RPM Relay - Fuel Priming

[JamesRGUK]

Quote:That'll be me then

I've banged on about this one ad nauseum, I've tried three RPM relays in my
D including ones that 'prime' other owners cars. Non of them prime mine.

Anyone who wants a full technical (and somewhat boring) electronics
explanation of why the RPM dosen't, hasn't and never will prime the fuel
system intentionally is welcome to email me....

So is another component in the chain feeding 12V to the pump temporarily?
just seems such a random problem.

I'm no electrical expert but....

If it's not the rpm then an interesting experiment would be to remove the RPM relay,
on a car which is known to prime before starting, and put a multi-meter across
the +tive terminal on the wiring harnes (where the rpm normaly connects) to earth
and see if there is a voltage spike when you turn the key to pos 2.

if you tried this accross the terminal that is normaly live only when the car ir running
then you could prove that the RPM is not responcible for the priming.

Presumable the RPM relay looks for current from the alternator to confirm that the
engine is running so is the alternator the key?

hope that sort of makes sence, it seams like an easy experiment

J