M50 fuel pump

[dicko]

I had my m50 conversion on the dyno last weekend and the bloke doing the run told me that it is running a little lean.
He suggested that i change the fuel pump and filter.
The filter is a no brainer ( ment to change it ages ago)but the pump is the other thing
I was looking on real oem and noticed that the m50 fuel pressure reg runs at 3.5 bar where the m20 only runs at 2.5 bar
I have noticed the pump getting nosier lately and was wondering is this because of the extra strain on it as it is now trying to pump at 3.5 bar
Have any of you lot had an problems and if ye have what pumps are ye using
Also have any of ye fitted " power boost vavles " or are these just a gimick .

[eko]

Power boost valve is a waste of time IMO and general view of them on here is they are potentially dangerous too.
Im using standard 325i pump on mine with no problems,and have done on all the other conversions ive done too.
Some do upgrade though but cant remember then name of the pump,sure someone will confirm soon.

[eko]

Walbro pump I believe?

[dicko]

Nice one eko I was thinking of getting a Walbro anyway
Did you put any of your conversions on the rollers
Or check if they were running lean

[DanThe]

Never had a problem with my pump either, if it was me I would change the reg before the pump

[punk_sy]

hey guys just wondering would my 318is pump be alright or should i put a 2.5 one in when i do the conversion??
i was going to get one but i dont need one ill save a bit of moneys??

[eko]

Nice one eko I was thinking of getting a Walbro anyway
Did you put any of your conversions on the rollers
Or check if they were running lean

First one(non vanos) was about 191/180 from memory
One in my sig 190/166

[DanThe]

318 pump is regarded as the better one because of the return

[Brianmoooore]

318 pump is regarded as the better one because of the return

?
All (ordinary) E30 fuel pumps are the same (housing differs), and should be well up to running a M50, if in good condition. You need a 316/318 fuel pump if you have the small fuel tank, and a 320/325 one if you have the larger fuel tank. Engine is irrelevant.

[DanThe]

The 4 pot pumps usually return through the pump body, meaning there is less chance of experiencing fuel starvation

[dicko]

Thanks for the advise lads that has cleared up some nagging doubts

[Brianmoooore]

The return pipe in a four pot goes in through the top of the pump and into the pot that the pump picks up from.
The return pipe in a six pot goes into the side of the tank and feeds an internal pipe that ends up in the pot that the pump picks up from.

[DanThe]

That was the conclusion reached on e3024v, never hacked a tank open myself but I remember some pictures posted up in the past that only showed one pipe running from left to right. Maybe it was a 4 pot tank....

[Brianmoooore]

With the fuel pump running, there is a constant flow of fuel emerging from the end of the pipe that's welded into the pot for the pump.
I drained a six pot tank earlier in the year, through the drain plug, and of course, only the RH side drained. To empty the LH side, I had to refit the pump (which was already out) and start the engine, but didn't refit the level sender.
Looking through the level sender hole, you could easily see a full bore flow of fuel from the pipe, feeding the pump and overflowing from the pot, and out of the drain.

[Theo]

At the risk of sounding a bit dense, how exactly does fuel from the LH side of the tank get to the fuel pump pickup?

[DanThe]

Good question

[Brianmoooore]

It is indeed a good question, and one I still can't fully answer, but it involves a syphon effect, primed by the fuel returning from the fuel rail. If you put a six pot tank into a four pot car, retaining the original pump and plumbing, you won't be able to use fuel from the LH side.