VOLUMEX SCAVENGE PUMP WIRING

[pewe484]

Any fellow VX owners out there who can offer some advice please?
I've used the engine for a different application (no argueing with terminal tin-worm on the HPE) but retained the wiring loom. Along the way I've dispensed with fuel cut-off circuitry and may have mis-wired then.
Can anyone tell me if the pump is wired to run until the water temp. drops regardless of the ignition being on?
It seems to be wired on the same feed as the low oil pressure circuit but this doesn't seem correct as that is wired into an ignition activated circuit and my recollection is that the scavenge pump ran until the engine had lost most of its heat.
Any thoughts/comments gratefully appreciated before I tear the rest of my hair out.
thank you, Pewe.

[1/4whit]

The system operates only when the engine is off & coolant temp.over 70c.The pump is operated by a thermo switch on the coolant circuit for the choke.The switch is fed direct from the rad.fan relay pos. connection & is earthed through the oil pressure switch &the fuel pump relay.Hope this helps you in it`s current installation.
Regards 1/4Whit.

[Guy Croft]

Sorry I don't have an OE manual for that Peter, but from memory (I think the manual said the pump when the engine is hot and switched off) and knowing that the little electric pump is supposed to clear the blower main casing of vapour after the engine is stopped, to prevent over-rich restart, I suggest it should be wired up so that the vent pump runs:
1) only after the engine is turned off
and
2) until the coolant temperature switch associated with that layout tells it that the engine temperature is low enough to turn off.

You don't want/need the pump running when the engine is on.

In effect it's a kind of time switch I suppose, that says after the coolant has dropped to some rpeset lowr temperature the blower can be assumed to be vapour-free.

Hope that helps some,

GC

[pewe484]

1/4 Whit & Guy, thanks for that.
Seems to make sense as the rad fan looks as if it runs off the same relay.
I do have an original HPE wiring diagram but presumably the VX was introduced after it was published as there is no provision shown for the scavenge pump.
Now all I have to do is get my head around it!
Incidentally if anyone would like a copy of the diagram let me know and I'll have it copied for beer tokens.
thank you, Pewe.