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Juan Crespo
Juan Crespo, Tech Trainer
Category: BMW
Satisfied Customers: 1497
Experience:  A.S.E. Master Technician, Advanced Level, Emissions - Asian, Domestic, & European
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Having a crank while starting issue on a 2004 BMW 745Li,

Customer Question

Having a long crank while starting issue on a 2004 BMW 745Li
JA: Will the headlights turn on? Is the battery fully charged?
Customer: Lights are on, battery is brand new, fuel pressure is at 0psi at initial startup, goes to 50psi and engine runs, however, when shutting off the vehicle, fuel pressure drops to 0psi, replaced fuel filter with integrated pressure regulator, replaced fuel pump assembly with OEM pump as well
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: Yes, fixing it myself
JA: Anything else you think the mechanic should know?
Customer: I work at an automotive repair shop, we replaced the valve cover gaskets, intake manifold gaskets, coolant tube under intake, front timing cover seals, and long start issue started after we completed work, having a hard time figuring out what is going on
JA: OK. To minimize me, please click the down arrow at the top right corner of this box.
Customer: How can we get a hold of the mechanic and how does the process work?
Submitted: 1 month ago.
Category: BMW
Expert:  Chad Farhat replied 1 month ago.

Hi, I'm Chad. Welcome to JustAnswer. I'm reviewing your question and I will be posting your reply ASAP.

Customer: replied 1 month ago.
Hi Chad! Thank you very much! :)
Expert:  Chad Farhat replied 1 month ago.

hey man ,how are you

did you scan it & retrieved any fault codes ?

have you checked your crankshaft position sensor ?

Installation location: CKP sensor , On transmission housing at bottom right.

Please let me know

Thank You

Chad Farhat

ASE Certified Technician

Customer: replied 1 month ago.
There was a fault code for a camshaft position sensor 2, how can we check the crank position sensor? Can we remove it and check resistence?
Expert:  Chad Farhat replied 1 month ago.

yes exactly , check resistance , i sent you the location .

also check wiring , for being pinched or routed wrong , and check for power and ground on it

Customer: replied 1 month ago.
Removed belly pan, found the ckp, there are 3 pins, which pins do you want me to check resistance on?
Expert:  Chad Farhat replied 1 month ago.

the outer 2 pins

Customer: replied 1 month ago.
Outer pins measure 12.65 M ohms
Expert:  Chad Farhat replied 1 month ago.

It should be 540 ohms -+ 10% ohms at 80 degrees F.

so 12.65 M ohms is way to much , I say change it

Customer: replied 1 month ago.
Awesome!! :) I will order the part and change it Monday!! Thank you!! Will update you!!
Expert:  Chad Farhat replied 1 month ago.

ok sounds good let me know , if does not work we can continue :)

A Positive Rating is Much Appreciated

This Post Will Stay Open for You To Come back and Ask me Any Follow Up Question You May have on this issue , Even After You Rate me

Thank You

Chad Farhat
ASE Certified Tedchnician

Customer: replied 1 month ago.
Perfect! Thank you!! :)
Expert:  Chad Farhat replied 1 month ago.
You welcome
Customer: replied 1 month ago.
Hey Chad! Received the new CKP sensor, however new sensor resistance reading is 12.35M ohms as well, the vehicle still has long cranks before starting, should we check resistance on the cam sensors? :)
Expert:  Chad Farhat replied 1 month ago.

yes lets do that please

Customer: replied 1 month ago.
What is the resistance specification for the camshaft sensor?
Expert:  Chad Farhat replied 1 month ago.

1800 ohm on the cam sensor for 04 bmw 745li

Expert:  Chad Farhat replied 1 month ago.
Cam sensor
Customer: replied 1 month ago.
Test the outer pins? Or which pins?! :)
Customer: replied 1 month ago.
Resistance seems to be consistant on Cam sensors all at 1.6ohms! do you know if fuel pressure should drop after engine shuts off?
Expert:  Chad Farhat replied 1 month ago.

the fuel pressure should not drop after you shut off, supposed to hols fuel pressure

if you did key off to key on pump will come on for fews secs and pressure should hold

if the pressure dropping we could have a defective pump that is leaking back in the tank and holding pressure at the rail

there is air bag module passenger side frame rail between the door, where the seat belt tensioner is .


Customer: replied 1 month ago.
I replaced the fuel pump with genuine BMW part a week prior, is there any way to test the fuel pump module? :)
Expert:  Chad Farhat replied 1 month ago.
With a scanner ,or there is fuel pressure port at the rail.
Or power straight to it
But like I mentioned if that srs module went bad ,it will not allow to comes on ,under seatbelt tensioner in the frame body
Customer: replied 1 month ago.
Used a fuel pressure gauge on the rail, engine off, 0 psi, while cranking, goes up to 50 psi, then when engine shuts off, fuel pressure quickly drops to 0psi! What do you think that could be?! Or what should we check next?
Expert:  Chad Farhat replied 1 month ago.
That side srs airbag module needs checking .that module is fuel pump control
Customer: replied 1 month ago.
How do we check the srs airbag module?
Expert:  Chad Farhat replied 1 month ago.

I dont mind helping you but you have not rated me yet and have asked more than one question , that is one question, one answer site and we are way beyond that.

Customer: replied 1 month ago.
I would be very happy to rate and pay for your time, however we have not gotten close to finding the answer for what is wrong with the vehicle. I feel that I have been making all the suggestions for faulty components, is there a place on this site where I can pay to get closer to resolving this issue promptly? Thank you Chad!
Expert:  Chad Farhat replied 1 month ago.
You welcome man ,I will open up the question for another expert for you so they can give it a shot
Good luck to you
Expert:  Juan Crespo replied 1 month ago.

Hi there. Different expert here.

BMW engineers designed the fuel pump circuit in such a way that power to the pump is cut off in the event of a severe collision. Using the logic that airbags should also deploy in that event, they used the satellite airbag module located in the passenger-side B pillar to serve as sort of an inertia switch. Problem is that, those modules tend to fail after a few years and cause power interruptions.

Another known problem is caused by failing fuel pressure regulators not being able to hold the pressure needed to start the engine and thus making the pump work harder - this latter would fit the symptoms you describe. Fuel pressure regulators are part of and built into the fuel filter assembly. Click here to see example from, other brand/sources available.

I hope this helps you solve your issue.

Best Regards.