# Question on diesel fuel filter change



## bayarea2007 (May 20, 2010)

I have a 2009 335d and plan to replace the fuel filter myself. Anyone has done that? It looks straightforward from what I saw on Youtube. Just have one question: no one on Youtube seems to include the fuel line bleeding step in their procedure. Does the 335d have a self bleeding mechanism after getting the new fuel filter?

Appreciate your input. thx.


----------



## quasimodem (Nov 9, 2011)

bayarea2007 said:


> I have a 2009 335d and plan to replace the fuel filter myself. Anyone has done that? It looks straightforward from what I saw on Youtube. Just have one question: no one on Youtube seems to include the fuel line bleeding step in their procedure. Does the 335d have a self bleeding mechanism after getting the new fuel filter?
> 
> Appreciate your input. thx.


Search the "other" forum. I started a fairly thorough DIY article in the diesel subforum and somebody did post a suggestion to remove the air from the system by finding the leads to the LPFP and hooking up a 12v battery directly to those leads and running the LPFP for a while. Seems like a great idea, just make sure you use the right amps and volts.


----------



## BB_cuda (Nov 8, 2011)

Seems i recall in the the "other forum" that Bav Technique cable and software were used to command the low pressure pump to do the same. I have no direct knowledge though.


----------



## FredoinSF (Nov 29, 2009)

Pardon ignorance, but what is the "other forum"??


----------



## quasimodem (Nov 9, 2011)

FredoinSF said:


> Pardon ignorance, but what is the "other forum"??


e90post .com or bimmerpost .com

There is a diesel subforum.

Take out the space after the "http": http ://www.e90post.com/forums/showthread.php?t=799059

Read the thread to the end because I did nothing to prime the pump while others propose various methods to prime the pump. somebody should suggest to the BMWhat developer a way of using the app to run the LPFP to prime the pump.


----------



## diesel fan123 (Nov 25, 2011)

I did this, worked great on my 2010:

Venting fuel system:

Turn on ignition and leave on for approx. 1 minute. In this
period of time, the fuel pre-supply pump is activated and the
fuel line to the H.P. pump vented.

use the "start/stop" button, but NOT starting the car (key in, do not press on the brake pedal, and then hit the button). Might take several iterations of either step to pump enough fuel.


----------



## quasimodem (Nov 9, 2011)

diesel fan123 said:


> I did this, worked great on my 2010:
> 
> Venting fuel system:
> 
> ...


So did it start right up immediately the first time you tried to start it after you did this? Or did it have to turn over a few times?


----------



## bayarea2007 (May 20, 2010)

thanks guys. 

I did talk to one mechanic about it. He did mention it's very important to keep air out of the lines. He actually pre-fills the new filter with diesel fuel before putting it up. I guess it would be messy but that would squeeze most of the air out. 

A related question: what if someone runs out of fuel, how would the diesel engine get fired up now that the fuel line is full of air? I would think BMW wouldn't require a typical stranded motorist to start to mess with the fuel pump in order to clear out air


----------



## quasimodem (Nov 9, 2011)

bayarea2007 said:


> thanks guys.
> 
> I did talk to one mechanic about it. He did mention it's very important to keep air out of the lines. He actually pre-fills the new filter with diesel fuel before putting it up. I guess it would be messy but that would squeeze most of the air out.
> 
> A related question: what if someone runs out of fuel, how would the diesel engine get fired up now that the fuel line is full of air? I would think BMW wouldn't require a typical stranded motorist to start to mess with the fuel pump in order to clear out air


Correct, BMW does not require the stranded motorist to prime the pump after refilling the fuel tank. BMW requires the dealership to which the vehicle was towed to prime the pump before restarting the car. Lesson: dont run out of fuel in a modern diesel. Now, theoretically you could have damaged the pump merely by running out of fuel, not to mention what could be done to it on restart.


----------



## DozerDan (Dec 18, 2013)

diesel fan123 said:


> I did this, worked great on my 2010:
> 
> use the "start/stop" button, but NOT starting the car (key in, do not press on the brake pedal, and then hit the button). Might take several iterations of either step to pump enough fuel.


This is what I did with mine.


----------



## BB_cuda (Nov 8, 2011)

quasimodem said:


> So did it start right up immediately the first time you tried to start it after you did this? Or did it have to turn over a few times?


No one ever answered Quasi's question directly? Yes, it will eventually start but the whole point is to not beat up on high pressure pump. Are you guys saying pushing start without foot on brake pedal makes low pressure pump run and fill line up to high press pump?

An answer of immediate start would imply high press inlet was purged of air (to me anyways).


----------



## FredoinSF (Nov 29, 2009)

quasimodem said:


> e90post .com or bimmerpost .com
> 
> There is a diesel subforum.
> 
> ...


Thank you.


