This is a 1991 model powered by a JD4039 engine. It is installed on a sand blasting trailer. I have been servicing and repairing for a number of years so I have knowledge of previous issues and service. It has less than 4000 hrs. Previous issues have largely been with the electrical system. Last year it lifted the safety valve on the separator/reservoir when the blaster unit was shut down instead of unloading. I found that the pressure control valve was not working and had not closed the compressor inlet valve. The safety, pressure control valve were replaced and the bleed off valve kitted. Recently it started passing excessive amounts of oil out of the separator. The separator element was replaced and oil system flushed and oil replaced. Testing revealed the minimum pressure was low. Inspection revealed the minimum pressure check valve was faulty and it was replaced. It was put back on the job and shortly after they started blasting the operator shut the supplied air off at the blasting unit and it lifted the safety dumping large quantity of oil as previously. Minimum pressure rested at 30psi. The pressure control valve and blow down were removed and bench tested and are working properly. The inlet unloader valve was removed inspected and tested OK. I have never been able to find documents on this unit. The air end is 3A219x531 (sn 3217x531), Seperator 3A69-841 (SN 74517) Need advise on how to proceed from here.
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