Using this relay for fuel pump?

[Fiat88]

Want to add a relay to my after market electric pump. I know they have kits already made but I rather use a fuse instead of the breaker and don't want to pay $40 bucks since I have most of the wiring and tools to make my own. Would this kit work for me, will wire up a inline fuse with it of course.http://www.summitracing.com/parts/PCO-5591PT/

[marty3d]

Relay should work fine - plenty of capacity (40A). Btw, the 1980 and later spiders with fuel injection use a relay on the fuel pump - with an emergency feature that cuts the pump out in the event of a crash. You REALLY don't want the pump to keep spitting out fuel if you are upside down... No fuse in the line though. The factory unit operates through a switch in the air sensor - no air means that the engine is not running so cut the fuel off. I would think that a pressure switch on the oil delivery side could do the same thing - no oil pressure, no fuel. Of course, it would have to be bypassed on engine start-up.

[Fiat88]

Relay should work fine - plenty of capacity (40A). Btw, the 1980 and later spiders with fuel injection use a relay on the fuel pump - with an emergency feature that cuts the pump out in the event of a crash. You REALLY don't want the pump to keep spitting out fuel if you are upside down... No fuse in the line though. The factory unit operates through a switch in the air sensor - no air means that the engine is not running so cut the fuel off. I would think that a pressure switch on the oil delivery side could do the same thing - no oil pressure, no fuel. Of course, it would have to be bypassed on engine start-up.

I was trying to find info about hooking up an oil pressure cutoff switch. Found this switch today from Summit racing http://static.summitracing.com/global/i ... -g1438.pdf. Anyone know the size of the threads on the oem style oil pressure switch? Is it metric or standard? The instructions say an oil pressure light can be hooked up to it as well.

[marty3d]

Most oil pressure switches will make contact with no pressure - turns on the warning light - but turns off when pressure rises above the minimum. You want the opposite, one that turns on with low pressure and stays on with higher pressure.

[Fiat88]

Most oil pressure switches will make contact with no pressure - turns on the warning light - but turns off when pressure rises above the minimum. You want the opposite, one that turns on with low pressure and stays on with higher pressure.

Marty3d,
Is there a way I could wiring the fuel pump to the factory oil pressure light / switch or do I need the special switch? BTW, thanks for the help!

[rlux4]

There is a fuse in the fuel pump circuit on our FI cars, it's an inline fuse on the brown with white stripe wire going to the dual relay. It supplies power to the fuel pump side of the dual relay. The other side of the relay is for injector voltage and that side gets fused power from fuse #1 through the pink with black wire.
Ron

[marty3d]

There is a fuse in the fuel pump circuit on our FI cars, it's an inline fuse on the brown with white stripe wire going to the dual relay. It supplies power to the fuel pump side of the dual relay. The other side of the relay is for injector voltage and that side gets fused power from fuse #1 through the pink with black wire.
Ron

Right you are. I forgot about the inline fuse for the fuel pump. The pink and black is fused but only operates the relay, the brown wire from the battery to the relay set is unfused and supplies the power for the injectors as opposed to power to operate the relay.

Back to controlling the fuel pump: I haven't looked for one, but I am quite sure that you can find an electrical relay that would work with the oil pressure switch as found on the cars. It would contain two sets of contacts, one of which is normally open and closes when voltage is applied, and the other that is normally closed and opens when voltage is applied. Through one pair of contacts, you would wire a wire to the start position and it operates the fuel pump while cranking, the other is wired to the ignition and operates it while running. One thing you should be aware of, is that loss of oil pressure will stop the fuel pump and then the motor.