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I want to start a parts 530i that has a missing fuel pump. I'd like to swap in a cheaper generic pump.What kind of pump pressure would I need?

canada karl wrote: ↑Sat Nov 26, 2022 2:03 pm I want to start a parts 530i that has a missing fuel pump. I'd like to swap in a cheaper generic pump.What kind of pump pressure would I need?

The Haynes manual says 3.0 metric bar.

Thanks

Karl
did you find one.

I bought a cheap one and used it yesterday ( On 77' 528i)- I ended getting fuel starvation as soon I tried to pump the gas - idled okay and I got to drive it for couple of hundred meters then it almost shut off.

https://www.ebay.com.au/itm/143907836308

or I may have a blocked fuel filter preventing fuel being passed through fast enough!

The link for that ebay pump did not show up? What psi does that pump put? I believe 30 metric bar is pretty high pressure. Looked it up and see that 30 metric bar is 435psi????. Can that be correct?

canada karl wrote: ↑Thu Dec 08, 2022 9:25 am The link for that ebay pump did not show up? What psi does that pump put? I believe 30 metric bar is pretty high pressure. Looked it up and see that 30 metric bar is 435psi????. Can that be correct?

I said 3.0 (three point zero) not 30 (thirty)

Doh! My eyesite must be going. So that would be 43 psi. I believe generic fuel pumps for carburetor engines would be 3.5 or 5 psi so not sure if that is enough pressure to run a fuel injected motor?

canada karl wrote: ↑Fri Dec 09, 2022 10:50 am Doh! My eyesite must be going. So that would be 43 psi. I believe generic fuel pumps for carburetor engines would be 3.5 or 5 psi so not sure if that is enough pressure to run a fuel injected motor?

Unfortunately the low fuel pressure for a carb engine isn't enough for any injected motor. The carb e12s had a low pressure pump running off a shaft connected to the distributor from memory.

Even our injection systems are low pressure compared to the 2002tii, whose mechanical pump did 80 psi I think. The e12 520i had that motor through 1975 in Europe, then switched to Bosch K-Jet with a drop of 5 hp and about 0.4 second slower 0-62 mph, according to the BMW brochure.

The blue book says the 518i/520i also used a 5bar (71 psi) pump.

The 3bar (43 psi) pump on the 528i / 530i has a delivery rate is 2.2 lpm / 4.6 gpm. It also lists the max power consumption as 6A.

I have a fuel pressure gauge in the engine compartment and a new Bosch OEM fuel pump, and am measuring a little more than 35 psi just before the fuel rail.

I think you guys are looking at it wrong. The max pressure of a factory pump is 80-100 PSI, enough to blow off many hoses and burst many non FI fuel lines. But that kind of doesn't matter. What matters is system pressure and flow at a given pressure. E12s use a 2.5 bar fuel pressure regulator with a specified minimum delivery rate at that pressure. At idle, full vacuum, system pressure is 32 PSI. Shut off with the pump running or at WOT, it's 38-39 PSI. With a certain delivery rate.

So you need to look at the pressurized side of the system and flow, not the pump pressure.

IIRC, early 530s used a different pump, one that was the same as used in the 2002tii, which was mechanical injection, not electronic, so it operated at a higher pressure. 77-81 E12s used a different one, similar, less expensive back when they were common and available and interchangeable on E12s, but probably not suited for tii's.

Thanks for getting our heads on straight, Mike. This makes sense.