Good Afternoon, I recently purchased my first Skidsteer which is a 1997 bobcat 773. I am having issues with power loss after about 30 minutes of use. When I engage the steering levers it bogs down to the point of shutting off. I have replaced the following and the issue is still not resolved. New fuel filter Fuel pick up tube ( it was broken off and the check valve was gone) New lift pump New primer bulb New fuel lines The last thing i did was drain and flush the fuel tank. It did have some trash on it. Any advice would be greatly appreciated. Thanks
Just to clarify, are you saying the engine rpm drops down losing power, or does the engine hold rpm when it loses power?
The engine RPM drops down losing power. If I release the steering levers it goes back to normal RPM.
Well, it looks like you covered all the bases, replace fuel pickup tube and check strainer, replaced fuel lines, replace lift pump, new primer bulb and new fuel filter. Yet if it's still stalling out, sounds like you're still lacking fuel delivery. Aside from the possibility of a faulty new fuel pump, strange things do happen, about the only thing left is the injection pump. One thing I didn't ask, are you certain the bleeder valve is in the closed position on the fuel return line at the injection pump? Pretty sure that can affect running operation, just don't know if it will affect it to the point of making the engine stall. thepumpguysc might have a little more insight that he could offer on this.
Thanks for the help. I have attached a video I took today. I ran it for about 20 minutes and it started losing power. I pumped the primer bulb and the RPM picked up.
If you pumped the primer bulb and the rpm picked up then you still have something starving the injection pump for fuel. I know you stated you replaced it, but lift pump could still be faulty. What about the fuel lines after the primer bulb, are they in good shape? Hose clamp connections good and tight not letting air in? Bleeder valve on fuel filter fully closed?
Just wanted to give an update on what I did to hopefully fix the issue. I ordered a 12 volt fuel pump from amazon and installed it after the factory lift pump. I ran it this afternoon with no starvation issues at all. Thanks for all the help.
I can see in your pic that your injection pump bleeder valve is broken, no thumb wheel on it, you need to replace that, that could be your problem.
Thanks willie59, is this what you a referringto?
Yes, the purpose of that valve is two things, to assist bleeding when changing the fuel filter and to keep proper pressure inside the injection pump. When you change the filter, you open the bleeder on top of the fuel filter, pump primer bulb until you get fuel, then close the bleeder. Then open the bleeder on the injection pump, turn knob CCW, pump the primer bulb about 10 times, close the valve. That bleeds the air from the lines and injection pump. Once the bleeder valve is closed a light spring and ball check restricts flow out of the valve to keep pressure from the lift pump inside the injection pump to feed the injection valves. If that bleeder valve is open, or the spring and ball check is faulty, you can't keep proper pressure inside the injection pump. Diaphragm lift pumps only produce a small amount of flow and pressure, if that valve were faulty it couldn't keep supply up. By fitting that electric pump, which it shouldn't need, it's now able to keep up. I think it would be worth a try to replace that bleeder valve.
Thanks for the detailed explanation. This is my first Skid steer and i have zero experience with diesel engines. I will replace the bleeder valve. Again, thanks for your help.
Well, since that's your first skid, a '97 model, likely a 773 F series. Not a bad machine. A G series would be better, but for real, a 773F is a solid machine. But do check where the bucket tilt cylinder attaches to the bucket coupler, look for cracks in that pin boss. And check the oil in the chain case. There's a plug under the belly of the machine, but it's not easy to access. Instead, remove the bucket from the machine, raise the loader arms and install the safety prop, then back the machine up a good slope. remove the plug at the very front of the main frame, that's the chain case oil level plug. See what comes out, especially if water comes out. Once drained, drive the machine to level ground and add either hydraulic oil or motor oil to the chain case through the level plug.
Thanks Willie59, I will check that area for cracks. I have already drained the chain case and added new oil to it. While i was doing that I discovered i had 2 bad wheel bearings. I went ahead and changed all 4 wheel bearings. (Inner and outer ) so I should be good to go on that part.
I have recently picked up a 773 “G”, just replaced the computer. Now to work on this same issue. Mine will stall when I over work it, not sure if that’s normal? If I tilt the bucket all the way back and hold, it Boggs pretty hard. If I over work and let off it will recover, if I keep pushing into the pile it will stall..I’ve ordered all new filters will test this upcoming weekend and update. Thanks for asking the same question I have.