1991 318iS with standard in-tank fuel pump - what pressure?

[russ325i]

I've been searching high and low but haven't found a definitive answer so I thought it best to put it out there - how many bar pressure does the standard in-tank fuel pump operate at in a 1991 318iS?

I'm just wondering if it's worth butchering a 3.5bar one from an E36 that I have kicking around or if it's already got a high pressure one in it as standard.

Any ideas?!

Cheers!

[rix313]

3.5bar is about the standard pressure for most petrol systems.

[Brianmoooore]

Fuel pressure is set by the fuel pressure regulator, not the pump, unless thre's something seriously wrong with it. On the E30 iS, the rail pressure relative to the partial vacuum in the inlet plenum is 3.0 bar.

[russ325i]

Thanks for the replies gents, what I completely neglected to mention is that the car is now fitted with an M52 rather than the original M42.

I can't find any specs for the standard E30 pumps other than there seem to be two setups used; a higher pressure in-tank pump on the facelift models and a combination of low and high pressure pumps on the pre-facelift ones. A friend of mine who's built both an S50 and an M62 E30 suggested I use the E36 pump but I just wanted to check before dismantling both and changing over the pump itself in case that'd be a complete waste of time.

I'm guessing that'd be a complete waste of time, right?

Cheers.

[jmc330i]

The standard E30 pump will be fine for an M52, even the S50B30 will be happy as it runs at the same 3 bar fuel pressure. Its only the S50B32 that runs at 5 bar that needs the pump swapping.

[russ325i]

Spot on, thank you James - that'll be why he suggested it in that case as his S50 is a 3.2 but it's good to know that there's no need to swap mine at the moment.

....especially as I broke the one I was intending to put in when removing the fuel line from it this morning!

Cheers,
Russ