The Triumph Dolomite Club - Discussion Forum

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PostPosted: Thu Aug 15, 2019 4:36 pm 
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Hello all you folk who understand electrickery. My 1850HL has developed a problem with the starter motor. Mostly it works, but sometimes there is just a click from the solenoid and no action from the starter. This can go on for quite a while until suddenly it springs into life.

As I have known this car for a very long time, I know that the starter is original, so thinking that the solenoid must be tired of life, I ordered a replacement starter with solenoid from the excellent bods at the club. What a job to fit it! Getting the top bolt in required lots of ingenuity, but it is in. Guess what? The same thing happens with the new unit.

I have replaced the cable from the key switch to the solenoid in case the old wire had got pinched somewhere, and I have made sure all connections are secure and clean. All I can think of now is that the old key switch can't pass enough current to power the solenoid properly. Is that sensible thinking? If so I can get around that by installing a relay between the switch and the solenoid. Do folk think that will solve the problem?

Mike

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(MGB GTV8, BMW Z3 2.2, and Dolomite 1850HL)


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PostPosted: Thu Aug 15, 2019 4:54 pm 
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Have you checked the battery connections?

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PostPosted: Thu Aug 15, 2019 6:14 pm 
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Have you checked the battery connections?
Good thought Tony, but yes. It was the first thing I did. The battery is brand new and the posts and connectors are clean and tight.

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PostPosted: Thu Aug 15, 2019 6:26 pm 
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A relay can't hurt, for the same reason that you relay headlights, save the car's aged switchgear!

Since you've tried all the usual suspects, i'd be inclined to blame the switch, with a side order of earth strap checking!

It's also possible that the switch is worn where the key barrel goes in, leading to under or over throwing of the switch, try turning the switch very slowly and see what happens when you do.

Steve

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'78 Sprint Auto with Vauxhall Omega 2.2 16v engine EGP 247T (The Dolomega)
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PostPosted: Thu Aug 15, 2019 7:14 pm 
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Maybe you did check already but the connector from the gearbox harness can be corroded sometimes.

Jeroen

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PostPosted: Thu Aug 15, 2019 7:21 pm 
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The earth strapping is fine. I always add an extra one when I rebuild a car, from the bell housing to the body. If the switch wasn't making contact I wouldn't hear the solenoid click, but it always does. Does anyone know how many amps the solenoid draws when activated?

Thanks Jeroen, but that's why I have put in a completely new wire from the key switch directly to the solenoid. No junctions at all along it's length.

Oh, and I've already added relays on the headlights, and since the overdrive switch in the gear knob seems so puny, I've put one on that circuit too. Keep the thoughts coming please. :posting:

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PostPosted: Thu Aug 15, 2019 8:50 pm 
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I am assuming that a 1850 starter motor and its associated solenoid is similar to the 1500 set up. If this is the case there is a need to be aware that the solenoid has two windings. One a heavy gauge pull-in winding and the other is a lighter gauge hold-in winding. When the battery voltage is applied to the unmarked terminal of the solenoid both the pull-in and the hold-in windings are energised, causing the solenoid plunger to pull-in. This action closes the main contacts to energise the starter motor and this also causes the pull-in winding to be shorted out. The hold-in winding is made from very fine wire and I do wonder if it has developed a short across some of its winding with the result that it is not holding the plunger in. My suggestion is connect a voltmeter to the motor terminal and then see it you are getting the battery voltage applied when the ignition key is turned to start the motor. If you have not got a voltmeter you could just use a 12v bulb. This would prove if the problem is within the starter or solenoid.


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PostPosted: Thu Aug 15, 2019 9:07 pm 
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I have just found a copy of the official 1850 repair operations handbook and this has confirmed that there are two windings in the solenoid. The Pull-in is 0.25 to 0.27 ohms and the hold-in 0.76 to 0.80 ohms. So it is not something that most people will be able to check.

The handbook also states the light running current is 40 amps, the load running current is 300 amps and the locked current is 463 amps.


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PostPosted: Thu Aug 15, 2019 9:31 pm 
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That's all most interesting Richard, but the fault is present with both the original starter/solenoid and the newly acquired reconditioned unit from the TDC. It's hardly likely that both solenoids have the same problem. As to the current draw, what I really wanted to know was the current draw for energising the solenoid (ie what current does the poor old key switch have to carry), not how much current the motor actually needs.

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PostPosted: Thu Aug 15, 2019 9:35 pm 
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Yes, the currents that Richard gives are quite correct... and quite large. This is why the MGBxx and its variants also with a 2M100 variant starter has a starter relay on the offside bulkhead. I dare say your V8 will have the same. Mr Triumph cut costs and tried to switch the starter solenoid directly from the ignition switch.
The Click-er-click-er-click syndrome is typical of the problem.
Mine was solved by fitting one of the high torque starters from Mr Rimmers.
P.M. to follow.
Tony.


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PostPosted: Thu Aug 15, 2019 9:44 pm 
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Hi Mike, have you thought about sod's law? And that you might have a faulty unit. I have had that many times in past..... Not with club stuff, but there is always a first time.

Tony.

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PostPosted: Thu Aug 15, 2019 11:13 pm 
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What I meant about the switch is that it's possible with a worn one to turn PAST the contact point that sends current to the solenoid.

So you'll get the brief click as it engages before it drops out again. Which is why I said turn the key slowly!

To confirm or eliminate the switch, just run a wire (a nice hefty one) from the solenoid to the battery and brush it on the +ve, yes you'll get sparks but if the starter turns every time, it's definitely not the motor!

Steve

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2 door '73 Toledo with Vauxhall Carlton 2.0 8v engine OWF 797M (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine EGP 247T (The Dolomega)
'91 Cavalier 2ltr 8v auto
'95 Cavalier 2ltr 16v auto
Spectrum Auto Services, Servicing, Repairs, Electrical, Recomissioning, MOT prep, Trackerjack brake fitting service.
Apprentice served Triumph Specialist for 45 years and home of Maverick Triumph.PM for more info or quotes.


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PostPosted: Fri Aug 16, 2019 7:01 am 
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I think Tony has the solution. My MGB V8 does indeed have a starter relay. I had no idea that the currents involved were so high. A relay shall be the next thing to try. Thanks for all your thoughts.

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(MGB GTV8, BMW Z3 2.2, and Dolomite 1850HL)


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PostPosted: Fri Aug 16, 2019 7:03 am 
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The starter sent to Mike was reconditioned to order and fully bench tested; highly unlikely to be at fault unless the courier damaged it, but Steve’s simple test is probably worthwhile to eliminate the possibility.


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PostPosted: Fri Aug 16, 2019 7:55 am 
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I don't think it was damaged in transit Alun. The package was quite secure when it arrived. I will get the old unit back to you soon, although I now suspect there is little wrong with it. :roll:

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(MGB GTV8, BMW Z3 2.2, and Dolomite 1850HL)


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