Problem started when attempting to fire up dozer after machine sat unused inside over winter. Initially started and immediately lurched to right as my brother quickly shut engine off. Machine has history of going berserk and we have remedied by shuttling pilot control valve spools back and forth as they seemed prone to sticking. But this time engine would not even start. Starts to crank and immediately binds up like it’s coming under a load that starter motor can’t overcome. Checked fuel system first. Fuel filter, put new fuel pump on. Didn’t really want to hold a prime. Checked tank suction hose with vacuum pump to see if there was any leaks. Okay. Loosened injector fitting to check for fuel and bleed air. So tried to see if it would pop on a snort of either. Nothing. Turned our attention to injection pump. Checked that fuel shutoff solenoid was working. Removed injection pump for testing and guess shops don’t just test anymore. Well, spent $2400 for replacement pump and injectors. Still engine cranks for moment and bogs right down. Also had pulled valve cover and valve operation checked out okay. When machine had previously run transmission filter had gotten hot. Gut feeling is that hydraulic system is binding up somehow that starter motor can’t overcome resistance. Don’t know how or what to check. Jacked tracks off ground to see if that would allow engine to start. Have service manual to interpret computer codes but not starting doesn’t help and currently just flashes a bunch of random codes that we question validity. Very frustrating. Any clues anyone?
If it's has a head gasket leak letting coolant into a cylinder it will bind the starter .
If you remove the cover from the TCU, scroll to codes, are there any listed in there? Record what you have, clear them, try to start the engine. Does anything return? Will the engine rotate around by hand? You might have to support the pump stack and pull it out of the pump coupler to see if the engine will start.
I’m a cat guy so i don’t know this machine well but what you describe is the hydraulics loading up when cranking. The lurch on first start means that it’s actively trying to drive all the time. If there’s a park brake it’s probably holding it from moving while cranking. You need to find out why the pumps are stroked up and get them back to neutral.
thanks guys for all the input. Checked crankcase oil and antifreeze for cross contamination. No evidence of, so hoping no faulty head gasket. Will try clearing codes on computer next. Cat man’s advice seems to hone in on possible culprit. In his words pump(s) are “stroked” and fighting parking brake. Machine’s schizophrenic history where sometimes starting normally and sometimes immediately lurching could be explained by pumps not neutraled out. Will try toggling pilot control valve spools again as they have been prone to being sticky. Maybe tweaking null adjustment to see if it calms down an angry pump. Thanks once again for the diagnostic help.