71 Fuel Pump Wiring

[tttz]

Hi All,

I am trying to install an RX-7 electric fuel pump into my 71. I have found the stock wires near the fuel tank (green and black), and i have found the stock wires behind the radio (green and black/white). Both sets of wires were wrapped in blue tape.

From what i've read, i can connect the fuel pump to the wires by the fuel tank, which is easy enough. But where do I connect the wires that are behind the radio? The wires behind the radio have a plastic female connector on them already, and I was wondering if there is a corresponding male connector hiding under the dash...

I've searched and found the following threads, which have been very helpful, but don't quite answer my questions:

http://www.classiczcars.com/forums/showthread.php?t=15897&highlight=wires+fuel+pump

http://www.classiczcars.com/forums/showthread.php?t=17496&highlight=power+electric+fuel+pump

http://www.classiczcars.com/forums/showthread.php?t=13725&page=2&pp=15&highlight=fuel+pump+cutoff

I've read the discussion about connecting the fuel pump to an oil pressure switch and I'm intrigued by this idea, but as mentioned in the following thread, the Datsun engineers might have already had an idea for cutting power to the pump.

http://www.classiczcars.com/forums/showthread.php?t=983&highlight=fuel+pump+wiring

Does anyone know if any cutoff switches or relays were incorporated into the stock design for the electric fuel pump?

Thanks to everyone for their contributions to this site.

-Ty

[beandip]

I have a wireing diagram blown up to a 2' X 3' size of a early Z . '72 and earlier . There is nothing to show a controll other than the ignition switch . My ' 73 as far as I can see is the same way , however my wireing diagram is small and hard to read . I have been uable to find a shut off control so far. I have removed all of my '73 wireing and repaced it with a loom from a '72 . Having said that . I have installed a pressure switch at the same outlet the oil sending unit is mounted . I bought a tee fitting and a switch that will close at 5 Psi, The engine will start with the fuel in the float bowls and the fuel pump operates untill I either turn on the ignition switch or the oil pressure drops below 5 psi. You need to connect the pressure switch in the power line to the pump. The all green wire . What I did was , I took my sending unit with me to the parts store and bought a tee that was compatable with the threads of the sending unit and the engine block . Then found a pressure switch that was compatable with the tee and had two bullet connections and the pressure I wanted . I hope this answers your questions and is of some help. Gary

[V8-240Z]

I just went through this when I wired the electric fuel pump to the stock wiring in my 71Z. The black wire at the fuel pump is grounded to the chassis at some point between the pump and the dash. to run the pump you simply need to supply 12+ to the green wire in the harness behind the radio. Its a mystery to me where the black wire in the harness behind the radio goes.

What I did on the rest of the wiring was to use the oil pressure switch to control the pump with the 3rd connection going to the starter solenoid to run the pump when its cranking since using the oil pressure only will prevent the pump from running until the car starts.

Last but I felt most important I put a fuel pump inertia shut off switch in the car on the drivers kick panel and wired it between the fuel pump side of the relay and the green wire in the harness behind the radio. I did not cut up the harness I simply used a male spade connector and shoved it into the green side of the plug to make the connection.

The inertia fuel pump shut off switch will shut off the power to the pump in the event you have a accident. It also will shut it off if you hit a speed bump going too fast. It happened too me once when I had the intertia switch under the hood. That is the reason I moved it in to the car where I can reach it. That one time is the only time it has shut off. The inertia switch has a red reset button that you simply push to reset it.

The inertia switch is from any fuel injected Ford from 1980-2000. its in the trunk on the left side behind a panel that is almost always marked that the emergency fuel cut off is behind it. Be shure to cut the harness as far back as you can when removing the switch. With out the 2 wire harness its going to be hard to connect

A anti theft fuel pump switch can be placed before or after the inertia switch to cut power to the fuel pump if you want.

I have a couple extra inertia fuel pump shut off switches if any one is looking to do this modification and does not want to go to a wrecking yard to get one.

[tttz]

thanks for all the information. You all have been a tremendous amount of help to me.

