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George
George, BMW Technician
Category: BMW
Satisfied Customers: 1861
Experience:  BMW Master Technician over 20 years BMW Dealership Experience. BMW Auto Repair Shop Business Owner
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2004 Bmw 745li: It hesitates when starting...engine turns

Resolved Question:

I have a 2004 Bmw 745li. It hesitates when starting. The engine turns over fine but doesnt' seem to fire up. It will take about 5 to 8 seconds before it starts. It usually happens when vehicle has sat for more than 2 hours.
Submitted: 5 years ago.
Category: BMW
Expert:  George replied 5 years ago.

George :

You will need to have performed what is called a fuel pressure bleed down test.

George :

Once the vehicle is shut down there is a check valve in the fuel system that prevents the fuel in the lines from draining back into the fuel tank.

George :

If this check valve is sticking or not seating properly it will allow all of the fuel in the fuel lines to drain back into the tank, which normally happens after sitting for some period of time.

Customer:

How is that bleed test performed?

George :

If this happens now instead of fuel being readily available at the fuel injectors when going to start the vehicle, the fuel pump has to re-fill all of the fuel lines with fuel again which normally takes about 5 - 8 seconds or so.

George :

The fuel pressure bleed down test measures the fuel pressure that is in the fuel lines when the engine is shut down, and it can be monitiored to see if the fuel pressure drops over a certain period of time to determine if the fuel lines are draining the fuel back into the tank, or if there is a possible leak some where in the fuel system.

George :

A fuel pressure gauge is hooked up to the fuel rail pressure testing port.

Customer:

is there an image of that test port that I can view?

George :

Give me one moment to see if I have a picture.

Customer:

k

George :

I do have pictures that I can supply you with, but since your original question was answered you would need to accept, and then I am always more then happy to answer any follow up questions you may have and supply additional information.

Customer:

back to the original answer. I was also told that it could possibly be the fuel pressure regulator. Does it make sense that the fuel regulator could also be the problem?

George :

It is not likely, but when performing the fuel pressure test and bleeddown test this will be obvious to tell if it is no good.

Customer:

if the fuel pressue test fails, what would be the part to be replaced?

George :

Sorry for the delay I lost my internet connection.

George :

You would be replacing the fuel pump.

Customer:

If I have a pressure problem, it wouldn't be the fuel pressure regulator, it would be the fuel pump?

George :

It would be the fuel pump if it is a fuel pressure bleed down issue, which would be the normal cause of such problems of a long cranking time after sitting for sometime.

Customer:

still researching?

George :

I don't understand what you mean by still researching.

Customer:

it said on "help" that if you're offline you could be researching...that's all i meant

Customer:

i hadn't seen your last answer...sorry.

Customer:

so the check valve located in the fuel pump?

Customer:

are you still helping me?

George :

Yes the check valve is part of the fuel pump as I stated before.

George and 3 other BMW Specialists are ready to help you
Expert:  George replied 5 years ago.

Thank you very much,

George

Customer: replied 5 years ago.
Can you send me that image where the fuel pressure bleed down test would be performed. thank you
Expert:  George replied 5 years ago.

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Expert:  George replied 5 years ago.

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