Have a problem with my kobelco SK 60 midi excavator. Under load or heavy acceleration starting at mid range of the rpm band it develops a miss. If i accelerate the throttle very slowly it doesn't miss even in the higher rpm range.If i have it running about mid range and start to work the machine it will also start to miss. This problem developed a few weeks ago . Since then i have done a complete service on the machine including cleaning the screen in the banjo fitting and a new fuel filter . The screen had a lot of crap in it and it was partially clogged . I was hoping that was my problem. The machine has a 4 cyl. Isuzu engine with about 4000 hours on it. I'm thinking it might be a bad injector but would like to hear other thoughts that are out there. Stephen
You stated that the screen in the banjo fitting was full of crap (which would have come from the tank). Have you opened the drain on the bottom of the tank frequently to rid it of the dregs at the bottom of the tank? Have you cleared the supply line from tank with compressed air?
Hey willie thanks for getting back to me . I did open the tank drain and had a little more crud come out but i didn't blow back through the supply line ...i'll try that later today . I was wondering if an inline filter of sorts might help some as the screen in the banjo fitting is in a PITA place . Thanks again ,Stephen
A water separator would be my choice. Isuzu and Mitsibushi used them on trucks, just a plastic bowl with a screen inside that's cleanable and can hold 1/2 cup of sludge, sometimes in tandem for the really green fuel
Hey Delmar, thanks that might be a good option. As per Willie i again removed the banjo screen and it was clean. I then blew through the feed line back into the tank and found little to no resistance. The fuel flow afterwards was real good but it wasn't bad before i blew the line out. I decided to crack the lines at the injectors to see if possibly there was some air in the lines. I did this after the engine was doing its fluttering -missing act. As i cracked open the first line it had a steady miss but when i closed it back up the fluttering was gone ....thought i solved the problem....WRONG ...i raised the throttle and the fluttering came back ... it did the same on all 4 injectors with the same results the flutter would go away and if i adjusted the throttle it would come back. I deem it as a flutter now as it is different then the steady miss i get when bleeding the injectors. Hey Willie or anyone else out there ...got any ideas?????? Thanks for trying to help me with this ...not thinking it is going to be an easy fix to find, Stephen
What's the serial number of this machine. I don't know if we're working on an SK60, or an SK60 Mark III, IV, or V. Stuff like this is very difficult for us to diagnose as we're not there at the machine hearing what it's doing. However, generally speaking, when a diesel like the engine in this one begins to flutter or stall out when it's under load, yet runs smoothly when engine is not under load, that's typically a fuel delivery problem. That involves a whole list of things, many of which you have already addressed. But even then there are the unusual things. I once had a Cat 320B that about drove me bat **** crazy until I finally figured out that the fuel shut off petcock on the bottom of the tank was messed up. It would screw CCW (open) until it stopped, but unknown to me, it still wasn't opened fully, threads were seizing or something. Fitted a new petcock, problem fixed. Not saying that's your problem, only saying these problems can be difficult to sort out. Having said all that, make certain the fuel lines are good. Follow the supply line from tank to engine. I know, that can be a PITA on a machine like that, but do the best you can. We know you first found crud in the strainer screen inside the banjo bolt. Is the lift pump before that screen? Or is the lift pump after the screen and fuel filter? In either case, you could have a failing lift pump that's not delivering fuel to the injection pump properly. Faulty injectors typically make a miss on a cylinder, you'll notice a loss of horsepower, not really a flutter, whereas lack of fuel delivery will typically cause a flutter, or rpm will lope up and down, or engine will stall out when under load. Again, all this is "generally speaking".
Hey Willie thanks for all the info .....sorry i didn't give you all the info on the machine. It is a Kobelco SK60 Mark 3 serial #LE16676. There is no fuel shut off on this unit and both feed and return lines look to be in good shape. I can follow both from start to end and they show no kinks or wear spots. The banjo bolt with the screen feeds into the lift pump that also houses the primer pump then feeds the main filter so it would be before the lift pump. This is definitely a flutter. One thing i did notice is that on the first start of the morning there is no flutter until maybe after 2 minutes of warm up no matter how fast i advance the throttle or if i put a load on the machine.At none of the times has the engine loped or stall out under load even when it flutters. What are your thoughts on something in the governor causing this? Thanks again for taking the time to help out, Stephen
Check the transfer pump check valves and maybe the check ball and spring in the fitting on the pump where the return line connects?
Also check the linkage for the governor control. On a Mark III the governor control servo motor is located behind the cab and has a cable that goes to the governor lever on the injection pump. Make sure all the levers and links for the governor control are tight. Also, on a Mark III, the shutdown is controlled by the governor control servo motor, there is not shutdown solenoid. However, there is a manual shutdown cable that comes from a knob control under the right side of operators seat. Make sure that cable/knob has not been pulled slightly, make sure the lever that the cable connects to on the injection pump is not slightly pulled into the shutdown position. Aside from this, and points mentioned previously, I don't know what else to tell you. Yes, you could have a problem with the injection pump governor, but I don't know enough about the machine and its problem to recommend yanking the injection pump, not unless we have some certainty that the problem lies there.
Hey lantraxco thanks for your idea i'll check on that . Again Willie thanks for all your help. Later today i'll look into the governor control linkage and the emergency kill shutdown cable . What is your opinion on installing a electric fuel pump and by passing the lift pump to rule out there being a problem with the lift pump? I know i would have to get a pump that runs on 24V and if so what type of pressure do you think i need to feed the injector pump?Thanks again all, will keep everyone informed as to how it goes, Stephen
about 25 psi.. no more than 40..
Thanks pump guy for the info. Lantraxco there is no spring and ball at the return side of the injector pump just a fitting with a metering hole so thinking there might be a check valve on the fuel filter housing ....if i find time today i'll check that out. I was also thinking i might try and put a fuel line in a 5 gallon container and go straight to the lift pump eliminating the feed line an tank assembly. Then if that doesn't help i'll try an electric fuel pump bypassing the lift pump. Willie i checked the manual stop cable and all the cables and linkages going to the injector pump and all looks tight and not binding or loose anywhere..... thinking it is in the fuel system somewhere just got to keep digging . I'll keep everyone posted and thanks for all the help so far, Stephen
If there's room to tee into the fuel line right before the injection pump, then run a line into the cab for a fuel pressure gauge, that will tell you what's happening as it is under load. That's not any easier than your alternatives, but you could say it is more certain.
Thanks to all who have been trying to help me. I just got in after trying a few more things with the same results but after i got in i started to wonder if possibly a loose baffle in the muffler might cause this fluttering condition. Think i will remove the muffler tomorrow and see what goes. Just wondering if anyone has run across a bad exhaust system and what the results were. Thanks all again, Stephen
Hey all just got a chance to work on the excavator again and want to thank all for the help and ideas. Not sure if anyone has run across this but the problem of the fluttering was caused by a loose baffle in the muffler.I noticed some black soot around the area of the muffler and removed it finding a rusted out seam when moving the muffler there was a large baffle that had also come loose . I started the machine with the muffler off and although a heck of a lot noisier there was no flutter . I was able to grab part of the baffle with needle nose pliers and weld it fast out the way. Also welded a plate over the seam just to make it usable til i get a new muffler. Thanks again to all who helped, Stephen