| Author | Message | ||
     Bob Reynolds Prolific User Username: bobreynolds Post Number: 158 Registered: 8-2012 |
1975 SS1 After several years, I finally got round to fixing my Choke Solenoid wiring. The insulation was crumbling, the supply had been disconnected, and the Scintilla switch had been backed off completely. After working on it for a whole weekend and virtually rewiring it, I can now see why it was disabled! I start the engine and after about 6 seconds, the engine starts hunting like mad due to an over-rich mixture. After about 20 seconds of misfiring and shaking about violently, the Choke Solenoid releases the choke flap and the engine gradually recovers and idles normally. So the obvious question is: 'How long is the Scintilla delay switch supposed to be set for?' Anything more than 6 seconds would seem to be disastrous, and it wouldn't be worth installing a delay at all if it was for less than 6 seconds. It takes longer than that to back the car out of the drive! I was feeling really pleased to have sorted all the wiring out and fix all the faults and get the solenoid working again. Now it seems like I wasted my time and will have to disable it again.  | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 1264 Registered: 6-2006 |
if it's bloody freezing , it will stay on for quite a while. If it's toasty it may not come on at all. All it needs to do is stop the flap oscillating while cranking and a few seconds extra. | ||
| Bob Reynolds Prolific User Username: bobreynolds Post Number: 159 Registered: 8-2012 |
The Scintilla switch is heated up by an electric element, and works like a flasher unit. So I wouldn't have thought that it would be much affected by ambient temperature. But what you are saying is that there is a significant difference in the delay with different ambient temperatures. How is one supposed to set it up after it has been completely backed-off? Say I put it in the freezer and cool it down to 0 degrees, what sort of delay should I be looking for? | ||
| Bob uk Unregistered guest Posted From: 94.197.122.92 |
That's old cars for you. I am sure that mine has an otter switch which is temp sensitive. I run my car on (smug) lpg so my choke flap is crudely wired open, and hasn't be used for years. I think mine drops out much quicker in warm weather. Maybe your off choke mixture is a bit rich thus the extra choke time is much to rich. Till you work out why maybe a small switch or simply unplug. Not a complete waste of time because no doubt the wiring looks better. Try taking the switch out and see if it drops out at say 40 centigrade. Once an engine is at 40c it should run smooth without choke. Also the engine breather sucks from behind the choke flap so if the breather is restricted the extra air the engine should be getting via the breather isn't there, to check open oil filler cap. I am totally unsure about the breather. I have noticed that most temperate gauges start at 40c as well. I never like auto chokes and thought that manual chokes with the fast idle only position was much better. The Shadow choke is one of the better designs. (Message approved by david_gore) | ||
| gordon le feuvre Frequent User Username: triumph Post Number: 51 Registered: 7-2012 |
The choke solenoid should only be energised below about 10degrees celcius. The operation mode is that a otter switch will determine temp and earth the circuit that feeds the choke magnet. This is run through the scintilla switch that is connected to the charging system, The idea is that the choke solenoid will hold choke flap in closed position until engine fires and the scintilla will receive a signal that engine is running because dynamo/alt, is charging. This then cuts off earthing of choke solenoid and releases same. This normally takes 5-6 secs only. You can "cheat" by adjusting the screw on scintilla switch to obtain the above by trial and error. There is info in Shadow and Cloud manuals, some under fuel system, some under electrical. If the wiring diagrams are studied as well, this shows circuit. My experience is that the choke solenoid only needs to work when ambient is around 2-3 celcius or below. | ||
| David Lacey Experienced User Username: dlacey Post Number: 28 Registered: 11-2010 |
I've also been having problems with this choke system in Malaysia (ambient 28-32C). In my case the problem was that under the shroud the stove pipe connection was loose, result was that the bimetal spring didn't heat as fast as it should by sucking 'cool' air. This resulted in the same misfiring & fouled plugs you describe. Now the issue is fixed with the stove pipe reattached and unblocked. I found it hard to get a full picture of how this system worked from the manual, and very little discussion of it on the internet. My conclusion also is that its a pretty rugged and reliable system, so therefore there's little need for webpages on its repair...i think thats a good sign! | ||
| Bob Reynolds Prolific User Username: bobreynolds Post Number: 160 Registered: 8-2012 |
Thank you people for your useful replies. There is actually no otter switch in my choke circuit, nor on the cct diagram. The nearby otter switch in the air intake is for the weakener system and nothing to do with the choke. They share the same wiring loom and Earth connections and I think that this leads to confusion. I've got no idea how the choke solenoid knows what the ambient temperature is, unless the Scintilla switch does indeed act as a crude form of thermostat as well as providing its delay function. Yes Bob you are right. The wiring is now tidied up enormously, with the removal of all those cracked wires and bullet connectors on the top of the engine. I was thinking of adding a manual switch like you suggested, but that would be a last resort. A manual adjustment of fast idle would be very useful though. Gordon - your understanding of how the circuit works is broadly similar to mine, except that there is no otter switch. Paul Yorke's reply inspired me on the obvious solution. No not to disconnect it again! But to wire the choke solenoid directly to the choke relay so that it operates during cranking only, and releases as soon as the starter switch is released and the engine fires. This seems to be the logical solution, what difference would a few seconds delay make - none at all. I've never had any problems starting the car with the solenoid disabled, even in very cold temperatures. As is well-known, the temperature in the UK is always very warm.  In the case of warm starting, the choke flap will already be open, so the choke solenoid will make no difference. The only difference my idea will make will be when starting the engine when it is very slightly warm and the choke flap has just started to move. The solenoid will pull the choke closed again whilst cranking the engine. If this improves starting I will leave it, if not I will disconect it again and leave it disconnected as it just isn't necessary. Like the weakener system, I do believe that this is another of those 'Crewe solutions looking for a problem'. | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 1267 Registered: 6-2006 |
you are answering your own question but can't see it. The switch works by heating up. It takes much longer to heat up in freezing conditions because it's starting from a lower temperature. In a boiling desert it's already hot, so will be off. ambient temperature is the only thing that controls it's timing really. wait until the winter and adjust it if you have problems with the choke flap bouncing. |
