Post Number: 173
|Posted on Friday, 29 March, 2019 - 22:50:
Hi, Just been to visit a friend with poor cold start problems. (Spirit)
I am not that familiar with the Spirit later carbs and linkage but appears same as Shadow regarding the choke solenoid and thermal delay.(Scintilla)
First question is did the Spirit do away with the need to push the accelerator down before starting to shut off the butterfly. I ask as the mechanism on the right carb shaft is not the same as my Shadow 1 and does not appear to have the linkage and cam to do this so not sure if it has been tampered with or just done away with on later cars as I know dump valves were fitted also so wondering if this feature no longer exists.
Second question the fault is definitely with the Scintilla thermal delay (corroded element wire inside and rotted contacts). OH and SO MUCH EASIER TO GET TO ON THE LATER CARS THANKFULLY).
Energising the choke coil manually or temporarily holding the butterfly shut the car starts fine.
Has anybody found an alternative modern time delay relay that can be substituted. I have an original Scintilla spare but reluctant to give mine away as if available second hand generally I have found the old original French ones always useless and not working despite sellers claims.
Post Number: 400
|Posted on Friday, 29 March, 2019 - 22:58:
FWIW, I bought a second-hand one from Paul Yorke and it worked a treat.
I kept my old one for rebuilding, but of course never got around to it. ;)
Post Number: 174
|Posted on Saturday, 30 March, 2019 - 01:32:
I am sure Paul Y is a very trusted source for spares.
I have cleaned contacts and re-adjusted timing in the past but this one is beyond repair. IIRC it was around 25 seconds delay but will have to see if I still can find those correct details.
I was hoping someone may have worked out a modern alternative as plenty of room and easy access.
Any advice on throttle linkage/accelerator would still be appreciated.
WOW just looked at Introcar although NO STOCK the price is 300GBP.
I could make something for less than
Post Number: 176
|Posted on Sunday, 31 March, 2019 - 00:08:
Just as I had spent a few hours looking through my old stock and indeed found I had two of them.
Well I kept searching and did find an old thread on this forum..
Quite amazing as Bob's solution to wire direct to starter solenoid seems so logical and makes you wonder why RR never did this from the start(er no pun intended). Not quite sure exactly how rewiring would need to be changed as choke solenoid has permanent 12v and is only earthed through Scintilla switch, but doubt it would not be too difficult.
Even second hand FSpares are asking over 100GBP. So quite a cost saving.
However just to correct a few points on that old thread the function of the Scintilla is not at all outside temperature related as implied.
The contacts are closed even at room temperature 20 degrees centigrade and I have put both mine in our conservatory currently at a whopping 35 degrees C this sunny March Brexit day (whoops)and I still get continuity across the connections B and C.
The adjustment screw allows specifically for adjusting the time in seconds. On one of mine it shows 'tested OK 10 seconds' albeit I thought the setting was around 20-25 seconds but I can't find anywhere this is logged. However I would assume if in very cold weather the bi-metal finger contacts would probably take a little longer to warm up from the heating element.
Inside the Scintilla is just a high resistance heating wire element wrapped around the bi-metal contact arms which are electrically insulated from the wire. If this is damaged or rotted as my friends repair is very difficult.
The windings are around both arms but much less turns on the adjusting arm. This is solely to ensure the adjusting arm is maintained tight against the adjustment screw and only the other contact bi-metal arm is allowed to move to break the circuit after a brief period.
12v Positive (14Ns) is supplied from the ICU on the pin marked M as soon as the ignition is switched on and power to the ignition control unit.
However anyone testing this Brown/Slate wire at the M with a multimeter may get a bit confused as it will show a permanent 12v and is why some have disconnected this wire and the unit. 'Current flow' (supply under load) will only occur when ignition is switched on so always test with a test light.
The normally closed contacts C (black wire permanent earth) and B (White/pink temporary earth) simply give the one side of the choke solenoid an earth (Shadow 1's maybe 11's not sure... do also have the otter switch in this circuit but not later cars). This momentary holds the choke flap tightly closed and prevents the air ram effect tipping open the choke butterfly. It is only required for the short period of initial cranking hence great logical solution from Bob to do away with the Scintilla all together.
However this high lights some very important points on starting of the Shadow 1 at least and later cars that have this choke delay switch possibly.
Firstly for those that switch the ignition on and wait for the SU pumps to stop ticking before cranking you will have probably passed the time limit of the Scintilla and the choke solenoid will no longer work as the Scintilla will have opened the earth supply to the choke coil. This of course will now not help cold starting.
Secondly again perhaps specific to earlier Shadow if you do not push the accelerator pedal to the floor before cranking the cam on the right hand carb will not release the choke butterfly to fully close. That then will keep the pick up lever on the butterfly shaft away from the choke solenoid magnetic effect and again will likely stop the whole choke process from working correctly on initial cold weather cranking.........
Obviously the colder countries would notice this problem more so than in hotter climates and explains why so many RR/B carbs I have done in UK in the past mixtures have always seemed to be set too rich due to choke functionality issues.
I will now leave the decision to my friend if he wants a replacement Scintilla or a Bob's fix. It certainly makes you wonder though why this switch would have been left permanently live regarding the heating element when with ignition ON and driving.
Post Number: 179
|Posted on Tuesday, 02 April, 2019 - 03:26:
Just an update. Installed the Scintilla today and all is well. The 10 second delay was just about right.
What I also worked out was the power supply to the Scintilla heating element only comes on when the engine/alternator is running and NOT when the ignition is just switched on.
This means that anyone with the early Shadows SU pumps and leaving their car for long periods can happily wait till ticking stops without loss of timing/supply when required to the choke solenoid as the Scintilla will not have open circuited the choke solenoid supply unless engine is running.
Again early Shadow related though... the accelerator will have to be pushed down and released to allow pick up of the butterfly lever by the choke solenoid.
Clearly though the later cars have done away with this need from looking at the linkage.
Pictures show the insides of the old Scintilla a bit beyond repair IMHO.
An interesting Bentley replica car was also in the garage today.
Robert J. Sprauer
Post Number: 207
|Posted on Tuesday, 02 April, 2019 - 04:19:
Now that's a real dashboard!
Vladimir Ivanovich Kirillov
Post Number: 1332
|Posted on Tuesday, 02 April, 2019 - 06:02:
Damn right Roger, that dashboard is the item indeedy! Love the polished blower too!
Post Number: 401
|Posted on Tuesday, 02 April, 2019 - 06:09:
That Blue Train replica is indeed sweet!
Post Number: 185
|Posted on Thursday, 04 April, 2019 - 02:56:
Well I have had to do some more research but for some reason cannot get a handbook download of the Spirit.
I have found a reference though regarding starting procedure for the Spirit (carb model) and indeed it does require the accelerator pedal to be depressed and released prior to starting but does it a different way than the Shadow carb model.
Also the 10 second timing set on the replacement Scintilla appears a little too long so will be reducing this down tomorrow to 5 seconds.
Thankfully we have ice cold conditions the next few days so should be a good trial.
Just updating to put records straight as I said originally I was unsure on how the later set up on the Spirit carbs worked with reference to my knowledge from the Shadow older carb set up.
My friendly Rolls Royce/Bentley breaker who I do clock repairs for kindly sent me half a dozen Scintillas so I could check/repair them.....sadly everyone had broken heating elements and as of yet I just don't think I can come up with a repair solution for the heating elements even if I could find a suitable wire.