My bobcat will run with a full tank and will stall when the tank becomes lower than 3/4's full and will not continue to run.( I believe this is due to fuel level higher than pump) I have done all the good things that I read in previous threads. I have changed the pick up tube & filter. The squeeze ball is hard. I ran a line from a gallon container directly to the inlet side of the fuel pump. Changed the bleader valve,replaced the fuel pump. Still I have the same problem where the machine won't stay running. If I squeeze the ball the machine will continue to run that's why I changed the fuel pump. The outlet side of the fuel pump just dribbles fuel when the machine is cranking over yet the fuel shoots out by squeezing the ball. Please help what next?
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So with the external fuel supply, did it work correctly?
I'm wondering if your fuel pump is still bad. I know you changed it, but they run off a lobe on the injector pump cam. As the fuel tank is higher than the engine, gravity will assist in giving you slightly better fuel pressure (only very slight).
Silly question, is the bleed screw screwed all the way in? if its out, it will not develope pressure.
I'm wondering if your fuel pump is still bad. I know you changed it, but they run off a lobe on the injector pump cam. As the fuel tank is higher than the engine, gravity will assist in giving you slightly better fuel pressure (only very slight).
Silly question, is the bleed screw screwed all the way in? if its out, it will not develope pressure.
Yes the bleed screw is in. I have replaced it due to a broken knob off the stem. I feel the new fuel pump is Ok the output is the same with both pumps which just dribbles. moving the pump backand fourth by hand pushes more fuel out than it does mounted on the machine when cranking. Is it possiable that the injector pump lobe is bad?
I wonder if its possible you were supplied a wrong pump. I'm sure there was a post years back about someone having issues of little to no fuel flow on a new pump, turned out it wasn't the right one. The depth into the engine block to drive off the cam was wrong causing it to only move a little bit because it was too short. Is there any chance this could be the problem?
The lobe on the cam is actually quite large, i hightly doubt its worn and causing an issue, the most likley is an incorrect pump....
Hopwfully others may have a better idea.
If all else fails, install an electric fuel pump and by-pass the one on the engine.
Thanks tazza The pump came form the dealer using the serial number . The original pump acted the same way. I put a pressure gauge in line with the output hose and got 8 psi at the start but as the machine ran for a few minutes the pressure slowly dropped to 5 psi then quickly dropped and machine died for lack of fuel. I am at a loss to look at next. My next move is to replace the primer bulb. Here is my reason and I am just guessing. I noticed that when I removed the output hose from the pump I had a bit of fuel continuing to leak out. I have another machine simillar (743B) and when I remove that hose there is no fuel comming out. I also checked the pressure on the second machine just as a refeferance point and it ran at a steady 5psi. So it does not make sence to change the primer bulb but I am running out of options. If any of this makes sence please comment. Thanks
It all seems very odd, it all makes sense what you have done. As stated, the 743B is essentially the same. The primer bulb must be the right way around as its giving pressure when squeezing it. You also get a good stream when you do do, just not from the lift pump.... You don't need much pressure, the 5psi should be heaps, you just need some pressure at the pump.
You can't really check the cam to see if its the problem, you would need to remove the injector pump to see it propperly. With the lift p ump out you could see a little with a torch and turn the engine slowly by hand, but not sure how useful it will be. Its something i guess?
If all else fails, electric fuel pump! Just hook it up to your switched power, key is on the pump is too.
Ok I am back, sorry I have to work. Now I believe I have done everything possiable and still have the same problem. Recap: Removed tank and cleaned it. "perfect". replaced all the fuel lines in and out of tank, replaced Shut off valve, cleaned the elbow on top of tank, new filter, new primer bulb (ball stays hard), new fuel pump, new bypass valve, loosen fuel cap, Even added a new electric fuel pump. What esle can it be??? Starts right up runs for a while (15 mins to half hour full throttle) then dies. starts up and runs again. I don't get it???????? Please help.
looks like you have replaced everything...like you said it runs when the tank is full. I wonder if the extra wieght of the fuel was helping add a few extra psi until the tank got lower How is the fuel shut off assembly, any wear? the leavers and cable. are they tight and not moving from vibration? also with some of our older JD tractors on the farm we had to add a deisel fuel lubricant into the tank now and then to help lubricate the rack in the fuel pump. we found that the newer fuels are dryer and over time the tractor would be hard to start or low on power because the fuel rack was hanging up....even added a little automatic transmision fluid into the deisel tank, works well as a lubricant
I have looked at the fuel shut off assembly and all looks good and tight. The shut off assembly is a manual one and only activates when pulled. As for the extra PSI with a full tank I tried using an electric fuel pump and had the same results. Stilled puzzled.