It sounds like there is no cut off switch circuitry built into the 240z model cars. I think i'll proceed with hooking my fuel pump up through an oil pressure cutoff switch.

Thanks again.

-Ty

[Marty Rogan]

I just went through this when I wired the electric fuel pump to the stock wiring in my 71Z. The black wire at the fuel pump is grounded to the chassis at some point between the pump and the dash. to run the pump you simply need to supply 12+ to the green wire in the harness behind the radio. Its a mystery to me where the black wire in the harness behind the radio goes.

What I did on the rest of the wiring was to use the oil pressure switch to control the pump with the 3rd connection going to the starter solenoid to run the pump when its cranking since using the oil pressure only will prevent the pump from running until the car starts.

Last but I felt most important I put a fuel pump inertia shut off switch in the car on the drivers kick panel and wired it between the fuel pump side of the relay and the green wire in the harness behind the radio. I did not cut up the harness I simply used a male spade connector and shoved it into the green side of the plug to make the connection.

The inertia fuel pump shut off switch will shut off the power to the pump in the event you have a accident. It also will shut it off if you hit a speed bump going too fast. It happened too me once when I had the intertia switch under the hood. That is the reason I moved it in to the car where I can reach it. That one time is the only time it has shut off. The inertia switch has a red reset button that you simply push to reset it.

The inertia switch is from any fuel injected Ford from 1980-2000. its in the trunk on the left side behind a panel that is almost always marked that the emergency fuel cut off is behind it. Be shure to cut the harness as far back as you can when removing the switch. With out the 2 wire harness its going to be hard to connect

A anti theft fuel pump switch can be placed before or after the inertia switch to cut power to the fuel pump if you want.

I have a couple extra inertia fuel pump shut off switches if any one is looking to do this modification and does not want to go to a wrecking yard to get one.

Dave,

I am putting an electric fuel pump into my early '71 (1/71) as well .

Wiring has to be my worst skill. I need to step through this one step at a time. Let me see if I have this right.

1) Mount the fuel pump near the tank and ground the pump to the frame nearby.

2) Connect the power wire from the pump to the green wire in the wiring harness near the tank with a spade connector.

3) At the connector near the right hand side of the radio, connect a power lead to the green wire witha spade connector.

4) Connect the power wire from the green wire to one wire on the inertia switch.

5) The second wire from the inertia switch is routed into the engine bay and connected to 1 of three lead on the oil pressure cut-off switch.

6) This is where I get a little blurry on the details. One connection from the pressure switch goes to the solenoid. The 3rd wire goes to the battery (with an in-line fuse) for power? Or is that wired into the ignitions switch somehow?

Where did you get your oil pressure cut-off switch from? What pressure is used for cut-off? did you use any relays?

TIA,

Marty

Schools for the wiring impaired.

[MAX]

Hi All,

I am trying to install an RX-7 electric fuel pump into my 71. I have found the stock wires near the fuel tank (green and black), and i have found the stock wires behind the radio (green and black/white). Both sets of wires were wrapped in blue tape.

From what i've read, i can connect the fuel pump to the wires by the fuel tank, which is easy enough. But where do I connect the wires that are behind the radio? The wires behind the radio have a plastic female connector on them already, and I was wondering if there is a corresponding male connector hiding under the dash...

I've searched and found the following threads, which have been very helpful, but don't quite answer my questions:

http://www.classiczcars.com/forums/showthread.php?t=15897&highlight=wires+fuel+pump

http://www.classiczcars.com/forums/showthread.php?t=17496&highlight=power+electric+fuel+pump

http://www.classiczcars.com/forums/showthread.php?t=13725&page=2&pp=15&highlight=fuel+pump+cutoff

I've read the discussion about connecting the fuel pump to an oil pressure switch and I'm intrigued by this idea, but as mentioned in the following thread, the Datsun engineers might have already had an idea for cutting power to the pump.

http://www.classiczcars.com/forums/showthread.php?t=983&highlight=fuel+pump+wiring

Does anyone know if any cutoff switches or relays were incorporated into the stock design for the electric fuel pump?

