checkmate1996

Listers,

My friend has a 74 2.7L engine and it starts very hard when cold. When warm, no problem. Here are some of things that have been done:

- new fuel pump
- new accumulator
- new cold start valve

Is there a temp switch or something to that effect that is blocking the cold start valve from kicking in? I'm more of a 928 guy but familiar with BOSCH CIS systems to some extent. I'm not familiar with the placement of all the items on the 2.7l though.

Any pics, guides, suggestions, tips would be greatly appreciated!

Droops83

The early CIS cars had a hand throttle to aid cold starts, it raises the idle to aid engine warmup. It is to the left of the handbrake handle, in between the seats. Pull up the hand throttle all the way prior to a cold start (don't touch the gas pedal). If it works, you will notice the engine idles a bit high, but that is good since it helps the engine warp up, and you can gradually lower the lever as it warms up, eventually putting it down all the way. In '75 Porsche added an auxiliary air valve to raise the idle during cold starts automatically, and eliminated the hand throttle.

If your hand throttle has no effect at all (a good way to test is to see if it raises the idle RPM at all when the engine is warm), then there are several potential causes. One of the most likely is worn bushings for the throttle bellcrank on the back of the engine (towards the front of the car). Unfortunately these are very hard to get to with the engine in the car, I always replace these on a CIS car when the engine is out. Another possibility is a coupling underneath the car. If you look under the car where the throttle rod comes out of the body, you will see a small cylinder-shaped coupling that is underneath the left side of the transmission mount cross-brace. These can wear out and break causing slop in the throttle linkage, and at some point Porsche updated it with a metal encased version to replace the previous all-rubber one. If all of the above is OK, of course check out the linkage at the hand throttle lever itself, and at the throttle pedal. Good luck!

---Chris A.

checkmate1996

Chris - Thanks! I will check it out those items out...

Peter Zimmermann

I'd like to add that the hand throttle is adjusted correctly if, with a warm engine, it brings the rpm up to about 3800 at its upper stop. Like Chris said, check all throttle bushings and linkage integrity prior to attempting to adjust the hand throttle.

pjc

Personally I would not raise the hand throttle all the way - as Pete states, this revs the engine to about 3.8 to 4K, much too high I suggest - may even cause a backfire/blown airbox. I raise mine about half way only.

Personal view based on 19 year ownership of a '76 911.

PJC