How to replace a starter motor

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Rob Bell
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How to replace a starter motor

Post by Rob Bell » Thu Jun 14, 2012 9:45 pm

I've just had to replace the starter motor in Project Shed - it really was as dead as a dodo... but fortunately proved to be disarmingly straightforward to do - with a couple of caveats - which I'll come to ;)

Tools you'll need:
DSCF0045.JPG
Socket set (specifically 18mm and 15mm sockets, a 18mm ring spanner, 13mm socket, a hammer and a bit of wood, a hole cutter, torque wrench, 19mm socket, a load of extension bars for above mentioned sockets, and a few other sundry items I've no doubt forgotten...

1. First we need to make ourselves a bit of room. The workshop manual says to release the charcoal cannister and the airfilter hose. Probably not entirely necessary, but improves visibility and space in which to work :)
Move charcoal cannister and top half of airfilter box out of the way
Move charcoal cannister and top half of airfilter box out of the way
2. Now raise the LH (nearside) rear and remove the road wheel. Support the car securely. Why do this, I hear you ask. Simple. You'll be undoing the starter retainer bolts from here :) There are two - 15mm head bolt, 18mm non-captive nuts at the other end. You can get a good view of them from the wheel arch (especially if, like me, you've removed the resonance chamber).

First, the lower of the two bolts - it's got the socket on it... but found that there was far too little space to work here doing it that way:
Lower starter retainer bolt
Lower starter retainer bolt
Second, the upper of the two bolts - seen here through a 'spy hole' in the wheel arch panel. Rover appear to have made this hole specially for this job - it's perfectly in line with the upper starter motor bolt :)
Upper starter retaining bolt
Upper starter retaining bolt
Edit (23/7/12): just wanted to add a note here - that hole in the wheel arch is actually one of the mounting holes for the air intake reasonator box on early MGFs like mine - and here, as you can see, I've removed the 'box from the system. If your car has a reasonator box, this route will be blocked off - but you could think of removing this piece of plastic if you've already upgraded your intake system.

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Rob Bell
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Re: How to replace a starter motor

Post by Rob Bell » Thu Jun 14, 2012 9:54 pm

3. Now we need to assemble a very, very long extension (luckily I have two socket sets - I used all the extensions from both to do this - as you'll see in the next photo - tackling the lower of the two starter bolts in this instance):
Long extension to lower mounting bolt
Long extension to lower mounting bolt
Putting the 18mm socket on a bar is enough to fix the nut, and enables the bolt to be undone (easiest if you have a nice long breaker bar)

4. Having removed the lower bolt, we come to the upper bolt. Now, Rover may have been prescient enough to have provided an access hole in the wheel arch to tackle this job, but they clearly don't use DIY tools, as none of the extensions I have with a 1/2" drive will fit through the hole! No problem says I. Enlarge the hole. I used a hole cutting bit on my electric drill. There are many ways to skin a cat: you could use a round file to enlarge the hole...
Enlarge access hole
Enlarge access hole
After doing this of course, you'll want to repaint the area - I used some black hammerite spray paint for this.

5. Now we can pass our stupendously long extension through the hole and onto the upper mounting bolt. The 18mm nut however had too little access for a socket - so a 18mm ring spanner is the best bet.
Long extension to upper bolt
Long extension to upper bolt

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Rob Bell
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Re: How to replace a starter motor

Post by Rob Bell » Thu Jun 14, 2012 10:06 pm

4. Once that bolt's out of the way, you've done the hardest bit! Remove the spade connector from the solenoid and undo the main power cable to the starter by undoing the 13mm terminal nut - keep safe.

5. Chances are the starter won't simply fall off: it'll need a bit of persuasion from the big angry hammer - and I used a bit of scrap wood to transmit the hammer shocks to the starter. A couple of judicious taps, and the starter will fall off. Withdraw and lift away :)
Old starter motor and solenoid assembly
Old starter motor and solenoid assembly
The old starter motor and the solenoid looked rather worse for wear with much surface corrosion evident. I couldn't get the motor to come out to play, even after directly attaching a car battery to it using jump cables. T'was dead. :(

6. Fortunately, a replacement arrived thanks to the ebay delivery pixies :D
Replacement starter motor
Replacement starter motor
This looked to be a much more promising substrate than the original - and so it was to prove. Clean up the mounting surface of the engine before fitting the motor...

7. And then the rest, in true Haynes manual tradition, is a reversal of the dis-assembly instructions. Very easy!Refitting took me no more than 5 minutes, honest!

I may strip the motor down to figure out what has gone wrong, but a cursory inspection hasn't revealed anything too obvious...
DSCF0049.JPG
DSCF0050.JPG
So that's it - get everything back together, and hopefully you'll now have a nice, functioning engine starter :thumbsu: Hope this is of help to someone! :)

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Stan_B
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Re: How to replace a starter motor

Post by Stan_B » Fri Jun 15, 2012 8:50 am

Pleased to say I have never had to get up close and personal with the TF starter motor. This looks easier than the MGB where you have to remove the steering column on my MK 1 car with the Bendix. Can you tell with the old one if its the solenoid or the motor? Does the solenoid read 5 or 10 ohms with the multimeter?

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Rob Bell
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Re: How to replace a starter motor

Post by Rob Bell » Fri Jun 15, 2012 10:45 am

I think that both are dead Stan. The engine had stood under a tarp for quite a long time before I had a chance to get the engine into the relative safety of the Shed's engine bay - and over this period, the alternator had seized and cracked (frost damage?), so in a way it is little surprise that the starter motor and solenoid were also worse for wear :( Lesson for the future I guess. :(

Solenoid resistance measurements - do you mean between the two posts Stan (live and the jump cable to starter motor)? Unless receiving a starter signal, the resistance across these is infinite. Well, it is on the solenoid I've got. If you mean between the signal spade connector and the starter motor strap, then I haven't measured that one?

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Stan_B
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Re: How to replace a starter motor

Post by Stan_B » Fri Jun 15, 2012 11:35 am

The light current solenoid terminal must have an earth return. I imagine it takes about 1 A so 12 ohms at 12v and yes until that pulls in the starter circuit is open. You may be lucky and get it going by just cleaning the commutator. I'm amazed that the alternator was killed by frost, or had it got wet first?
Anyway, it can be looked at in the close season and you can enjoy your track car for now.

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Rob Bell
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Re: How to replace a starter motor

Post by Rob Bell » Fri Jun 15, 2012 12:36 pm

Yes, I am pretty sure it must have gotten wet and then frozen Stan. Not good being sat out over winter exposed to the elements :(

I plan to strip down the starter and see why it isn't coming out to play - it actually doesn't look at that bad, and perhaps I could get it reconditioned as a spare :)

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MGTF_avengers
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Re: How to replace a starter motor

Post by MGTF_avengers » Sun Jun 17, 2012 9:28 am

Very nice "How To" rob ;)

Don't have cause to do this......yet.

One thread to bookmark methinks!
Better to ask a silly question than to be a fool who remains in the dark....

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Rob Bell
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Re: How to replace a starter motor

Post by Rob Bell » Mon Jun 18, 2012 11:24 am

Thanks - and hopefully you never will. Apart from sticky solenoids, these starter motor assemblies appear to be very robust and reliable :)

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