Good, but only half the story! At the same time, you always have a check the basic adjustment of the CIS. This basic adjustment defines that particular (time)point when the lifted sensor plate lever switches on the fuel pump and starts injecting fuel. People still don't want to recognize this relation: Both settings must always be seen in conjunction! Why? Basically the mixture screw is nothing else than a fine tuning for the sensor plate height and second it defines the transmission of the lever relative to the sucked air (the sensor plate lever is a lever system of two levers connected at the end of the counterweight). The travel the lever makes all the way from idle to WOT therefore defines a sliding working window of amount of injected fuel. If this window (the lever travelling way) is either adjusted too low or too high the amount of fuel will never fit to the actual required fuel and engine ever won't run properly. So - make the basic adjustment of mixture control screw as described in the manual page I posted.
We had a similar discussion earlier: https://forums.pelicanparts.com/porsche-911-technical-forum/1158127-air-sensor-plate-height-why.html#post12203484

As RSNellie suggested - take the AAR out of the car, connect it to a 12v power supply and see if will close after 3-4 mins as expected. It won't fully close, a small crescent moon will remain (and this air is calculated in and still required).

Check also both vacuum valves (flying saucers) on right side of the engine. JoeEngineer made some good notes about this:
joe engin e e r dot com/porsche-911-cis-subcomponents-and-testing/ or https://rb.gy/vave3m


Popping exhaust always indicates an improper adjusted mixture for that operating condition...this means there's a misconfiguration between air and fuel...

Had almost the same issues - couldn't get the engine run on ambient lower than 10°C / 50°F and when, I also had to push the accelerator 2-3mins until engine has warmed up a bit...
Issues were: several vacuum leaks, WUR / wrong pressure, bad thermo time switch (and therefore no extra fuel from the cold start valve), and - applause, fanfare - a bad plastic flange at the cold start valve not letting any extra air through...

https://forums.pelicanparts.com/porsche-911-technical-forum/1020014-csv-flange-911-110-264-00-alert.html
https://forums.pelicanparts.com/porsche-911-technical-forum/1069752-cis-fuel-pressure-test-results-scrutiny-2.html#post11722791

This flange was mounted by the previous workshop without drilling a hole. So this way never any air could flow from AAR, start valve and vacuum limiter...:eek::o:rolleyes:

Checking every output of the FD is always a good idea, but I'm sure this is not your main problem now. This hangs together with running culture at all, performance and efficiency...

Thomas

If you have CIS, all fuel lines flow at the same time. So as long as the lines can reach the injectors from the FD, order does not matter.

On my SC the pump runs when the key is in the crank position regardless of the plug cuttoff. It cuts off the pump in the run position (if the plate is at rest) and not the crank position. Not sure how well the cuttoff works in a rollover, with plate upside down :o

Schulisco,

Thank you for all of the information it has been a great help and pardon my ignorance this is the first CIS car I have ever delt with.

Upon looking at the CIS manual about setting airflow sensor plate and comparing it to where mine is currently set. It looks like it might be .5-1mm to high in the venturi. its sitting level but the edge of the palte doesnt quite sit parrallel with the square part of the venturi. it looks like the thickness of the plate worth above that spot.

My concern is that the level screw looks to have never been moved it still has the yellow paint on it. Ill try to move it down and report back.

If your plate moves smoothly and does not bind, it's likely fine. Get a feeler gauge and check around for the gap. Verify you need to adjust it before you F with it.

Joseph,

Why is WCP only 2.5 bar? That is out of spec and hoping you were NOT using a HF pressure tester. My record says the WCP was set at 3.6 bar. Plus WUR-090 is NOT a vacuum assisted WUR. The post on top of the WUR should be connected to a vent (atmosphere) at the TB.

Could you test again your fuel pressures and inspect the vent hose on top of the WUR? Thanks.

Tony

Joseph

Why is WCP only 2.5 bar? That is out of spec and hoping you were NOT using a HF pressure tester. My record says the WCP was set at 3.6 bar. Plus WUR-090 is NOT a vacuum assisted WUR. The post on top of the WUR should be connected to a vent (atmosphere) at the TB.

Could you test again your fuel pressures and inspect the vent hose on top of the WUR? Thanks.

Tony[/QUOTE]

Tony,

No its not a HF tester, I am using the one from the host site works much better.

And yes will test again later tonight, wont hurt maybe I missed something. I have ensured all the vacuum lines are at the right connection. I have the WUR vent line going to the upper port on the front of the TB above the vacuum advance line.

