Here is what the problem is. Have a 743b bobcat diesel and after about 10 hours the motors starts to slow down even with the throttle wide open.Then it stall's out. Sometime's it will start back up and run a while before this happens again.If I let the machine sit overnight the next day it will run a few more hours before this happens again.I changed the fuel filter and it runs great just like new but its only a matter of time before the whole cycle starts over again.Done this about 5 times already its only a temp fix.Nothing in the glass bowl or filter not even a fleck of dirt sludge ect Looks clean.Just drained the tank thinking there could be dirt sludge ect let the diesiel sit in a 5 gallon bucket and that was totally clean nothing in the fuel at all.Any ideas what could cause this thought this would be a easy fix but it has me stumped. Basicly motor bogs down and stall's out change filter and all is well .
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Bobcat 743b fuel problems Any IDEAS?
- Thread starter tomscarpt
- Start date
willie59
Administrator
Welcome to HEF tomscarpt. :drinkup
If I recall correctly, I think the 743 and 743B used the rubber primer bulb in the fuel line. If so, when it stalls, immediately see if that primer bulb is sucked flat.
If I recall correctly, I think the 743 and 743B used the rubber primer bulb in the fuel line. If so, when it stalls, immediately see if that primer bulb is sucked flat.
It has the rubber primer bulb never seen it go flat.When I change the filter and sqeeze the bulb it don't let much fuel go threw take quite a few pumps to get the filter filled .
franklinute
Well-Known Member
You have a fuel restriction somewhere. I own an 843 and I can take a coat hanger and pull the pick up end out of the tank. There is a screen
on the end of this line and sometimes it gets clogged. Also the pickup line will get soft and can deteriorate on the inside blocking fuel flow.
Does your machine have a fuel shutoff valve? My 843 does over by the hydraulic tank. Take the fuel line off and blow air back thru the line
to be sure it is clear.
on the end of this line and sometimes it gets clogged. Also the pickup line will get soft and can deteriorate on the inside blocking fuel flow.
Does your machine have a fuel shutoff valve? My 843 does over by the hydraulic tank. Take the fuel line off and blow air back thru the line
to be sure it is clear.
willie59
Administrator
I understand tomscarpt, but can you clarify that you have checked the primer bulb at the very moment it stalls? If you wait for several minutes after the stall the primer bulb will go back to its proper shape. Important information.
I understand tomscarpt, but can you clarify that you have checked the primer bulb at the very moment it stalls? If you wait for several minutes after the stall the primer bulb will go back to its proper shape. Important information.
Update to what I did
I changed the pickup tube in the gas tank went to the bobcat dealer and got the flexible tube with the screen filter on the end.
put in a new fuel filter
changed the primer bulb direction of flow is correct
started it up and it ran perfect better than it has in years full throttle to idle then after about 5 minutes it stalled out and would not start back up until I pumped the primer once then it ran for about 4 minutes did the same thing. The primer bulb did not collapse it stayed it's shape stood there and watched while the engine stalled out.
Now I am lost even the bobcat dealer thought this would fix it. Can it be a electrical issue ? I must of moved a wire while changing the fuel lines cause the gas gauge don't work now it did before.
franklinute
Well-Known Member
I still think this is a fuel issue. If you only had to pump the primer bulb once then you should be ok on the fuel supply side. If you can check the pickup screen easily I would do that first. You may have the troubles within the fuel pump itself. On the return line from the last injector to the pump there may be a fitting with a glass ball in it. If it has trash in this fitting your engine will lose power. I don't know if this is on your machine but
I had this problem on my dozer a couple months ago. Most people knock out this check ball and keep running knowing that pump work is coming.
When you take the line off the fuel pump does fuel flow freely? It should. I would take that line off and let it run for a few minutes. It is gravity flow
from the tank to the pump and the flow should be constant.
I had this problem on my dozer a couple months ago. Most people knock out this check ball and keep running knowing that pump work is coming.
When you take the line off the fuel pump does fuel flow freely? It should. I would take that line off and let it run for a few minutes. It is gravity flow
from the tank to the pump and the flow should be constant.
willie59
Administrator
If the 743B used the same engine as the 743 there should be a lift pump mounted on the side of the injection pump housing. With the things you've described, most likely failed lift pump. The next time it begins to stall, don't let it die completely, try pumping the primer bulb and see if it continues to run. If so, likely lift pump problem as you're basically doing the same thing manually with the primer bulb by delivering fuel to the engine.
