Re: 75 Cosworth Vega how do I install carbureted F/pump circ

[mikeceli]

Hello Folks!

This lifetime car guy and son recently purchased a 1975 Cosworth Vega. The previous owner (PO) converted it to a Weber carburetor and installed a funky engine compartment fuel pump, powered by a toggle switch. I have removed said pump and switch.

I have purchased the 3 prong Vega oil pressure switch (OPS) and want to wire my INTANK pump, as the factory did on carbureted Vegas.

I have read other threads and studied the diagrams posted on this forum. I can't quite understand the circuit.

Exactly how do I run the wires to the "P , I (normally open) and S (normally closed) terminals on the OPS? Which of the 2 fuel pump fuses, in the factory fuse box do I connect which wire? Do I get 12v from the starter solenoid? (I think not).

Please, lets leave relays out of the discussion at this time. I have tested the in tank pump and it works.

Thank you !

[spencerforhire]

The OEM oil pressure switch had 3 wires- pink(ignition), blue(pump) and purple(start). At rest, the pump terminal is connected to the starter wire so there will be fuel available while cranking. After there is sufficient oil pressure, the common pump wire switches to ignition. Tracing the blue pump wire can be tricky, as it changes to blue/white at the firewall bulkhead connector, and then to pink as it goes through the fuse box and then back to blue at the rear body harness connector.
You asked that relays not be discussed. but I will point out that the OEM oil pressure switch is of sufficient current capacity that a relay is not necessary unless the fuel pump is being replaced with something much, much larger.

[mikeceli]

Anyone ever converted from FI to carburetor? Did you add the 3 prong OPS? I'm really trying to figure this out! Thanks.

[dindin]

how did you get the tank pump to work for testing?

Al

[mikeceli]

how did you get the tank pump to work for testing?

Al

I unplugged the connector at the right rear quarter panel, and supplied 12 volts to the blue wire, that goes to the pump. 4 PSI.

Thanks for you response.

[dindin]

I sent you a PM, this should give you what you need.

Al

[mikeceli]

We have got it figured out. Once the car is road tested and validated, I'll post a "how to".