Weber Carbs Fuel Pump Recommendation

[kupcar]

Hi Guys, It's time to start the winters project list. I have a 2.2 liter running Weber 40's. The previous owner had a Facet fuel pump without a regulator or pressure guage installed. I havent had any issues, but I feel a better setup is required. Any recommendations on a system that works well with the Weber 40's?
Thanks.

[Bergo]

previously I ran a stock low pressure pump with my 2.2 w/ weber 40's. Last winter I upgraded to a walbro high pressure pump (255, inline pump), and used a PMO pressure regulator to drop the pressure back down to 3.5 ish (can't recall exact pressure off the top of my head) runs well!

[chris_seven]

I don't understand the benefits of a high pressure pump and a pressure reducing valve.

In any fuel system a pump is basically a source of flow and as a carburettor doesn't need pressure the lower the system capability the better.

Pressure is only required to overcome restrictions in the fuel line and if the size of fuel hose is optimised and the number of restriction is minimised then very low pressure pumps do work well,

Pierberg makes a small electric pump that runs at a maximum of 2.3psi and we have used these pumps very successfully on 2.0 litre Race Engines using Solex 40Pl carbs.

We also use low pressure Walbro Pumps at around 3 psi on 3.0 litre engines with 40IDAs or Zenith 40TIN carbs.

There is a also a 3.5psi Hardi Pump used on a 2.0 litre 1967 911S that is still available in Germany that works well.

We never use a pressure regulator and a higher pressure pump as inline of blocking regulators commonly suffer from either pressure spiking or pressure creep.

[lrodri64]

Hi,
I use a carter low pressure high volume.
Don't remember the model.
Bought it on the Internet.
Really good.

[kupcar]

Everyone, Thanks for the input. I was told that the Facet pump I have runs less than 4psi. The car runs good but I have no way of knowing the exact psi. Maybe a pressure guage should be added just for verification. I'd hate to mess with something that seems like it's running right, but I was under the impression that Facet pumps weren't of high quality.
On another note, is it possible to dilute the oil with fuel if the pump is left running when the motor is off? I was doing electrical work which required me to turn the key to the accessory mode. I hear the fuel pump clicking away. I'm so used to fuel injection so I never really thought about what the fuel pump was doing? Can the pump push enough fuel to wash down the cylinders or does it require vacuum? I ended up disconnecting while doing the work. Would it be beneficial to run a fuel pump cutoff switch? If you couldn't tell, I'm still learning carburetors. Thanks for the help.

[Bergo]

I went with a higher pressure pump because I'm planning to go EFI, and was re-running the lines anyway.

[paulthe2nd]

I used a facet years ago with a regulator I would adjust between 3-5 PSI per my engine builder. I would incrementally adjust the pressure between 3-5 PSI in small increments and performance test it and found zero difference between the pressures between 3-5 PSI

[chris_seven]

Fuel pressure only affects carburetted engines when there is too much pressure and the needle valve leaks.

If you pressurise the float chamber due to this problem then you will screw up the calibration of the main jet as the 'head' will be incorrect.

A float valve in good condition should seal up to around 5 psi but 3.5psi is a good safe limit.

Facet pumps - apart from cheap and nasty copies - are quite reliable if mounted correctly.

The problem has been that over the years they have commonly been mounted horizontally and then they do fail.

The manufacturers recommendation has always been to mount them vertically and on rubber bobbins.

Factory Escorts used to mount the pumps flat on the boot floor and then add a second pump to deal with the unreliability that this action created in the first place.

The problem is that this has stuck and people now always fit two pumps as Facets are 'unreliable.' I have never understood this mentality.

I have a 1965 Bendix Silver Top in a February 65 911 that looks really scruffy but works well.

The other problem is that people always buy a Red Top replacement as they are always told that this is a 'better' pump. You can then also be sold a 'Regulator' as an essential fitting.

It is higher pressure but that is not a benefit but a weakness.

IMHO a fuel system of this type is good for sales as you spend money on parts that are not really needed but the engineering theory is weak.

Fuel pumps of this type are not well understood and it seems to be a common belief that maximum flow occurs at maximum pressure.

A Bendix Pump at maximum pressure has ZERO delivery. The pump simply stalls.

The maximum delivery is nominally at zero pressure ie when the outlet is delivering fuel into an open bucket.

In reality there is a cut off at about 1 psi to overcome internal resistance inside the pump.

If you build a crummy fuel supply system with small diameter hoses, loads of bends, connectors, one way valves and all other garbage we are sometime told we need you can end up with a raised fuel line pressure and a pump that won't deliver enough fuel at WOT and end up with melted pistons.

This is a little different to using an in-line or blocking pressure regulator which has a different effect.

The 'clicking' of the pump is simply the pump cycling to maintain its pressure it isn't generally delivering fuel in this condition.

When it 'clicks' very rapidly is when it is delivering fuel.

Providing the float valves are sealing and there is no pressure in the float chambers then there will not be any bore wash and the jets will not be delivering fuel without the manifold vacuum or venturi effect.

If your float valves are not sealing you should see fuel stains on the outside of the carbs and the engine would be obviously running rich and quite badly.

It is custom an practice to set up pressure regulators with a gauge and then remove the gauge as if they are left in line they tend to either fail or develop an offset.

I just find low pressure pumps are simple remove all uncertainty and if there are issues it is generally due to poor float valves.

My comments really only apply to fuel pumps and carbs, I accept and understand the needs for high quality pressure regulation for EFI systems and that the By-Pas regulators used are much better devices than often used with Facets and carbs.

