Hi everyone I just installed the intellitronix gauges in my 91 camaro but I was trying to figure out where the oil pressure sending unit is located so I can replace it with the one they sent. Would it be near the distributor or by the oil filter on my car. I kno this is kind of a stupid question but I was just looking for any info please. Thanks!

 

Hi, they are usually behind the distributor on a brass pipe tree. There are usually two of them back there, one for fuel pump and a larger, usually silver in color that is for the oil pressure. It should be a single wire unit.

Louis

 

On a '91 it is part of the fuel pump switch above the oil filter.

 

Okay sounds good. Thank you for the help!!

 

In before the inevitable "Hey guys, my car won't run since I changed my oil pressure sending unit" reply.

Pro tip: Don't remove the stock oil pressure switch, or the ECM will be unhappy. Get a T fitting.

 

Sounds good. Thanks for the heads up!

 

ECM could care less about a missing oil pressure switch. And if the fuel pump relay is good then the fuel pump will start and run, as the engine also will.

The oil pressure switch and fuel pump relay are wired in parallel. Making the oil pressure switch a backup to the fuel pump relay.

RBob.

 

RBob:

Doesn't the ECM supply ground to the relay for only two seconds, then connects it during cranking?
After that the fuel pump switch connects the fuel pump directly to the battery.

 

Sorta'. At key-on, the ECM sends +12 volts to the relay to enable the fuel pump (FP). If the engine isn't cranked over then after two seconds the ECM will stop sending power to the FP relay and the pump shuts off.

While cranking the engine over the distributor sends reference pulses (DRPs) to the ECM. The ECM will respond to this by again sending +12 volts to the FP relay. And as long as the DRPs keep arriving (via cranking or a running engine), the ECM will continue to send +12 volts to the FP relay.

These same DRPs will also cause the ECM to fire the injectors at the appropriate time.

As for the oil pressure switch, once the oil pressure is above 4 psi (or so), that switch will close. Since it is wired in parallel with the FP relay, it is just a backup to it. One sign that the FP relay system has failed is long crank times. Need to build oil pressure before the FP runs and the engine can start.

Both the FP relay and oil pressure switch get battery power from the same source. The under-hood feed to that circuit and battery power for the ECM. This feed has a 20A inline fuse.

RBob.