Porsche Forum - Porsche Enthusiast Forums

Go to www.924board.org and do a search or check the FAQ. A few have switched to carbs and some have done some EFI work and have been very successful but be ready to do some fabrication or pay to have someone do it.

The CIS can be very reliable, once tuned. But if you aren't sure how to do it, you need a Haynes manual, at the least, or the Bosch tuning book for CIS. The most important thing to check is vaccum hoses. You need to replace them and make sure you have NO vaccum leaks before doing anything with the CIS because unmetered air will upset the balance. If you haven't replaced the large boots that go from the metering head to the intake manifold, you might want to considerit. My largest problem came from those boots having cracks around the area that clamps to the metal frombeing taken on and off over the years. Then replace every vaccum line you can.

A fuel pressure gauge setup is essential to trouble shooting the CIS system due to the system pressures needed to operate correctly and determine if the pump(s) is delivering or if the Warm Up Regulator (WUR) is working correctly. A bad WUR usually results in hard starting, rough running at start up and then dies. It will repeat this until you can feather the throttle enough to keep the car running for the few minutes it takes to warm up. Then it will usually smooth out.

In addition, there is an Auxillary Air Valve and Cold Start Switch that must be working correctly and you must have a good battery/charging system for those to work correctly because they use bi-metal sensors that must heat up properly to tell them when to turn on/off.

The fuel pressure tester is available at JC Whitney for about $60.

After getting my CIS working properly, I can let the car sit for 6 months (stabilize the fuel), put the battery in it and it starts right up every time.

Good luck.