The Triumph Dolomite Club - Discussion Forum

As Jonners says, I think Tony is being more of a salesman than an auto electrician here. The addition of a relay will only stop a problem occurring in the first place, not make an existing one go away. If it turns out to be the ignition switch, I'll eat my chocolate hobnobs!

On my 1850 their is a heat shield that clips on to the solenoid. I suspect it is indeed the heat from the proximity of the exhaust manifold causing short lived starters. I believe the heat shield part on mine is standard fit but probably many have been lost through the years.

I'm pretty sure that the heatsheld was only fitted to later cars ( possibly when reports of failure started to arrive?).

Just to add a quick update, today I received a relay from Tony (MIGwelder) which I fitted to the car and it started 6 times in a row with no troubles, which is basically unheard of!

It's definitely starter motor/solenoid based, as I was already hitting it with a hammer to get it running. Sometimes if I left the solenoid engaged too long when it was 'clicking', the clicking would stop after that when I turned the key, no starting at all, until a good tap from a hammer.

My car has one of those later type heat shields, but they aren't very substantial in my eyes.. Maybe they absorb more heat than I realise, but I wouldn't be surprised if the exhaust was the cause of the problem.

Plan is to see how she starts over the next few days, wait for the 'new' starter to arrive and maybe swap it in, and then improve the heat shielding as a long term fix. If I get the old starter off I'll take it to bits and look at the bushes.

That'll be the brushes you mean....carbon brushes....

I suspect your starter switch is on the cusp and saved by the relay....

I'll do this relay thing next time mine does it...

Jonners

no no, definitely bushes here is a picture of the inside of my starter motor hope it helps

Galileo wrote:As Jonners says, I think Tony is being more of a salesman than an auto electrician here. The addition of a relay will only stop a problem occurring in the first place, not make an existing one go away. If it turns out to be the ignition switch, I'll eat my chocolate hobnobs!

Oooooh !! Goody ! A challenge ! I like that.
I've found a source of cost-concious high current well specified relays now so I'll see what I can get made up.
I hope you like chocolate Hob-nobs.
And of course in keeping with the B/B's policy of not advertising, other equally excellent chocolate covered snacks are available.
T.M.

Jon Tilson wrote:That'll be the brushes you mean....carbon brushes....

I suspect your starter switch is on the cusp and saved by the relay....

I'll do this relay thing next time mine does it...

Jonners

Ooooh ! Ooooh! Ooooh . Jon me 'ole mate !
The starter brushes are copper aren't they ? Much lower resistance.

Copper Beech perhaps for the previous reply ?
T.M.

MIG Wielder wrote:

Galileo wrote:As Jonners says, I think Tony is being more of a salesman than an auto electrician here. The addition of a relay will only stop a problem occurring in the first place, not make an existing one go away. If it turns out to be the ignition switch, I'll eat my chocolate hobnobs!

Oooooh !! Goody ! A challenge ! I like that.
I've found a source of cost-concious high current well specified relays now so I'll see what I can get made up.
I hope you like chocolate Hob-nobs.
And of course in keeping with the B/B's policy of not advertising, other equally excellent chocolate covered snacks are available.
T.M.

I like chocolate flour, fat and sugar based delights as much as I like physics! If the contacts have eroded due to previous high currents and wear developing into a smaller contact area (or heavy oxidation, copper oxide is not conductive) means a high resistance which in turn leads to a lower current being delivered to the solenoid. Enter into that equation a relay that requires far less current to operate, then what you have done is buy yourself more time for the existing switch, not eradicated the issue.

I stand by what I said, a faulty switch is still a faulty switch, give a person with a gammy leg a crutch and they can walk again, doesn't fix the issue with the gammy leg though!

OK, I am still confused (the British bake off didn't help).

As I understand it a solenoid is just a relay but it still takes takes quite a lot of current. The stock answer seems to be to use another relay to activate that relay.

However my problem seems to be tied in with heat so would replacing it with an old style remote solenoid in help?
e.g.
http://www.ebay.co.uk/itm/12v-universal ... Sw5ZBWJgvk

A solenoid isn't a relay, what it does is move the starter gear into mesh with the starter ring on the flywheel, it has a secondary function in that it then also energises the starter at the end of it's travel. This gives a more refined start, and is less damaging to the ring gear on larger engines that need more torque to turn over than the simpler bendix style that work on the principle of centrifugal force to fling the gear along a concentric groove to mesh with the starter ring.

If you see the teardown video I posted way up this thread, that might be clearer.

A solenoid isn't a relay, what it does is move the starter gear into mesh with the starter ring on the flywheel

I really should have realised that. Now it's a lot clearer.

I wonder if the heat makes it harder to move?

Hi Alan,
[quote=]I wonder if the heat makes it harder to move?[/quote]

From my comment back on page 1 I reckon the temperature coefficient of the copper wire in the solenoid is the most relevant item.
References :
http://www.cirris.com/learning-center/g ... -of-copper
Dolomite Sprint w/s manual
The temperature coefficient of resistance of copper wire is +0.393 % / deg C
Solenoid pull-in coil resistance is 0.25 ohms.
Holding coil resistance is 0.76 ohms in round numbers.

Now for some maths.
With our near perfect wiring we will see a current at 12V of 12V / 0.187 ohms ( 0.25 // 0.76 ohms) = 64.1A
Now the starter motor is bolted to the cylinder block so lets assume it runs at about 80 deg C when hot.
Assume ambient temp is 15 deg C.
So the resistance rises to 0.234 ohms.
So the current is now 12/ 0.234 ohms = 51.2 A
Supposing we have our poor wiring / switch etc; and the loop resistance down to the starter is 0.1 ohms.
So our initial current is 12V / 0.287 ohms = 41.8 amps.

So getting a bit marginal already.
But let the temperature rise to 80 deg C and the current drops to
12V / 0.334 ohms = 35.9A . About 56% of ideal.
So I'm not surprised that some starters fail to operate when hot.
HTH,
Tony.

I had exactly the same issue with starting my 1850HL. I could hear the solenoid clicking in but the starter did not turn. Often it would take around 20 attempts of flicking the key into the start position before the starter eventually turned.

Tony (MIG) sent me a relay and wiring which has been fitted for almost a year now and the starter has worked perfectly every time. Absolutely no more problems with starting due to electrical problems. I also wrapped the manifold in titanium heat wrap similar to this: http://www.ebay.co.uk/itm/High-Quality- ... Swqu9VUcuW It makes a massive difference to under bonnet temperatures.

Hi all,

Had the same problem with my 1850HL, would start sometimes and others not, always a clicking solenoid, but no action from the starter! Bloody annoying and hitting the starter sometimes brought some life.. turned out it was a high resistance connection on the main battery cable at the crimped connection to the motor itself.

I ordered a new main cable through auto sparks and bingo problem solved!

hope this helps

Cheers

Iain