7140

[caterpillar guy]

On the boxcar models how does one read the fuel gages or any of them for that matter. The fuel gage jumps around in display. One time it will be a solid line then it will be a broken line and it can also be way off from full or empty. Was chisel plowing yesterday and had all of those scenarios show on the fuel gage. I've seen the fuel gauge do this action over the last couple of years since we got it. I don't think there is a book for it or my brother has never said anything about one. His tractor. The exhaust gage seems to vary while idling like when I'm waiting with the grain cart it will increase if I increase throttle slightly it will sometimes go down some. The temperature gage seems like the only steady and constant in the dash. Always seems to read in a correct manner with littler variability. Just wondering if this is normal for these as the fuel gage makes it real hard to know if the fuel is low. I don't run it much. Yes we usually just fill it each day if it has run hard like tillage work. My brother will run it down to the dregs if he can when planting. He's even run it out a time or 2 trying to get that last round in before the fuel got there.

 

[BarnyardEngineering]

Clearly that's not normal. You've got a 30-ish year old tractor there with minor electrical issues. Maybe a bad gauge cluster. Maybe some bad grounds.

An owner's manual isn't going to tell you anything about fixing something like this. The service manual probably won't, either. It's a matter of good old fashioned mechanicin'. Tracing out wires. Cleaning connections. Lots of hours for maybe zero gain. Not something you're just going to twist a screwdriver once, and it's fixed. Since it's your brother's tractor I'd say it is up to him if he wants to spend the time and effort, or pay someone, to figure it out.

 

[the tractor vet]

Don't ask me , way to new for me . and way to new for any of my friends .

 

[CRSUTTON1981]

I've run into this a couple times before and most times it has been a bad ground connection on the sending unit. At the base of the back cab window, there is a narrow plastic cover held on each end by 1 screw. Remove this cover and it will reveal the upper sending unit. There is 1 wire that is screwed to the metal plate that makes the sending unit cover. Remove this and clean up this connection good then reinstall. This should take care of the faint/flashing black lines unless it truly is empty of fuel. If it has a lower tank also that sending unit could be failing but its usually the upper one.

 

[MARK ROBKE]

One thing I would try, is to remove the sender, and operate it slowly thru its range while someone watches the gauge. I agree that a bad connection could be the cause, but I have found bad sender units this way, many times. Mark.

 

[pete 23]

Been like 25 years since working on those Magnums but if memory serves me right, every other bar means open circuit. Now with a wire running all the way from the gauge down to side tank, through sender in side tank, hooking to a couple more connectors, up to sender in rear tank and then the ground on the rear tank sender, those are the places that bother.

Like other poster said, first and easiest place to start is the ground terminal on upper tank, then work your way down to lower tank if that doesn't solve problem. The gauge is seeking ground through the variable resistances in the tank units so by providing a known good ground at various places in circuit you can pin down the area that is bothering.

Sender in either tank can be the problem as they wear through the finger running over the resistor.

Tell you a little story of one from many years ago. Fuel gauge reading every other bar constant. I found the connector between the two tanks had pulled out due to a clump of mud under fender. Fixed. Soon , same problem, this time ground on upper tank rusty and corroded. Replaced connector, problem solved. Few more weeks, same problem, open circuit. Found rear tank sender had failed, replaced sender problem solved.

Except. Customer is getting hot that I can not figure out what is wrong. Well, three different problems solved, not related to one another, I quickly diagnosed each one correctly but he was convinced I didn't know what I was doing. Guess I should have put in a new gauge, wires, sending units etc first time, then he would have squealed.

 

[caterpillar guy]

Thanks guys. Will look at it this winter. As for being my brothers tractor I use all of the equipment and fix all of it as needed. We both use each others equipment making it much cheaper for both of us. Got to finish chisel plowing and disking cornstalks down first.