Help needed on 73' 911S!!!!

[rupydoo123]

hi all, i have got a 73' 911S which i brought back to life last year. I am in need of help setting the engine up. It would be good to have another set of ears listen to the engine to see if i am wasting my time. I have also got a problem with the rpm transducer/speed switch, so if any one knows who is able to fix this, it would be great. It would be nice to try another one to make sure this is the faulty part. I have checked the switch on the TB's which works fine and i have also checked the solenoid on the mfi pump, which is also fine, but if you hold the switch down and rev the engine, it just revs up where as it should bounce between 1300-1500 rpm. I live in harlow, essex so if anybody lives nearby and is willing to lend a hand it would be much appreciated. Any info would be much appreciated on this matter.

 

[38F3E1]

If you need an indi to look at it then Jaz in Wembly, JZ Machtech near Kings Langley or Bob Waston near Oxford have the right skills.

Your diagnosis of the transducer sounds correct. Have you checked with Porsche to see if they are still available new?

Ian.

 

[rupydoo123]

Thanks for the info. As for the transducer, it turns out it's the micro switch. I took the board off and run fresh wires to each point and had a lamp on the output side. The lamp lit up and turned off at the right Rpms. Turns out it's the micro switch after all. Measured the resistance of the switch when closed and it was over 125 ohms. I have taken it apart to investigate and found the contact points pitted and dirty. Cleaned it with some fine paper and have now got the resistance down to 2.5 ohms. Gonna give it a go later and see if it now works. Thanks again

 

[Gary C]

ORIGINAL: rupydoo123
Cleaned it with some fine paper and have now got the resistance down to 2.5 ohms. Gonna give it a go later and see if it now works. Thanks again

If you have it in bits, it would be false economy not to replace the switch.

Switches and relay contacts are usually coated with a much harder compound to resist pitting and corrosion. While cleaning with a bit of Emery will bring it back to life, if you have exposed the underlying conductor, it will soon pit and corrode again.

At work we have thousands of relays (as the station was built in the 80's). On our control rod drive relays we use the correct contact cleaning strips, but on minor equipment relays, a bit of clean paper squeezed between the contacts and then pulled through removes oxidisation realy well, though if they are badly pitted, then its time for replacement.

 

[PORKA]

Hi if you need someone only 7 miles from Harlow try Carrera Engineering in Nazeing 01992 892333, ask for Tony, he owns a 1974 2.7 Carrera which he rebiult over something like 13 years, won the national concours some years back and has excellant knowledge of these early cars and also the later ones.
Has looked after my porsches for 20 years and vey good at what he does.
Has all the right equipment so your car is no problem.[]