Fuel filler door aka gas cap spring modification

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Introduction

This mod lets you open the fuel filler door open further.  It should work on all VW TDI up to 2010-2011 when they changed to the "press in and release" door.

The VW mk4 fuel filler door only pops open 1cm when you press the button to open the "gas cap" door.  This makes it harder to open and could cause fingernail scratches on the paint.  Fingernail scratches are also common on the cabin door handle, ashtray, or radio knobs.  While removing the fuel vent (only for diesel cars, NOT for gas cars, do not attempt to remove the fuel vent on a gas car!) I modified the spring so that the door pops open 2-3 inches.

There are 2 springs on the door.  Under the solenoid shaft (when you press the fuel door release button this retracts) there's a spring that pushes the door open.  The other spring holds the door full open but creates resistance to opening the door even a little.  By bending the "push open" spring to increase its force and the "hold open" spring to reduce its force, the door opens much more when you press the button but still holds in the full open position when you open it all the way.  If you don't care that the door snaps to the full open position then remove the "hold open" spring and see how you like it.

Procedure to mod the door

Remove the fuel filler door assembly, 1x T20 torx screw.  Put a clean paper towel in the filler neck so that dirt on the back of the assembly doesn't fall into the fuel tank.  Then pivot the black assembly out and to the right - then pull it a little to the left to clear the right side hinge.  This will let you remove the fuel door assembly from the car.

Remove the latch strike to increase the force of the "push open" spring by bending it out.  Use a thin pry and push the spring in before pulling it out to release the middle piece of the spring.

The "hold open" spring is behind the hinge of the filler door assembly.  Remove the door by prying the plastic door pivot out.  Don't try to pry the spring out first because you might break the plastic door.  The spring is shaped like a S.  If you hold it to the side it looks like a N or 2!  If you don't care that the door stays full open then remove the spring, reassemble, and see how you like it.

If you want the door to stay open, flatten the spring to reduce its force and replace.  Use a screwdriver to push it onto the rib perches during installation.  However, the "hold open" spring still prevented the filler door from opening much so I flattened it more.  Unfortunately, not enough pressure caused it to pop off its perch and not function.  To solve this, I used a dremel to cut a groove in the 3 ribs that are the spring's perch.  Without the grooves, the spring would click and pop off the perch when the door was closed.  With the grooves, the spring was held securely.

Also make sure that the spring is bent so that it makes contact with all 3 rib spring perches.  If it's at an angle the spring isn't seated on all the perches and it encourages the spring to pop off.

A dremel cutting disk with an extension through the latch hole of the assembly cut the grooves at the correct angle.  

Here is a side view.  By cutting a groove in the rib, it holds the spring and prevents it from popping out because of less spring pressure.

Final result - much easier to open the door!

Find many more useful DIY Maintenance and modification tips for your VW Jetta TDI, Golf TDI, or Passat by searching below.  Feel free to post in the TDI discussion forums if you liked this article!