Fuel Pump Safety Switch Wiring

[Pattymac]

So I'm tidying up all the unnecessary wiring at the moment, and need some help with the fuel pump circuit. At the moment, it is powered by a "Peel" gas controller thingamajig which is triggered by the -ve side of the coil.
Now that's where I thought it would end but the 12v source to the safety switch is from a relay which is triggered by the oil pressure switch? Am I right in assuming I only really need one of these, if so which one is better? The Peel box is a lot larger and the mounting point has broken so if I can toss that and keep the little relay that would be preferable. Lemme know!

Cheers

[ira11y]

Not sure which engine you are referring too and whilst i dont know anything about "Peel" gas controllers, most Fuel pump relays really work like two relays, they have a Neg trigger feed from the ECU and positive trigger feed from the starter circuit, the ECU circuit from memory triggers the prime when you turn on the ignition, then the starter circuit takes over on the second relay once cranking. the ECU provides the safety circuit for roll over, it is triggered when the crank sensor no longer sends a signal to the ECU and the ECU drops its signal to the COR.

Anyway to answer your question I would keep both connections (although personally triggering the safety off the oil sender is not preferable but is a simple solution) unless you decide to do away with the safety. Alternatively pick up a second hand COR and wire it up properly.

[Pattymac]

Crap I forgot to mention sorry, TA22 with a carbed 2TG so no ecu. OK, so in my situation if I understand correctly, the oil pressure relay is for priming in the on position, and in cranking the coil switches to the peel unit and continues to use the peel unit whilst the oil pressure relay switches off? So both are completely necessary?

[ira11y]

Not completely necessary but I would keep both.

[dougTA22]

If you have got a gas controller in there I would remove the wiring from the oil pressure switch. The aim is to cut off the fuel pump if the engine isn't running e.g. in the event of a crash. I could foresee the oil pressure switch being an issue if (for example) the car has sat for a while and the fuel bowls have dried up, and if your oil system doesn't build significant pressure during cranking - so you wouldn't be able to activate the relays and get fuel through to the carbs. The -ve coil triggered tachometric relay / gas safety switch is sufficient for what you need to do. The oil pressure switch setup is normally used when people want a cheaper way out of it as tachometric relays can be a little bit expensive. The other option can be wiring a relay in from the alternator charge light feedback, but not needed in your case as you already have the coil triggered relay.

Cheers,
Doug