I have been observing my starter motor slowly failing over the last 5-6 months. Works great when the engine is cold, but really struggles when the engine is hot. Seems counter-intuitive as a warm engine should be easier to start and with warm oil, be easier to spin.

There are at least 3 reasons a starter motor will turn slowly - failing battery, corrosion/high ohmic loss in the wiring/and gummed up internals. The battery checked out, and I figured I'd look at the wiring when I went in to remove the starter.

On the DB9, after disconnecting the battery, you (of course) have to get the car in the air, remove the right front wheel/fender liner and then remove the lower two heat shields from the cat & header. You also have to remove the two downstream O2 sensors. All of this so you can jam your hand into remove the solenoid and main starter power leads and the two bolts that hold the starter in place. The nuts for the two bolts are captive on a carrier, so you don't need a second wrench. Once you have removed the starter bolts you can drop it down and slide it between the header and the block. Just fits!

I then found a number of videos on the web that show how to take apart a Ford PMGR starter (Permanent Magnet Gear Reduction). Pretty straightforward to follow the video. Mine didn't need new brushes or bushings, but did need to be cleaned out and regreased the rotors/steel ball (don't lose the ball!) with white lithium grease. There are 4 bolts, two circlips and one half moon holding it together. The circlips have 1mm holes which required me to find a tool with tiny tips. But all in all pretty simple to get it apart, back together and reinstalled.

I also cleaned the leads where they attach to the starter and the combination seems to have cured my lazy starter. Took 3 hours to get it out (so little room...), 2 to rebuild it and a couple of hours to get it back. I used anti seize on the bolts and dieletric grease on the connections. Hopefully it will be easier if I ever need to do it again (meaning, I really hope I got this right!)

Some pictures for the curious.

solenoid and primary shell.

brushes, end cap and one of the 4 gears

The rotor that holds the 4 gears rotating inside the plastic hub. These gears engage the bendix.

Armature and hub that has a gear that engages the flywheel / ring gear. I also polished/cleaned up the armature.

 

Pretty cool, thanks for sharing!

 

Back when I still had my Vantage I had a similar issue which I thought was a problem with the starter. I bought one and was about to replace it when I found a terminal junction where the nut had completely fallen off and the terminals were barely making contact. It's on the passenger side, behind the front wheel arch. You have to remove the aft portion of the RH inner fender liner to see the stud. I don't know if the DB9 has the same stud but if it does, make sure you check it.

Replacing a $4 nut saved me a LOT of time and hassle replacing a starter that wasn't bad.

 

I love this! Another example of the fact that these cars are just ... cars! Not some fancy mystical object that needs to be taken to fancy mystical wizards at exclusive Aston Martin dealerships where you pay eye watering prices for the privilege of them sprinkling holy dust on your car!

Thanks for posting and congratulations on the repair!

 

Bumping this up and adding an addendum to my starter motor rebuild saga...

The problem returned so I decided to take it out and send it off to a pro... While disconnecting the ground strap I decided to check the positive lead to the quick disconnect (impossibly, I thought it had moved). Sure enough one of the nuts was loose, and the contacts all corroded. I cleaned it all up, torqued it down and covered it in silicone. The starter is getting what it needed and now spins well. I had cleaned up the contacts at the starter and in the wheel well but failed to check the ones at the disconnect. At least I figured it out BEFORE I removed the starter!

 

Happy to help. Loose lugs and nuts can cause a lot of weird problems, and can also cause your battery to not charge properly. So if anyone else is having this starter issue, or a battery problem, make sure you physically follow the power and ground wires everywhere you can and check for disconnects and terminals that aren't obvious. They might not even be on the wiring diagrams.

 

That’s a project right there..hope I don’t have to get into it..but thanks for posting..

 

Nice job

 

can you elaborate on where is quick disconnect and nut you are talking about is located.


My 2009 DB9 with 62000 miles is having some issue and I also think its weak starter

sometimes car won't start even after it has been on battery tender and had 80-100 % juice plus battery was recently replaced but then if I connect Nocco jumper it will start and sometimes it will start without any problem.

thx

 

after you pull the aluminum lid off the battery, immediately behind the battery is a disconnect switch. I traced the positive lead from the battery to that disconnect switch and discovered one of the two nuts (one pre-disconnect switch, one after) was loose.

I then disconnected the ground lead (for safety) and cleaned up both nuts/washers/metal and reconnected. There is also a connection near the firewall aft of the right front tire. I had previously cleaned it and the lead on the starter.

 

thx will try over the weekend