911 sc cis residual pressure

[ahh911]

George,

I did the test you asked. Car ran yesterday afternoon, just now I cracked open the 14mm FD to WUR connector at the WUR (I did not crack open or remove any other fuel line), pulled the hose up and away from the WUR, shook it and still not one single drop. Just like I remember.
Garage temperature today is hotter than usual, overnight maybe 22, at time of test 28DegC.

Note:
1981 sc us.

Over 20000 km and only one or two double starts. The last time I was playing with the wur so it doesn't really count. If each trip is 50km, then 400 successful starts, and one double start. That's my car, what can I say.
Should add, temperature of starts where I run was -5C to 38C. Mostly between 20 and 30C. I don't start in winter or below -5C in the garage overnight.


Phil

[boyt911sc]

Originally Posted by Schulisco

Tony, please don't get me wrong, but now I'm confused about your last posting, because I think it distracts from the important things we're facing now ...

I don't understand why you're now talking again about the CSV again...as George in the beginning of this discussion mentioned - with the CSV his engine won't start, without the CSV it would. So conclusion is pretty clear to me - the mixture is too rich to start the cold engine with the CSV. Nevertheless - the CSV is, as you wrote correctly, required for a proper start. But this also requires the rest of the system works also well. And this is the point - it is not.

With the CSV it gets even way more richer and this prevents the start of the engine. Now we're getting closer as George this morning figured out, that his control pressure doesn't really exists until he cranked the engine several times, clearly seen in the video.
This means totally clear that the FD enrichens the mixture far beyond because of lack of fuel in the hose. This is a inacceptable situation antd the root cause of the problem. With the upcoming control pressure above 1,3bar the mixture is getting lean enough that the engine will start finally - with the CSV connected. So he has to figure out why and where the control pressure and the fuel at this place is drawning away ...

The CSV in Georges car works as it should. But it's not the culprit.

Beside that - you're absolutely right about the spray pattern and so on...but this is IMHO currently not helpful in finding out, why Georges engine drawns the WUR hose from fuel as he figrured out. Do you have an idea where and why the fuel could going from there?

No offense.

Thomas

Thomas,

I spoke to George yesterday for a while. During the conversation I emphasized that the culprit was not the CSV. For a cold start, you need a CSV. So focus on identifying the culprit that is causing a cold NO start.

It is something right in front of our noses but have not thought about it. That is the reason I ran the 2 motors in the garage specially the ‘78 SC. The last time it ran was 2 months ago.

And I am installing right now an SC motor that I purchased 2 years ago on my test stand for a start-up. Just to demonstrate how easy and simple to make an SC motor run. Hope to get this motor running before George’s (just kidding). I need a week to get everything set-up.

Tony

[pete3799]

This was mentioned by someone earlier in this thread but not verified that i could find.
Was this part changed also?
CSV flange (911-110-264-00) Alert......

[boyt911sc]

Pete,

I asked George about this CSV flange during our telephone conversation yesterday and said it has the hole.



George,

Please confirm the CSV flange. Thanks.

Tony

[Schulisco]

Originally Posted by pete3799

This was mentioned by someone earlier in this thread but not verified that i could find.
Was this part changed also?
CSV flange (911-110-264-00) Alert......

I mentioned it ... see https://forums.pelicanparts.com/porsche-911-technical-forum/1119098-911-sc-cis-residual-pressure-4.html#post11702682

Originally Posted by Schulisco

An example: My car also still had serious cold start issues. I examined every part of the CIS...almost everything was either bad (airbox, TTS, FD, injectors, vacuum lines, switches, temp sensor) or a wrong part (in my case the WUR). I replaced them (TTS, WUR, airbox) pr let overhaul them (FD), injectors, temp sensor, switches), adjusted the sensor plate etc. And still the car won't have a proper idle on cold....
The reason I found later - that red plastic flange for the CSV was one of that false series with no hole - it was closed for the air line coming from the vacuum valves and the AAV....so the engine could not start either when cold. It immediately ran on too rich mixture every time when cold. I could keep it running while playing with the throttle. But then the mixture was quickly too lean because the engine was cold...it took me everytime several minutes until then engine was warm enough before I could get it out of the garage...very frustrating and annoyed neighbours...

I identifed the problem with a smoke generator filling the vacuum lines from one of the vacuum valves and closing each other - after a while the filling line of the generator popped out due to overpressure...
I already recommended to use such a device at my first posting here as Tony did as well...

That's what I mean when working on a going crazy CIS car...you cannot rely on any part of it unless you examined and proved it...

But same here - this cannot be the culprit because Georges car before current trouble began started without any issues from my understanding...so this can't be the cause for his trouble now.

