Well, this question comes up quite often:

Q: my starter makes a single click noise, but doesn't turn the engine over. My battery voltage is over 12.5v
A: If your battery is good, then your starter contacts are likely worn out.

Q: How do I change the contacts?
A: It's pretty simple to do, the hardest part is taking the starter out. There's many methods to take the starter out. Illustrated here is the "remove exhaust manifold method" where you undo the exhaust manifold, slide it out about an inch, then pull the starter out the back.

First things first. You'll need to access the underside of the car. So you'll need a jack and jackstands.

Before you begin, disconnect the battery negative terminal

Start with removing the 3 nuts holding the exhaust manifold to the front pipe, plus the nut that holds the brace in place. You get one from above, and the other 3 from below, using a 14mm plus long extension.

Use a 24mm socket and large ratchet to remove the EGR pipe "banjo bolt"

Next remove the manifold heat shield to access the manifold nuts and bolts. There are four 10mm nuts to hold the heatshield on. Then there are five 14mm nuts/bolts: 2 nuts, 3 bolts hold the manifold to the head.

Once the manifold nuts are undone, you get to remove or pry back the upper manifold about an inch.

There are two 14mm bolts that hold the starter to the transmission. You can reach them from either above or below. Take those off. Then turn the starter around until you can undo the 12mm nut that holds the fat wire from the battery onto the starter. Also, unplug the little wire from the starter. It may be helpful to remove the oil filter to get more space.

Once those are all undone, you can take the starter out from the backside.

Phew. That was hard work. Take a 5 minute break, and then put your starter into a bench vise, and take the heatshield off (10mm bolt) and remove the other terminal wire (12mm nut)

Remove the endcap from the starter. Most use 8mm bolts, some use 7mm bolts.

After taking off the cap, the plunger comes out, and you expose the contacts themselves.

Take a good look, usually only the one terminal is worn out, and the other might be re-useable. But it's a really good idea to change both.

Carefully remove the starter contacts from the starter. You can hold the inside with a 13mm wrench while you carefully undo the 14mm outside. I use a 3/8" impact wrench, you can use a 14mm wrench or socket, whatever you like.

With the contacts on the table, you can see in the pix what's good and what's not. The dead contact has a deep groove worn into it.

Here's a pic of the plunger before cleaning it up with a wire wheel. And another pic of the contacts themselves. Write down the part number for the contact, as it's a special order item from most dealerships.

Carefully wire wheel the plunger contact to clean it up a bit. Easy does it, no need to be harsh, just a gentle brushing with the wire wheel. Note that there is very little material removed, but all the carbon tracking is gone.

Next, install the new contacts back into the starter. The new, improved, wider "previa" contact replaces the worn out one. Use a 13mm wrench to hold the "bolt-head" in place to keep the contact from twisting. Be sure that the contact sits square in it's spot, without being twisted to one side.

Re-install the fat motor wire to the one starter contact. Be sure all the plastic bits, curved washer, and O-ring are in place.

Put the plunger back in, then the endcap, and the outer cap with three screws. Re-install the heatshield, then it's time to test the starter operation. You'll need an SST which is super easy to make from a couple non-insulated spade terminals and a short bit of wire.

Take your regular jumper cables, and put the positive clamp on the starter terminal, and the negative clamp on the starter frame. Your SST plugs into the small terminal on the starter.

Once you're sure you have the connections right, you can brush the SST against the starter terminal to apply +12V to the small connector on the starter. The starter will lurch (unless it's firmly held in a vise as shown) and the starter gear will spit out about an inch and spin up simultaneously. Keep your fingers clear!

Resting position, no power applied

Starting position, with +12V applied

Once you've tested your starter, carefully disconnect your jumper cables etc, and then put your starter back into the car.

Installation is the reverse of removal procedure