743 fuel gauge

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jessemead

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Jan 5, 2009
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i have a 1992 743b that the fuel gauge does not work. does anyone have any ideas to test to see what is not working i.e. gauge, tank, wiring?
 

skidsteer.ca

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Jan 20, 2006
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My 721 has the same issue so I'll be listening.......................
If the guage itself is working you should be able to ground the wire at the fuel tank and the guage will either go to full or empty depending on which way it is designed to read with 0 ohms resistance.
If the needle does not move remove the dash and check and see if you have both a power and a ground wire at the back of the guage when the key is on.
The sender wire should go to the guage and have a ohm reading of 30 to 300 (my best guess , not from manual) and it should vary (the ohms) depending on how much fuel is in the tank. Add to fuel to check the sender is working.
Ken
 

Tazza

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If the guage itself is working you should be able to ground the wire at the fuel tank and the guage will either go to full or empty depending on which way it is designed to read with 0 ohms resistance.
If the needle does not move remove the dash and check and see if you have both a power and a ground wire at the back of the guage when the key is on.
The sender wire should go to the guage and have a ohm reading of 30 to 300 (my best guess , not from manual) and it should vary (the ohms) depending on how much fuel is in the tank. Add to fuel to check the sender is working.
Ken
Good advise!
I check it the same way, ensure the gauge is getting power then short the sense wire to ground, the needle should flick. NEVER apply power to the sense wire or you will blow the gauge, only pull it to ground. If the needle doesn't move the gauge is bad, if it moves you have a wiring or sender problem. The senders I'm sorry to say are rather spendy, especially on the older machines. Still, its still a good idea to know how much fuel you have left!
 

ddsprint

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Dec 23, 2008
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46
Good advise!
I check it the same way, ensure the gauge is getting power then short the sense wire to ground, the needle should flick. NEVER apply power to the sense wire or you will blow the gauge, only pull it to ground. If the needle doesn't move the gauge is bad, if it moves you have a wiring or sender problem. The senders I'm sorry to say are rather spendy, especially on the older machines. Still, its still a good idea to know how much fuel you have left!
if you use this machine alot or push it to the limit so to speak, I will give you a heads up on fuel gauge, I'm speaking owning a 743 since 1991, there are not of the best design, flip up the cab and there it is, but you will find at least for me, I could fix it in the morning and the next day it stops working, I got so pissed with joke system that we would just shove a shovel handle in or whatever and see what the level is, you know where your at, and then you think what if you run out of fuel, pump up the ball, crack the 1st injector line to get air out and the way you go, I'm telling you, you will fix the gauge in the cab and will quit working again, you will see, those fuel gauges just can't take the abuse. hope this helps
 

Tazza

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if you use this machine alot or push it to the limit so to speak, I will give you a heads up on fuel gauge, I'm speaking owning a 743 since 1991, there are not of the best design, flip up the cab and there it is, but you will find at least for me, I could fix it in the morning and the next day it stops working, I got so pissed with joke system that we would just shove a shovel handle in or whatever and see what the level is, you know where your at, and then you think what if you run out of fuel, pump up the ball, crack the 1st injector line to get air out and the way you go, I'm telling you, you will fix the gauge in the cab and will quit working again, you will see, those fuel gauges just can't take the abuse. hope this helps
Well i personally haven't killed mine YET. I did install a new gauge and sender though, i had to fiddle with the sender to read the level even sort of rite. It would not give me an idication of a full tank of fuel, i had to use conductive paint on a few of the windings on the resistor, but now its pretty accurate.
 

sledesigns

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Jan 23, 2009
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94
Well i personally haven't killed mine YET. I did install a new gauge and sender though, i had to fiddle with the sender to read the level even sort of rite. It would not give me an idication of a full tank of fuel, i had to use conductive paint on a few of the windings on the resistor, but now its pretty accurate.
My fuel level guage works best when its almost full. If it gets too low I have to use a flashlight, squint one eye, and shake the machine. :) (M600) Worst case you could put a Stewart Warner guage ($25) and sender ($25) in. I've found many things are replaceable with good hotrod parts. Id imagine you could even find a liquid filled guage....if factory prices or reliability push that direction.
 
