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-   -   E-Fuel Pumps for Carbs (https://www.alfabb.com/bb/forums/carburetors-fuel-injection-air-intake/666942-e-fuel-pumps-carbs.html)

AlessandroM 08-19-2018 08:43 AM

E-Fuel Pumps for Carbs
 
Hey there

I converted my car recently to an electric fuel pump (Facet Cube 7-10PSI) that I got cheap from "some guy" that used it for his webers on a Golf (Rabbit). Well ever since I mounted the pump i had problems. The car would overheat slightly especially when the weather was hot. I used the original fuel regulator that came with the car. I swapped the old regulator then for a slightly more modern one (https://www.merlinmotorsport.co.uk/p...r-8mm-pf-reg-5)
It ran fine at first but eventually my car started stalling or only running well at very high RPM. You guessed it: the carbs were floated. I tried turning down the regulator but it didn't help. I eventually got home thanks to the lambda probe which would let me turn on the pump when the carbs were leaning out ... not really a fun drive, but I was happy i fitted the probe. :)

I ultimately looked at my cube and stupid me finally realized that I bought the strongest version that pushed the said 7-10 PSI or Way too much :frown2:

Long story short:

I know i need a "smaller" pump - and I get to chose between 1,5-4 PSI and 3-4,5 PSI from facet. What have others chosen here?

...and why do they cite a range instead of straight 4 PSI? Is because it can be regulated between those numbers?

Thanks a lot and bear with me. :)

Thanks!
Alessandro

Gordon Raymond 08-19-2018 09:09 AM

2 Attachment(s)
This is fairly simple. The correct fuel pump is the low pressure high volume FACET pump pictured below. It must be mounted back, by the tank, as this pump "pushes" fuel. It does not "pull" or lift fuel very well. If you wish to use an aftermarket filter / regulator, the best is the Filter King pictured below with an Alfa FRB 11 for comparison. The Filter King has a greater range of pressure adjustment than the FISPA FRB11. Fuel pressure should be set at 3# or less.

AlessandroM 08-19-2018 09:16 AM

Hey Gordon,

Thanks for responding

That is exactly where I have my current fuel pump mounted. Pushing is not the problem here but it pushing too much.

I have been using the regulator/filter on the left of your picture before I resorted to the one linked.

Why would you go for the "old"-style pumps? Do they have a clear advantage that i wasnt able to find? I see plenty of people using the cube or posi-flow ones. They seem to have gotten the pressure correct though...

kind regards
Alessandro

Gubi 08-19-2018 09:17 AM

The little Facet cube ones are not great pumps. The larger Facet Gold ones are better.

I've got the one Centerline sells. It's been working well with a similar regulator to yours to knock it down to a consistent ~2.5 PSI.

https://centerlinealfa.com/catalog/f...p-bendix-repro

Alfajay 08-19-2018 09:20 AM

Quote:

Originally Posted by AlessandroM (Post 8303570)
The car would overheat slightly especially when the weather was hot.

That is odd. I believe cars will run hotter when the mixture is too lean. But with excess fuel pressure, I would think your car would have been running too rich. You may have a separate problem with the cooling system.

Quote:

I ultimately looked at my cube and stupid me finally realized that I bought the strongest version that pushed the said 7-10 PSI or Way too much
As Gordon wrote, a low pressure, cylindrical, Facet pump is the way to go. The cube-shaped Facet pumps will work OK (again, use a low pressure model), but I believe the cylindrical pumps are higher quality for not a lot more money.

AlessandroM 08-19-2018 09:32 AM

@Alfajay

Yeah I was also thinking lean = hot. It only really got hotter when I had to drive slowly. And not excessively but noticeably. But to be honest I haven't driven the car in over a year (restored the underbody in that time) So it could just be me...


@Gubi & @Alfajay

Why is it then that the cylindrical ones are so much better? I tried to investigate before I bought the cube but I haven't found a single argument besides the cylindrical ones being "period correct".

Gubi 08-19-2018 09:43 AM

Higher quality. Supposedly smoother pressure pulses. Integrated, cleanable filter at the bottom of the pump.

Oh, and the cube doesn't have the anti-drainback valve, which is a nice feature.

AlessandroM 08-19-2018 09:56 AM

I really don't mean to defend the cube (after all mine wasnt the correct one..) but I have a hard time believing that the pulses are worse than the mech pump I had before.

You're right the cube doesn't but the posi-flo's ("newer" cube) do have it.


What is it then with the max and min pressure - is it that the pump can be regulated between these boundaries?

Gordon Raymond 08-19-2018 11:21 AM

You need a regulator AT THE WEBERS to adjust pressure. Webers may need high flow rates for racing with modified 2L's but pressure is not helpful. Particularly with brass float Webers. The floats weigh 26 grams, and with needles and seats of 2.0 or larger, it is possible for pressure to overwhelm float weight causing flooding. Later design Webers that used plastic floats have different float hanger geometry, and will tolerate a bit more pressure. How much? I don't know as I've never checked.
However, the regulator serves 2 or 3 purposes. Most have a built in filter. The diaphragm absorbs a bit of the fuel pulses from most types of fuel pumps, reducing wear to the float "paddle" from the needle. The third purpose is to be sure pressure is low enough not to overwhelm floats, yet volume high enough to keep the fuel level in the bowls constant.
Suggested pressure for Webers with up to 2.0 N & S is 3# running. This is for brass float designs, and is fine for plastic floats as well. The low pressure will depend somewhat on engine use, the intent to keep fuel level in the bowls from dropping with constant high rpm use.
From my personal experience with Webers over many years.

alfaparticle 08-19-2018 01:01 PM

As Gordon wrote, the Facet pump pushes well but it does not suck very well and it is a good choice for a tank where the fuel line is from the bottom. In my experience it is not the best choice for a tank with a fuel line that goes in through the top unless you also have an in-tank pump.

AlessandroM 08-19-2018 01:05 PM

Hey Guys

Maybe I'm missing something but how is the level of lines and pump relevant for my initial question? :-) I have too much fuel - not starvation. And the regulator is in its original position next to the carbs.

My initial questions were really:

1. What facet pump have you guys chosen with what pressure? (Cylindrical I see but there are different psi rating and ranges)
2. What does the PSI Range mean?

Thanks!

Gubi 08-19-2018 01:15 PM

1) See the one I linked to. 4-5 psi.
2) It probably depends on flow rate. The pump can produce more pressure at lower flow.

AlessandroM 08-19-2018 01:30 PM

@Gubi Thanks. But why the 4-5 when everyone says one should go for 3psi ~? Because of question 2.?

Alfajay 08-19-2018 01:36 PM

Quote:

Originally Posted by AlessandroM (Post 8303596)
Why is it then that the cylindrical ones are so much better?

- I suspect the cylindrical pumps last longer.
- The cylindrical pumps probably can deliver more volume (which may be irrelevant for a small-displacement street car).
- I don't know, but perhaps the pressure pulses are less pronounced on the cylindrical pumps.
- The cylindrical pumps have a built-in filter.

Gubi 08-19-2018 01:43 PM

As I said, I've got a regulator in-line at the carbs to drop it to ~3 PSI. The lowest pressure pump in the Gold-Flo line looks like it's 2.75-4 PSI, so you'd probably still want a regulator with that as you're targeting 2.5-3 for the Webers. The regulator also helps smooth out the fuel pulses, I'm sure.

I don't think those little disc regulators deal too well with too high an input pressure, but they'll easily step it down from 5 to 3 PSI.


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