Electric Fuel pump query

[Paul Johnson]

Hello All

I have come across a few posts which discuss the fitting of electric fuel pumps and appear to suggest that these can either be wired to operate via a switch and function to prime the system prior to start-up or, wired to run continually when the ignition is switched on.
Mine is the latter type and am I correct in assuming that they don't flood the carbs as they regulate themselves by sensing pressure? It just surprised me when I recently purchased the car ( Series 2 Fulvia) switched on the ignition and the fuel pump ran and didn't stop!

Also, How long should I let it run before cranking?
Many thanks
Paul

[lancialulu]

A few questions

Does the car still have its mechanical pump (all Fulvias were produced with mech pumps not electric)?

What make/model of electric  pump is fitted and is it plumbed directly to the carbs or through the mech pump?

Is there a regulator such as a filter king between the electric pump and the carbs?

Are you certain there isn’t a separate “priming” switch for the electric pump?

To answer your question on how long to wait, the pump changes tone when the carbs are full and you can start the engine then.

[peteracs]

Hi

One last and important question, If the pump is used as a mechanical replacement, is the pump wired to any ‘accident’ switch so it is disabled in the event of a shunt etc?

Cars with mechanical pumps will stop when the engine stops, electric ones may not and hence may continue to pump fuel even if the engine is stopped and the fuel line is damaged.

Peter

[nistri]

Mechanical fuel pumps (if original ones) rarely fail even after many dozen years of use. The electrc pump is best used for priming the carbs after a longish inactivity. On S2 Fulvias there is a fuel return line to the carb, making it difficult to flood the carbs IF the electric pump makes the correct pressure (max 0.5 bar) and IF the carb needle valves work OK. Thus, the fuel pressure regulator is useful on S1 cars but not so much on S2 cars.
It is not rare to find the wrong needle valves and aftermarket mechanical pumps of questionable efficiency. Andrea

[Paul Johnson]

Hi All,
Lancialulu, you ask really sensible questions, I just wish I had sensible answers! but hopefully the attached photos will help explain what my current set-up is.
Peteracs, I cannot find a switch and can only identify wiring for the fuel pump (and electronic ignition) picking up power from the coil.
Appreciate your thoughts.
Paul

[lancialulu]

Those cube "Facet" pumps are generally only used to prime carbs on Fulvias. They do provide enough for general driving but not continuous enthusiastic driving. I would say it is poor/lazy practice to pick up the power from the coil (clearly activated when the ignition is on). I would re wire to a priming switch taking power from the fused supply from the ignition switch with its own 4 amp fuse, and plumb it in series with the mechanical pump (maybe you need to buy a new one) which is located under the alternator (look under the airbox....).

[Jaydub]

Tim, whilst I recognise your undoubted knowledge of all things Lancia, I don`t think it good practice to run an electric pump in series with a mechanical pump. The electric pump has to overcome the valves in the mechanical pump and vice versa, putting extra pressure ( forgive the pun) on both units, and should one of them fail/valves stick, that set up puts both out of action.  I know people have run them that way but that`s my thoughts on the matter.

Jaydub

[andyps]

If I can jump in on this topic, my car has an electric pump fitted which seems to run continuously, although I haven't had the engine running myself but did hear it running when I bought the car. I've replaced the mechanical  pump on mine as I'd rather use that but like the idea of the electric one for priming. I've not changed the plumbing yet so just wondered how people have done that when using both mechanical and electric pumps, any advice gratefully received.

[GG]

There are different ways to do this, but over time, have settled in on a simple approach that works here in the US. Different gas may have different needs, but here's one approach:

An electric pump is mounted back at the fuel tank, just on (and pressurizing) the line that goes to forward to the mechanical pump. this way, its out of side, discrete, and powered separately (w/ small switch under the dash). It is used to prime the carbs which drain down after long inactivity, and to help with vapor lock in the event of hot running issues. Sometimes on a spirited day, it might be on for 15-30 min, but not all the time.

I find this works well. Prefer leaving the mech'l pump in place and doing most of the work (for originality), with the electric pump in play only when needed. There is the issue that all the pressurized fuel  is running through the mech'l pump, with its small valves and diaphragm, but (knock wood) hasn't been an issue. But recommend using a low pressure pump, around 2.5-3 psi. Been doing this for 20+ years on Aurelias. Haven't done it on the Appia, as its carb pumps up pretty fast on its own.

The Facets line of pumps are largely advertised as fail-proof, so only 2 have failed so far. But by mounting close to the tank, they are easily replaced and there's room to work. If you are stranded somewhere, any simple pump of low pressure can be mounted pretty easily in the field.

One other thing - some folks like to over-pressurize the system, and use the 4-8psi pumps,  not recommended. It stresses the mech'l pump diaphragm, and there is the issue of too much fuel pressure. The low pressure pump is fine.

When Walt Spak rebuilt my B20 s.2 motor, he took apart 3 mech'l pumps to make one good one - when he checked the pressure output of the mech'l pump on a running motor, he found they varied a lot in their output pressure - especially at different RPM ranges. His conclusion was that wear in the ends of the pump activator rod was the issue. He also found setting up the mech'l pump was extremely sensitive, as even the thickness of a gasket changed the pressure significantly. Its worth checking carefully.   

Hope this helps.

[lancialulu]

Tim, whilst I recognise your undoubted knowledge of all things Lancia, I don`t think it good practice to run an electric pump in series with a mechanical pump. The electric pump has to overcome the valves in the mechanical pump and vice versa, putting extra pressure ( forgive the pun) on both units, and should one of them fail/valves stick, that set up puts both out of action.  I know people have run them that way but that`s my thoughts on the matter.

Jaydub

Jaydub - this is discussed on another thread.... I have been running in series (primarily for priming - pardon the pun) for decades now and never had an issue. I know others also run like this and my friend Andrea runs a parallel solution. I use my cars and so I cannot speak for the occasional user as to reliability but from my point of view if the fuel is filtered the electric does a good job of cleaning the mech pump valves

[Paul Johnson]

Well that's nice and clear then 😀😀 lots of different opinions.

The thing I certainly don't like about my system is the fact that the pump is not switchable, so that will have to change. What I am uncertain about is the state of the mechanical pump which I will now investigate.

[peterbaker]

As I see it an electric pump should have two functions. One to prime carbs, therefore putting less pressure on battery. However there is a plus side to not firing straight away, it allows oil to circulate before running. Secondly, in the event of the mechanical pump losing its efficiency through age, its nice to have the electric back up. For those in a hurry, ie. rallying it also allows instant recovery without having to fiddle about, and quite possibly, as I have done, disturb the wiring to the alternator in the process.