Patrick Feeley
Full Access Member
If the Low Pressure Oil Pump (a.k.a. lube oil pump like most engines) is not working, obviously the engine isn't going to function very well, at least with zero oil pressure. The High Pressure Oil Pump (which provides the high pressure oil used to actuate the injectors (remember the HEUI stands for Hydraulically-actuated Electronically-controlled Unit Injector) gets its oil from the reservoir which is fed from the lube oil pump. The reservoir is at regular lube oil pressure and that's where the switch is at. Notice I mentioned switch; because that's exactly what it is (as was previously mentioned above) and it does not provide a variable resistance with pressure as a normal sending unit would do. The setup is supposed to read mid-scale with any oil pressure above the switch setpoint (6 or 7 psi). If you take the wire off the switch and ground it (key on), you should get a mid-scale reading on the gauge. If not, the gauge or the wiring to it is bad. Mine has not worked for sometime and I think it is probably the wiring as I used to have it setup as a real oil pressure gauge using the same wire and it was funky then too. Cheers!
