Paul's charts (post 13) are from the Porsche Troubleshooting Guide, which is also shown on my CIS Primer site. It covers all '73 - '76 CIS models, and is not peculiar to Canada. '75 US cars had a vacuum WUR, while '75 Euro cars used the non-vacuum WUR same as the '74 cars. There is a discrepancy with the WUR pressures in several publications, as I note below.

911 CIS Primer - Testing: Pressures

See the notes on this page under "Warm-up Regulator Specifications".

The Troubleshooting Guide was generated for both US and ROW cars, while the Shop Manuals available to us here in the US were for US only, not Euro cars, except where some models overlapped.

Thanks, guys! Somehow that "Blue Manual" escaped me through my career - never saw one! My numbers came from the Porsche factory manual, but I neglected to mention the difference was probably due to the vacuum vs non-vacuum WURs, as Jim so helpfully pointed out.

Ive been home a few days and got some time to tweak, all pressures and residuals are spot on.

Its been cold here the past few days though, 25-35F and the car is feeling like its running lean till it warms up completely, unfortunately with as cold as its been the oil temp doesnt seem to be rising much above 120 and nowhere near the 170 mark on the gauge. Its hesitating, sputtering and backfiring at low rpms, ive given it a 1/4 turn clockwise to richen the mixture, but its trying to snow right now so i havent taken the car out to check but noticed something in the process..

In the airbox under the distributor it is occasionally squirting fuel into the airbox directly beneath the distributor and metering device.

Cold starts are still a problem, but when i "prime" the fuel system first by pushing the plate briefly, the car catches on the first try, runs for a few seconds then dies when it runs out of fuel. I assume this indicates some sort of issue with the cold start valve? since it seems the car has air and good spark, just no fuel till youve been cranking for a while. If you give it fuel it catches and runs perfectly till the fuel runs out.

Is there some component that controls fuel injection while cold starting for the first 10 or so seconds that im not aware of that would be gumming up the works.

Im eager to get this car running perfectly because it seems to be so close, and once it does we can start taking it on trips further than 100 miles from home since thats the limit of what AAA will tow for free.

There is a cold start injector, but it is not in a position where it would squirt fuel directly where you have indicated.

Sounds like you may have a worn out fuel distributor. Fuel may be leaking past the control piston into the air-cleaner side of the air box.

A 1/4 turn on the mixture is way too much adjustment unless it is REALLY too lean.

At NO time should you see fuel in the visible, open to view, part of the air box.

The cold start valve is opened by the starter voltage unless the engine is warm (above 45˚C, IIRC), or it is being cranked much longer than normally required.

"If you give it fuel it catches and runs perfectly till the fuel runs out."
What is meant by giving it fuel, and till the fuel runs out? How do you "give it fuel"? and until the fuel runs out of what?

Please give us a little more info -

Does your car have a Themo-Valve? It should.

Car has a thermo-valve, one of the wires, not the yellow one, was connected with a butt connector which i snipped out and soldered in a piece of wire instead, no change on starting behavior.

by giving it fuel i mean forcing the injectors to activate by pushing on the plate for the distributor for a second

But with fuel leaking into the intake box theres a bigger issue with the distributor

I will go back off the mixture before driving as well

That's the last thing you want to tinker........
 

ethlar,

Tinkering the mixture setting before verifying the absence of air/vac leak is the most common blatant mistake many people commit in CIS troubleshooting process. You could be right that you 'feel' it LEAN and there are two side of the coins: lean condition because of excess air (metered & unmetered) or lean because of insufficient fuel supply. You don't know the condition at this point. Do this adjustment later on and attend to the more critical ones.

Before you even attempt to troubleshoot the cold start problem fix the fuel leak coming from some where the FD. There should be no sign of fuel leakage any where around the FD or in the whole car. Pressure test the system by running the FP and check for fuel leakage. Avoid lifting the AFS arm to prime the fuel lines because you are also dumping raw fuel in the combustion chambers.

If your FD is defective or not, has to be tested and confirmed. In your eagerness to start the engine and test drive it, you might end up with a file of ashes in your garage or worse, burn your house down!!!!! Sit back and relax. Your problem is minor and you are just overwhelmed at this stage. I've not seen or known a CIS problem that these guys could not diagnose correctly.

All you have to do is have an open mind and listen to suggestions. Feedback on a timely manner and reply to questions brought up. If you don't have the time to attend to the troubleshooting work, simply let us know. Don't ignore and you'll be rewarded.

Tony

Thanks Tony.

We had the vacuum leaks previously tracked down prior to the installation of the pop off valve. The whole intake system was tested and rebuilt with new gaskets etc and the engine re tuned and leak checked. My concern is that this was done in the peak of summer, 90% humidity 95F days, and the car is having trouble coping with the cold weather.

I agree the fuel leak in the FD needs to be addressed, today was the first time that ive watched the car start with the air box open to even see it. Normally i dont and i dont intend to continue priming the fuel system, it was just an attempt to get more understanding of the situation.

At this point our plan is to deal with rebuilding or replacing the FD and going back to the mechanic for tuning with gas analysis, then we can return to focusing on the cold start problem

Blue Book & Good Gauges
 

NIZE Restoration! I bought the blue book many years ago and the BB is a great technical reference. That 10 BAR is out of bounds. IMHO Since you have probably blown out the WUR & FD with that CRAZY PRESSURE, call Larry @ CIS Flow Tech and get your CIS parts fixed then start over after dealing with the high pressure. I have a spare running -031 WUR if yours is FUBAR. Best of luck. :)

It is likely that the Themo-valve being 30 years old is not working properly. But it sounds as if you have other issues as well. You can do a simple test of the thermo-valve by testing it to see if it opens and closes based upon ambient temperature. Many people simply bypass the thermovalve and turn mix up or adjust timing to compensate.

Definitely going to be calling Larry, just saw the price of new FDs

Im hoping its the thermo switch as well, i left my voltmeter in my apartment when i brought everything else up to work on the car.

My car had the same hard start cold and after sitting issue. I replaced the fuel accumulator and fuel filter.... All was well after that!

I wish I could say it that well. Heed this advice in this forum and it will save you thousands and make you some good friends.

Only thing I will throw in is, if you have some form of leak in the FD and you pressurize the system AND the car starts, the cold start system is probably working. The car will NOT start easy if the cold start system is NOT working and you re-fresh the residual pressure when cold.

If you refresh the residual pressure when warm and it starts (where before it would not) then you have a residual pressure issue. You said residual pressure was spot on. That means it holds 20+ psi for many several tens of minutes.

The car has no issues with warm starts, its that first start of the day that takes 5 or 6 long cranking attempts before it catches, when it catches its rough for a bit and then smooths out to perfect.

Im putting all further testing and tinkering on hold until the FD is resolved, with a leak going on, any current tuning and tweaking will need to be redone when the FD gets rebuilt or replaced.