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Only because I'm interested in test results: Recall it takes long cranking to start, trailer hitches cold, noisy pump.

I've got new pump and fuel pressure regulator. To report back, learn something, which first ? and how long to see if anything improves ?

Probably test cold start valve first, and if trailer hitching doesn't improve after above, replace oxygen sensor, then swap AFM.

I've got to take a pic of my fuel pressure tester one of these days to show just how easy it is to make it and test fuel pressure. Maybe even put it in the FAQ. But that's really where you want to go. Beyond that, maybe run it, stop it, then pull the return line off the FPR and see if it leaks. That should give you more direction.

By return line you mean the vacuum tube off the top, correct ? So far, it hasn't had any fuel come out the top on two checks.

If I may...

This is a generic off-the-shelf kit. The separate piece is an interface I made up that goes between 'our cars' and this meter. It is a brass female to female coupler (I forgot what size) to which a male fitting screws into the female counterpart to the tester and a male ribbed fitting to which the cold start fuel hose temporarily connects. YMMV regarding specific connections depending upon how a specific tester is built.


Be very very careful dealing with fuel under pressure. The clear hose is a 'bleed-off' to release fuel under pressure to a suitable container.

Thank you. Simplicity for the uneducated: Buy new regulator, install. If it runs obviously better, junk the old one, move on. If not, keep the old one. Move on.

The other alternative is a FAQ, explaining the function of the fuel pressure regulator, schematic of lines in/out. How, why they fail. Or Googling the web for general information.

Your test kit. How to use the tester: what to look for on the dial, etc. How common failure is, after installing a new one. I.e., if a garage mechanic will ever use the time, money expended on the tester, testing, again.

Is there an acronym Google dictionary ? YMMV.

YMMV = Your Mileage May Vary.

If interested, replacing fuel pressure regulator made no immediate, noticeable improvement. Pump still makes audible spinning sound, not so with my other 528i. Let it sit, see if it starts faster. Either way, pump is next.

Then oxygen sensor, as I suspect it's a cheap test to see if it fixes (cold) throttle stumble that improves when up to temp.

To change a fuel pressure regulator, don't try to horse the big nut off with a box wrench, cattywompus vice grab on the bracket. Neat way to bend the bracket. Air wrench will spin the nut right off, once you fit a standard chrome socket on the nut. You'll see the bracket was engineered to not have enough space between the big nut and the bracket, without some bending, tapping, screwing around.

T.Hanson wrote:By return line you mean the vacuum tube off the top, correct ? So far, it hasn't had any fuel come out the top on two checks.

No, not the vacuum line. I'm assuming you have a 528i, and if so, the return is the rubber fuel line attached to it. It should not be under any pressure. Flow yes, the excess fuel which is pumped but not needed, is released there and drains back to the tank. The metal connection the the 17 or is it 19MM nut, is the high pressure side, which should be around 32PSI at idle.

Hi,
just wondering if you solved the problem of slow star after car sitting for a few days.
Mine does the same, like looses fuel pressure and takes a while to star.
I know you repalced the fpr and pump, did it fix the problem?
I did a new fpr ,but still the same
Thanks
Wil

I wish I could report problem solved by replacing X. As it's not a daily driver the best I can say is the few starts seem better, probably normal, with more sitting and starting to go.

I doubt it was the fuel pressure regulator. Slow start to me means it's not got fuel at the ready, either a pump allowing it to drain or the cold start not squirting. I replaced the pump over the axle to guess that was a help. Inspecting the in tank found very little crud on the screen. Filling the tank made the in tank pump quiet again, most of the time.

Far as I can tell from posts here the drat thing doesn't do much, and it looks like it. The size of a C battery, plastic, it's odd it can even make noise.

Still driving it, needing a cat, O2 sensor next. Maybe swap the AFM, check throttle switch wires after that. Probably spring though.

I will check the cold start injector, haven't done that, and then I will move to fuel pump.
wondering where is the valve that keeps fuel pressure between pump and fuel pressure regulator, in the pump itself?
Thanks for your help

I replaced the cold start valve, although 60 degree day, the car started with neither valve squirting fuel into the container.

Replaced the fuel pressure regulator on a friend's 2005 Hyundai, cured the slow start problem to instant start. Go figure.

I think the outside fuel pump impedes reverse fuel flow. Far as I know there is no separate one way valve (anything) in the system.