What did you do to / for your E53 today??

[Henn28]

Originally Posted by X5only

Changed the fuel filter after more than 6 - 8 years.

I’ve got the same filter set-up on my 2002….correct me if I’m wrong please, but We don’t have the valve that keeps pressure at the rail on our filter. I can t figure out where that valve is on our cars, or if it even exists. I loose pressure at the rail within 10 min with the key off. Not a huge deal as I usually turn the key to posit 2 and then strap in, giving the pump a second or two to build full pressure.

I don’t know if our cars with this older filter didn’t have a no-return valve somewhere, or if I just can’t find it.

[80stech]

There is a check valve built into the fuel pump. The only difference with some of the older cars AFAIK is that the pressure regulator is removable from the filter on some of the older ones.

[Henn28]

Originally Posted by 80stech

There is a check valve built into the fuel pump. The only difference with some of the older cars AFAIK is that the pressure regulator is removable from the filter on some of the older ones.

Ok, so then my 2 yr old Delphi fuel pump could be the culprit. Its also only putting out 40psi at the rail, so maybe I need to spring for an OE BMW part. I seem to recall 50psi is the magic number but will look in Bentley.

[80stech]

Maybe you need a better fuel pressure gauge or connection? The pump check valve is the most common point of leaking fuel pressure but the regulator, injectors and all the lines and connections need to hold as well. Maybe start a thread if you want to look into this further?

[andrewwynn]

50 is the magic number. If you FPR comes off like mine did you might find a leaky o-ring that vented the pressure back to the tank.

When check valve holding you should have 20-30 psi overnight but the FPR o-ring also must seal.

[Henn28]

Originally Posted by andrewwynn

50 is the magic number. If you FPR comes off like mine did you might find a leaky o-ring that vented the pressure back to the tank.

When check valve holding you should have 20-30 psi overnight but the FPR o-ring also must seal.

Sounds good, thanks Andrew. But where is the FPR on the smaller (older, I think) filters like in the picture above? It isn’t a separate part, so is it part of the pump?

[andrewwynn]

Bummer i think it's built into the filter.

You could confirm the problem is in the pump or the FPR by pinch off the return line. There's a TSB on the exact procedure but if i did it i would have a helper so i can pinch the return line as soon as i turned off the key.

Or: i think foxwell can engage the pump. If your pump primes on key on you can listen for it to stop after ≈ 6 seconds.

The check valve is in the pump.

If pressure stays with the return line pinched the problem is like mine was: internal leak at the FPR draining. If it still drops it'll be the pump check valve.

If the pump check valve fails but the pump is ok, people will often just add an inline check valve.

[80stech]

First look into why you have only 40 PSI of fuel pressure.

[EODguy]

Well boys and girls, it's that time again (2.5 yrs ) so the 1st parts are in....

Front was a couple of months ago, along with brakes, tires, fluid/filter change and hood cables/latches.

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[andrewwynn]

Brings back memory of doing mine.