----------



## bayarea2007 (May 20, 2010)

diesel fan123 said:


> I did this, worked great on my 2010:
> 
> Venting fuel system:
> 
> ...


Just want to clarify: when you say "use start/stop button", do you mean "press it once, release, then wait for a minute" or "press and hold for a minute"?
thanks.


----------



## quasimodem (Nov 9, 2011)

bayarea2007 said:


> Just want to clarify: when you say "use start/stop button", do you mean "press it once, release, then wait for a minute" or "press and hold for a minute"?
> thanks.


I dont think he means to press and hold for a minute. At least not from the language he used. He probably means just to turn on the car without starting the engine (you do this by inserting the fob and then hitting the start button without touching the brake pedal) and leaving it in that "car on/engine off" mode for a minute. I tried this but didnt hear any results, maybe I should have done it more that once. So after the filter change, it did take about fifteen seconds of turning over for my car to start it, but it has been 30k miles and no HPFP problem yet. Of course, I would like it to start up immediately.


----------



## Hoooper (Jun 17, 2013)

I used the bavtech tool both to flush the filter for a second and to prime the pump. Pretty convenient


----------



## Flyingman (Sep 13, 2009)

I suspect our fuel system is self priming/purging, within reason.

If all you did was replace the fuel filter the rest of the fuel system should still have fuel in it. If the entire system were drained, perhaps you may want to do a full purge and venting.

Most diesel fuel systems have return lines back to the fuel tank, a type of recirculation which helps provide cooling to the fuel injection pumps. The transfer pump (which I beleive is submerged within our fuel tank) provides a constant flow under all conditions, providing some quantity greater than what the car needs for full load condition, the excess is just returned or recirculated back to the fuel tank. The fuel injection pump(s) just takes what it needs from this fuel supply header.

This type of system would generally purge any air without the need to vent, but there could still be a high point that may need venting.

Worth talking to an expert about this if you are really concerned. Clearly running a fuel injection pump without fuel (i.e. with air) could lead to damage.


----------



## d geek (Nov 26, 2008)

Maybe I'm missing something in the explanations above, but I don't see anyone describing purging the new filter of air before reconnecting it to the HPFP feed line. I would not introduce a slug of air into a diesel system if I could avoid it. I suggest that before the filter outlet line is disconnected from the old filter you clamp the line close to filter outlet to not allow that one to empty out. This is assuming it is a flexible line. If it is a hard line then you should plug it as soon as it is removed.

After the new fuel filter is connected to the supply line from the low pressure pump in the tank, leave the filter outlet open. Turn ignition on without starting. This will activate the low pressure pump for a period of time. I'm not sure how long so you may need to repeat a few times until you see fuel coming out of the filter. Once the filter is primed this way, reconnect the feed line to the HPFP. This method will minimize the volume of air sent to the HPFP.


----------



## d geek (Nov 26, 2008)

quasimodem said:


> I dont think he means to press and hold for a minute. At least not from the language he used. He probably means just to turn on the car without starting the engine (you do this by inserting the fob and then hitting the start button without touching the brake pedal) and leaving it in that "car on/engine off" mode for a minute.* I tried this but didnt hear any results*, maybe I should have done it more that once. So after the filter change, it did take about fifteen seconds of turning over for my car to start it, but it has been 30k miles and no HPFP problem yet. Of course, I would like it to start up immediately.


The low pressure pump is in the fuel tank. I think it would be difficult to hear it operate.


----------



## Hoooper (Jun 17, 2013)

d geek said:


> Maybe I'm missing something in the explanations above, but I don't see anyone describing purging the new filter of air before reconnecting it to the HPFP feed line. I would not introduce a slug of air into a diesel system if I could avoid it. I suggest that before the filter outlet line is disconnected from the old filter you clamp the line close to filter outlet to not allow that one to empty out. This is assuming it is a flexible line. If it is a hard line then you should plug it as soon as it is removed.
> 
> After the new fuel filter is connected to the supply line from the low pressure pump in the tank, leave the filter outlet open. Turn ignition on without starting. This will activate the low pressure pump for a period of time. I'm not sure how long so you may need to repeat a few times until you see fuel coming out of the filter. Once the filter is primed this way, reconnect the feed line to the HPFP. This method will minimize the volume of air sent to the HPFP.


That is what I did using the bavtech tool. Flushed the filter a small amount, so the filter was full, then primed the system using the tool. I wouldnt expect there was any significant air left at that point

If I remember correctly, its easy to hear when it runs


----------



## d geek (Nov 26, 2008)

Hoooper said:


> That is what I did using the bavtech tool. Flushed the filter a small amount, so the filter was full, then primed the system using the tool. I wouldnt expect there was any significant air left at that point...


OK- I didn't understand that from your previous post.



Hoooper said:


> If I remember correctly, its easy to hear when it runs


From the driver's seat?


----------