We're looking for sth, which has going bad over time whithout changing anything on the vehicle. So at least one thing has gone bad. We see that the cold CP is far too low, raises far too slow. This enrichens the mixture over all frontiers that the car won't start with the CSV. Without the CSV it will start after longer cranking. Either the WUR is bad or more likely somwwething else, because the fuel hoses at the WUR are dry after the car sits over night or several hours. From my understanding and what I've seen on my car is - there's always some fuel. But George reports there's not even a drop. And that's weird froim my point of view. My concern is the dry fuel control pressure line between the WUR and the FD. We see in the 2nd video that it takes way too long to fill it up and building some pressure...
And if he got the car starts and runs, it runs fine George said, right?

Thomas

[ahh911]

Thomas,
On my sc the line appears completely dry after sitting, but is it really? zero issues starting (over 20k km). You have fuel dripping out of the fd to wur connection the next day. Either I'm lucky, or it doesn't matter or there are conditions on shut down that we simply don't understand. My system is very... very original, no work was needed to recover any modifications to the engine or kjet, except for a new bosch fuel pump that comes with a check valve, I just changed it because it's cheap and I don't want to be stuck somewhere for such a simple replacment. 81sc, usa. Sorry, new injectors as well when the top end done two years ago, again cheap and just makes sense to replace.

I'm always up for an improvement, cost is very low for most of these components, so if you can prove that there should be fuel dripping out of the line, then I can learn, or improve even further a very decent performing car. Just for your info, at 3500rpm, when the pedal is pressed to the floor, there is a shock of acceleration, so I assume my accumulator is acting properly. The acceleration doesn't let up either. This car has been driven it's entire life, so the fuel dist system has not sat. I've read that you've replaced several parts, probably more than me, either I am off factory, or you are. It would be great if someone else can verify or we can solve the discrepancy. Also, when the wur is cal'd right, it will start on first crank, warm/cold/hot so the basic intended functionality of the device is in order as well as all other elements required to keep the pressure up after shut down.

I guess what I'm saying is, don't look too much into the FD to wur line dripping after sitting for 12 to 24 hours as a very important piece of information until more data has come in from many others. I've provided my facts, you have a different result, if no other info comes in then this dripping or not dripping is questionable in the attempt to solve the issue, at this point. It's a very easy test to do, took me two minutes, if and when this is solved, if fuel comes out the next day for George, I will be very happy to benefit from this post, was not expecting anything in return, we'll see.

tschuss,

Phil

[boyt911sc]

Originally Posted by Schulisco

This enrichens the mixture over all frontiers that the car won't start with the CSV. Without the CSV it will start after longer cranking.

We need a rich mixture for a cold start.

Originally Posted by Schulisco

Either the WUR is bad or more likely somwwething else, because the fuel hoses at the WUR are dry after the car sits over night or several hours. From my understanding and what I've seen on my car is - there's always some fuel.

The empty fuel line between the WUR & FD is normal after several hours and won’t affect starting. Go check your engines and inspect the fuel line. It would be bone dry. Reconnect the fuel line and start the motor. The motor should run.

Originally Posted by Schulisco

And that's weird froim my point of view. My concern is the dry fuel control pressure line between the WUR and the FD. We see in the 2nd video that it takes way too long to fill it up and building some pressure...

Test and verify. Confirm that your concern about empty fuel line is fact or myth. Not everything you hear or read in the Internet are facts. Let me repeat this again, the fuel line between the WUR & FD could be filled with fuel or bone dry and has no effect to the starting of a CIS motor.

This is a Technical Forum, feel free to discuss and disagree. This is how we learn from each others’ experience.

Tony

[leonardo911sc]

Originally Posted by ahh911

George,

I did the test you asked. Car ran yesterday afternoon, just now I cracked open the 14mm FD to WUR connector at the WUR (I did not crack open or remove any other fuel line), pulled the hose up and away from the WUR, shook it and still not one single drop. Just like I remember.
Garage temperature today is hotter than usual, overnight maybe 22, at time of test 28DegC.

Note:
1981 sc us.

Over 20000 km and only one or two double starts. The last time I was playing with the wur so it doesn't really count. If each trip is 50km, then 400 successful starts, and one double start. That's my car, what can I say.
Should add, temperature of starts where I run was -5C to 38C. Mostly between 20 and 30C. I don't start in winter or below -5C in the garage overnight.


Phil

Good day Phil

Thank you for the test.

So no fuel from FD to WUR line after many hours engine stopped. Since your engine is always starting i consider your test valid.

So no problem there.

[leonardo911sc]

Originally Posted by pete3799

This was mentioned by someone earlier in this thread but not verified that i could find.
Was this part changed also?
CSV flange (911-110-264-00) Alert......

Hi Pete, Tony

If you have the wrong CSV flange (without hole) then engine's rpm will not increase during cold start as the extra air from AAV and AAR will not pass. This is not my case.

