2005 525i Fuel Pressure Problem? (stalls on cold starts!) - BMW Forum - BimmerWerkz.com
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#1 (permalink) Old 09-29-2009, 02:51 PM
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Arrow 2005 525i Fuel Pressure Problem? (stalls on cold starts!)

Hey All,

I'm looking for help with a problem that neither the dealer nor my repair shop can diagnose.

My 2005 525i sport (58k miles, out of warranty) stalls or won't start when cold starting... sometimes.

When I turn the key on a cold (more than 20 minutes since it last ran) start, one of three things happens:

1. It starts, but at low-ish RPM and stalls out quickly
2. The starter cranks away but it does not start
3. It starts!

If it actually starts, it stays running and purrs like a kitten. The computer reports no problems anywhere. My current mechanic indicates that the problem occurs when the vehicle is in a cold/damp condition, but the problem started when I was living in Florida in August which is not cold (though it is humid). I only use 93 octane Chevron/BP. I've run through multiple tanks of gas since the problem started.

I've had the crank sensor, the fuel pump, and the fuel filter (as well as the Schrader valve on the top of the engine) replaced, and the problem persists.

It *appears* that the vehicle is losing fuel pressure when not running and that may be contributing to the issue. Once I watched the pressure drop from 3.5 bars to 1.X bars in about 30 seconds once while a mechanic tried to start the vehicle. It does not appear to lose fuel pressure once running.

So, I'll ask a few questions and then hope someone knows what is going on:

1. Do e60s maintain 3.5 bars of fuel pressure constantly? Or is it normal for the pressure to drop when the vehicle is off.

2. When BMW NA and the dealer both won't help financially because the vehicle is out of warranty, am I truly just SOL?

3. Has anyone else seen this happening or know what is causing this? I've read the other threads about bad fuel pumps and such but that doesn't seem to be my problem.

Lots of thanks in advance.

-Matt
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#2 (permalink) Old 09-30-2009, 05:27 PM
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Hi mxp74,

I am just taking a guess here - but have you checked the fuel pressure regulator? It is located near the fuel rail. It allows fuel to return to the fuel tank when fuel pressure is to high at the fuel rail and maintains the proper fuel pressure going to the injectors.
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#3 (permalink) Old 10-02-2009, 12:54 PM
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The dodge I grew up with to test for faults with these was to put pressure on the rubber hose after the pressure regulator by either fitting some sort of clamp or soft jawed pliers to close it up .

Close the pipe up a bit and get some one to turn the key,if it starts every time it would point to the regulator being at fault.

Most vehicles upon the turn of key to ignition pressurise the fuel rail with the pump heard to buzz and then click off as pressure in the rail is reached,if the regulator is faulty the pump may well just keep running.

Last edited by MADDOUG; 10-02-2009 at 12:57 PM.
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#4 (permalink) Old 12-14-2009, 06:52 PM
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step 1 check cam shaft exhaust and manifold sensors, it is really common with this symptom starting problem, both senors help for fire order to the ECU. how many miles do u have on the car?
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