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fuel pump conversion


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Why not just put it where the original pump is?

 

The one that's already wired in the way it should be.

 

Or at least re-use the wiring even if the new pump is an external.  Not sure that the one being replaced is an internal as I'm not familiar with Z-cars specifically but thought it might be a valid point.

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In an accident (a rare occurrence) you may be hurt (it happens) and unable to get out of the car or turn the ignition and fuel pump off. (less likely) The car may be involved in a fire, (very rare) and the fuel system may be ruptured or the car over turned, (even rarer) the fuel pump will just keep feeding a fire till it runs out of gas.  

 

Yes, your 280z should already have a safety relay that works without any input from you. The 720 trucks have one that I believe is like a room lamp timer. Open door lamp lights, close door timer counts down, in about 20 seconds the light goes out. The 720 fuel pump relay even looks like a room lamp timer.

 

Turn key ON,  pump starts and timer begins. Turn to START and this will go around the timer and hold pump on. As long as you are cranking the starter, the pump relay is on. When key is released from START timer begins all over to count down.... UNLESS engine is started and running. How will the timer know if engine running? Well there would be oil pressure when running and the oil warning lamp off. No oil pressure is a ground condition at the oil pressure sender that turns the oil light on. This ground condition could be used to hold the fuel pump relay on. If oil pressure it's assumed the engine is running. In the event of an accident, engine stops (presumably) no oil pressure, pump relay times out and pump stops. I think the 720 relay also uses the charge light on the dash. When alternator is not charging, the one side of the charge lamp is grounded through the alternator.

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I'm not familiar with the 280zx fuel system.  If it has an external fuel pump at the rear of the car like the 280z does, then you could easily used that wiring.  The 1975-1978 280z has the positive wire going down the passenger side and actually has a connector in the line just behind the passenger seat mount rail.

 

However, if you remove the mass of wires for the EFI in the engine compartment and under the dash, it is likely that you removed at least one of the five relays that control the fuel pump.  Ask me how I know!

 

For my 1975 280z, I created a separate wiring circuit and used an oil pressure switch (teed in with the oil pressure sender at the block) and a single standard relay to provide power to the pump.  The relay provides power only on the starter circuit and when the engine has oil pressure.   Total cost for the relay, the oil pressure switch and wiring, the BSPT to NPT adapter, a tee and the wire was about $25.  

 

That provides the safety that datzenmike mentioned above.

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