ok. so my boss, not internet savy, has a 590 sl that starts with ease, seems to be running fine at low or high idle, hydraulics all work... but when any load is put on the hydraulics, it stalls. first let me tell you a bit about this backhoe. the fuel sytem has been jerry rigged a bit. the fuel pickup isn't used. he has a small pump with a hose going into the filler cap of the tank. has not had a filler cap on it in years. the exhaust is also broken off above the turbo. so all of the startup smoke gets sucked into the air filter. the fan belt was just changed the other day. the stalling issues happened the next day. though he also ran it out of fuel the next day. he thinks is has something to do with the hydraulics because of the timing. now that that is out of the way.. we have replaced one of the two fuel filters. once he saw the top layer of duct tape (used for his filler cap) sucked into the filter... he decided to change it. but did not change the filter screwed into the pump. the main air filter been changed. the water separator has been changed. getting good flow from return (idle).... checked after radiator, but before it goes down into the tank. questions: the turbo wastegate. if that is stuck open (i cannot freely open and close as there is losts of rust on the turbo), will it cause this problem the fuel return. can there be plenty of flow and still not have the pressure needed? the secondary air filter. it looks brand new. but has not been changed in ten years or so. he says he was told to never touch it. as removing and replacing can cause issues. can it look new and still be bad? the regular air filter is usually black after a week. but will last months. hydraulics. i am worried that the banging and prying we did on the bracket the bolts into the pulley might have damaged the spindle. it didnt want to line up when bolting it back up. this was due to us loosening the main bracket that bolts into the block and onto the frame. but when engine is on... i dont see any warping to the spindle. bottom line. the good flow in the return tells him that it isnt the fuel. putting in a brand new air filter tells him it isnt the air. it idles high/low fine (although it bogs a touch when idling up), so he doesn't think there is a problem with the injectors. any thoughts? i see there is a screen in the ip. i have read fuel cutoff needs to be open all the way, is that for diesel? air in the fuel, but it has idled for at least a half hour. and has ran for a few hours like this. a main releif valve on the hydraulics (unlikely but could be stuck closed). <-- we did have metal in the hydraulics and very well still could. we had a bent stabilizer. replaced it last week. connectors before and after water separator could be clogged. thats about all i know to try. i am sorry this is so long. i just can see this has been asked a lot. and want you to know i am using search. any help would be greatly appreciated. thanks, patrick.
You can't make this stuff up Does it blow black smoke as it stalls? or hardly any smoke at all compared to running normally? The rest is mostly irrelevant. The return flow at idle does not mean that there is enough fuel pressure being supplied to the pump under load, to test that, you need a pressure/vacuum gauge teed into the supply line to the injection pump so you can see what the fuel pressure is under load.
thanks for the fast reply. no smoke when it stalls. i think i know where you are going with this. no smoke means not enough fuel?
Exactly. You say there's several things wrong with the fuel system, and there's no smoke... There's two methods of fixing stuff, diagnosing the problem then fixing what you find wrong, or trying something and then seeing if it worked. Sometimes there's not much difference. This is one case where you might as well forget about testing the fuel pressure and just drain the tank, clean it out, and then clean out everything up to the filter.
I would start by getting rid of all the jury rigged crap on the tractor and start over, I would replace both fuel lines and go back to the original pickup configuration. If the transfer pump is doing its job and there is good pressure and flow to the injection pump in all likely hood it needs repair. Those pumps are not at all tolerant to low pressure or supply and will pound themselves to pieces if ran under those conditions.
Well... Got her fixed. After painstaking hours of work, cuts, and getting covered in grease...it turned out to be the air cutoff solenoid. Behind the IP. Don't have the solenoid... But got a coat hanger holding it wide open. Runs like a champ. Thank y'all for your help.
Prolly just needed a ground to the fuel selinoid.
Thanks. Will try that tomorrow.