Jonny Hart

According to the element website it has a CE mark but is also subject to this consumer ‘alert’. Hmmm.

That is very lucky. Usually the higher voltage from a starter/booster will cause internal component failure, rather than just a connector to ‘pop’. It’s the same failure as when the voltage regulator fails. The Bosch CDI unit does not have internal voltage regulation so the spark output is proportional to battery voltage. Over about 18 volts, the spark voltage gets so high that the energy would rather find a path to ground inside the box, than travel all the way to the spark plug.

Jeez Doc, everybody’s nightmare right there! Fingers crossed you can get it recovered back to the UK.

Never seen a fuel cut limiter either, it’s a US thing. There’s a thread on them here: http://forums.pelicanparts.com/porsche-911-technical-forum/8700-911-sc-3-0-rev-limiter.html The only things that controls the fuel pump relay in a UK SC is the ignition switch being in crank/start and the air flap sensor on the intake. Neither can be be damaged by the voltage spike produced by the relay coil switching off, so the red relay isn’t really necessary.

Ok, time to bust another Porsche myth. The only reason for a diode to be fitted across a relay coil is to prevent a ‘back emf’ from destroying any electronic device (eg a transistor) trying to drive it. Since a UK spec SC has no transistor type device driving the relay it makes no difference whether a red or black relay is fitted. With a US spec car, the rev limiter is electronic and is used to switch off the fuel pump. This DOES use a transistor and hence it must be protected by the use of a red relay which has the protection diode. It was probably much easier for Porsche to standardise on the red relay with diode for the fuel pump, even though it is only necessary for cars with the electronic fuel cut rev limiter.

Is this the guy that rang me yesterday? Works at Ford? I gave him a few pointers (green wire etc) but have heard nothing further. 6 pin CDI+ units in stock for UK next day delivery.

Wise words. My new ones lasted less than 5 miles.

You mean this one?

Yes, 917 wiring diagrams aren’t that easy to come by!

^ That would be my diagnosis too. I would not push your luck with an over voltage situation as other systems in the car may be damaged. Have the alternator tested.

Ok. so we are back at starter motor or solenoid or wiring.

When you say ‘it won’t start’ does it crank? It it is cranking but not starting I would suspect the timer relay that is unique to the Turbo. This allows the ignition to run on for a few seconds after the ignition is switched on. When these go wrong, there is no power to the CDI unit. So next time it doesn’t start, see if the CDI box is producing its characteristic whistle.

Good place for an AC rad!

Looking good!