Electric Fuel Pump - Parallel versus Series

[Tjoek]

Hi Guys,

My electric fuel pump is installed in series with the vacuum pump. The electric pump is close to the fuel pickup, upstream of the filter. The vacuum pump is downstream of the fuel filter.

Can anyone comment / advice on series versus parallel installation of the pumps?

This question relates to my engine out earlier today.

Cheers
Tjoek

[Duck Rogers]

Parallel is the way to go.

Morph has some good drawings and info on the set-up. No doubt he'll post for you :D

[DarkHelmet]

We had this discussion a while back. In series was the conclusion - with the electric before the fuel filter and mech pump.

Parallel adds more points of failure.

Just to clarify - series = tank to electric pump to fuel filter to mech pump to engine
parrallel = tank to filter then to electric and mech both then to engine?

[Duck Rogers]

Parallel gives you a redundency system. A nice back-up. More pipework though, but peace of mind.

[Morph]

Duck,

in a parallel system, how do you stop the fuel being pumped via the pulse pump from returning via the electric pump and reducing the puel pressure?

[RudiGreyling]

I have mine in series, it was a simple drop in after the fuel filter but before the pulse pump.

Small grid can, (unlikely but have been known to) stop the electric pump, hence my decision to put after filter. The other side of the coin is that the facet pumps are better suited at pressure than sucking. So that creates a case for it before filter. But then again if you get a filter blockage, the grid 'may' have affected the pump already useless if it is before and you need it. Pro's and Con's both ways.

I can see benefit of parrallel but additional pipework, and maybe one way valves to help with pressure losses makes more complicated.

One thing most people agree on is to try and fit the pump low, to help autopriming (Remember pump is better at pressure, compared to sucking). Read the manual, I think the pump is good for autopriming up to 12 inches of height. Don't quote me on that, just check the manual.

In my case my pump is inline with top of tank, since it was easier to 'drop' it inline at that location. It works for me.

Use me just a reference point, but check your own merits, pro's, con's.

Regards
Rudi

[RudiGreyling]

Link to the old discussion of 3 pages long, good info there:
viewtopic.php?t=309&highlight=
Rudi

[Duck Rogers]

The Facet pump and the Mikuni both have built-in valves. Not necessary to install any sort of non-return valve in either system, as long as the line from the Facet connects to the carbs AFTER the Mikuni.

Rudi is right....the Facet is primarily a "push" type pump and not a "pull" type, though it will "pull", but not very high. In a pusher configuration, I have seen it pump over 2 metres in height, and quite strong at that too.

If you install any other type of pump other than the Facet, make sure it has a non-return valve or else you end up with check valves that need to be opened and closed......sort of defeats the objective, doesn't it?