743 B fueling problem

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RPeschon

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Joined
Nov 11, 2024
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Over the last year or so, my 743 starves for fuel. I can always get it started again. Always seemed to be when under heavy use, or so I thought. Last month I undertook removing buckthorn out of my grove, and a general clean up of the grove. I'm using a fence post puller for smaller trees. A spade for larger ones, and a grapple for clean up. Three different times it wanted to stall out over the last month. Each time it took almost exactly 4.5 gallons of diesel fuel to fill the 12 gallon tank and then it runs like a top again.

Is it possible theres something going on with the fuel pickup line in the tank at that level? Is it a gravity flow, or is there a pump?

I'm not well versed with diesels.. thanks
 
Over the last year or so, my 743 starves for fuel. I can always get it started again. Always seemed to be when under heavy use, or so I thought. Last month I undertook removing buckthorn out of my grove, and a general clean up of the grove. I'm using a fence post puller for smaller trees. A spade for larger ones, and a grapple for clean up. Three different times it wanted to stall out over the last month. Each time it took almost exactly 4.5 gallons of diesel fuel to fill the 12 gallon tank and then it runs like a top again.

Is it possible theres something going on with the fuel pickup line in the tank at that level? Is it a gravity flow, or is there a pump?

I'm not well versed with diesels.. thanks
The fuel pickup lines do get old and can crack or break off and then the machine will suck air when the fuel gets to that point.

Also, there is a screen / check valve on the end of the fuel pickup tube that can get clogged if the fuel is dirty.

Here is a link to the parts catalog so you can take a look at the schematics for your fuel system:
 
Ok, I've got it torn apart and both grommets out of top of tank.
Rear tube. (Slightly larger) has a rubber hose drop that is 21 inches long, which is the specified length of pickup tube, but its open on the bottom. (No filter/ check ball) This larger line runs down to the manual fuel shutoff petcock at the bottom of the tank to shut off fuel to change filter.

The front Grommet just had the 90 degree elbow on it but the elbow into tank, has a barbed end like there's supposed to be a drop. I'm assuming this is a return line and is correct and just dumps excess fuel back in on top.

Im thinking this is not going to fix my fueling problem if these are correct.
 
Ok, I've got it torn apart and both grommets out of top of tank.
Rear tube. (Slightly larger) has a rubber hose drop that is 21 inches long, which is the specified length of pickup tube, but its open on the bottom. (No filter/ check ball) This larger line runs down to the manual fuel shutoff petcock at the bottom of the tank to shut off fuel to change filter.

The front Grommet just had the 90 degree elbow on it but the elbow into tank, has a barbed end like there's supposed to be a drop. I'm assuming this is a return line and is correct and just dumps excess fuel back in on top.

Im thinking this is not going to fix my fueling problem if these are correct.
Check the pickup tube for cracks. I have seen tubes that look ok but when I plug one end and put pressure or vacuum to it I find small cracks.

Since you have it out I would just go ahead and replace the tube. It may keep you from having to take it apart again. Check the parts catalog to see if your serial number is supposed to have a fuel pickup screen on it or not and replace it if it should.
 
Check the pickup tube for cracks. I have seen tubes that look ok but when I plug one end and put pressure or vacuum to it I find small cracks.

Since you have it out I would just go ahead and replace the tube. It may keep you from having to take it apart again. Check the parts catalog to see if your serial number is supposed to have a fuel pickup screen on it or not and replace it if it should.
I took it apart yesterday morning and replaced it with OEM parts. I think tightening up the connections on the fuel sending unit may have fixed that issue
I was having also. I took it out and ran it hard with a stump digger and ran fine, but, it's full of fuel. I may siphon some fuel out of it and try it while the weather is still decent and before I need it for snow removal.. thanks
 
Hi from Estonia.
I have had similar problem several times in different Bobcat`s.
1. Fuel picup line inside of the tank were cracked.
2. The 90-degrees elbow coming out from tank were clogged.
3. Connection before pump were not tight.
4. Water inside of the fuel filter.
5. Fuel stop solenoid rod was not pulled in completely- there was some dirt or something, i just cleaned it and it works again.
 
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