Fuel pump relocation and wiring Options

[captjm]

I need some help with wiring a 914 fuel pump being relocated to the front fuel tank location exactly like the 75/76 914's. The car is a 1971 914/4 being set up for a carbureted 2.4 six cylinder. My question is about where to pick up the power to run the pump correctly.
I would like it to have any relay protections like the original if that is the way it is suppose to be. I think the positive power is to come from the engine compartment relay board from the forward connector pin 13? I plan on running the positive wire from pin 13 under the driver side rocker panel forward to to the fuel tank bay and picking up the ground from the closest grounding point nearest to the tank bay. Any comments or advice would be helpful. Thank you

[dtmehall]

it was 40 years ago when i did this. i believe your estimation of the relay plate is what i did. but i did run the wire up the tunnel.

[JeffBowlsby]

It’s a 12 ga wire.

[dtmehall]

it was 12 gauge for the fuel injection pump. i would suspect that whatever pump you are using for carbs, will draw far fewer amp. hence a lower gauge wire requirement

[North Coast Jim]

I ran the wire thru the tunnel wired as above. Bought a 2 conductor, red/blk paired wire from West Marine. It had a jacket around the pair, white in color, similar to Romex. Worked great. Oh and the stranded conductor count was IFRC was 19.

[North Coast Jim]

I ran a two conductor wire thru the tunnel wired as above. It was a red/blk pair jacketed like romex, white in color. Bought it at West Marine. Worked great. Oh, if IIRC the conductor count was 19 strands.

[davep]

it was 12 gauge for the fuel injection pump. i would suspect that whatever pump you are using for carbs, will draw far fewer amp. hence a lower gauge wire requirement

But the wire length is about double. The original wire seemed undersized to me when I looked at 20 harnesses with most pump wires cooked. I would not go less than the 12AWG that Jeff recommends.

[dtmehall]

below is a website to calculate wire size based on estimated current. 8 amps comes out to 14awg in a raceway

http://wiresizecalculator.net/calculators/wiresize.htm

[SirAndy]

If you still have the original wiring the fuel pump connector should be somewhere under the engine shelf on the passenger side.

Why no just extend your wiring from there to the front?
You don't even have to cut the harness, you can literally just add a spade connector to your new wires and plug them into the stock connector.

http://www.914world.com/specs/SirAndyCarbFuelPumpRelay.php

That way you retain the full factory setup with fuse and relay and as a bonus not a single wire needs to be cut.
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[dtmehall]

That's a good idea. It wasn't possible in my case, as my car is a 73. The original factory fuel pump was below the engine compartment, underneath the battery.

[worn]

That's a good idea. It wasn't possible in my case, as my car is a 73. The original factory fuel pump was below the engine compartment, underneath the battery.

Which is the situation tha Sir Andy described a solution for.

[worn]

That's a good idea. It wasn't possible in my case, as my car is a 73. The original factory fuel pump was below the engine compartment, underneath the battery.

Which is the situation tha Sir Andy described a solution for.

You use a spade connection to the OE connector and run your wires forward.

[bkrantz]

If you still have the original wiring the fuel pump connector should be somewhere under the engine shelf on the passenger side.

Why no just extend your wiring from there to the front?
You don't even have to cut the harness, you can literally just add a spade connector to your new wires and plug them into the stock connector.

http://www.914world.com/specs/SirAndyCarbFuelPumpRelay.php

That way you retain the full factory setup with fuse and relay and as a bonus not a single wire needs to be cut.
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Yup! I did this on my 73, and got fancy when I rebuilt the wiring harness by extending the fuel pump power lead as part of the bundle, all the way to the front. But you can certainly do in the tunnel (just be careful to protect that wire where it might be loose and/or rub and short out someday.

[ClayPerrine]

If you pull the fuel pump wire back and reroute it forward with the factory harness, it will reach to the front of the seats. Just extend it from there. I suggest following the factory harness all the way to the front, and putting in a ground wire that goes from he ground point over the fuse box and follows the harness to the fuel pump location. That way it looks like it was done from the factory.

[JeffBowlsby]

Prob with that Clay is that the 70-74 FP wire is only 18 GA. The 75-76 cars FP wire is 12 GA. The difference is the greater ampacity needed for the longer run.

[Literati914]

If you pull the fuel pump wire back and reroute it forward with the factory harness, it will reach to the front of the seats. Just extend it from there. I suggest following the factory harness all the way to the front, and putting in a ground wire that goes from he ground point over the fuse box and follows the harness to the fuel pump location. That way it looks like it was done from the factory.

Prob with that Clay is that the 70-74 FP wire is only 18 GA. The 75-76 cars FP wire is 12 GA. The difference is the greater ampacity needed for the longer run.

I'm guessing lots have done as Clay is suggesting, myself included. Is there solid evidence that this set up will definitely be too much amp draw for the stock (size) wires when ran all the way to the front? I added a cut-off switch between the two and rather than go back and try to replace the entire wire length with bigger, I'm thinking just adding an additional fuse just before the cut-off switch and see what happens ... unless there is overwhelming evidence to say it's a given failure point waiting to happen.

Anyone with any time on a FP relocation set up using stock wires?

[dtmehall]

This thread started when captjm said that he wanted to relocate the fuel pump for a carbureted six cylinder. AA lists a Pierburg Electric Fuel Pump for this application. It draws <= 2.0 amps. An 18 or 14 gauge wire should have no trouble carrying that much current from the rear to the front of the car.

[ClayPerrine]

Prob with that Clay is that the 70-74 FP wire is only 18 GA. The 75-76 cars FP wire is 12 GA. The difference is the greater ampacity needed for the longer run.

Jeff,
I realize that is a drawback to this idea. But we ran Betty's 914 like that for years with no issues. Maybe I was just lucky. I have the harness out of her car right now, so I am replacing the fuel pump wire with 12ga with the proper color and tracer.

Clay

[JeffBowlsby]

That's excellent Clay. Better safe than sorry.

I am not an EE, but I pointed out the factory harness 12GA wire design for those wanting to relocate the pump, because Porsche originally engineered it that way so it is a good precedent. I imagine that it was a conservative approach considering all factors that could be encountered at the time - electrical draw of the pumps available then, plus effects of greater resistance over time, heat degradation, etc., plus a safety factor.

If todays pumps create less load then great, but anyone contemplating that relocation should be aware of the wire size and be prepared to replace that pump when necessary with a similarly efficient pump to avoid overheating the wire and inform the next owner also.

The fuse for the FP circuit is the big 25A fuse on the relay board. Adding a secondary fuse inline...not sure how that will behave.

[Literati914]

..
The fuse for the FP circuit is the big 25A fuse on the relay board. Adding a secondary fuse inline...not sure how that will behave.

I feel like that big fuse is too much to catch an over heating FP wire by itself .. potentially leading to melted FP wires that are now running thru the tunnel, in the event of a short. An extra 8A in-line fuse just seems like a smart move imho. I've not heard of an extra fuse causing problems. Of course I'm no EE, either.