325i misfire on start up

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Bonymaenjack
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Tue May 07, 2019 3:38 pm

My 325i m20 has developed many problems on start up , this is a new one. When starting from cold , I have difficulty starting the car , 10-15 seconds before she'll start reluctantly .If I press the throttle to the floor then turn the key she starts and runs if I start her without touching the throttle she'll start but misfire for an age before clearing .There is a smell of fuel within the engine bay ( no leaks with new fuel pipes fitted ) and I believe she's over fuelling when running . are these linked?
I've tested the fuel pump pressure and the injectors have been cleaned with 4 thousand miles added
Thanks in advance
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Brianmoooore
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Tue May 07, 2019 5:37 pm

The poor starting from cold, poor running for a while after it starts, but starting and running better with the throttle wide open are classic symptoms of fuel pooling somewhere in the inlet plenum while the car is parked.
As a test, instead of stopping the car with the key, pull out fuse 11 (fuel pump), while the engine is running. After several seconds the engine will stall, when you can turn off the key and replace the fuse.
The next time you start it from cold, it will be slow to start, because it has to build up fuel pressure, but when it does, it will run normally, if the problem is as above.
Fuel can enter the plenum when parked via one or more leaking injectors, or, rarely, via the small pipe that connects to the fuel pressure regulator.
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Bonymaenjack
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Thu May 09, 2019 9:03 am

Brianmoooore wrote:
Tue May 07, 2019 5:37 pm
The poor starting from cold, poor running for a while after it starts, but starting and running better with the throttle wide open are classic symptoms of fuel pooling somewhere in the inlet plenum while the car is parked.
As a test, instead of stopping the car with the key, pull out fuse 11 (fuel pump), while the engine is running. After several seconds the engine will stall, when you can turn off the key and replace the fuse.
The next time you start it from cold, it will be slow to start, because it has to build up fuel pressure, but when it does, it will run normally, if the problem is as above.
Fuel can enter the plenum when parked via one or more leaking injectors, or, rarely, via the small pipe that connects to the fuel pressure regulator.
Thanks Brian,
Once established that is indeed the problem ,what injector upgrade would be suitable for a stock engine? The injectors have been refurbished and I'm reluctant to purchase another set and have those refurbished only to have a similar problem. There are plenty advertised but would they be suitable as the operating pressure quoted varies
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