I have a Bobcat 743 that will run great for 15 - 45 minutes and then it acts like it runs out of fuel. Will restart with a little effort but will stall out again within a few minutes. It does blow white smoke constantly which is supposed to be caused by a stuck ring according to the guy I bought it off of who just put a new head on it but didn't touch the bottom end. When it is running it has power and seems to work fine. Any help in figuring this out would be greatly appreciated.
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All i can suggest is to replace your fuel filter. Run the machine and if it stops again look at the primer bulb, if its flat your have a blocked pickup filter inside the fuel tank. If you still have problems and those didn't do it, your problem could be the lift pump diaphragm has a split allowing air in. Also check that the bleed valve on the pump is fully closed.
Just a few things to try.
Is the smoke white or is it blue? It could be a bad injector, you can test them by pulling the injectors and attaching a fuel line to the pump and hang the injectors off it and spray down and cranking the engine, you can check the spray that way. Or you can get them checked at an injector shop.
White is un-burnt fuel, blue is burning engine oil, black is excessive fuel.
He bought it with the motor out and the head off. Guess the bottom end looked good so when the mechanic finished the head and it smoked they assumed some moisture got in the bottom end and rusted a ring in place. Said it might pop lose after awhile but hasn't after 3 hours of running. It's not terrible but it's a noticable amount of smoke. Any ideas on where to buy a rebuild kit for the bottom end. Seen one on ebay for $1400 but thought that was expensive for a little 4 cyl Kabota.
Thanks I'll try those suggestions and see what happens. It's white smoke and doesn't seem to be burning any oil. The head, injectors, and fuel pump all are supposed to be new and look super clean but I'll try checking the injectors also. There is fuel that seeps through the top of the governor I think it is. Is that normal? Thanks everyone for the help. This was supposed to be cheaper than renting one for a month but not so sure about that now!
Thats probably about rite for a rebuild kit, that will include ALL gaskets, including head gasket. New liners, pistons and rings. If you can live with the smoke and sort out the fuel problem why not just keep using it? You did say it still has heaps of power, it may come good, you never know. If you are really worried, you can pull the pistons out and check the rings, give the bores a flex home and check for wear. All you will need is a new head gasket and maybe a new set of rings. I have done this before with excellent results!
If you need more details just yell.
thetool
Well-known member
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- Mar 22, 2008
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So if you let it set overnight, then start it and run it it will run fine until warm-up?
In this case, 9/10 of the time I have seen this is because of gasoline or too much conditioner in the fuel.
When I roll up to a guy who says it works fine until it warms up, I always check the fuel first.
Good luck
One thing that i thought of while driving to work, if you do decide to replace the rings and flex hone the bores, ensure you have good oil pressure before you do this. There is no point spending the money on new rings and a head gasket if your bearings are all worn giving low oil pressure.
Thanks for all the info I'm new to this so it's great. Turns out the primer bulb would suck in so I'll get after that over the 4th. Thanks again!
Just an update. The tank and pick up screen was covered with what appears to be very tiny pieces of rubber. So cleaned the tank and replaced the fuel lines. Guessing the screen had a certain amount of blockage and as it ran more and more rubber would build up on the screen. After awhile some would fall off and it would run again. Once I get the axles done I'll see if that fixes the stalling issue but judging from the amount of crap that came out of the tank that was the issue. Thanks to everyone for all the help.
