while mowing that the fuel gage was not moving. Secretly I was hoping th fuel efficiency was getting better but I knew better.

I checked and the tank was about 1/2 full.

Here's what I know.

- The gage reads full when the sending unit is plugged in and the key is on. When I shut the key off the gage stays at the full position.

- The gage reads empty when the sending unit is unplugged and the key is on. If I unplug the sending unit when the gage is reading full and the key is OFF it still reads full.

- If the gage reads full, the key is off, and I unplug the sending unit, then turn the key on the gage begins to move toward empty. If I shut the key off during this process (it takes about 45 seconds or so) the needle stops in its tracks. When I turn the key back on the gage continues to drop. This also happens if the gage is reading empty, I plug the senfing unit in and turn the key on and off as the needle rises. Difference between the two though is going from empty to full takes 2-3 minutes.

- I have pulled the unit out of the tank and I "ohmed" it and it reads fine. At full it reads 1 ohm and at empy position it reads 117 ohms.

- When I move the float with the unit REMOVED FROM THE TANK, the gage responds normally. I did not test to see if it would go to empty if the key was turned off, I forgot to do that.

- I checked the 7.5 amp fuse, removed and cleaned the chassis ground, and disconnected all the connectors under the floorboard (clutch side) and reconnected them.

- I checked voltage on the harness side of the plug and I'm only getting 7 volts. According to the schematic i should be getting 12.

Okay, I think that's it. I'm stumped. Has anyone else ever had this happen? Anyone know of something I'm overlooking?

 

[mrutkaus]

Um is there a accessible "wiper" moving on the resistor in the sending unit in the tank?

If so, maybe try cleaning it gently and compressing the wiper so it presses harder on the resistor?

Mike

 

[PAB_OH]

No, not that I recall. It has a sheetmetal housing around the inards to protect it I guess. From what I'm not sure. Most sending units I've worked on in cars are open.

I generally don't like to touch that stuff anyway. I'm no electrical engineer so if it's got electrons zipping through it I usually default to the experts. I can usually figure out IF it's bad, not always WHY it's bad. This one has me scratching my head.

I'm not in a bind or anything so I can use the machine as is and wait for some suggestions to roll in here. If it gets to be a pain I'll take it to my dealer.

Thanks for the suggestion.

 

[Gittyup]

You wrote: "When I move the float with the unit REMOVED FROM THE TANK, the gage responds normally."

Doesn't this indicate that the float is getting stuck on something in the tank that does not allow it to actually float on the fuel? If so, I think there have been posts about this kind of problem on here in the past. Something about having to bend it so that is can move freely in the tank, as I recall.

 

[PAB_OH]

I wondered about that too. But the kicker is that the gage reads full all the time. It should return to EMPTY when the key is shut off. This is what led me to believe it is an electrical problem.

I will tell you this, that float arm has more bends in it than the old country roads around here. I can definitely see how it could get hung up if any of the bends get out of line. But how does that happen? I can't for the life of me figure out how it could get knocked around enough to cause this. I'm not saying it hasn't happened before, I just can't come up with a scenario in my head where it could happen.

I'll pull it out again this afternoon and shine a flash light down in the tank to try and see if it is maybe hanging up.

Thanks for the suggestion.

 

[gravel13]

My gauge would read whatever the float was with the key off. If I filled it, then started the tractor it would take a while for the gauge to move to "full" and as the gauge dropped to say 3/4 full it would stay there even when I shut off the tractor. My only problem is now that it seems to be hanging up. The last time I filled it up, pretty much to the top, the gauge read "E" the whole day while it was on. The next time out about an hour into working it it now read 1/2 a tank and that is where it has been. I was going to search the threads as someone posted how they bent the arm and there gauge was working fine after. As Gittyup stated there are a few posts about this, it just a matter of finding the one that had the pics attached that shows how the float arm should be bent.

 

[IXLR8]

Guess I am not the only one with a flaky fuel level gauge. First tank I ran almost empty, put in 5+ gals, for the next two days of usage it showed empty. When I was using it the following week, the level showed about 2/3rds full. The next week, it showed full and it has been dropping steadily since. I have to say... I am going to get a rod and put some level markings on it... I don't trust this gauge.

 

[George2615]

Since you pulled the sending unit and tested it with an ohm meter and it and the gauge perform as normal then it seems to me that the float itself may be bad or is hanging up on something in the tank. If its a plastic or brass float they sometimes get a small hole in them that will fill with fuel and not let it float. If the float is removable take it off and shake it to see if there is fuel inside. It could also be the sending unit ground is not good.

 

[DirtHauler]

Yeah these gages are about as accurate as a scud missile! These gage/senders aren't like the one's used in cars and trucks which use what they call "pulse" units which constantly send pulses of electric current to the sender and the gage reads the resistance and adjusts.

If you feel real brave, you could check to see if the gage it self is working right but maybe more of PITA then it's worth, you'd have to remove the gage from the dash and the board, attach a 6 volt battery to it and it should read 1/2 ..... 10-12 volts should be full.

 

[sodamo]

Yep, this has been noted before. I used to be concerned, but now I just watch the hour meter and add 5 gallons (approx) every 5 hours. Not particularly accurate, but so far haven't run her dry.


David