An easy way to tell if you have the correct CSV flange is to remove the corresponding hose from the intake boot , start the engine and put your finger on the hose open end. If there is vacuum present then the hole on the flange exists. I did this test also and believe me the vacuum is very strong...

[leonardo911sc]

@ Tony

""""Hope to get this motor running before George’s (just kidding). I need a week to get everything set-up.""""

Challenge accepted!!!

One week deadline

hahahaha!!!

[leonardo911sc]

Hi Guys

Yesterday i went to visit a friend.

Since i was there i hooked the car to his analyzer.

Results:

1. CO% idle after basic mixture setting: 5.5%
2. CO% idle after adjusting the allen screw : 1.58%


3. CO% @3000 rpm: 0.69


Note the HC readings also. These engines had incredibly low emissions for that time!
This is also a good indication that engine has no vacuum leaks.

[SkiVT]

Many posts ago your idle mixture data was in the 2 to 2.5% range. This new data started at 5.5% before being adjusted to 1.58%? Did you determine why this difference existed? Has the change impacted the problem?

[boyt911sc]

George,

Please help me understand where you are now regarding your car status.
Question #1:
After sitting overnight, how many attempts (start) before you could make the motor to start? When I do this test, I just reach for the ignition switch through the window and turned the ignition switch. I do not touch the gas pedal.

Share what ever observation you have noticed or anything of interest. Example: What are the control pressure readings versus time, etc. Give me numbers instead of using adjectives.

Question #2:
Could you re-start a warm motor after 30 mins? After an hour? etc.

I want to replicate your problem/s so knowing your conditions is critical to my next test. Thanks.

Tony

[leonardo911sc]

Originally Posted by SkiVT

Many posts ago your idle mixture data was in the 2 to 2.5% range. This new data started at 5.5% before being adjusted to 1.58%? Did you determine why this difference existed? Has the change impacted the problem?

Yes. It was adjusted to 2.5%
If you read previous posts i reset the system to basic mixture setting.



Yesterday i checked the CO% with the basic setting (5,5%) and adjusted to 1.58% afterwards.

Thanks

[leonardo911sc]

Originally Posted by boyt911sc

George,

Please help me understand where you are now regarding your car status.
Question #1:
After sitting overnight, how many attempts (start) before you could make the motor to start? When I do this test, I just reach for the ignition switch through the window and turned the ignition switch. I do not touch the gas pedal.

Share what ever observation you have noticed or anything of interest. Example: What are the control pressure readings versus time, etc. Give me numbers instead of using adjectives.

Question #2:
Could you re-start a warm motor after 30 mins? After an hour? etc.

I want to replicate your problem/s so knowing your conditions is critical to my next test. Thanks.

Tony

Hi Tony

I have provided numbers for all my tests. This is a technical forum and i respect that.
Have conducted all the tests proposed from all parties involved into this thread. Thanks everyone one more time for your assistance.

I need your help for a test.

1. Connect your pressure gauge
2. Prime the system. Start engine or pump
3. Let the engine relax for at least 12 hours.
4. Try to start without throttle, only key start (as you mentioned)
5. Compare gauge pressure raise with my video.
6. Does your control pressure take that much much time to build up?

Video link
https://www.youtube.com/watch?v=GPXHHIFnsUw

Thanks

[boyt911sc]

Originally Posted by ahh911

Thomas,
On my sc the line appears completely dry after sitting, but is it really? zero issues starting (over 20k km). You have fuel dripping out of the fd to wur connection the next day. Either I'm lucky, or it doesn't matter or there are conditions on shut down that we simply don't understand. My system is very... very original, no work was needed to recover any modifications to the engine or kjet, except for a new bosch fuel pump that comes with a check valve, I just changed it because it's cheap and I don't want to be stuck somewhere for such a simple replacment. 81sc, usa. Sorry, new injectors as well when the top end done two years ago, again cheap and just makes sense to replace.

I'm always up for an improvement, cost is very low for most of these components, so if you can prove that there should be fuel dripping out of the line, then I can learn, or improve even further a very decent performing car. Just for your info, at 3500rpm, when the pedal is pressed to the floor, there is a shock of acceleration, so I assume my accumulator is acting properly. The acceleration doesn't let up either. This car has been driven it's entire life, so the fuel dist system has not sat. I've read that you've replaced several parts, probably more than me, either I am off factory, or you are. It would be great if someone else can verify or we can solve the discrepancy. Also, when the wur is cal'd right, it will start on first crank, warm/cold/hot so the basic intended functionality of the device is in order as well as all other elements required to keep the pressure up after shut down.

