Oil pressure gauge and T questions

[GNRick]

A local gn guru informed me today that the relay is needed even if you have a hotwire. I can't find my factory oil sender wires so he thinks they are bypassing the fuel pump relay on the fender.

 

[GNRick]

Double post

 

[bobs84ttype]

Just wondering how the pressure switch completes the fuel circuit.

ECM provides a 3 second prime pulse to fuel pump then shuts off. then the oil pressure switch turns pump on after oil pressure goes above 4 psi . Then when ECM detects a run condition it closes the relay to the on position . Oil pressure switch fills the time during cranking between the prime signal and the engine running signal that the ECM puts out to the relay

 

[aminga]

ECM provides a 3 second prime pulse to fuel pump then shuts off. then the oil pressure switch turns pump on after oil pressure goes above 4 psi . Then when ECM detects a run condition it closes the relay to the on position . Oil pressure switch fills the time during cranking between the prime signal and the engine running signal that the ECM puts out to the relay

Actually the oil pressure switch is backup to the relay to energize the pump in case the relay goes bad

 

[jopaustu]

Actually the oil pressure switch is backup to the relay to energize the pump in case the relay goes bad

That's how I'm seeing it as well...

 

[jopaustu]

ECM provides a 3 second prime pulse to fuel pump then shuts off. then the oil pressure switch turns pump on after oil pressure goes above 4 psi . Then when ECM detects a run condition it closes the relay to the on position . Oil pressure switch fills the time during cranking between the prime signal and the engine running signal that the ECM puts out to the relay

So the ecm sees a run condition when oil pressure closes the pressure switch above 4 psi? Then the signal stays constant from the ecm to the fuel pump relay? Trying to determine whether this is redundant or is a kind of a interlocking control before I put put this car back together with out the factory sender connected

 

[bobs84ttype]

The way I understand it. ECM does not close relay untill a run condition is set. there is the time from key on to cranking to a run condition set by ECM. Oil pressure raises almost instantly when cranking closing the switch . after run condition is set It is a redundant power supply to pump
Pump will operate with either or both switched closed

 

[aminga]

A run condition in the ECM is RPM > 400 RPM as I recall.