Fuel Pump Location-Rear Firewall, Suggestion Other then Up Frunk Options

[914_teener]

I never took pictures of my 1.7 with stock D-jet and when browsing for new projects I found a car almost exactly like mine with the fuel pump relocated exactly where I relocated mine. Just posting like this since I see threads about it and always the first thing that comes up is relocating it up front, running the electrical, which circuit to use, how well does it fit inear the steerig rack...ect. ect.

Its an excellent location and required nothing more than a couple of rivnuts and the stock isolators.


I DIDN't use and don't recomend the fuel line clamps or hose but the location is the same that I used years ago.

Easy to check on the filter or service without taking off the rack pan cover or unraveling the fuel line and reinstalling without kinking it.

ONLY my opinion....like the other thing...everybody's got one.

[ClayPerrine]

There are only two problems with the fuel pump in that location:

1. Fuel pumps are better at pushing than pulling. Mounting it closer to the tank makes it work better.

2. The fuel pump there is known to vapor lock due to the proximity to the engine heat.

That's the reason that Porsche moved the pump up front in 75.


Clay

[914_teener]

There are only two problems with the fuel pump in that location:

1. Fuel pumps are better at pushing than pulling. Mounting it closer to the tank makes it work better.

2. The fuel pump there is known to vapor lock due to the proximity to the engine heat.

That's the reason that Porsche moved the pump up front in 75.


Clay

Clay....come on!

1. The stock pump is a diaphragm pump AND it's loaded from the tank by gravity at that location.


2. It's no where near the HE's in fact, in that location it's getting a negative airflow and while it's next to the air deflector....it's getting airflow.

Had my stock pump in this location for 10 years in Palm Springs idling in traffic in 120 ambient air temps....no vapor lock.

Just trying to help out folks who may not want to do the other work required to put it up front.

Like I said...others may disagree.

[wonkipop]

There are only two problems with the fuel pump in that location:

1. Fuel pumps are better at pushing than pulling. Mounting it closer to the tank makes it work better.

2. The fuel pump there is known to vapor lock due to the proximity to the engine heat.

That's the reason that Porsche moved the pump up front in 75.


Clay

Clay....come on!

1. The stock pump is a diaphragm pump AND it's loaded from the tank by gravity at that location.


2. It's no where near the HE's in fact, in that location it's getting a negative airflow and while it's next to the air deflector....it's getting airflow.

Had my stock pump in this location for 10 years in Palm Springs idling in traffic in 120 ambient air temps....no vapor lock.

Just trying to help out folks who may not want to do the other work required to put it up front.

Like I said...others may disagree.

not a diaphram pump.
its a roller cell pump.
it actually works better than a diaphram pump off gravity flow.
but the diaphram pumps were ok, strictly on the carb vw cars. low pressure.

not sure about the later frunk ones.
but think they were also still roller cell pumps at that time.

the problem with the original location is two fold.
1. after shut down the magnesium fan shroud is where all the heat from the engine block flows to. its a conductive flow and the heat wants to travel to the magnesium.
and from there it radiates.
2. the dump valve on the heat exchanger heater tube blows hot air out in the general vincinity of the fuel pump and it basically can form a bubble of hot air right in there while you are sitting still at idle. less so on the move of course.

there was a factory fix for the heat exchanger dump valve and jeff bolwsby has it on his website. basically they took the dust shield on the valve off and clamped a short section of heater hose heading backwards.

there is no cure for the magnesium fan shroud radiation physics.


having said all that i keep my fuel pump in stock location under engine bay.
i don't like the idea of pressurized fuel lines running through the cabin.
just my personal preference.

(IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/biggrin.gif)

its not so much the pump that has the problem.
its the section of fuel line that feeds into the pump and travels across the back fire wall.
that fuel boils and then the pump just cavitates.
reflective insulation on the fuel lines is one answer that works.
or at least it has for me.
when i changed to metal lines i found the problem got way worse that when it had the original plastic lines. the insulation fixed that.
my experiment convinced me the pump was not really the problem.

[ClayPerrine]

not a diaphram pump.
its a roller cell pump.
it actually works better than a diaphram pump off gravity flow.
but the diaphram pumps were ok, strictly on the carb vw cars. low pressure.

not sure about the later frunk ones.
but think they were also still roller cell pumps at that time.

the problem with the original location is two fold.
1. after shut down the magnesium fan shroud is where all the heat from the engine block flows to. its a conductive flow and the heat wants to travel to the magnesium.
and from there it radiates.
2. the dump valve on the heat exchanger heater tube blows hot air out in the general vincinity of the fuel pump and it basically can form a bubble of hot air right in there while you are sitting still at idle. less so on the move of course.

there was a factory fix for the heat exchanger dump valve and jeff bolwsby has it on his website. basically they took the dust shield on the valve off and clamped a short section of heater hose heading backwards.

there is no cure for the magnesium fan shroud radiation physics.


having said all that i keep my fuel pump in stock location under engine bay.
i don't like the idea of pressurized fuel lines running through the cabin.
just my personal preference.

(IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/biggrin.gif)

its not so much the pump that has the problem.
its the section of fuel line that feeds into the pump and travels across the back fire wall.
that fuel boils and then the pump just cavitates.
reflective insulation on the fuel lines is one answer that works.
or at least it has for me.
when i changed to metal lines i found the problem got way worse that when it had the original plastic lines. the insulation fixed that.
my experiment convinced me the pump was not really the problem.

(IMG:style_emoticons/default/agree.gif)


The pump location was not optimal. Moving it to the side away from the heater box outlet helps. Moving it up front like a 75-76 is a better solution.

That being said, the pump in our 70 six is a factory pump in the original location. We have not have vapor lock with it (knock on wood). But with Betty's car, she had multiple instances of vapor lock before we moved the pump. We moved the pump up front in 1986, and have not had any vapor lock since.

Maybe the modern gas doesn't boil to vapor as easy as it did in the past???