240z Electric Fuel Pump Installation

[w3wilkes]

I would want it on the "engine running" position rather than the accessories position.

[jalexquijano]

Why?

[w3wilkes]

If I put it on the accessory position and I use that position to do things like listen to the radio with the car not running I wouldn't want the fuel pump running while the car is not. If the fuel pump is in the engine running position I can turn the key to that position and let the pump charge the fuel line for a few seconds and then start it.

[jalexquijano]

Is this how all the owners are wiring the electric fuel pump?

[Mike W]

They way that @w3wilkes has described the hook up is the exact way my pump is wired.  It makes no sense to wire it to accessories as the pump would run when the engine was off and you would not want this situation.  In addition you would not want it wired to just the start position as the pump would turn off after the car was started.  You need the pump wired to the "on" position on the switch.  This way you can go to "on" before starting the car so that the pump will run and prime the carbs (a necessary requirement with triple Webers as the bowls tend to evaporate when the car is not driven frequently).  Once the car is started and the key is in the run position, the pump will continue to run while the engine runs.

However, you should also install an inertia switch in the circuit as well so that in the event of an accident the inertia switch will trip and shut off power to the pump.  You would not want the pump to continue to run after an accident especially if the engine shuts down as a result of the collision.

Mike.

[gundee]

7 hours ago, Mike W said:

They way that @w3wilkes has described the hook up is the exact way my pump is wired.  It makes no sense to wire it to accessories as the pump would run when the engine was off and you would not want this situation.  In addition you would not want it wired to just the start position as the pump would turn off after the car was started.  You need the pump wired to the "on" position on the switch.  This way you can go to "on" before starting the car so that the pump will run and prime the carbs (a necessary requirement with triple Webers as the bowls tend to evaporate when the car is not driven frequently).  Once the car is started and the key is in the run position, the pump will continue to run while the engine runs.

However, you should also install an inertia switch in the circuit as well so that in the event of an accident the inertia switch will trip and shut off power to the pump.  You would not want the pump to continue to run after an accident especially if the engine shuts down as a result of the collision.

Mike.

 Mine is wired the way Mike describes it. That way I can prime the Mikuni's before starting engine. I picked up an inertia cut out switch that I have to install yet.

[thumper300zx]

Does anyone know how they wired these with a fuel pump in the factory? Empty harness, what did it hook up to? 

Then, in theory, if you connect the black wire to a manual switch to the green wire, that would power the green wire with ignition switched on? But in OPs setup, he used black wire to oil pressure switch to relay then to green wire?

When I got my Z, I flew out to get it and had to drive back. Half way home, fuel and fire both went out on me. Stuck overnight, the next morning in a small Idaho town, they put in one of these electric pumps powered by running a wire from fuse box to pump, slapped it right in line before the mechanical (still connected) and put in new points (dist). It ran better than when I picked up the car, but just a patch job to get me home. I've had issues with fuel ever since I got back and removed it and replaced the mechanical, so I'm going to install a new electric pump (the other one sat and won't spin).

Edited August 3, 2017 by thumper300zx

[JSM]

11 hours ago, thumper300zx said:

Does anyone know how they wired these with a fuel pump in the factory? Empty harness, what did it hook up to? 

70-72 they did not have pumps.  73 and 74 had the pumps.  Not sure if the 70's had the wires, but 71 and 72 do as part of the harness. Maybe the JDM had FP in those years like the fog lights and it was easier to just include them and not use instead of having separate harnesses for each market.

My 71 was wired just like the original post.  Black and green wire to the tank and just hanging unplugged behind the heater console.

[w3wilkes]

Here's what I know. Bought a '73 brand new in July '73. It had mechanical pump only, no electric pump. Later that summer I took it in complaining of vapor locking. The dealer wrapped the fuel rails around the valve cover with a reflective metalized wrap. Took it back later, still vapor locking, but not as bad. The dealer installed an electric pump back at the tank. To be honest, the vapor locking was never completely cured in heavy summer traffic for the 20+ years I drove the car.

I now have a early '71, manufactured December '70, I'm the 2nd owner. I believe it's a series 1 car based on things like body vents on hatch, position of ash tray, rear window defroster line direction, etc.. It has the green / black wires for a fuel pump hanging down back at the tank. Haven't hunted yet but I presume the other end to be in front of the fuse box in the front left of the console area. I plan on converting to electric fuel pump in the next month, so I'll be digging into the console to find the wires to jumper with an inertia switch to activate the wires back at the tank. Under the fuel gauge sending unit on the tank are a couple of pre-drilled tabs that I'm guessing are for mounting an electric fuel pump. Based on my car I'm betting that the Z's were plumbed from the git-go for electric fuel pumps.

Side note: Found a blue taped wire w/bullet connector coming out of the harness right under the battery that is hot when the ignition switch is in the engine running position. How did Datsun know I needed that right there for my electric fan controller? 

Edited August 4, 2017 by w3wilkes

[thumper300zx]

2 hours ago, w3wilkes said:

Here's what I know. Bought a '73 brand new in July '73. It had mechanical pump only, no electric pump. Later that summer I took it in complaining of vapor locking. The dealer wrapped the fuel rails around the valve cover with a reflective metalized wrap. Took it back later, still vapor locking, but not as bad. The dealer installed an electric pump back at the tank. To be honest, the vapor locking was never completely cured in heavy summer traffic for the 20+ years I drove the car.

I now have a early '71, manufactured December '70, I'm the 2nd owner. I believe it's a series 1 car based on things like body vents on hatch, position of ash tray, rear window defroster line direction, etc.. It has the green / black wires for a fuel pump hanging down back at the tank. Haven't hunted yet but I presume the other end to in front of the fuse box in the front left of the console area. I plan on converting to electric fuel pump in the next month, so I'll be digging into the console to find the wires to jumper with an inertia switch to activate the wires back at the tank. Under the fuel gauge sending unit on the tank are a couple of pre-drilled tabs that I'm guessing are for mounting an electric fuel pump. Based on my car I'm betting that the Z's were plumbed from the git-go for electric fuel pumps.

Side note: Found a blue taped wire w/bullet connector coming out of the harness right under the battery that is hot when the ignition switch is in the engine running position. How did Datsun know I needed that right there for my electric fan controller? 

So you plan on going from live (on ignition) black into inertia switch then to green wire? What is the black wire even for at the back? These little aftermarket pumps can be grounded to the frame, so if black is coming from powered source to then go to green, why a black wire at back?

[thumper300zx]

Photos of harnesses, exactly where expected. So, here's my question... The green from console to tank in continuous wire. Black shouldn't be, right? But also, if not, why is the black there? To ground somewhere?

[thumper300zx]

Ok, tested. Black gets voltage with ignition in ON position. Green from console is direct (zero resistance) to tank green (last photo).

Seems like inertia switch between black and green at harness would work great.

Still not sure what black is at back, though.