3.6 conversion fuel pump mounting location help

[Duc Hunter]

As I work through the challenges of my '75 3.6 converted car, cleaning up what PO's have done to get it running and on the street, I have come to the fuel pump. It was mounted down loon the drivers side of the rear suspension area. Not an ideal location to me, especially as the rear swayer cannot be run with it in its current location. Regardless the existing pump needs to be replaced because someone more vied the check valve and damaged the pump internals over tightening the banjo bolt they installed.

Since this is a 75 tub, there is no provision for one up near the front axle, like my 89 has. So..I thought I would ask here (after hunting picture of others work, to no avail).....where have others mounted their fuel pumps in conversation cars?

I would think up high in the engine bay would be a good spot, or up front in the trunk maybe? Keep in mind the engine is not coming out (at least so far it is not, and I hope it does not have to for a few years).

[James Brown]

high pressure pumps should be mounted as close as you can to the fuel source. So i would think the original location would be best. Mounts can be easily fabricated. hope there is a return fuel line also in the 75 fuel tank (cis fuel injection should have it)

[Duc Hunter]

Well the car run...albeit on 4 cyclinders right now (#2 & #6 not firing at the moment). This would lead me to believe there is a return line plummed. I will look though. So, since I cannot get it under the body as the 964 had it...in the trunk is the best spot?

Originally Posted by James Brown

high pressure pumps should be mounted as close as you can to the fuel source. So i would think the original location would be best. Mounts can be easily fabricated. hope there is a return fuel line also in the 75 fuel tank (cis fuel injection should have it)

[James Brown]

yup the 3.6, if your using the stock intake, needs a return line. high pressure pump supplies more fuel than the engine needs at full throttle, so it bypasses the unused fuel back to the fuel tank. this is a must have

[umgang]

i have a 1975 911S w/ 3.6 conversion.
On my car the original fuel pump was craddled near the driver rear wheel in a cradle there.
This caused some issues with vapor lock when the pump got hot from nearby exhaust.
It now safely resides behind the steering rack guard plate snugged up near the fuel tank.

[Duc Hunter]

Mine was put in the same spot by a PO. I will move it to the Frunk (and validate the return line). Thank you all for the help!!!

Originally Posted by umgang

i have a 1975 911S w/ 3.6 conversion.
On my car the original fuel pump was craddled near the driver rear wheel in a cradle there.
This caused some issues with vapor lock when the pump got hot from nearby exhaust.
It now safely resides behind the steering rack guard plate snugged up near the fuel tank.

[Duc Hunter]

Originally Posted by James Brown

yup the 3.6, if your using the stock intake, needs a return line. high pressure pump supplies more fuel than the engine needs at full throttle, so it bypasses the unused fuel back to the fuel tank. this is a must have

I did confirm the return line was plumbed back, which was good news.

Originally Posted by umgang

i have a 1975 911S w/ 3.6 conversion.
On my car the original fuel pump was craddled near the driver rear wheel in a cradle there.
This caused some issues with vapor lock when the pump got hot from nearby exhaust.
It now safely resides behind the steering rack guard plate snugged up near the fuel tank.

Do you a have any pictures of this, and the bracket? I will need to come up with something.

[umgang]

i can take a picture of it but it might be Monday as we are having real winter cold here now!

[safe]

In my conversion I put the pump in the engine bay up over/behind the left wheel arch, partly because someone put it there in a previous engine conversion.
Maybe the right side would be better because there is more space there and the engine is feed from that side.

[BoxsterGT]

Here is a late pump located up front in a early 911.......



Locating it near the tank as the factory is best, as these hi-pressure pumps are more efficient pushers than they are suckers.

I stock a large selection of Metric Fittings and adapters for most Porsche models, and Metric Hose for both Fuel (E-85 rated) and Oil systems. I make custom Fuel & Oil Lines and Hoses that are considered by most to be factory level or higher.

Please inquire by email only.

Len at Autosportengineering dot com

[Duc Hunter]

Len...great picture!! Just an update....my Indy wants to move it into the engine bay because he says the 3.6 pump is a high pressure pump, and he woudl want to run a new pressure line through the tunnel from the front of the car to the back. He would not trust the 41 yr old line that was run for a low pressure system. To do so he says the motor and tranny really needs to be out. So...I may just have him mount it in the engine bay for now, and I can move it later.

[BoxsterGT]

I would say that his recommendation is a mistake. The factory went to a front pump for a reason, and the Polyamide tunnel lines really are bulletproof. What you see in the photo above is a 3.6 pump, and it is mounted "up-front".

Again, a hi-pressure pump is much better as a "pusher" than as a "sucker". A pump in the engine bay is exposed to much more heat than one up front. With heat comes vapor-lock and fuel delivery issues. There are no advantages whatsoever to run a "hi-pressure" pump in the engine compartment.

The factory parts have been proven over time. It is a very simple system and a lot less costly than anything "custom". You do not need to drop the motor or trans. Simply support them and remove the tranny mount. With Polyamide tube, it is flexible and will pull right through with minimal effort. Many, many fellow Pelicans have done this at home in their workshop or out on their driveway.

CIS normally runs at higher pressures than EFI, so the factory system is more than adequate.

The best for "hi-pressure" and cool running is "Up Front" where it has a 12mm supply, a short run directly into the pump, and has less resistance than a long supply run back to the engine bay. Most importantly, the fuel stays as cool as possible.

An added benefit is if you ever wanted to go to a turbo for more performance, you are already E-85 capable.

Just my 2 cents.

Len

[arrivederci]

Agree with Len here. I moved mine up front. Used mostly Porsche factory parts from a carrera (ordered through Pelican with some lines from Len).

[rbogh901]

Dang, that's a sweet underside. And nice pump install.

Being a plumbing wizard, do you feel that this hose clamp should be better served by replacement with the fuel line type that is less likely to chafe through?



ps. Another vote for the front mount. Seems to be the consensus.

[BoxsterGT]

Looked back to find the above question.........

The inlet or suction side of the pump requires nothing more than a good quality Norma type hose clamp.

One that has a smooth inner surface that does not cut into the hose.

No movement to speak of so no reason for chafeing (sp?) here.

Len