Heavy Duty Fuel Pump Relay

[Chris Hawes]

Thanks for the kind offer Rich. Let's see how long it lasts as it stands!

[stunned_monkey]

Just to clarify, the RPM relay is not "meant" to prime the fuel pump when the ignition is turned on. It switches on when it sees an ignition pulse (ie spark) and switches off after one second of no sparks.

Some ignition amplifiers (grey box under the idlespeed control ECU) put out spurious sparks when powered up, some even do it when you flick the headlights quickly.

It's very handy to do, esp when the engine is cold, but just because the pump doesn't always prime doesn't mean there's anything wrong with the relay.

I've also seen ones where heat generated by a poor contact on one of the power pins has melted components and tracks internally. In those cases, replacing the connector in the plug was required as well as replacing the relay.

[NickT]

It should run for 1-2 seconds to prime the fuel system.

NickT

stunned_monkey Wrote:Just to clarify, the RPM relay is not "meant" to prime the fuel pump when the ignition is turned on. It switches on when it sees an ignition pulse (ie spark) and switches off after one second of no sparks.

Some ignition amplifiers (grey box under the idlespeed control ECU) put out spurious sparks when powered up, some even do it when you flick the headlights quickly.

It's very handy to do, esp when the engine is cold, but just because the pump doesn't always prime doesn't mean there's anything wrong with the relay.

I've also seen ones where heat generated by a poor contact on one of the power pins has melted components and tracks internally. In those cases, replacing the connector in the plug was required as well as replacing the relay.