You state that it runs fine for 15 mins before shutting down is very odd. There are no electronics or electrics to make it shut off. What works when cold, should keep working when warm....
The only thing left is the pump, but its just weird that it shuts off then starts right back up. I wonder if it could be something to do with the govenor too. It pushes and pulls on the rack on the injector pump to alter the amount of fuel delivered. If that gets too low, it will stall out. But i thought there was a lower limit set by bolts on the throttle, you never know though....
Did you figure this problem out? My 743 did this a few times over the winter and I never figured out the cause. The only thing I did was replace the old battery which was barely turning over the Kubota when it was cold. Since then the issue has disappeared, but I doubt that was the issue since the alternator is/was plenty strong and the battery usually had enough juice to start the engine after it cut out. -Paul
1st post here! I just had the v1702 rebuilt in my 743B and after about 7 hours running time started to do the same thing. Good running for an hour and then sputter down to the point where it slowly stalls. Motor will start immediately after. Any progress since this thread has started? (I'm thinking somthing like the governor because this motor is practically brand new)
willie59
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- Jun 26, 2011
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JPL, the thing that is curious to me and negates all other items, i.e. fuel lines, filter, etc., is that it still didn't operate proper when connected to a short hose coming from fuel container. It just sounds like your lift pump isn't moving far enough to pump, considering you stated you could work the primer lever on the pump and get good fuel delivery. Do you have a thick gasket where the lift pump mounts to injection pump? I'm wondering also if you could remove the shut down lever cover and remove the injection chamber assembly and get a good view of cam and cam lobe that drives lift pump.
cpar - have you tried squeezing the hand primer bulb? does it feel firm or can you feel air?
Its possible you have a cracked pickup tube, if you can ttry running it from an external fuel supply, that would eliminate the lines from the tank to the engine.
The Fuel cap has an air breather valve incorporated into it I believe. Its not letting air equalise inside the fuel tank. Try leaving the fuel cap off to see if the engine keeps running. The only other thing is maybe an air leak in the fuel line at the top of the tank at the two elbow joints that go in the top.
HI, FIRST THINGS FIRST , FLIP UP THE CAB, MAKE SURE SAFTY LOCK WORKS, IF NOT USE A CHAIN, PULL OUT BOTH ELBOWS ON TANK, ONE WILL BE A BLANK, THAT IS THE FUEL RETURN LINE. THE OTHER WILL HAVE ABOUT A 3 FOOT PIECE OF CLEAR TUBE ON IT WITH A ONE-WAY FILTER ON THE END, INSPECT AND REPLACE IF THESE ARE BAD, IF YOU SEE THE FILTER END ALL CLOGGED UP, YOU NEED TO REMOVE YOUR TANK AND CLEAN IT OUT, VERY SIMPLE, JUST REMOVE THE 1 3/8" BOLT FROM THE STRAP. SLIDE OUT THE TANK AND DUMP, RINSE WITH CLEAN FUEL, AND RE-INSTALL. PUT ON NEW FUEL LINE AND A NEW IN-TANK FUEL FILTER. ALSO CHECK THE FUEL LINE FROM THE TOP OF THE TANK TO THE PRIMER BULB, THESE DO DETERIOATE OVER TIME. WHEN YOU BLEED USE THE HAND PRIMER ONLY, DO NOT CRACK ANY PRESSURE LINES, PUMP WITH PRIMER VALVE OPEN, THEN CLOSE WHILE PUMPING. THIS WILL ENSURE AIR IS PURGED. GO AHEAD AND START AND YOU SHOULD HAVE FULL POWER.
Thanks for all the suggestions guys. My problem was solved when I loosened the gas cap on the tank.
I appreciate the wealth of knowledge and support here!