Coil over heating

[kauri]

Hi all
Have just got back from Windermere where I had problems with 12v coils overheating, the engine is a 105E with a dynamo. Tried a new rotor arm but still got so hot engine missfired and cut out, can anyone help as going to Cardiff on Friday.
Regards Geoff.

[sean-nós]

It might be that the coil has just gone bad or lost it's oil/tar and not sending a spark to all the plugs causing the chamber to have a bit more fuel in it next time it fires, might also be worth checking the gap in the points if it's too big or they are sticking it could be making the coil work harder. Also check the ballast resistor if you have one, the timing,a short in the wiring or bad ground,and you have the right plugs and good plug leads.
Maybe someone will know a bit more about your engine and have better ideas.
Good luck with it.

[Howstar]

Did you have the tachometer on the 2nd time the coil got hot, bit of a long guest have you checked the output on the dynamo should be around 14 volts.

[kauri]

Fitted new coil, rotor arm and condenser today but coil still cooking so checked voltage at 20,000rpm, 15 volts so ordered a 12v ballast resistor hope it comes befor Cardiff on Friday.

[eastcoast]

Hi Geoff, was going to say on the phone yesterday, if it still keeps playing up disconnect the charge lead from dynamo, run on straight battery power, take a spare batt and charger to swap over.

[Howstar]

http://www.youtube.com/watch?v=eKWsI2vN ... plpp_video

Could be the faults is that over charging. it might be best if you just run it with out any wires to dynamo. the ballast will drop the voltage down about 3 volts
so 15 - 3 = 12 volts that ok

But when it starting from cold you luckly to get 12 volts at the coil , you could might only get 9 volts , as the starter is taking most of the current ,
so 9 - 3 volts = 6 volts this will give you poor starting from cold see these helpfull videos from moss which will explain a lot more on regulators and ballast coils

[Tatra Man]

The correct setting for the voltage regulator on a 12 volt dynamo system is 14·7 - 15·3 volts at 20°C so that isn't the problem. Coils for use with ballast resistors are rated at 7 volts and the ballast resistor is shorted during starting by extra contacts on the starter solenoid. Add a ballast resistor to a 12 volt coil and you'll get a weak spark.

Coils do get hot - but the question is, how hot? If your engine is still cutting out with the new coil, check that nothing is shorting inside the distributor when it's on full vacuum advance and that the action plate moves freely. (Too long a clamping screw holding the condenser can jam it.) The next thing to change is the HT lead to the coil and then borrow a distributor cap and check that by substitution. After that, change the plug leads.

[Mirak]

Kauri,

Make sure the coil is mounted upright (preferably, not on the engine itself). If it's on its side, it will get hot on the upper side as the cooling oil is at the bottom.

With it upright, the bit where there is no oil is at the top and not near the coil winding itself - weird, but worked for us.

Spent most of a season chasing this one down on a Chris-Craft a year or so back.

cheers,
Scott

[Tatra Man]

I don't think Lucas restricted mounting positions. On the Series I and II Sunbeam Alpines the coil was mounted horizontally on the side of the cylinder head! On later models it was moved to one of the scuttle bracing struts but was still tilted over more horizontal than vertical. I don't know for certain but I suspect there was very little air inside them.

[solitaire]

Please forget about what happens under the hood of a car! - these are marine applications - think enclosed hot engie compartment - modern Lucas (prince of darkness) coils made in PRC, poor quality oil filled jobbies, not resin filled - and little used electrics so that generators are always charging hard and banging out 14 1/2 - 15 volts from the time the engine starts
From the hours talking about it at Cardiff, it seems like a visit to the Distrutor Doctor 's website and a decent resin filled coil (you can mount them any way up you like), a good bit of ventillation and a good battery fully charged go a long way to fixing out problems (as demonstated and working so well on the Lotus Delta at Cardiff)
I did work as a service engineer for V/Penta (back in the day) and cannot ever remember seeing coil problems with the good old Bosch Blue coils (resin filled and 12v - non ballast) - I must have seen and woked on hundreds
The good old Bosch Blue's can still be found (much favoured by the air cooled VW chaps with v/high under "trunk" engine compartment temps) - but beware lots of pirate ones around, - cheap PRC copies with blue sticky labels, but plenty of info on getting a good one on the web! (mostly Mexican or USA made)

ps - no longer Sinbad - I have no problem with identity - Andre/Solitaire