how to wire new type of starter motor

[Dion]

Had a nasty experience a few weeks ago.

Turned the key, and after a few tries (the "click" was there but no turning) the engine turned and sprang into live. But the starter motor did not disengage! Luckily the engine switched off but the starter motor continued. Turning of the key did not have any effect, so I popped the bonnet, grabbed a spanner and removed a battery post clamp.

The starter motor had become worse during the last weeks: slow cranking speed, increasing number of clicks but no cranking.

So I decided on a new starter motor, the new lightweight type. Comparing costs was interesting (all including P&P): local suppliers (I'm in Holland) were around 350 euros, UK suppliers from 270 - 300 euros, and an USA supplier could do it for 170 euros! The last one was ordered (a TR6 starter motor) and arrived two weeks later - the journey from USA - Holland took 5 days, customs Holland needed another 8 days.... and charged 22 euros VAT.

Yesterday evening I removed the old starter motor - the top nut was very difficult to access. Comparing the two starters: old 7,5 kilos, new 3 kilos. Old is about 1,5 times as long and thick.

Now the nasty bit. The new starter motor only has two electrical connections: one for the big brown wires, and one for the ignition wire. The old one has three connections, one extra which feeds the ballast-resisted coil and distributor.

I can understand the reason for the extra connection: when starting this wire bypasses the ballast resistor so the coil gets a full 12V instead of the 6V. But why is this on a extra connector? Surely only current will flow to the coil this way when the starter motor is engaged via the ignition key.

So I thought I could use the connection for the ignition wire for the coil wire too.

Now the engine will not start. The cranking speed has improved quite dramatically, and the engine is on the verge of starting but just does not do that.

Any ideas? What should I do with the starter motor coil wire? Does the old starter motor has an extra internal switch? For what reason?


Dion

[AlanChatterton]

You're so nearly there yourself!

There are 2 types of ignition system. 12v and 6v. (can't remember which car has which, anyone else?)

Basically, the starter motor you have is from a 12v system.

You car is a 6v system. Normally, once the engine is running, the coil only uses 6v to supply the sparks. But, on cranking, the extra wire gives 12v to the coil to help give the ignition system a big boost to get it started.

Without this 12v boost, the car will not start. Especially from cold.

Options. You could rig up some kind of feed to the coil to give you 12v, but you need to change this 6v as soon as the car starts otherwise you will burn out the coil/points.

The best option is to get another starter motor with the correct 3 connections on.

Hope this helps.

[Deleted User]

Dion

In the destructions that came with the new motor should have been a wiring diagram I think there is a link you put on for cars with  that had wiring for seperate solenoid it might be you need to put this link on to get 12v on you coil in the cranking position

What you could do is run a wire (are you MK1 or MK2) from the ignition switch terminal that  supplies power to the starter  in the cranking position to the coil -this is what I did on the Shed as it was a MK1 with old style starter (no pre-engage and intergral solenoid) that I converted to new stlye pre- engage intergral solenoid

Have you a multimeter you could measure 12v at the coil as you crank her -this would find the fault

[Deleted User]

To get 6v across you coil you need a ballast resistor as the coil is or should be 1.5 ohm you need a ballast of 1.5 ohm-non ballast coils are 3 ohm

Put the two in series- as the  max potentail  is 12v and the two resitances are 1.5 ohm 6 v will be dropped across each resistor

ie R=R1+R2  (3= 1.5+1.5)

Vmax=(V1+V2)    12=(6+6)

So total resistance of the circiut is 3 ohms total voltage is 12v
You have two resitors of equal value in series so
V1 = Vmax/2

V1 = 6V

[AlanChatterton]

Quote:

ie R=R1+R2  (3= 1.5+1.5)

Vmax=(V1+V2)    12=(6+6)

So total resistance of the circiut is 3 ohms total voltage is 12v
You have two resitors of equal value in series so
V1 = Vmax/2

V1 = 6V

..............he says, (laughing in a mad-proffessor type way)
;D

[Dion]

[quote by=AlanChatterton link=Blah.pl?b=2000,m=1158931211,s=1 date=1158932933]But, on cranking, the extra wire gives 12v to the coil to help give the ignition system a big boost to get it started.

Without this 12v boost, the car will not start. Especially from cold.
[/quote]

Agreed. The question really is why this wire to the coil does have a separate connection on the old starter motor. Current will only flow when the starter is cranking. The same applies to the ignition wire: current will only flow when cranking. So why is one connection on the starter motor, where current flows whens starting, not enough? Why the extra connection?

Confusing!

BTW: the cars is a 1975 2500 TC with ballast resistor.

[Dion]

[quote by=ajp25tc link=Blah.pl?b=2000,m=1158931211,s=2 date=1158933252]
What you could do is run a wire (are you MK1 or MK2) from the ignition switch terminal that  supplies power to the starter  in the cranking position to the coil[/quote]

Yes - but it is a lot easier to do that on the other end of the wire that brings current from the ignition switch to the starter motor - at the starter motor!
So I connected the ignition wire and the coil wire.  To no avail.

