# 4bar vs 6bar Fuel Filter



## teh1 (Jul 27, 2012)

Hi,

Spec calls for 4bar fuel filter. What are the implications of using a 6.6bar? Both general implications and possibly implications specific to this engine.


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## killerbunny (Jul 10, 2008)

teh1 said:


> Hi,
> 
> Spec calls for 4bar fuel filter. What are the implications of using a 6.6bar? Both general implications and possibly implications specific to this engine.


The filter acts as a fuel pressure regulator, so you would not be running at the correct pressure. I don't think the car would be able to compensate in any way and would be spraying a lot more fuel than requested.


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## teh1 (Jul 27, 2012)

That doesnt sound right at all...

For example, this theoretically is on my car:
http://www.carid.com/2007-volkswagen-jetta-fuel-delivery-parts/item-8829661.html

Any other possible inplications?


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## killerbunny (Jul 10, 2008)

teh1 said:


> That doesnt sound right at all...
> 
> For example, this theoretically is on my car:
> http://www.carid.com/2007-volkswagen-jetta-fuel-delivery-parts/item-8829661.html
> ...


Here:

http://www.ngpracing.com/newstore/f...essure-regulator-vw-mk5-rabbit-jetta-2.5.html

http://www.ngpracing.com/newstore/f...k5-r32-eos-2.0t-audi-tt-mk2-2.0t-a3-2.0t.html

are those the two you are talking about? read the descriptions.

I have never seen that piece in my fuel rail so I am not sure about that. Also when you build a return style fuel system for these cars you have to run a different filter because of the regulator. You then setup a fuel pressure regulator and any excess fuel is returned back to your gas tank/surge tank. We have a returnless system stock, so the order is tank->pump w/filter(sock)->filter w/regulator-> fuel rail-> injectors. The options are to have the filter and regulator separate, or as VW did with our cars combine the two into one unit.


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## teh1 (Jul 27, 2012)

That makes more sense. Thanks!


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## loudgli (Aug 3, 2005)

I accidentally installed a 6.4bar filter in my rabbit a few months ago.

About a week later the fuel pump started squealing. 

Thought the pump was failing. I randomly checked the fuel trims and they were off about 10-12% (rich).

Searched around and found a thread here where the guy installed the wrong filter. 

Then it his me on what I had did.

So yeah.. dont install the wrong filter.


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## teh1 (Jul 27, 2012)

Crazy. I returned my 6.whatever bar filter and got a 4 bar. I installed it and everything is running smoothly. I can't say for certain, but I think the car is a little more responsive. The fuel that came out was pretty black.


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## teh1 (Jul 27, 2012)

Bummer. It ran better for a while, and the main stall I was experiencing was fixed, however now the thing that had happened one time, where the car stalled on start repeatedly, is becoming very frequent.

I purchased a new in-tank fuel pump. It's in the mail. The car is going into the shop tomorrow for a hands-on diagnosis. I am convinced it must be the in-tank fuel pump, but since I need to go on a vacation with the car soon I am taking it into the shop to verify for certain. Either way, the fuel pump gets changed. It's cheap enough.


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## loudgli (Aug 3, 2005)

Sucks these ecus dont measure fuel pressure like the fsi ecus do. 

Sent from HTC M8 while in burnout mode


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## teh1 (Jul 27, 2012)

Yeah. Who the hell designed these things?  Good thing it's my GF's car and my car is a BMW2002!


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## DubAutowerks (Oct 1, 2014)

Fuel pumps are pretty hard to diag unless the shop has an oscilloscope, which can see the wave form. Not sure what problems you had in depth, but the stalling does sound like the pump.

And, the car will attempt to compensate the fueling, but probably can't fully compensate, unless it is tuned for the larger pressure, it isn't going to do anything but run rich. I think you did the right thing by having the shop take a whack at it.


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## teh1 (Jul 27, 2012)

Well. In the end the problem was caused by a leak between throttle body and intake manifold. Massive one, I guess. Causing the MAF to sense that no air was coming in and caused "dead spots" on acceleration, and "stalls" while idling. Crazy! No one guessed it, out of everyone I talked to. One person thought that it might be vacuum system related, but on the other side not the intake.


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