Fuel Pump Location, and Other Nominal Questions

[dondarnell]

I am fitting a 2.4 with Webers to a 1966 912. I purchased a Pierburg fuel from a fellow on this site, and I intend on installing it in the front. I have reviewed many postings about such things, and some general research on fuel pumps in general, safety, etc. I have no doubt that the best place for the fuel pump is in the front of a 911. But, the question is: Where? I would prefer to mount it on the outside of the smugglers box right behind the tank, together with a pre-filter. But, I have seen some information that suggests not mounting a fuel pump in an enclosed space such as the trunk. Also, does the Pierburg pump have to be mounted lower than than the tank? It seems to me that the fuel pump is just another connection of fuel lines in the trunk, no different than those of the filler system or the line out of the tank. It just happens to be an electrical source, but there many other electrical sources in the trunk. I would also note that it was originally in the engine compartment, which is not so different from the trunk. So why should it really matter?

Second question. I will probably use a Holley pressure regulator. I would use the PMO one sold by our host, but it has return lines too, which will go unused in my Weber application. The Holley device is adjustable and is simpler and cheaper. I believe, based on my research, that the pressure regulator should go in the engine compartment just before the carbs, and then another filter after that. I don't know much about accumulators, and what they do, but one sounds unnecessary for a carb application. Am I on the right track?

[dondarnell]

Nothing huh? Nobody has an opinion whether its okay to put the fuel pump in the trunk?

[RWebb]

people usually mount it on the front suspension crossbar - that is where P AG put it

[Roger 911]

I converted my '72T to Webers many years ago. I used a Pierburg pump mounted inside the smugglers box, with a filter between the tank and the pump, and small in-line filetrs before each carb. I tried it originally with the Holley regulator. For some reason, I could not get the car to run right with the regulator. I removed it and ran it with no regulator, just a fuel pressure gauge. The Pierburg had a built in regulator that kept the pressure right at 3.5 psi. Car ran great for 8 years with this setup, mainly DE use.

Hope this helps.

Roger

[dondarnell]

RWebb - that's what I have been seeing - just wondered if there was a compelling reason to put it there.

Roger - That's interesting that you put it in the smuggler's box - I wonder why more people don't put it there?

[Tidybuoy]

Well I'm no expert on this issue, the fuel pump on my 914 is mounted "up front" in the factory location which is underneath the fuel tank. In a 914, the fuel thank is "in" the trunk so i don't think there is an issue with mounting within an enclosed space.

Vern

[RWebb]

safety is a compelling reason for me - in the late model stock location it goes under the car

if in the trunk it is in an enclosed area and near the battery (sparks)

[Tidybuoy]

Originally Posted by RWebb

safety is a compelling reason for me - in the late model stock location it goes under the car

if in the trunk it is in an enclosed area and near the battery (sparks)

Good point - the 914, which I quoted earlier, has the battery in the engine compartment.

[dondarnell]

The chance for spark has certainly occured to me. But the pump was originally in the back with the starter, which has a better chance of sending a spark then battery (but its not so enclosed). There's really electrical sources everywhere, right? Is there something about a battery in particular that is bothersome? Mine is an drycell (still working on the installation).

[wayner]

Check out post 684 on Jeremy's thread

Well here she is -

[Roger 911]

Originally Posted by dondarnell

RWebb - that's what I have been seeing - just wondered if there was a compelling reason to put it there.

Roger - That's interesting that you put it in the smuggler's box - I wonder why more people don't put it there?

I'm certainly not the first to put it there. It's a pretty straightforward installation, isolated from everything, etc. It's also not exposed to the elements.

Roger

[RWebb]

Originally Posted by dondarnell

... (but its not so enclosed). ...

I think that is the key - vapor

[Roger 911]

Originally Posted by RWebb

I think that is the key - vapor

Sorry, I'm not sure what you mean by "vapor". Are you referring to "vapor lock"? That certainly wasn't a problem with the pump up front.

Roger

[RWebb]

fuel vapor - think about stoichiometry

[mreid]

An electric pump is far more efficient at pushing fuel than pulling it, so as close to the tank as possible is best. Where you mount it vertically has more to do with the kind of impellor. A gerotor is better at lifting fuel and can be mounted above the fuel tank, while a rotary vane needs to be at or below the bottom of the tank for best efficiency. A 100 micron filter between tank and pump and a 10 micron between pump or regulator and carb ensures clean fuel. I prefer a return regulator as it stays accurate through temperature and pressure variations. A deadheaded regulator can fluctuate pressure which is critical when using Webers. An adjustable pressure fuel pump is actually a better option as most recirculate fuel internally similar to a return style regulator. As for location, I would not mount a fuel pump in an enclosed space. I know someone will chime in that they have had theirs in the trunk "for years" with no problem. Fine, I just won't do it. I might point out that in a 911 the front bulkhead is not a firewall...