[stownsen914]

Using a high pressure pump is a fine solution IF you set up your fuel circuit with a regulator and a return line back to the fuel tank so you don't overwork the pump. A simple "dead-head" regulator like you can buy at Pep Boys will kill a high pressure pump if you dial the pressure back to several psi for a carbureted engine.

Note that high pressure pumps do not automatically deliver fuel at high pressure. If you run one in an open circuit (dumping into a bucket), you will get pressure comparable to that of a low pressure pump. It's only when you properly restrict the fuel delivery, usually done with a pressure regulator (think of a dam in a river) that high pressure pumps actually operate at high pressure.

Scott

[KTL]

I like the modern pumps like Mallory or Aeromotive that are the gerotor type (internal mechanism looks like meshing gears) of pump. They run quiet, cool and last a long time. The rotary vane-style pumps (rather crude, with metal paddles that scoop fuel into & out of the ports) like the Holley Red, Blue, Black are pretty loud and not all that reliable. I'd stay away from those.

My racecar purchase came with four spare Holley Red pumps. Granted, the fuel system was plumbed with two pumps in parallel to provide redundancy if one failed. The added flow (plumbing them in parallel doubles the flow, pressure stays same) of this installation wasn't the goal. But the point is, what does that tell you when you have a collection of six pumps for a car?

[kupcar]

I'm learning a lot about fuel pumps and carburators. Thanks everyone for the info. I guess I should feel fortunate that my pump has been trouble free. I know the saying "if it isn't broke, don't mess with it". I almost wonder if I should just leave the Facet in and wait for it to crap out. The car runs great. Would a pressure guage be a good idea to have to monitor the pump?

[1QuickS]

Per Chris's comments above; use the gauge to check pressure at tune-up time & remove otherwise, the vibration will kill the gauge if left attached to the engine assembly.

Porsche specification for fuel delivery pressure converts to 3.56 psi. Anything from 3 to 4 psi is fine by me. Higher pressure will put more pressure on needle & seat without purpose. Low pressure could be an issue for lack of adequate delivery if the engine consumes a lot of fuel as in race application and/or large displacement.

Since fuel delivery pressure isn't extremely important it is probably not necessary to adjust it with a regulator. On my web site I do recommend this as the second of three fuel delivery system recommendations. I personally use a 6 psi pressure Mallory rotor gear pump & a pressure regulator to set delivery pressure to 3.5 psi. If the pump decides to lose output pressure, then the carbs will still get 3.5 psi.

[Ayles]

I use a Mallory with my set up as well, so far so good. They are rebuildable too.

[1QuickS]

I did try a Holley Red Top fuel pump but even in my car, without sound deadening, suspension pivots of Delrin and spherical rod-ends, K&N intake filters and 911R "muffler"; the Red Top was too noisy!!!!! I switched to the Mallory & have been very happy.

[RobWeiss]

Ive been using a Carter P60504 on Webers for years. It operates at 3.5psi so, no regulator required. $39 at Summit.

[James Brown]

love the 911R look if you can swing this

[chris_seven]

There are just a couple of details that fall out of this discussion.

Using a high pressure pump and a By-Pass regulator will certainly work and I agree that unless restricted pressure will be low.

The disadvantage of using this type of circuit to produce a low pressure is its sensitivity to pressure drops in the fuel return line.

Any small flow restrictions will lead to rapid pressure build up and potential problems.

It is customary to use returns lines with about twice the cross-sectional area of the feed line to avoid this potential problem.



The above diagram shows the output flow vs pressure relationship for a Pierburg pump.

It is difficult to find this data for a Facet but the 'shape' of the curve will be similar.

If the engine consumes more fuel than the pump can deliver then a larger pump is required.

I don't think using a higher pressure will help as flow will fall further. If the float valve is open these pumps which all tend to be self-priming will always deliver to a maximum of their capability and the pressure they produce is simply a function of pressure restrictions.

With an in-line or 'blocking' regulator there is effectively a fuel control valve which is a diaphragm controlled by a spring.

When the float valve closes the pressure in the fuel line increases and this closes the fuel control valve at the set pressure. Changing the spring tension changes the set pressure.

The disadvantage of this type of regulator is that as fuel pressure reaches the maximum value to which the regulator has been set, the internal valve must close to prevent the inlet pressure from getting to the outlet side of the valve. This action requires an initial extra force (fuel pressure) to fully close the valve and this creates a spike in fuel pressure as the valve reaches the closed position.

The result is a slightly higher outlet pressure that could over-pressurize the carburettor and overfill the float bowls.

The seat of the Fuel Control Valve also tends to be prone to dirt preventing compete sealing.

I may be a bit old-fashioned but I prefer low pressure pumps without regulators as they are simple and effective.

I do realise that I am out of step however.

[kupcar]

Well I found some time to play around with the car today. I did a pressure test on the Facet pump. It turns out that it reads a pretty consistent 3.5-4psi. Sounds like that's right were I want to be. The Facet pump seems a bit wimpy and makes that rat-a-tat sound but should it be replaced? Is it a reliable pump?

[chris_seven]

They have always been noisy and made a regular ticking sound.

If it works why change it?

[Big Mack]

chris_seven -

Regarding the Walbro pump you mention in post #3 - where do you mount it? Looks like the Walbro FRB 20-2 is a good candidate at 2-4psi and 33gph, but it's pretty tall at almost 6" without fittings, and I don't see an easy place to put it below fuel tank level.
Thanks, Mack