i have a 91 rs with a carbed 350 in it. i recently changed my oil pressure sensor by the oil filter. after driving it today i turned the car off and my fuel pump continued to run until i pulled the fuse for it. i put the fuse back in and disconnected the fuel pump relay and it still ran. it only stops when i disconnect my oil pressure sensor. do you think my sensor that i put in a week ago is already bad and constantly sending power to the pump? it still reads oil pressure just like it is supposed to when running and it goes to 0 when i turn the car off.

also i have been thinking about putting a switch in for the fuel pump. what is the best / easiest way to wire a manual switch into the system?

 

Would appear so

The circuit in the sender for gauge is separate to the circuit for pump

 

The fuel pump can still run without the relay. Almost certainly your new switch is jammed on.

 

Even though the gauge part is working the contacts for the pump circuit may be closed

 

It's possible that the parts counter gave you the wrong switch. Most cars with instrument panels using idiot lights used a normally closed oil pressure switch, so they are fairly common. The auxiliary switch on our cars must be normally open, closing on rise at 10 PSI and opening at 7 PSI.

 

it worked correctly for awhile. then it just started making the pump run all the time. here is the one i got...http://www.autozone.com/autozone/par...4_652063_8450_

 

It is very likely the switch is bad.
The parts store brand electronics are sketchy at best when it comes to longevity.
Whenever I need sensors/modules/or any other under hood electrical item, I buy OEM if available, or the top of the line NAPA offering if I can't get OEM.

 

LIFETIME WARRANTY! You only have to provide the labor (again).

 

yeah they said to just bring the old one in when i swap them!! woohoo!!!