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The fuel flap lock was fitted to all fortwos from mk4 onwards (year 2000+). Should you notice that your fuel flap doesn't lock or, if you here a loud squeal when you lock the car, then you need to replace the lock motor.

To access the locking system you need to remove the right interior boot trim. In this guide, we remove the whole trim for clarity but you can unclip just the front edge.

If you have the round side pockets, open these first. You will then need to remove the single TX20 screw within. If you have the grey trim with the luggage net, you will see the screw just above the net.

The trim with the side pockets is held in place with a split rivet. You only need to remove this if you want to remove the whole trim. You can leave it in place and reach behind the trim to get to the fuel flap lock. To remove the rivet, carefully pull the trim as shown. The peg in the middle of the rivet should begin to come out. Don't push it in as it will fall inside the tridion and be lost forever!

Remove the rivet as shown.

Now firmly pull the trim. The white cups on the back of the trim will unclip from the yellow pegs. If you have left the split rivet (above) in place, be careful you don't snap the trim!

Now remove the rear light cluster which is held in place with two 10mm plastic hex nuts. Unplug the wiring indicated below (lift the retaining clip first).

The lock motor can be see inside the void.

To remove the motor, remove the two TX25 bolts shown as follows. If you haven't fully removed the interior trim, you will need to use an angled Torx Key.

The lock assembly hooks onto the tridion so you will need to lift it up slightly. It will then be free to remove.

To remove the lock from the back plate, remove the two TX20 bolts as follows:

Now unclip the motor from the lock arm.

Replace the motor and reassemble.

Fit the lock assembly back to the car. Ensure that you feed the lock arm through the hole in the fuel filler neck before securing it in place.

We recommend testing the lock before re-fitting the trim and light cluster.

So why does the motor break?

A common cause of failure is an incorrectly closed fuel flap. In the following picture, the flap hasn't been pushed fully closed.

The lock arm needs to locate with the hole on the back of the flap. If it isn't closed properly, the arm will strike the plastic either side of the hole.

Therefore, always check you fully close the flap to avoid this failure.

We performed a post-mortem on a failed lock. The casing is in two sections and with multiple clips holding it together:

Inside the lock, there is a simple 12V motor which turns a plastic cog and extends the plastic arm (shown coming from the right of the lock):

If the lock arm can't extend (as in the case of a poorly closed fuel flap), the small cog on the motor will strip the teeth on the plastic cog. You can see the damage to the top of the plastic cog here:

Removing the cog from the lock, you can see the damage quite clearly. This is one for the bin!

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