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My fuel level guage works best when its almost full. If it gets too low I have to use a flashlight, squint one eye, and shake the machine. :) (M600) Worst case you could put a Stewart Warner guage ($25) and sender ($25) in. I've found many things are replaceable with good hotrod parts. Id imagine you could even find a liquid filled guage....if factory prices or reliability push that direction.
Stewart Warner 391C-D - Stewart Warner Fuel Tank Sending Units Fuel Tank Sending Unit, 240 - 33 ohms, 15 in. To 24 in. Height, Picked this up from Summit Racing. You do not need the install kit. There is a definite bolt pattern that needs to be observed. The small hole in the rubber gasket is your alignment, it faces the bucket, and the old screws need to be reused. Drop it in and away you go. Works with the original gauge. I would call it a direct replacement. Bobcat wanted $200 for new and $100 for used. This was $30. Hope this helps Ed
 

Tazza

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Stewart Warner 391C-D - Stewart Warner Fuel Tank Sending Units Fuel Tank Sending Unit, 240 - 33 ohms, 15 in. To 24 in. Height, Picked this up from Summit Racing. You do not need the install kit. There is a definite bolt pattern that needs to be observed. The small hole in the rubber gasket is your alignment, it faces the bucket, and the old screws need to be reused. Drop it in and away you go. Works with the original gauge. I would call it a direct replacement. Bobcat wanted $200 for new and $100 for used. This was $30. Hope this helps Ed
Great information, i remember cobbling one up for my 731 years ago from a sender from a car, it did work, after some fiddling.
I'm sure this will help others wanting to replace their fuel sender.
Now, to find a drop in replacement for the later model machines with the tank under the engine.
 

Crash734

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Jun 4, 2020
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Stewart Warner 391C-D - Stewart Warner Fuel Tank Sending Units Fuel Tank Sending Unit, 240 - 33 ohms, 15 in. To 24 in. Height, Picked this up from Summit Racing. You do not need the install kit. There is a definite bolt pattern that needs to be observed. The small hole in the rubber gasket is your alignment, it faces the bucket, and the old screws need to be reused. Drop it in and away you go. Works with the original gauge. I would call it a direct replacement. Bobcat wanted $200 for new and $100 for used. This was $30. Hope this helps Ed
I know this is an old thread so I may not get a response, but does anyone know if this Stewart Warner sending unit will work in a 1990 bobcat 843? replaced the gauge after testing and concluded it was bad. Now that the new gauge is giving me some response with testing but still reading empty at normal, assume its the sending unit? It reads full when it is full but after about half an hour of operating it bounces from empty to full consistently and than after about an hour or so it drops to empty again... I know that's not the case when I can clearly see the fuel is at about 3/4 of a tank if not higher when it stops working. Have yet to pull it out of the tank
 

foton

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Mar 1, 2018
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I know this is an old thread so I may not get a response, but does anyone know if this Stewart Warner sending unit will work in a 1990 bobcat 843? replaced the gauge after testing and concluded it was bad. Now that the new gauge is giving me some response with testing but still reading empty at normal, assume its the sending unit? It reads full when it is full but after about half an hour of operating it bounces from empty to full consistently and than after about an hour or so it drops to empty again... I know that's not the case when I can clearly see the fuel is at about 3/4 of a tank if not higher when it stops working. Have yet to pull it out of the tank
the gauge has to match the sending unit as ohm readings go. there is no standard with these things so the one we got was a marine type universal one that would reach the bottom of the tank, with these things one has to be careful to make sure that you have the sending unit arm just right so it does not rub on the side of the tank , they are so narrow , factory bobcat is pricy . aftermarket marine around 30 bucks, not a bad job to do either really.
 

Tazza

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the gauge has to match the sending unit as ohm readings go. there is no standard with these things so the one we got was a marine type universal one that would reach the bottom of the tank, with these things one has to be careful to make sure that you have the sending unit arm just right so it does not rub on the side of the tank , they are so narrow , factory bobcat is pricy . aftermarket marine around 30 bucks, not a bad job to do either really.
I actually got a cheap universal sender and gauge for like 30 bucks off ebay that i used on my excivator. As Foton said, you need to match the sender to gauge.
 
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