Cat 302.5 ca. year 2000. Bought the machine used. 3000 hours. Installed new filters and new oil, both engine and hydraulic. The issue: Hydraulics «studder» real hard, and the oil pressure lamp lights up at the same time the studdering goes on. Seems to change a bit when I change the idling speed, but I seldom seem to shake the problem. I don’t know if you quite get what I mean by studdering. You know when the hydraulics should extend or retract smoothly - it goes just bit by bit and real shaky, and the mentioned lamp kinda flashes at the same time. It is not just the digging, the problem also occurs when tracking.
As always, it's a good idea to start with a Serial Number. Model years mean little or nothing on these machines. 4AZ-prefix maybe.?
Right you are - my apologies 4AZ01827
Could this be caused by a malfunction in the engine oil pump?
Which lamp is lighting up.?
Number 3
Does it kinda flash or come on steady.? Either way I would suggest to find the oil pressure switch on the engine, plug an analogue gauge into it and check the pressure. There is no illustration showing the exact location but is seems as though it's close to the fuel shutoff solenoid and the air inlet pressure switch to measure air filter restriction. The switch is fed by a single wire #405 Grey.
It flashes. I will try, and post my progress. Do solenoids in the hydraulics ever act up and produce this kind of studder?
The only solenoid I can see is the hydraulic shutoff (safety) solenoid which either ought to work or not, there are only 2 possibilities. I'll send you the electrical schemaitc.