743 running rough

[canaanchamp]

I've got a 743 that I bought last year. It has been running well for about 100 hours. It uses about half a quart of oil every 10 to 15 hrs. I was using it on a tree spade last week and ran it for about 2 hrs. and had to stop to make a meeting. As I was putting it in the shed at idle it began running very rough. I was late and couldn't check into it further than quickly checking the oil. Fast forwaqrd to today. Checked all fluids before starting. Eng. oil 3 quarters of a quart low. Hyd. oil 1 qt. low. Used pre heat for 5 min. befor turning over on a 30 degree day. Still ran rougheer than a cob but quickly smoothed to normal when throttle is over half open. Sounds and runs normal at full throttle. All guages and lights ok. I'm thinking fuel pump or injectors. I've got a buddy that knows these to look tomorrow evening but want to narrow things down quick. I've got 100 trees I'd rather not hand dig by Saturday. Any ideas ? Also, Inj. pump has fuel on it for the first time. It's always been clean before. Long post but want you to have the whole story. Thanks

 

[ddsprint]

sounds like the glow plugs are dead, the time has run out, the diesels need the glow plugs to start easily, can be very difficult to start without glow plugs, as far as your enegine using some oil, what do you expect, do a compression test, see what compression is, although I will say start with the glow plugs, easy check, just like a spark plug, take it out and test it on a battery with a few jumper wires, one to +, one to -, if it gets red hot it is good, if not throw it away and get some new ones, hope this helps,

 

[bobcat1505]

never preheat for more than 45 seconds in cold weather or you could burn out glow plugs. you can do a spark test on plugs. remove the cords between plugs use a jumper between the posiive cable to glow plug threads if it sparks its usally good. as for fuel on injection pump its probably the oring seals on the delivery valves. they can be replaced but caution should be done before attempting it your self.

 

[canaanchamp]

never preheat for more than 45 seconds in cold weather or you could burn out glow plugs. you can do a spark test on plugs. remove the cords between plugs use a jumper between the posiive cable to glow plug threads if it sparks its usally good. as for fuel on injection pump its probably the oring seals on the delivery valves. they can be replaced but caution should be done before attempting it your self.

Thanks for the tips on the plugs. I'll check them out. Just to clarify, preheat for 45 seconds one time only and then start. What if it doesn't start? Preheat again?

 

[bobcat1505]

Thanks for the tips on the plugs. I'll check them out. Just to clarify, preheat for 45 seconds one time only and then start. What if it doesn't start? Preheat again?

yes.

 

[thebobcatguy]

Fuel on injection pump=fuel leak=air in system hence rough running. Good luck.

 

[Tazza]

Fuel on injection pump=fuel leak=air in system hence rough running. Good luck.

Even if your plugs were bad the rough running would only last a few seconds till the other cylinders caught. I'd start with injectors and compression test. I agree, don't glow for more than 60 seconds! you glow too long and they will burn out.

 

[canaanchamp]

Even if your plugs were bad the rough running would only last a few seconds till the other cylinders caught. I'd start with injectors and compression test. I agree, don't glow for more than 60 seconds! you glow too long and they will burn out.

Thanks for the lessons on the glow plugs. I had a Bobcat mech. out tonight to have a look. He's pretty sure its the u-joint between the engine and pump. He'll work on it at his place for quite a bit less than what the dealer charges for his services. Anything I should have him look at while the engine is pulled? I'm gonna have him put in a freeze plug heater as well as check those glow plugs for me while he's got it at his place. I guess I'll sharpen up the old tile spades for those trees I've got to dig. Thanks again

 

[bobcat1505]

Thanks for the lessons on the glow plugs. I had a Bobcat mech. out tonight to have a look. He's pretty sure its the u-joint between the engine and pump. He'll work on it at his place for quite a bit less than what the dealer charges for his services. Anything I should have him look at while the engine is pulled? I'm gonna have him put in a freeze plug heater as well as check those glow plugs for me while he's got it at his place. I guess I'll sharpen up the old tile spades for those trees I've got to dig. Thanks again

don't think you can get a freeze plug style heater for 743 you have to use tank style

 

[Tazza]

don't think you can get a freeze plug style heater for 743 you have to use tank style

You meant rough as in vibrations? that could be U-joints or bad engine or pump mounts. Its something you need to see in person i guess.
I hope you get it all fixed cheaply! Being a bobcat mechanic he should be able to do it pretty fast. I think i got remove/replace including the U-Joints was about 2 hours. Thats from running to running.

 

[canaanchamp]

You meant rough as in vibrations? that could be U-joints or bad engine or pump mounts. Its something you need to see in person i guess.
I hope you get it all fixed cheaply! Being a bobcat mechanic he should be able to do it pretty fast. I think i got remove/replace including the U-Joints was about 2 hours. Thats from running to running.

Turns out that of 3 of the 6 bolts holding the flywheel on were snapped off. U-joint looks ok.

 

[Tazza]

Turns out that of 3 of the 6 bolts holding the flywheel on were snapped off. U-joint looks ok.

Well that saved you a few extra bucks
Puzzling how they could snap off though...

 

[daved]

IF you do try to pull glow plugs to check them be very careful, as Ive been though this one cold day on my gooseneck that wont fit in my shop. 2 out of 4 snapped off in my head. These are fairly cheap and yours are probably bad if you have to preheat that long. This cheap quick fix resulted in head removal and machine work to get busted ones out. Luckily threads were salvagable and got new ones in, Works just like it should. 30 degree morning 20 second pre heat and it fires on all 4 and clears up nicely in 5 seconds or so. I would look into it, lets face it its just way handier than tank heaters unless your in extreme cold temps. Just remember dont do what I did and try swapping them out an hour before a job because they are not hard at all to break off if they are original ones. Oh and If you put new ones in I used anti-sieze to help next time. Good Luck