Maybe, when the starter motor went on and on, possibly the solenoid jammed?, 12V was put to the coil for a too long period of time - destroying the coil?
Could be the reason why the engine will not start.

[Richard B]

Could be time to go back to basics; have you got voltage to the coil? Checked the points & condenser? Spark at spark plugs? Rotor arm , cap & leads ok?

Ps Canleys sell a kit to convert your own Nippon Denzo starter motor.

[Deleted User]

Sounds to me also you need to check the basics are there-tell you what? get a helper to crank the car over and you hold a bit of wire striaght from the battery to the ciol and see if it fires if not  go back to basics as Richard B suggests?

[Deleted User]

I remember a mate spending a whole day trying to fire his mini up after doing a few jobs on it..he wasted about 5 hrs before he noticed the rotor arm sitting on the roof!

[AlanChatterton]

Quote:

he wasted about 5 hrs before he noticed the rotor arm sitting on the roof!

;D ;D

...............been there, done that!

[Greeks]

yeah, I spent a little time at the side of the M25 at silly-o'clock in the morning  panicking trying to get a GT6 to re-start to make it to a rally on time ... turned out it was a rotor arm  ;D

[juppy]

The solution is simple, the first thing to do is to  not connect the coil feed wire and try to start the car. You should find that the extra speed of the starter more than makes up for the "overdriven" coil in a balasted system. If this works then leave it as it is. If you find the engine fires when it is turning over but stops as soon as you release the key to the run position, then you need to feed the coil 12V via a relay. What you CAN'T do is to conect this coil feed to the second smaller terminal on the new starter. the reason for this, is that while the starter is spinning you get 12V to the coil, but as soon as you turn the key back  to the run position, what you are effectivly doing is grounding the coil through the solenoid windings. This drags the voltage down to a fcouple of volts which is not enough to get the coil to produce a spark.
The difference between the old and new starter is internal, the original Lucas type has seperate contacts inside which keep the solenoid coils separate from the 12V supply to the coil.

I hope this makes some sort of sense!!

[Crockett]

[quote by=juppy link=Blah.pl?b=2000,m=1158931211,s=12 date=1159189346]...feed the coil 12V via a relay. What you CAN'T do is to conect this coil feed to the second smaller terminal on the new starter. the reason for this, is that while the starter is spinning you get 12V to the coil, but as soon as you turn the key back  to the run position, what you are effectivly doing is grounding the coil through the solenoid windings.[/quote]

I agree. Fitting a relay into the cicuit (to be pulled in via the starter solenoid signal) to then supply +12v to the coil (thus bypassing the ballast resistor) seems like the way to go to me and relays are cheap enough.

[Deleted User]

[quote by=Greeks link=Blah.pl?b=2000,m=1158931211,s=11 date=1159048169]yeah, I spent a little time at the side of the M25 at silly-o'clock in the morning  panicking trying to get a GT6 to re-start to make it to a rally on time ... turned out it was a rotor arm  ;D [/quote]

It was a new one! had only been a few miles and failed! we got there in time!

[Deleted User]

[quote by=dd829 link=Blah.pl?b=2000,m=1158931211,s=13 date=1159219080]

I agree. Fitting a relay into the cicuit (to be pulled in via the starter solenoid signal) to then supply +12v to the coil (thus bypassing the ballast resistor) seems like the way to go to me and relays are cheap enough.[/quote]

Makes sense

[Deleted User]

Had a look at the wiring for the Taxi which has a high torque starter from chris witor-must admit I didnt bother with the 12v "boost start" she fires up fine

[Dion]

Well, all is fine now.
The wire to the coil is left hanging loose. She fires up great, no problems.
Where is the ballast resistor located? I cannot find it at the first (or second) glimpse.

About the new starter motor: the starter noise is very different now, like an american car. Spinning a bit faster too.
I needed about 5 mm extra clearance  - it sat too close to the starter ring - which gave an awful noise grinding the new teeth from the startermotor.....

Job's a good 'un, as you all say.

[Glenn]

On your age of car it's the wire itself that gives the resistance.  If you fit a 12v coil you would need to do away with the wire and run a new one altogether.

The pre-facelift Mk 2 cars had an actual resistor which was bolted to the block via the coil bracket, facelift use a ballast resistor wire.  Don't know about Mk 1.

[Dion]

Update.
Although starting on 6V was fine when everything was top, it became worse when the time went by. Tappet adjustment needed, weather becoming colder, etc did not help starting.
So my brother came up with an idea to re-attach the lose wire and insert a diode in between. This diode directs the current one way only, so coil cannot ground via this wire.
This did the trick. Immediate starting, even on LPG, even on frosty mornings.
So at last the new modern type starter motor is much recommended.
I will post a wiring diagram.