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HybridZ

On/Off Switch for fuel pump.


N3RB

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Find the line for the fuel pump and install a toggle switch...

 

You can either:

 

Run wire from the pump to wherever you want your switch. (not a good idea)

 

Or, I'm not sure which wire it is under the dash, but it's your best bet to look at a wiring diagram and wire the switch there.

 

Just snip the wire and attach each end to the switch, nothing special.

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  • 3 weeks later...
It would also be a good time to install an inertia switch or oil pressure cut-off switch for safety reasons. The original zcars did not have any accident safety devices for their electric pumps.

 

I'm pretty sure the 280z's did. The earlier ones in the AFM (hence when some of the front fire they shut off haha) and the later ones with the oil pressure switch (like the 280zx's).

 

Mario

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It would also be a good time to install an inertia switch or oil pressure cut-off switch for safety reasons. The original zcars did not have any accident safety devices for their electric pumps.

 

They ALL had fuel pump cutoff in case the engine stalled:

 

Earlier Versions had a set of contacts in the AFM that would enable/disable the fuel pump.

 

Later Versions had a contact inside the Oil Pressure Swtich that would enable/disable the fuel pump.

 

It is a FMVSS requirement. The inertia switch can be a PITA because it shuts off the engine on a bump and you have to reset it. Ford Tempos were notorious for getting bumped in parking lots and being rendered inoperable till someone came out to reset the switch (which was in the trunk!) The Rangers were mounted on the passengers floor under the carpet---really accessible places to have to go and reset your car. On the Tempos, you would play 'bumper cars' with Rentals: Bump the co-worker in front of you hard enough to stall him, but not hard enough to damage the 5mph bumpers permanently...which is all the bump you needed to disable the car.

 

I prefer the stalled engine shutoff, myself...

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I should have been more specific about the "original" zcars which did not have electrical cut offs for the fuel pump. I believe all the FI cars did have a factory cut off system. The 240Z carbureted cars did not. They were wired for auxiliary electric pumps, but no cut off switch was provided as far as I know.

 

I have been using an inertia switch on my 71 240Z for 2 years and have not had it trip once. Maybe thats because I mounted it within easy reach under the dash :-). The other advantage over an oil pressure switch is you can prime the carbs just by switching on the ignition for a few seconds before cranking the engine.

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  • 3 weeks later...
i just bypassed the stock wires all together (was tired of diagnosing why i wasn't getting power to the pump) and ran wires from the battery to a switch, to the pump.

 

Car still won't start tho....haha

 

hah i'll vouch for this guy...i had the same problem and used the same solution...except my car will start, it just wont stay started...yes i know it sucks

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Actually, I cannot speak for all 240's, but my '73 (which came from the factory with the electric pump) had some safety circuitry built in. There were two small modules under the dash. I referenced them in my '73 factory service manual, and if I remember correctly, one of them cut the fuel pump off under something like 300 or 400 rpm, and the other overrode that when the key was in start to run the fuel pump during cranking.

 

It is totally possible that this was all add in stuff at the dealer to help combat the vapor lock issue. The modules were wired into the fuel pump circuit with connectors that tapped into the little in line fuse under the dash, and the starting circuit was referenced via a wire running along one of the heater hoses to the starter terminal! The connectors were all factory, but the wire routing certainly was not.

 

And as of late, Megasquirt cuts off the fuel pump after two seconds when the engine is not running, so I'm good.

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  • 8 years later...

They ALL had fuel pump cutoff in case the engine stalled:

 

Earlier Versions had a set of contacts in the AFM that would enable/disable the fuel pump.

 

Later Versions had a contact inside the Oil Pressure Swtich that would enable/disable the fuel pump.

 

It is a FMVSS requirement. The inertia switch can be a PITA because it shuts off the engine on a bump and you have to reset it. Ford Tempos were notorious for getting bumped in parking lots and being rendered inoperable till someone came out to reset the switch (which was in the trunk!) The Rangers were mounted on the passengers floor under the carpet---really accessible places to have to go and reset your car. On the Tempos, you would play 'bumper cars' with Rentals: Bump the co-worker in front of you hard enough to stall him, but not hard enough to damage the 5mph bumpers permanently...which is all the bump you needed to disable the car.

 

I prefer the stalled engine shutoff, myself...

I had noticed that later 280z's have an oil pressure with two male blades configured in a T. Does anyone have drawing of the internals?   If it is a simple ground contact, then that may be as simple as wiring the ground side of a relay directly into one of those terminals.  It can't be that simple.  

 

I need something to kill the electric pump in event of an accident.

 

G

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My 72 240 came with a mechanical fuel pump but the wiring for an electric fuel pump was also installed at the factory. I found the fuel pump wiring ( I think it was a fused green wire but you may want to look at a wiring diagram) behind the radio which ran all the way to the rear near the fuel tank. When I converted to a turbo system and fuel injection I ran a heavy gauge hot wire to a relay in the rear to power the fuel pump and used the factory installed wiring to trigger the relay. I installed a toggle hidden near the driver's seat to switch on/off the relay using the original wiring. You may want to install a roll over stitch as well. Fairly straight forward and easy to do. Good luck.

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N3RB - If your 280Z is still pretty stock and unmolested you should be able to lift the carpet behind the passenger seat and see the leads to your fuel pump. There should be bullet connectors there where the pump leads are connected to the wiring harness.  That would be a fairly easy place to reach from the driver's seat but not too obvious location for a cut-off switch.  I've thought about doing it many times but just never bothered.

Edited by Phantom
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I had noticed that later 280z's have an oil pressure with two male blades configured in a T. Does anyone have drawing of the internals?   If it is a simple ground contact, then that may be as simple as wiring the ground side of a relay directly into one of those terminals.  It can't be that simple.  

 

I need something to kill the electric pump in event of an accident.

 

G

 

TonyD has talked about a Ford inertia switch a few times.  Upon impact, it will kill the fuel pump. A quick Google brings up quite a few results.

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  • 1 month later...

I had noticed that later 280z's have an oil pressure with two male blades configured in a T. Does anyone have drawing of the internals?   If it is a simple ground contact, then that may be as simple as wiring the ground side of a relay directly into one of those terminals.  It can't be that simple.  

 

I need something to kill the electric pump in event of an accident.

 

G

Inertia switch?  Putting an 81zx drivetrain, 78 wiring harness, in my 74 260z.  Eliminated EFI and going carbuerated.  Going to install the inertia switch on the passenger side of trans tunnel behind the seat.  Think this is a good way to cut fuel to the electric pump in case of accident.  If it does happen to trip then it's within reach to reset.  Should have it all figured out in the next couple of weeks.

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