Thanks to everyone for their contributions to this site.

-Ty

Hey Guys,

I'm a little behind the times but am just now getting around to installing an electric fuel pump on my 73 240. I agree with everyone's assessment about the safety concerns of shutting down the fuel pump in the event of a wreck. If I am correctly interpreting the 73 wiring diagram from the Datsun Shop manual, it appears as though Datsun figured out a solution to this without the need to add any switches (oil pressure or inertia).

OK, so here's how I see the wiring in the book and perhaps someone can tell me if this is correct. I haven't taken out a volt meter and verified this yet.

In any event it appears that the power for the fuel pump comes from the alternator and thus if the alternator is not turning there won't be any voltage to supply the pump.

From the schematic it looks like the green wire from the pump goes through a 20A in line fuse located under the radio area. A black/white wire exits the fuse and makes a T. One run goes to another 20A fuse in the fuse box and then on to the voltage regulator (I'm assuming this is the un-regulated voltage input to the regulator). The 2nd split off the T goes to position 2 on the ignition switch. Just for the record the black/white wire also feeds several other places as well....Nevertheless, it appears that position 2 on the ignition switch gets voltage from position 3 when in the RUN or START position.

Now....there is a White/red wire going from position 3 back to one of the contacts on the alternator....(as well as other places).

So is this what I think it is. Does the alternator indeed feed unregulated voltage to various places in the car via the ignition switch....ie. places like the fuel pump....

Please help as I could certainly use some better eyes looking at this as well..

[Ksteve]

MAX,

I had this suspicion as well after looking at the 73 wiring diagram, but after wiring up my pump I found it wasn't so. The pump has continuous power when the ignition is in the run or start positions. I will be installing the oil presure cut off.

The nice thing about the factory wiring is all you need to do is bridge the two spade terminals in the T shaped connector behind the radio with an inline fuse (3 amp or otherwise specified on pump) and then you will have power at the pump. The oil presure cut off can be incorporated into this same break in the wiring as long as the inline fuse is included in the circuit.

Make sure you get a pump with 5psi presure or less. I made the mistake of getting one rated for 4-7psi thinking a couple extra pounds wouldnt hurt, but the extra presure overwhelmed the float bowl needle valves and they were flooding the carbs (round top SUs).

Hope this helps.

Steve

[MAX]

Hey Steve,

Thanks for your reply..

Is that your 240ZG in your Avatar...Very awesome

Hmmmmmm.

Well, I think it is time I get out my voltmeter and do some testing. Going from the wiring diagram I thought I had found the correct in line fuse ( 20A ) which is pretty much under the radio and lying in front of the fuse box....But perhaps this isn't the correct one. ...I also find 2 other in line fuses back in the wiring. And from the diagram it appears that one goes to the accessories relay and the other to the rear window defroster...

I have owned this car as new and can remember taking it back to the dealer in the early 70s and they installed the kit to correct the fuel line vapor lock problem. The kit included an electric fuel pump which had since crapped out and I removed it years ago and am just now completing a restoration and installing a new one. But it seems from what you and others are saying that there is another T in the wiring and that no fuse was installed for the fuel pump in the original place....I'll have to dig further into the wiring behind the radio.

By the way I just ordered a Mallory 4070LP electric fuel pump which is supposed to be internally limited to 4PSI. Others have commented that is the quietest one out there.

Randy

[Ksteve]

Randy,

I wish it was my car, I just liked the styling. I beleive I found the picture in the gallery here somewhere.

My 73 never had the electric pump installed so the T connector behind the radio was left open and taped back to the wiring harness. It seems like it even had a white tag on the wiring labeling it as "fuel".

If your car had a dealer installed pump that has failed, I would check the wiring back at the tank to see if you get 12v with the ignition in the run position. If not maybe it is just a blown fuse?

Good luck,

Steve

[MAX]

thanks Steve,

I'll have to trace out the wires coming from the fuel pump and see where they go up under the dash.....

And good luck to you.

Randy