If the 743B used the same engine as the 743 there should be a lift pump mounted on the side of the injection pump housing. With the things you've described, most likely failed lift pump. The next time it begins to stall, don't let it die completely, try pumping the primer bulb and see if it continues to run. If so, likely lift pump problem as you're basically doing the same thing manually with the primer bulb by delivering fuel to the engine.
Thought this was fixed.Tightend all the bolts on the fuel filter mount. Found a bolt going into the fuel filter mount with a bad o ring installed a new one snugged every bolt on it. Started the machine up and it ran perfect for about 1/2 hour. Now back to the same thing. Runs then dies out.
I did manage to pump the primer one sqeeze before it died and it continued to run not for long maybe 3 minutes longer . Possible the lift pump ? Can do explain that to me not even sure I know where this is. thanks in advance.
willie59
Administrator
The thing I'm not certain about is that it's a 743B, that series began in 1991, I'm more familiar with the 743 which started in 1981, I'm not certain they have the exact same engine. I can't stress enough to look closely at all fuel lines and all fuel line connections. A crack in a fuel line can suck air and yet not leak fuel. And it sounds like you have that POS CAV fuel filter that has the top housing, the filter cartridge below it, and the water bowl on the bottom, all held together by a machine screw in the center. If that's what you have, make absolutely certain that you have the seals rings fitted properly, those things can cause all sorts of problems if they're not fitted up properly.
I think what I would do at the point is locate the fuel lift pump, identify the hose that feeds the pump from tank, fit a new length of hose and drop that hose in a clean jug of diesel fuel. Run engine and see if it now continues to run. If it dies off, faulty lift pump is still a likely suspect.
Again, I don't know if it's the exact same engine, but this is the lift pump from a 743, it's mounted on the side of the fuel injection pump.
I think what I would do at the point is locate the fuel lift pump, identify the hose that feeds the pump from tank, fit a new length of hose and drop that hose in a clean jug of diesel fuel. Run engine and see if it now continues to run. If it dies off, faulty lift pump is still a likely suspect.
Again, I don't know if it's the exact same engine, but this is the lift pump from a 743, it's mounted on the side of the fuel injection pump.
You described the fuel filter exactly and the picture of the lift pump is what is I also have . Going to go threw the filter again and check all the o rings as well as a new fuel line into a bucket of diesel to test the lift pump. Let you know what happens going to take a few days.
franklinute
Well-Known Member
Willie is right even the smallest crack in a rubber line or an oring too loose or too tight can cause a slight air leak. I've gotten frustrated before and replaced all the fuel lines and put in as few connections as possible. It could be a combination
of several very small problems. Good luck.
of several very small problems. Good luck.
Tried today with a new fuel line into 5 gallons of diesel fuel could not get it to start.Maybe I did it wrong connected the new line to the fuel pump the diesel was on the ground and there was about 4 feet of hose I would think the pump would suck it up and try to start.Then after I gave up reconnected the old line pumped the primer once and it started right up ran about 10 minutes perfectly then died. My next thing is going to replace all the lines from the tank to the pump recheck all the o rings on the
I am in exactly the same position. New fuel filter, new fuel pickup in tank, the 21" hose with screen on end.
The machine got water in it and at the first freeze the filter needed its annual replacement. Ran fine for an hour each day for three days. Now it will not start at all. Priming bulb in cold weather is a joke, almost as hard as steel. The lift pump works as I removed the fuel line and ran a clear hose to a five gallon tank on ground. It sucked up fuel, slowly. I raised the hose and drained the fuel into the pump and it would run fifteen seconds or so. Did same and blew on hose and fuel moved into pump again. With the bleeder valve open no fuel ever comes out. It hasn't come out in years of restarting after running out of fuel.....many times.
Help!
Happy Thanksgiving to all.
