[Vwdiesel] Fuel system check valves

Terry Briggs vbriggs at stny.rr.com
Fri Apr 17 20:00:57 PDT 2009

no worries, I understand all of that, it's the solid stream of bubbles  
I'm dealing with that bugs me right now. Once I get that taken care of,  
I should be set relatively speaking.
On Apr 17, 2009, at 8:02 AM, Patrick Dolan wrote:

> Don't expect to ever eliminate the bubbles in the fuel line.
> ALL liquids at atmospheric pressure contain dissolved air and other  
> gasses.  Just the mere act of moving them through the little fittings  
> in the fuel system is often enough to liberate some (think of taking  
> the cap off of a carbonated soft drink).
> This is an incredibly important thing for any diesel enthusiast to  
> understand.  It is one of the reasons that our engine technology  
> lagged so far behind gassers for a century.  All of that liberated air  
> gets through the pump and enters the lines to the injector, and must  
> be compressed before the injection event can take place - resulting in  
> differences in injection quantity at the cylinder and differences in  
> timing between what the eingine THINKS is happening mechanically and  
> what IS happening in fact.
> Very few systems have ever dealt with this massive variable  
> successfully.  If you look at #3 injector on a VE pump TDI, you will  
> see how VWs suppliers cleverly did so.  The needle lift sensor in that  
> injector tells the computer EXACTLY when that one opens, and adjust  
> the timing for all cylinders to compensate.
> HPCR engines don't have any such concerns because from the time the  
> fuel gets to the high pressure pump, the fuel system pressure stays  
> above miscibility level, so nothing can break the solution.  Result:  
> possibility of exceedingly accurate timing (which today's piezo  
> injectors can utilize).
> Sorry for the lecture, but this is what I do for a living (make  
> equipment that degasses petroleum).
> ----- Original Message -----
> From: Terry Briggs <vbriggs at stny.rr.com>
> Date: Thursday, April 16, 2009 2:27 pm
> Subject: Re: [Vwdiesel] Fuel system check valves
>> I've got line now, I'll spend saturday running lines and see where
>> that
>> gets me. Thanks for the direction and ideas,
>> Terry
>> On Apr 15, 2009, at 5:42 PM, LBaird119 at aol.com wrote:
>>> In a message dated 4/15/2009 3:17:41 PM Central Daylight Time,
>>> vbriggs at stny.rr.com writes:
>>>> I even get air
>>>> bubbles on the filter side of the line when priming things with the
>>>> mity-vac.
>>>   Leaks on both sides of the pump will end up with bubbles on
>> the inlet
>>> side of the pump.  :-P
>>>      Loren
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