HI there, i have a very old (7500hrs) cat 305cr excavator. Its been running fine no dramas. I was using the blade to push some light dirt around to level off, wasn't running the machine hard, no overheating signs or anything and then just complete sudden loss of power. No burst hoses, engine runs fine, the arm to engage hydraulics next to seat seems fine. I dont have any gauges to measure pressure. Any ideas what i could look for?
Welcome to the forum. Very possible that it is the rubber pump coupling that connects the hydraulic pump to the engine. Check where the pump mounts to the motor and see if there are any bits of rubber coming out of any of the inspection holes or any black “dust” around that area. Any chance you could smell rubber when it quit? I would also confirm that you safety switch is definitely working.
Post a Serial Number and some illustrations of the coupling may be forthcoming.
Safety switch seems fine? Use a DMM and confirm that it is. Next is buying a pressure gage and test hose.
I couldn't smell rubber. I'll have a closer look at the junction of the pump and engine.
the serial number is *00019518* which coupling are you referring to?
Can you post a photo of the Cat data plate please.? It should be located on the RH side of the upper frame close to the boom foot pins. The one between the engine flywheel and the implement hydraulic pump. You say "it feels fine" but how did you test the implement lockout lever and the switch that it operates.?
yeah OK
Coupling is #7 on the attachment. I'll send you an electrical schematic to help you test the implement lockout switch. Keep an eye on your message inbox.
Thanks so much I really appreciate this. Im not currently in the same location as the machine so can't take any action right now but when im there i need to get it resolved
Have you done any basics yet such as checking fuses.?
Probably not the engine/hydraulic pump coupling. When the coupling on my 305CR gave out, it essentially stalled the engine and was almost impossible to restart, plus I could smell burning rubber before it fully gave out. Check under the cab directly under the seat for a small hydraulic block with an accumulator on top. It is behind the joystick hose manifold, if looking through the little door to access the joystick pattern change control. There are two solenoids on it. Make sure the wiring is intact. The top solenoid is what the armrest safety switch controls. I had similar symptoms on my 305CR and it was because a rat chewed the wires to the solenoid.
Hi Nigel, so im back at the location where the machine is. No rubber bits in the junction between the pump and motor, all the fuses are fine. The engine starts perfectly. Im not sure how to check electrically the implement lock out lever?? I do have a multi meter however ... I can also take photos now if required. thanks for your help
See the schematic. The LH switch is supplied with Batt+ via wire 304-A49-YL when the key is ON. Check for that first. Then when the switch contacts close that same voltage goes to the RH switch via wire 330-A54-YL. Check for that next. Check that power arrives at the RH switch once you have proved the LH switch is working. Next check that the RH switch is operating and power is going out on wire P977-A81-PK. Wire 977 goes to 2 places. The start disable realy and the Implement Lock solenoid. Well your engine is starting so power must be getting to that relay. the question is whether or not it is getting to the implement lock solenoid.
Hi Nige, Im sorry but i have no idea how to do that....my experience with a MM is limited to whether a battery is ok..... I dont know where to even start on what you've described above...
In that case I would suggest you need to get hold of someone who does. The information required to carry out the diagnostic procedure is all there in the schematic and the illustrations accompanying it.
Look up the continuity instructions for your DMM and practice on a known good switch.
If you’re going to work on stuff yourself, you’re going to have to watch a lot of YouTube videos, just remember, half the stuff you watch is either dangerous or stupid.
I replaced the coupler on a 304cr last year. Operator described same, no warning, no smell and I couldnt find any rubber remnants (till I split the bellhousing). It was out in a field so I did an unscientific test by loosening the pump output fittings a bit and hid in the cab and started engine for a quick second and had zero drips from lines. Not recommending that but worked for me. I was able to replace coupler with cab and counterweight on but was pretty tight/not fun.