fuel pressure question

[X53Jay4.8is]

Originally Posted by jfoj

Thanks for updating the thread, too bad the thread had to take the direction it did.

BMW uses different pumps across some of the chassis, some are Siemens/VDO, others are Pierburg. From the E46 chassis, the pumps are Siemens/VDO except for maybe the M3, and based on history, EVERY E46 should have a replacement fuel pump by now if you want a reliable vehicle.

Pretty much hold true for the E53 even if it may run a Pierburg pump, which it may as the E53 is a cousin of the E39.

For the pump price and the ease of replacement, it makes no sense to brag about how old or how many miles the fuel pump may have. I prefer to proactively replace electric fuel pumps by the cars 8-10th birthday because I do not like walking when I should be driving.

I think everyone will see that the E53 pumps will soon start failing in large numbers if they have not already started. The no starts tend to begin in the Winter months with the cold temps and after the vehicle has sat over night for a good cold soak. But before the pumps cause no starts, they get soft/weak and cause driveability problems and will cause the sucking jet/siphon pump to not work properly and the vehicle will also "run out of fuel" with the tank displaying 1/4 full.

I am sure everyone will have their own opinion and make up their own mind, but I highly recommend replacing the fuel pump as a preventative measure.

This is sound advice.

[oldskewel]

In defense of Bernoulli, and regarding the suction effect upallnight refers to ... assuming steady, inviscid, incompressible flow, sea level, port is perpendicular to the flow ... 100 mph air speed would result in a suction of 0.17 psi.

The 100 mph is a nice easy number which is way higher than actual. And 0.17 psi is not much. It's about how much atmospheric pressure drops when driving up a 300 foot hill.

My apologies for the standard units. This all seems to support jfoj's assessment.

Thanks jfoj for all the accurate information here. I recently replaced the fuel pump in my '01 with ~170k miles. Lucky for me it died while parked in front of my house. After cutting open the dead pump, everything looked great except that the brushes had worn past their limit.

EDIT - I wrote all the above after only reading part of page 1. The numbers don't lie and can cut through a lot of the problems with words and opinions. I forget who said it, but it was something like: "everyone is entitled to their own opinion, but they can't also have their own set of facts." Regarding the advice to replace pre-emptively based on mileage, I agree, but that is tougher when you know you don't have complete service records. Another thing in my case that was surprising was that there was no soft/flaky zone - it was running at 100%, then dead (failed to start one day - in fact it started up, ran for a few seconds and then died, luckily in front of my house, unluckily not in my driveway).

[80stech]

Geeze I just changed the fuel filter and had to figured this all out on the weekend. I wish I had seen this post about the M54 not making use of manifold vacuum on the fuel pressure reg. I first assumed that someone had previuosly connected the hose wrong since mine had body work done on that side! I couldn't understand it because it looked factory but didn't make sense. I guess they didn't want to vent the regulator underneath the car and also make use of the same filter fittings/lines. Good to know for sure!