Hi All, I have an odd problem that I hope someone cane point me in the right direction. On a 1992 Case 580 SK backhoe, the machine can be working fine for a while at 2200 RPM, and then all of a sudden, RPMs drop to idle for a second and then come back up. Then a bit later, the machine will just die. It will not restart on its on, but a shot of starting fluid brings it right back to life for a while and then same issue recurs. It seems to be after the machine has been working a while and is running warm but don't have any definitive data to confirm that. Machine has about 4400 hours and is pretty much original other than normal maintenance items. Filters changed, new lift pump installed, and same behavior. Any ideas? Thanks, Bob
Bob, did u back-blow the system when u changed out the supply pump.?? Don’t they use “olives” (rubbers) on the lines that screw on it.?? EVERY SK I’ve been on have severely rusted tanks.. It’s not hard to diagnose, the inside of the cap and the neck are rusted.
I did not back blow the system when I changed the lift pump (I am not quite sure what that even means to be honest). All connections to the lift pump are hard lines that have no washers or gaskets - I believe they are both compression fittings. The tanks look good to me - I see no rust at the top of the tanks or on the caps and fuel is running cleanly from the tank to the the filters (I dumped enough of it to see if there was water in the tank). Bob
Back blowing the system is using an air gun and blowing air in the lines in the opposite flow of the fuel flow. It a temporary fix because, it just blows all the crap in the line back into the tank. Have you checked the tank for a vacuum situation due to a plugged vent when it dies ?
That’s 3 swings and a miss for me, I’m out..
stuck check valve? Not allowing enough fuel past?
I did find out the injection pump holds a lot of fuel. Enough for the diesel generator I was working on to run 15 minutes and then die. If you waited a period of time, it would crank and start back up. The longer you waited, the longer it would run before it would quit. Turns out there was a small brass screen on the fuel supply banjo fitting that goes into the injection pump. You had to take the banjo fitting apart and pull it out to see the screen on the end. It was plugged and was slowly letting fuel past at a very low rate. Cleaned the screen, all is good. Not sure if all injection pumps have this little screen.
It's possible it's an electrical problem, but most likely by far that it's a fuel blockage.
Thanks for all of your replies. Can you point me in the direction as to where the check valve might be on the 580SK? Is it inside the injection pump? I don't see anything between the first fuel filter, the lift pump, the main filter, and the injection pump. I will take off the supply line to the injection pump and see if there is a screen although with two filters before the pump, I am not sure how any debris could make it that far on this setup. Thank you all all again, Bob
It is located at the fuel tank outlet. #12 in the diagram that gggraham posted. Unless someone has removed it. That would be a real bad thing to do. It would cause the pump to lose its prime when the engine is shut off.
In my case it turned out they had been running bio diesel in the generator. That is nasty stuff and it caused a rubbery build-up in that screen. It had several filters on it before the injection pump like yours. You never know what you will run into with this old equipment. This was a old John Deere 6 cylinder I was working that ran the generator head.
makes sure you have a free flow on return line and fittings,, its a line from the enjector pump back to fuel tank, there may be a check valve in the return fitting on inj. pump Good Luck
Thanks for all your responses. In the past two days the behavior has not reappeared. Maybe the lift pump was the ultimate problem.
thanks for letting us know, did the clearing of retutn line and fitting work? ha ha