I guess what I'm saying is, don't look too much into the FD to wur line dripping after sitting for 12 to 24 hours as a very important piece of information until more data has come in from many others. I've provided my facts, you have a different result, if no other info comes in then this dripping or not dripping is questionable in the attempt to solve the issue, at this point. It's a very easy test to do, took me two minutes, if and when this is solved, if fuel comes out the next day for George, I will be very happy to benefit from this post, was not expecting anything in return, we'll see.

tschuss,

Phil

Phil,

There is nothing wrong with the control fuel line. The fuel in the line would slowly seep out through the WUR after several hours. And would be filled up again in the next start-up. What is critical is to have the system pressure present immediately during start up. The control fuel pressure will come next after the system pressure.

To measure the system pressure in your CIS, you need the valve for the gauge closed and open for control pressure. This is the conventional way how the CIS pressure gauge is connected to your motor. You could leave the gauge installed and run the motor to measure the control pressure but NOT the system pressure. To overcome this problem, I installed 2 set of gauges. One for the control pressure and one for the system pressure.

So at any given time the motor is running, I could monitor both control and system pressures simultaneously. But this is not for everyone. Unless you have a curious mind.

Tony

[Schulisco]

@leonardo911sc

I suppose that you set up the CO on the warmed up engine. Because a valid CO value for those cars is nowhere listed, probably nobody can tell you a evan a approximation of a CO value on cold start, they vary greatly from one vehicle to another...
1,58% CO (on a warm engine) is pretty pefect, afaik the euro SC starting '81 with 204hp should run between 1-2% CO.

The topic of the discussion is "residual pressure" and yoiur cold start problems and that weird behaviour, that the car started without CSV far better. And you wrote that the WUR is in spec. But the video tells us another story. The CP should start above 1bar, better ~1,4bar. I already wrote that the CP raises from too low.

The supposition was that either the FA or sth else is leaking and therefore the pressure is that low - and as you wrote that the WUR is in spec.

Q: How did you verified the WUR that is in spec?
Q: Did you already checked the check valve & the FA?

Thomas

[leonardo911sc]

Originally Posted by Schulisco

@leonardo911sc

I suppose that you set up the CO on the warmed up engine. Because a valid CO value for those cars is nowhere listed, probably nobody can tell you a evan a approximation of a CO value on cold start, they vary greatly from one vehicle to another...
1,58% CO (on a warm engine) is pretty pefect, afaik the euro SC starting '81 with 204hp should run between 1-2% CO.

The topic of the discussion is "residual pressure" and yoiur cold start problems and that weird behaviour, that the car started without CSV far better. And you wrote that the WUR is in spec. But the video tells us another story. The CP should start above 1bar, better ~1,4bar. I already wrote that the CP raises from too low.

The supposition was that either the FA or sth else is leaking and therefore the pressure is that low - and as you wrote that the WUR is in spec.

Q: How did you verified the WUR that is in spec?
Q: Did you already checked the check valve & the FA?

Thomas

Hi Thomas!

I set the CO% with hot engine and as per spec you provided (1-2% CO). Thanks for that.

WUR pressure setting:

1. Engine stone cold
2. Check WUR temp with infrared temp gun
3. Jumper fuel pump relay and turn ignition key ON
4. Pump working
5. Set cold pressure as per diagram spec with WUR power supply disconnected and vacuum applied.
6. Install the plug and wait until rising pressure at gauge gets stable.
7. ALL within spec.
8. Pump and check valve are new
9. Accumulator is new
10. Residual pressure test is above spec

If you see the video the WUR will reach the 1.4 bar but takes long time. While cranking is below 1 bar. This is where i am focusing now. I will do some tests and let you know.

Thanks

[ahh911]

Thomas, Tony,

I want to point out that the next start after I opened the FD to WUR line for the test asked by George, the car caught fire up as usual (csv & AAV* dominated), but then the rpm dipped to 400 for several seconds (Rich) then back up above 1000rpm. This was a unique start and I believe attributable to the opening to atmosphere of that line several hours earlier, requiring a re-build of pressure and a lower first 5 seconds of control pressure to evacuate the air introduced in the line. This tells me that even though the FD to WUR line looks empty, it's not filled with air, but I'd guess a vacuum, big difference in the meaning and understanding if that's the case.

Phil

[Schulisco]

Originally Posted by leonardo911sc

Hi Thomas!
If you see the video the WUR will reach the 1.4 bar but takes long time. While cranking is below 1 bar. This is where i am focusing now. I will do some tests and let you know.

That long time delay is our enemy...the WUR should reach those 1,4bar asap, even after several seconds when engine fired up.

Could you make 2 videos with the fuel pressure gauge connected to see how the pressure behaves after switching off the engine?
1. control pressure (not important if the engine is warm, but the WUR should have reached the warm cp)
2. system pressure

Thomas