Hello all, new to this forum. I have a 1986 Mitsubishi 380 excavator. I am having problems with one of the main hyd pumps cutting out when the engine is revved up (works perfectly at an idle or slightly above idle). The pumps on this unit are side by side. The left pump failed and we rebuilt it and it is the one that cuts out ever since rebuild. We thought that the problem might be the regulator assembly attached to the bottom of the pumps, so we tried switching them from one pump to the other. This has not helped, conclusion nothing wrong with pump regulator. Have done some testing with pressure gauge. On the right pump which is working fine the pump shows 500 psi and the load sense line 500 psi at idle, when tracks engaged load sense falls to 0 and pump goes up to 1500. When the machine is revved up the pump pressure steadily rises with tracks traveling. The left pump also show 500psi at pump and load sense line at idle. When tracks engaged load sense drops to 0 and pump puts out 1500 psi, however when engine is revved up everything drops to 0 on the left pump. This has me completely puzzled. Have we put something together wrong when we rebuilt the pump? Has some brass gotten in somewhere when the old pump died? Ideas?? Any help really appreciated Neil
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