SC starting problem

My 83 SC starts on the first turn of the key from cold. However if I subsequently stop the engine before it has warmed up, it's an absolute pig to restart. The only way to get it going is to crank the starter for a minute or two while keeping the throttle fully open - very embarrassing!

Any thoughts on what's causing this would be much appreciated.


Cheers

Phil

I would guess that the thermo/time switch on the left cam cover is faulty. It must be working when cold (or it would not start well the first time) but over-compensates for the slightly warm engine.

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Graham Archer
83 911SC Cab

Graham

Thanks for your reply. Do you know the procedure for checking this switch?

Cheers

Philsy

I had a quick check though the archives and found this (must have too much time on my hands )
http://www.pelicanparts.com/ultimate/Forum3/HTML/003144.html

There are loads of previous posts about starting problems. It would be well worth your time having a bit of a trawl.

billyb

BillyB

Thanks - guess I should have checked the archives first!

I'll do some fiddling around at the weekend.

Phil

Phil - -
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We'll give you more SC starting advice if the Queen will give us back our country. Deal?
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Chuck
83SC

Chuck

Had a word with Liz, and she says you can have your country back cos she can't cope with driving her Rolls on the wrong side of the road...

Phil

There are two wires that connect to the thermo-time switch. One provides power to the heating element in the switch, the second controls the cold start injector. When the switch is closed (by lack of heat from either the engine or the heating element) the second wire is grounded. This turns on the injector.

I'm not too sure about this... but I guess you could have an assistant start the car cold, while you are measuring the resistance between the second wire (still attached) and a grounded spot on the engine. After several seconds, the resistance should go from zero to infinity. Try the test again on a partially warm engine. This time the resistance should go from zero to infinity in a second or two. Do the test again on a warm engine. There should always be infinite resistance.

Warning! I'm totally guessing here. But it's worth a try.



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Graham Archer
83 911SC Cab

Graham,

Thanks again. This makes sense, I'll have a go and report back at the weekend.

Phil

I had the same problem. My car would start great when cold. If the car sat for about an hour after driving, it wouldn't start and basically the engine would flood.(im guessing due to the heavy gasoline odor) I ended up reading a book on CIS and came across the cold start valve. During startup, power is sent to the starter motor and the cold start valve. If I'm not mistaken, the ground wire has to go through the thermo-time switch to complete the circuit and open the cold start valve. To make a long story short, everytime I turned over my engine, I was shooting extra gas in there via cold start valve. If the engine didn't start right away, it flooded. I'm guessing that my thermo-time switch is bad because it is sending ground to the cold start valve at all times. My quick fix cause I'm cheap--pull the wire from the thermo-time switch that goes to the cold start valve. I'll connect the wire if the car has sat for a couple of weeks and then disconnect it after I get the engine started.