Also, would a low warm control pressure mean that the engine is running too rich all across the rpm range?

Yes. The control pressure is a counter weight for the FD plunger and the sensor plate lever. It totally changes how the mixture is set on all operating conditions. With a too low control pressure the mixture won't be never appropriate.

Had a break in between class and tested my pressures. Is about 75 F out maybe a little warmer engine was dead cold.
System Pressure valve closed
http://forums.pelicanparts.com/uploa...1728429022.jpg
Cold Control WUR heating element unplugged valve open
http://forums.pelicanparts.com/uploa...1728429022.jpg
Warm Control after 5 mintues with WUR heating element plugged in valve open
http://forums.pelicanparts.com/uploa...1728429022.jpg

Got my WUR back from tony and warm control pressure is right on the money at 3.6 bar. Car still starts hard when cold. Residual pressures are well within spec after hours of keeping the guage hooked up. Still have that pesky exhaust popping when under deccel. Checked for vacuum leaks again. Still no leaks although the test doesnt permit the install of the intake boot and oil breather lines. How does one smoke test with the entire system put together including the intake boot. Also am I just chasing a false problem with the popping because I have SSIs and a 2 in 1 out dansk sport muffler? Now at a total loss because WUR is working perfectly and still experiencing the same problem?

Here is a video of the popping when revving the engine with no load. Same as the popping under deccel.
https://youtube.com/shorts/RsruD6ZlwFU?si=t-RYT-XJyh-WwkA6

Leaking exhaust gaskets can also cause deceleration exhaust popping.

I will check that out. Is there a good way to check an exhaust leak in with a rubber hose or a smoke tester?

I haven't done that (yet), but I would try capping off the air intake or throttle body and push smoke in the tailpipe.

Since your wur was out of spec… do you suspect it was tuned to run well warm to compensate for the wur pressure being incorrect? If so, now that the pressures are correct, your mixture setting would now be wrong for both warm and cold.

If you now have a higher wcp, your system would be lean which could result in popping in the exhaust and hard to start cold. You can do a quick and dirty check by disconnecting the o2 and lifting up on the arm under the fuel distributor. If it starts to increase in idle a little then you’re lean. The idea is to get it to idle worse when slightly lifting up ( typically to rich and oscillates) or pulling down on the arm (starts to die). That means you’re very close to the ideal setting.

You can get a far more accurate closed loop mixture adjustment by hooking up to the multi meter and checking the duty cycle - mixture setting. I don’t have a lambda but I know from reading you can do this without a gas analyzer. For me not having lambda in a 78 the arm test gets me really close then I use a gas analyzer.

I may not be describing this perfectly so anyone else feel free to correct me if I am wrong.

sounds easy enough ill test that out.
I am suspecting more and more of an exhaust leak since now the car runs perfectly in all loads and rpms with no hesitation and only popcorn pops when I lift off throttle.

Well I think I figured out my cold start and mixture issue. I made a bone head mistake when putting my new air box in. I installed the wrong CSV flange. I installed an early version with the air line plugged instead of the later CIS version with an open air line. Took almost 7 hours to change it out but I didn’t need to drop the engine just patience and lots of small drive bits. Installed correct flange and fired up for the first time with no added throttle. Still making a popping noise under deccel but I am going in the right direction.
http://forums.pelicanparts.com/uploa...1731601539.jpg

OMG
Had exactly the same issue years ago. Workshop replaced the correct drilled one with a new closed one like yours... I would drill this one ... 7 or 8mm should do the trick.

Porsche part no. 911 110 264 00

Was also an issue earlier here:
https://forums.pelicanparts.com/porsche-911-technical-forum/1020014-csv-flange-911-110-264-00-alert.html

https://www.pelicanparts.com/More_Info/91111026400.htm?pn=911-110-264-00-OEM

I recommend to order the rubber O-ring in conjunction as this is no standard sized ring with 20x2,5mm. Those standard O-ring are thicker and then the mounting of the CSV is even heavier as the CSV then won't sit flat and crushes the thicker O-ring...

Thomas

Made a discovery by surfing other forums on here, removing and plugging the ignition vacuum line made the popping disappear entirely and the car starts better. Havent adjusted the timing at all but it currently sits at 5 degrees BTDC at idle instead of 10 ATDC. advance maxes out at around 21 degrees. Hope this can help someone with the same set up as me.