| Re: [GMCnet] Idea - Use a Vega fuel pump relay [message #145613] |
Wed, 05 October 2011 10:30  |
Gary Casey
Messages: 448
Registered: September 2009
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I might be wrong here - it happened once before - But as I recall (let's see, was it the long or short term memory that goes first?) the Vega and other GM cars didn't use a relay for the fuel pump. Many GM cars of that era used a carburetor with an electric fuel pump and they were all wired the same. The oil pressure switch was a SPDT switch instead of the normal SPST switch used before. The common was connected to the battery and the NC(normally closed) terminal was connected to the warning light. The NO(normally open) terminal is then powered when you have electrical power and oil pressure. Also connected to the fuel pump was the "other" terminal (forgot what it's called) on the starter that was normally used to bypass the ignition coil resistor on cranking, no longer used with HEI. That way the fuel pump will be energized when you have oil pressure OR are cranking. No relay required. And I think you can pick up the oil pressure switch
by asking for a "three-terminal oil pressure switch" at the local auto parts store.
Gary Casey
I was just blowing the cobwebs out of my cranial storage and the talk of electric fuel pumps set a pointer that lead to our '73 Vega Z-29 (not all that different than vanilla).
It had an electric in tank fuel pump. It also had a relay that was connected to the start or ignition circuit and a lube oil pressure switch. This caused the pump to run during start up, but shut it down if it lost lube oil pressure. (The later was a very good plan - if you remember the Vega motor.)
We need to find (or maybe build) that pump control for GMCs with electric fuel pumps. I don't even have any idea where to look for a GM part number. I would not bet that it is even still available, but the maybe out of the rust belt there are some surviving examples.
Matt
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| Re: [GMCnet] Idea - Use a Vega fuel pump relay [message #145614 is a reply to message #145613] |
Wed, 05 October 2011 10:44  |
WayneB
Messages: 233
Registered: July 2008
Location: Ontario, Canada
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GM used a similar oil pressure switch on the 1991 to 93 TBI Roadmasters, the engine wouldnt fire until the switch saw oil pressure and allowed power to the coil.
Its installed above the oil filter on the L/H side of the block.
I replaced the one on my wagon this year (they leak after a while), it was $65 and you will need a weatherpack connector to wire it.
A couple of the wires are for the electric OEM oil pressure gauge, the Caprice didnt have the gauge but it may not have had the low oil pressure no start feature on its idiot light switch.
Wayne
1976 23' GMCII By Explorer
[Updated on: Wed, 05 October 2011 10:44] Report message to a moderator |
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