2003 E53 3.0d M57 crancking but not starting issue
 

I have been having trouble starting my car, its cranking but not starting up.

I was told it could be a faulty fuel pressure sensor, so i changed it with no result.
The battery is fine, fuel pump is working, I have changed the fuel pump relay. Also all the fuses are fine, I have changed the fuel pressure sensor as well.
After all this the car is still not starting

Now I have no idea what else to do.
I am open for suggestions

The obvious question what trouble codes it showing with diagnostics? If it's a pure rail pressure problem you can start it with help of some brake cleaner or easy start into intake manifold while cranking.

Can you explain to me how can I use break cleaner and what do you mean by
easy start into intake manifold while cranking?

Brake cleaner or easy start will work as burning accelerant. Remove boost hose going to intake manifold (EGR valve) and spray in the intake manifold. This works if for example a leaky injector causes too low rail pressure on start up.

How much of brake cleaner should I spray?
Do I need to spray before I start the car or while I am staring it?

2003 E53 3.0d M57 crancking but not starting issue
 

A puddle of laquer thinner in the intake will run an engine for 20-30 seconds.

Common method to determine if fault is in the fuel supply.

The thinner evaporates over time to be perfectly explosive in the cylinder

It's the same concept as the brake cleaner but one person job and lasts a while

Oops just noticed diesel engine. I don't know if you can use flammable vapor trick


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Works better if you can do it while another person is starting but can work if you spray for a few seconds just before you crank.

I guess evaporating thinner would work the same like andrewwynn suggested.

You aren't going to get very far with this unless you scan it for codes etc. - you are flying blind. :dunno:

What was the basis for the mechanic telling you it was a fuel pressure sensor? Just a wild guess on his part?

And please don't start multiple threads for the same issue - it gets hard to keep track of what has been tried already. :thumbup:

Here's your earlier thread....

https://xoutpost.com/bmw-sav-forums/...re-sensor.html

They did a diagnostic and fuel pressure was very less in fuel rail, so they assume that it has to be faulty fuel pressure sensor.

Here's the fuel pressure testing instructions for the M57TU - while the details are a little differnt the basic process of elimination may apply to your engine...

https://www.newtis.info/tisv2/a/en/e...ontrol/2wZTOhh

By the way, I'd avoid trying to start the car via some of the methods described above - even if it fires (which I doubt) it's not going to tell you anything useful and it could lead to bigger issues. :yikes:

If pressure tests indicate low fuel rail pressure, you might need to look at the HPFP and the pressure regulating valve on the back of the HPFP.

But as I said earlier, without scanning for error codes you're just going to have to make guesses...

Of course proper diagnostics and monitoring live status values would be the best way proceed. But if you can start the engine simply with some aid of brake cleaner it usually runs normally after it has started. So actually it tells quite a lot meaning a pure rail pressure problem on start up. And in this case most likely caused by leaky injector (measure injector leak off) or failed o-ring on rail pressure regulating valve (at the rear of HP pump).