Mike
The machine got water in it and at the first freeze the filter needed its annual replacement. Ran fine for an hour each day for three days. Now it will not start at all. Priming bulb in cold weather is a joke, almost as hard as steel. The lift pump works as I removed the fuel line and ran a clear hose to a five gallon tank on ground. It sucked up fuel, slowly. I raised the hose and drained the fuel into the pump and it would run fifteen seconds or so. Did same and blew on hose and fuel moved into pump again. With the bleeder valve open no fuel ever comes out. It hasn't come out in years of restarting after running out of fuel.....many times.
Help!
Happy Thanksgiving to all.
Mike
Its fixed:beatsme Thanks to all, that help me narrow this down. Here is what I did in case you have the same problems:Banghead.Changed all the fuel lines including the return line to the tank. New primer bulb . New suction line with screen into the tank.Changed the o rings on the fuel filter ports that are basicly just a short bolt plugging the extra hole's for different engines .Mine had 4 .Also put new hose clamps on 1/2 the fittings just to make sure they were tight some looked a little to big for the fuel line. Do your self a favor change them all I changed one tested it ran, then back to the same problem waisted a lot of time, Took 17 feet of 5/16 fuel line a dozen clamps plus I got to put the primer bulb a little closer to the back to make it easier to reach in to prime it. Who ever did this before had it slammed as far back as they could :Banghead:Banghead:Banghead(Took about a hour to get the hose clamp of the way it was postioned .Not sure what actually fixed the problem but it runs great have about 15 hours run time so far .Plus this must have been a ongoing problem because the engine and throttle run the best they ever have in years . Never really noticed it so much until this was done. Again Thanks to All.:beatsme:beatsme
willie59
Administrator
I've had to do the same more than once tomscarpt, tinker and tinker with something until I get ticked off enough and say "to hell with it, off with its head!" and rip everything out and start over. :drinkup
huckleberry
Member
I had fuel issues with my 863 all summer. it started when I was digging out a tree. had about 3/4 tank of fuel. I was down in the hole & machine quit. so I filled machine up & it ran good until I got it back to garage. I searched this forum. and to make a short story long, I found the pick-up tube had broken off. got a new tube and installed. machine would run great until it had 1/2 tank. changed all fuel lines & same problems. by-passed line at pump & machine ran great. tore machine apart again which is a pain. removed pick up tube & found it was loose at elbow. called dealer & they said their is a clamp on the line but they never use it. I bought clamp for $4.00 & installed & it runs great now. A simple clamp that they don't want to use caused a bunch of problems that could have been prevented. sorry for rambling on just mad
One thing I thought was crazy and I never knew it was there was the fuel shut of valve was way under the tank never new it was there until I removed the fuel line.Eliminated that mess for a better flow. Extended some lines for future access . I was the same with change a line start it get my hope's up that it would be fixed and BAMM back to the same problem.The machine was out in the woods when this happened once I got it started enough drove it by the garage so at least at night I could see with a drop light.That's when I decided to change it all.Glad I did its all new and got a great understanding on the fuel line setup.$60.00 fix less than what I paid for thinking changing the fuel filter each time would fix it.
franklinute
Well-Known Member
Congratulations on fixing your problem. I think about how many machines with a little age on them get traded because they are down on power or have expensive repairs to injection pumps and injectors because of this low fuel flow dilema. It seems when this problem starts we all go straight to the fuel filter or start dumping in all kinds of additives in the fuel to fix it.
I bet if you cut some of the old fuel line apart it will be spongy and deteriorating on the inside so when the pump needs fuel the fuel line collapses and can't flow the fuel. I think it is wise to replace all this rubber fuel lines every 5 years or so if you
run an older machine.
I bet if you cut some of the old fuel line apart it will be spongy and deteriorating on the inside so when the pump needs fuel the fuel line collapses and can't flow the fuel. I think it is wise to replace all this rubber fuel lines every 5 years or so if you
run an older machine.
Hooddoctor
New Member
I'm new posting with hopes the mod from this post willie59 can help me out. Willie shows a picture of a mikuni lift pump thats actually the only picture I have found on the web. I have this on a military marine Kawasaki KLR650 diesel motorcycle that was specially modified by Hayes Diversified Technology in 2006 and is no longer used by the military. This lift pump is leaking at the seal and I need a rebuild kit or new one but cant for the life of me find ANY info on this to get this bike back going. Can willie59 or anyone point me to where I could find what is in the pic(says its from 743 but I cant find anything on). Any help would be greatly appreciated!