I have a 305CR that stalled under load and now won't restart. I was digging with it and it almost stalled a few times while under a high load, then it finally stalled while under high load digging. I tried to restart and it would turn over a few times, then act like the battery was weak. There was a small amount of grey smoke coming from the rear of the engine, between the engine and the hydraulic pump after it stalled. I checked several areas on the engine and pump with an infrared thermometer and nothing seemed to be overheated. I'm suspecting it has to do with the hydraulic pump, as prior to it stalling, there had been an intermittant whining noise at high RPM, but I could not locate the source of it. Any help is appreciated. I'm digging into the service manual now...
OK, an update. I jumped the excavator and got it to crank over nice and fast, but it won't start. It looks like it's getting fuel, as there is dark grey smoke when I crank it over. The fluids look and smell good - no burnt or milky oil, no oil in the water. Time to dig deeper into the service manual.
Since your getting smoke it should start.... I would check power to glow plugs and see if they're drawing current.
Dark grey smoke is weird. Check the air intake, if it's starving for air it might do that. Stalling the starter after cranking a couple seconds sounds real bad, like bad hydraulic something or other, hopefully there's an easier solution.
Is fuel shut off opening all the way?
Can you uncouple the hydraulic pump from the engine and see if the engine will start. That would help to pin point where it is engine or hydraulic.
possible a unloader valve not unloading
That’s on my list of things to check.
Not something that is easy to do, but it may come to that.
I cracked the lines at the pump, thinking it might be something like that, but it made no difference.
Serial number ? Ceck hyd filters
Can you give us an update?
Haven’t had a chance to dig into it further. Hopefully in a few days.
Finally had a chance to dig into this. I got it started, and it ran with lots of black smoke and rough. It cleared up a bit and I had no hydraulics plus the smell of burning rubber, so I'm guessing the hydraulic pump coupling let go. Next step is to remove the pump from the motor...
Make sure the pump TURNS before you go to the trouble of breaking a new pump coupler.
Should I be able to turn the pump by hand once it is disconnected from the motor?
Yes, you might have to put whatever coupling there is onto the shaft to get a grip. That little four cylinder is not going to be capable of huge torque, and it should turn without hydraulic load with no controls operated.
Well, the coupling is definitely shot. I don’t think the pump is seized, as I can turn it by hand (using a wrench on the splined input shaft). It’s not an easy task to get it swapped out. I have the pump off, but still need to remove the “bell housing” plate that the pump bolts onto so I can replace the coupling. Why don’t the designers keep ease of maintenance in mind when they design a piece of equipment?
Got it running today. It was quite the process to get the coupling changed out. The Cat service manual calls for the removal of the engine to replace the coupling. No way I was going to do that. Cat, in its infinite wisdom, didn’t leave quite enough room to remove the hydraulic pump from the engine with it still in the machine. I think it could be done if you could remove the counterweight, but I didn’t have the ability to do that. I was able to remove the pilot pump from the main pump, then main pump from the engine. Things would have been a lot easier if I could have unbolted the muffler from the exhaust manifold and removed it, but the bolts were pretty rusted. Anyway, I got it done and put back together and running today. Attached are photos of what is left of the old coupler and the new coupler installed. It appears the new coupler is of a different design and it had a new part number from Cat as well and, shockingly, it was significantly less expensive than the original part number.
Nice job. I replaced that coupler in my 305 last year when I rebuilt the motor. Machine had 1500 hrs on it. Original coupler had stress cracks in it. Dealer said they use to be close to 400 dollars but now they are around 100. That was a nice price reduction.