very long cranking before engine starts

Couple months ago my 99 E39 (528i) would not start. My friend/mechanic comcluded the problem to be either the fuel pump or the fuel pressure regulator. Being these components are oringal and nearly 16 years old, I
decided to replace both, plus a new fuel filter.
After the new fuel pump, fuel pressure regualator and fuel filter were replaced it takes an extremely long time to start the engine when you turn the key. It cranks for maybe 7 seconds or more. It always starts, and once it starts runs and idles fine.
Once in a while it will start up like it should, but most of the time takes way too long.
Any suggestions?
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Try the following: -
Switch on the ignition and wait several seconds, then try and start.
My guess is that you have a problem I had on an old 1983 E23 once it reached about ten - namely the fuel was running back down to the tank, it therefore took a few seconds for the pump to pump it back up (you could hear it) before the engine would start. There may be a valve(s) somewhere in the injection system that should stop this.
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Try it with the gas cap open. Does that help? If so, you have a venting issue.
What does the fuel pressure (as measured at the rail) read before and after it starts up? How long does it take to drop back down after you shut the engine off?
The thing about these is that because there is feedback control on the fuel mixture, the fuel pressure can be _way_ too low and the car will run just fine until you push it hard.
When you replaced the pump did you also replace the backflow valve? On some models it's built into the pump but on some it's external.
It also would not hurt to make sure the pump is turning on properly. While you're under there, attach a light and see. That's unlikely to be an issue but it's easy enough to check while you have it up. --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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I tried the previous responder's suggestion. I turned the key to the on position and waited 5 seconds and then it starts instantly like it should! I've consistantly did this a dozen times.
Now about that valve you are talking about. Is this something that can be adjusted? I know it wasn't replaced unless it comes with the new fuel pump.

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Diagnosis I think!

Dunno on this model, but you could always try one inline as near the engine as practicable.

Another possibility, but unless the seal is perfect, usually only a problem restarting after a long run.
Amusingly some engines misfire if the oil filler cap is left off or not fully tightened (something to do with scavenging the fumes from the crank-case and breaking the vacuum, but this is beyond my ken).

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On Thu, 7 Aug 2014 14:07:30 +0100, "R. Mark Clayton"

I think it's a far better idea to find and fix whatever check valve that BMW put in there. And if you *did* decide to put an extra one in for some reason, then it should be as near to the pump as possible, not the engine. Oh, and make sure that the 'check' action is facing in the right direction, too ...
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Depending on the model, it may or may not come with a new fuel pump. Check the service manual.
Where did the replacement pump come from? Did you get a full kit from Bavarian or did you get the cheapest possible rebuild from AutoZone? --scott
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"C'est un Nagra. C'est suisse, et tres, tres precis."

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