[AFB24911S]

I have read the Bosch book, Jim's Basement CIS Primer, and the excellent CIS Troubleshooting for Dummies thread. Here we go, the fear-inducing injection system!

My car:
1977 Porsche 911S Targa, original engine & stock cylinders, cam, etc., CA market, but now with an 11-blade fan and the EGR circuit cut off.

The problems:
Cold start - cranks for about 5 or 6 seconds before starting. It coughs within the first half second as if it wants to ignite right then, but then it keeps cranking until it starts.

Warmup - between minute 3 and minute 15 of driving, which is also right up until about 180°F oil temp, it bogs/hesitates at low revs under load.

Running - lots of body shake at idle, rough even at 1,000-1,100 RPM. During normal driving it makes decent power and I am getting about 20-23 mpg.

All of these problems have persisted since I bought the car about 5 years ago, but a collapsed suspension, messed up seats, and other issues took precedence. Now, I'm finally getting to the fine tuning.

My car has been at a local shop that I asked to fix these issues for the past two weeks, but they haven't solved it. After they explain what they did, I'm going to work on it.

I have the CIS pressure test tool, so I'll start with that and check pressures. As long as they are in range cold and hot, I'm going to check the check valve (LOL). If it leaks, bleeding off pressure between the pump and the fuel accumulator, it may be causing the long cranking at start. I don't think it is because I used to have the engine wired to run the fuel pump when the ignition was on. When I first bought the car, I would leave the ignition and the pump running before trying to start and it still took a while to crank. But, easy to verify. Is it possible that a fuel line between the pump and the accumulator could be letting in air? I never smell fuel or see it leaking. What about fuel tank air leaks? I bought a new gas cap, might as well put that on (but mostly because it was shiny and $12).

Then, I'm going to check the cold start valve. First to see if it sprays in a nice pattern, then to see if it leaks when it shuts off. I've got six gorgeous plastic volumetric cylinders for that.

If that thing does its job right, I'll move on to the AAR and the AAV. Last I checked the AAR was good, but it's worth checking again. I only looked through it to see if it was closing, but even if it is it could be leaking, right? I'll try blowing through it or pulling vacuum through it while hot. Same thing with the AAV, but I'm not sure the test I tried to perform 5 years ago was correct. Jim's Basement website says it's supposed to just cough until vacuum comes up, so I'll try to pull some vacuum on it and see if it flows or holds. Thinking a rubber cup attachment and some electrical tape will be my friends here.

If the cold start valve works, the AAR works, and the AAV works, I'll start chasing down vacuum leaks. Throttle body, vacuum lines, injector O-rings, both types. Plan is to spray some starter fluid around the engine bay and see if anything happens. I bought a bunch of vacuum hose to replace old, cracked ones, so I can inspect the ends of the hoses first.

Then, I can try to test the injectors for spray pattern and volume. If I find a bad fuel injector, I'll swap fuel lines at the distributor to see if the problem moves. If I haven't found a problem by then, I'll be out of ideas and send out the fuel distributor for rebuilding.

Hair-brained theories: I think the fuel pump check valve is screwed, the pump isn't pushing enough volume, or there's a serious vacuum leak. And at least one of the injectors isn't fully working, maybe just not spraying nicely at low flow rates.

Any flaws in my game plan? Other, better ideas?