Mechanical Fuel Pump Breather References

[SF_Mini]

Can anyone link some photos of how they have setup their mechanical fuel pump breather hole? In the U.S. the only kit available is through Minimania and does not come with any fittings, so my plan is to source an NPT threaded 'bib' but not sure if I want to run that to a catch can etc, so looking for references of what some of you are doing here. Thank you!

[mk1]

I didn't know that mechanical fuel pumps had a specific breather.

But I haven't used a mech pump on a Mini for over 30 years

[Spider]

Like Mark, I've not seen a 'plumbable' breather on any of the Mechanical Pumps, standard or after market.

All I have seen on some is on the underside of the Pump a small hole, about 3/32" dia, that's open to atmosphere. They are just a hole and not threaded or somewhere that a fitting can be placed.

Got a Photo of what it is you're looking at here ?

[Ronnie]

Crankcase ventilation

[timmy201]

He’s talking about this part, which by all accounts is a good way to empty your sump into a catch can

https://www.minimania.com/part/C-2A265/ ... p-Mounting

[mk1]

Never seen one of those before.

I do however use the mech pump hole as a breather.

To do it successfully, you need to have a pipe that vents above the top of the engine with a fume can on the top. Or that how I have always done it. Use a pipe thats too thin or too short & you do release all the oil from the sump.

Something like this.

breather.jpg

[SF_Mini]

Sorry, to clarify talking about crankcase pressure relief via the mechanical fuel pump hole. The above information is very helpful. You must have a specific breather for the mechanical fuel pump hole in that photo?

[SF_Mini]

Another example of a breather for the fuel pump hole here:

https://www.dsnclassics.co.uk/retrospor ... sport-5-8/

This is going on an Austin America motor, so need as many breathers as possible. My main question is how to direct the hose & filter and whether to use a can or not etc.

[SF_Mini]

Where have you found the pipe/fume can that fits the mech fuel pump hole? Haven’t seen that before.

Never seen one of those before.

I do however use the mech pump hole as a breather.

To do it successfully, you need to have a pipe that vents above the top of the engine with a fume can on the top. Or that how I have always done it. Use a pipe thats too thin or too short & you do release all the oil from the sump.

Something like this.

breather.jpg

[Desmodromic]

He’s talking about this part, which by all accounts is a good way to empty your sump into a catch can

https://www.minimania.com/part/C-2A265/ ... p-Mounting

I use one of those on my 1275cc A+ engined Sprite, and I've never heard of anyone losing excessive oil through one.

It is baffled internally, and does an excellent job of adding crankcase ventilation.

[Spider]

He’s talking about this part, which by all accounts is a good way to empty your sump into a catch can

https://www.minimania.com/part/C-2A265/ ... p-Mounting

Ah, OK, thanks Timmy !

If you need more breathers on 99% of engines, than the factory items, I really think you need to look elsewhere other than for more breathers.

In part, in might be an option say you (think) you need 2 and don't want to fit one in one of the other factory locations, however the opening from the crankcase in to it is way to small to work properly, it's more likely to take oil from the sump and have little drain back. It needs an oil separator, which could be fit remote, but even then, it's not going to help with drain back.

If you look at the factory items, they have a very big opening, a bigger again chamber, and a small outlet. The bigger opening allows gases to flow in at a small gas speed rate (about 1/4 of the separator's total flow rate) and that, in part, is what allows the oil to flow back and not get drawn out.

[Terence]

You can make one using a fuel pump blanking plate & a breather canister. That’s what I use.