5 pin vs 4 pin Fuel Pump Relay

[elplatano]

Howdy Folks!

I was looking into adding some type of security system to my 1995 350 TBI ECSB and stumbled on the Mobilistics remote controlled fuel pump relay where you can kill power via a remote control. After looking into it, they only offer a 4 pin relay system, however in my truck I have a 5 pin relay.

After looking into it, the 5th (Center 87A) pin is a redundancy circuit that can energize the fuel pump from the Oil Pressure Sensor in case of a relay failure.

So my question is, can I run a 4 pin relay and in place of the 5 pin relay with no ill effects? The only downside I can think of is if the relay fails, the truck will die.

Anyone else have any input?

 

[GoToGuy]

Compare the relay circuits which side is the smaller relay not powering?

 

[elplatano]

Compare the relay circuits which side is the smaller relay not powering?

after looking at the relay circuits, the missing pin from the smaller relay is auxiliary power from the oil pressure switch. All pins are and logic are the same besides 87a. Which is NC when at rest and NO when energized.

From what I have read it’s a safety mechanism that if the relay fails mid drive, the engine will not stop and a long crank condition will ensue.