best location for electric fuel pump

[JeffP]

I have a 1969 Elan Plus2 what is the best location for an electric fuel pump?

[alaric]

Hi. I can post pics of the install on my +2 if that helps. It's under the rear seat on the left hand side, tucked up against the corner of the bodywork. So it's pushing the fuel up to the front of the car. It was put in by the previous owner, and is covered by a neat ally box. The pump is a little facet effort with a regulator at its output.

Here's some pics:

Sean.

[512BB]

'I have a 1969 Elan Plus2 what is the best location for an electric fuel pump?'

The dustbin.

[Quart Meg Miles]

'I have a 1969 Elan Plus2 what is the best location for an electric fuel pump?'

The dustbin.

That's harsh from someone who keeps his Sprint in one!

[gherlt]

I have a 1969 Elan Plus2 what is the best location for an electric fuel pump?

For a start you should indicate if the pump is a push or a pull pump.

[alan.barker]

If you fit electric pump fit a "Huco" pump, no regulator needed. Also fit it inside the boot in the dry and easy access. Supplier webcom or eurocarb.
I'm running "Huco" on my TVR 3000M and 3000S. You have 2 choices of pressure.
Both are fitted in boot. One model in 3000S and the different model in 3000M. Both run 100% even though paperwork says one should be near Tank and other in Engine compartment.
On a +2 Elan with the Fuel Tank in it's high position the Pump is well primed.
Imho don't fit under the car in all the dirt and wet. Like they did on Austin Cooper S always corrosion problems
Alan

[HCA]

I have a 1969 Elan Plus2 what is the best location for an electric fuel pump?

Maybe this question is not applicable, but just in case: Are you planning a new fuel tank as well? If so, then do consider installing a pump in the tank...

[alaric]

Hi.

What's the benefit of installing in the tank? Sounds to me like a special tank is needed, and its hard to access in the event of problems. It would be in a fuel saturated environment so no risk of igniting the fuel. So that's OK i.e. safe.

Re installing under the car vs in the boot I see that in the boot would be away from the elements, but it will also be in a sealed volume. The repercussions of a leak might be significant, as you start with an unsaturated volume of air, whose fuel air ratio may build up as more fuel evaporates. I'm nervous enough with the right angle hose from filler to tank and vent pipes in the +2, without adding pressurised fuel lines that may end up fighting with tools for space; we have to consider the idiot actions of others in a road car I'm afraid. I am nervous of the idea of installing the pump in the boot, as it only needs to leak once.

On my own car I would like to protect the pump more than it is at the moment, but I am happy that it's outside, well ventilated.

My vote: under the car, protected, but we'll ventilated.

Regards.

Sean.

[pptom]

My Huco is in the engine bay on the inner wing. All I had to do was extend the fuel line about a foot and run a power feed.
Don't see the advantage in overcomplicating things, it's out of the cabin, easy access and easy to run a cable there.

[StressCraxx]

The in-tank electric fuel pumps are installed from the top. They include a "stilling well" to allow the float to provide a relatively stable indication of fuel level. They usually require a larger opening in the top of the tank and a threaded insert ring for mounting. They are much safer than an external mounted electric pump because of the reduced number of fuel fitting connections and therefore fewer leak paths. The fuel in the tank provides cooling for the running pump. The issue is finding the right combination of diameter and length so the pump fits and the float gives an accurate indication of fuel level.

[Andy8421]

Jeff,

This came up some time back. If you plan on using the car as a weekend cruiser, then putting the pump somewhere dry and accessible seems a good idea. If you plan on some spirited driving, then other issues may come into play.

Under heavy braking or acceleration, there is a column of fuel in the pipe needs to be accelerated or decelerated. For the sake of discussion, lets say you have mounted your pump next to the tank, the fuel pipe is 4 1/2 feet long to the front carb, and the Elan can generate braking and acceleration forces of 1G (it can't). This would equate to a 2psi change in pressure at the carb end of the pipe at 1G acceleration. Lets also say that you have set your fuel pressure for 3psi to suit your Webers. As you brake hard before a bend, potentially the fuel pressure at the carbs would rise to 5psi flooding the carbs, and as you accelerate out of the bend the fuel pressure at the carbs would drop to 1psi leading to fuel starvation. Fanciful stuff, but the effect is real. There was a post from a gentleman sometime back who had a fuel pressure sensor at the carbs and could easily detect these changes in pressure under braking and acceleration.

How do you get around it? Mount the pump next to the carbs, or have a higher pressure pump at the tank and a fuel pressure regulator next to the carbs.

Is the effect a big deal for a road car? probably not.

Edit: FWIW, and nearly off topic for those who care, the Saturn V of Apollo 6 nearly failed because of this effect. Small changes in acceleration of the rocket caused small changes in the fuel pressure at the engines which caused small changes in the acceleration of the rocket ..... and so on. The effect built up and up until the resultant oscillations nearly destroyed the rocket. The effect is appropriately enough called 'pogo'. It is still an issue for rocket designers. https://en.wikipedia.org/wiki/Pogo_oscillation

[alan.barker]

I didn't know you could compress fluid/petrol.
This is new to me, please educate me.
Alan

[Andy8421]

I didn't know you could compress fluid/petrol.
This is new to me, please educate me.
Alan

Alan,

You are quite correct, for the sake of simple modelling, liquids can be considered incompressible. That isn't the effect at play here.

At 1G acceleration, from the fuel pipe's perspective, it is the same as if the car was stationary, but pointing straight up. The fuel in the pipe would then have a higher pressure at the bottom of the pipe than it would at the top because of the 'weight' of the fuel. This is exactly the same effect if the car was being accelerated down the road, and is why you get pushed back into your seat under acceleration.

Rgds,

[alan.barker]

Andy,
accelerating at what speed with Radar Cameras everywhere
I couldn't tell you when i last time i tried to match the official acceration of an Elan to be honest. What is it for a Sprint on paper 7 secs+ 0-60 mph. on the road 0-60 mph is measured in minutes .
If you race in competition like Rohan you fit a completly different Fuel pump set up.
For normal legal driving on the road this to me is OTT.
Sorry but that's how i see to be honest Andy no hard feelings.
Alan

[2cams70]

Yes best not to overthink things. Back in the day there were millions of different cars running around with AC glass bowl fuel pumps and with complete reliability.