How To: Jump the RPM Relay

[DeLorean03]

The RPM relay is located in the electrical compartment behind the passenger's seat. It looks like this:

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Once you've located it, unplug it from the electrical connector it's hooked up to. It'll only go back on one way specifically, so don't worry about how to reconnect when the time comes. From there, you need to devise a "jumper" - a wire with 2 male spade connectors - one on each end of the wire. Spade connectors typically are rectangular in shape. Once you've made the jumper, "jump the RPM relay" as seen in this picture:

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This, in essence, forces the fuel pump to run even if you are not trying to start the car. Once you've jumped the RPM relay as seen in the picture above, try to start your car. If it starts in this case, your RPM relay may be working intermittently. Unhook your jumper, re-hook the RPM back up to the electrical plug, and try to start your car normally. If it starts, good deal. If not, might need to look into a new RPM relay.

[sean]

FYI, the wires in question that you are connecting with this jump:
Brown
and
White/Purple.

[Farrar]

I would like to add that if the relay fails while you're on the road and you need a way to get your car safely elsewhere under its own power so that you can order a new relay, you can stick the other end of the jumper wire in the green wire's slot, instead of the brown wire's slot. The result is that the fuel pump will run when the key is on.

The usual disclaimer about this being only a temporary solution applies. Also, I think it is a good idea to keep a fused jumper in the car for this, in case you have an electrical problem which caused the relay to blow.

Farrar

[sean]

I would like to add that if the relay fails while you're on the road and you need a way to get your car safely elsewhere under its own power so that you can order a new relay, you can stick the other end of the jumper wire in the green wire's slot, instead of the brown wire's slot. The result is that the fuel pump will run when the key is on.

The usual disclaimer about this being only a temporary solution applies. Also, I think it is a good idea to keep a fused jumper in the car for this, in case you have an electrical problem which caused the relay to blow.

Farrar
Great addition Farrar!

[Farrar]

Great addition Farrar!

Thanks; I had my second cup of coffee just before I wrote that. :lol:

Farrar

[Bitsyncmaster]

The photo in the first post shows a green case green connector. That is the only RPM relay I can not accept as a core for my solid state relay. The pin footprint does not match my circuit board.

An emergency jumper should have three pins. So you also power the Lambda circuit with the fuel pump.

So you don't need to remember what colors or pin number.
The pump wires are the two large gauge wires.
Brown wire is always the power (battery +).
The double wires in one pin is the Lambda.

Running the pump on the green wire, I do not recommend to do. Our stock pumps run about 7 amps and some run 10 amps.

[MacStainless]

Thank you for posting this! After hitting my head against a wall trying to figure out what was wrong, this got my DMC running in 5-min. Also let me know definitively that my relay was shot and I needed a new one. Vital information.

[Chris 16409]

Thank you for posting this! After hitting my head against a wall trying to figure out what was wrong, this got my DMC running in 5-min. Also let me know definitively that my relay was shot and I needed a new one. Vital information.

Contact Dave McKeen (Bitsyncmaster) to purchase one of his solid state RPM relays. It's a no brainier upgrade. You send him your old relay to modify.

[BobLS]

FYI, the wires in question that you are connecting with this jump:
Brown
and
White/Purple.

The guy from DMC says to jump the black and the black/purple. See here at 12:40:

https://www.youtube.com/watch?v=gRjOu6Zi3Gw

[Bitsyncmaster]

The guy from DMC says to jump the black and the black/purple. See here at 12:40:

https://www.youtube.com/watch?v=gRjOu6Zi3Gw

Black is ground. There is no black/purple on the RPM relay.

You jump the brown to white/purple to power the fuel pump but if your going to be driving the car you also want to jump brown to the double yellow/red wires so the lambda also gets powered.

[Ron]

The guy from DMC says to jump the black and the black/purple. See here at 12:40:

https://www.youtube.com/watch?v=gRjOu6Zi3GwThat's for an inertia switch test...