The correct ccp spec is tied to the air temperature (more accurately the temp of the wur) when you took your reading. The graph would say 1.5 bar is within acceptable range if the temp is 12 to 18 celsius so you need to confirm that tenperature. The wur has to fully cool down to get another ccp reading. Looks like your watch has heartbeat but maybe not air temperature!!!!

The watch is not mine! :)

Taking this chart into consideration...
http://forums.pelicanparts.com/uploa...1614875279.jpg

The temperature at this moment is 17 C.
From the chart, ideal CCP should be between 1.4 bar and 1.6 bar... Am I reading it right?

Yes, vacuum assisted as you were doing. My bias is to the lower end of the range for slightly richer AFR at cold start. Also, remember to watch the gauge when you eventually do a cold start of the engine. From prior posts, your TTV should hold off vacuum for 30 seconds or so. At 17C, the cold pressure should be about .6 bar lower than the CCP you set with vacuum, so like .8 to 1.0 bar. This ensures a very rich mixture in the first seconds of "cold running" after the engine first starts.

Stuart, I have been also preforming the residual test and after 20 min, pressure was 1.2 bar.
Despite I think value is within specs, before the last chart I have been presenting, I pull two injectors out.
They were both wet. I have cleaned them with paper and after a few seconds, they were leaking again... very little but it shows on the paper.

Important to say that I have been preforming a CCP reading before taking out the injectors. Fuel pump relay was bridged and no movement was applied to the sensor plate.

Could this indicate stuck injectors? My god...this one was the second set I bought...

Well, that is something. With the engine not running, no fuel should flow from any injector. Old injectors sometimes can start leaking (the cure being new injectors), but with new injectors I'd not suspect that they were bad (though, of course, they could be).

What could cause this? One possibility is that the mixture adjustment screw is screwed too far down, thus allowing a little fuel through - the plunger is a hair open. One procedure to set the mixture after having everything apart is to crack one of the injector lines, and with the fuel pump running, turn the mixture screw clockwise until fuel starts to start coming out of the loosened fitting. Than turn back a bit until it stops (or some fraction of a turn, including having it stop).

In your case, you could just crack a fitting and run the pump and see. If fuel starts coming out, turn the mixture screw counterclockwise until it stops. Keep track of how far you have turned so you could get back if none of this works out. Of course, if it doesn't, maybe there is an issue with the fuel distributor.

Thanks Walt! I will try that!
This is really frustrating when you spend a lot of money in new/restored parts and then problems start to arise, from the components you have invested in...

It isnt uncommon, after refreshing old parts, vacuum lines, etc to have your mixture off. The mixture may have worked before because it was adjusted with existing air leaks, etc. Assuming the system is now tight, it could be too rich. How things like your wur turned out to not be in spec after paying to be rebuilt is something that would make anyone unhappy. A smile will return to your face when you solve this with your persistence.

This may be worth a read as well:

http://forums.pelicanparts.com/porsche-911-technical-forum/232089-cis-idle-speed-mixture-setting-without-analyzer.html

CIS troubleshooting...........
 

Alex,

Let’s start doing the basic tests and report the test results. Test run the FP:

• Pull all the six (6) fuel injectors and place them in individual appropriate container. There should be no sign of fuel delivery at this point.
• Disconnect fuel injectors from the fuel delivery lines and observe for any sign of fuel drips or leak.

A couple of small drips after you start the FP is normal. But no drips after 10 sec. of running the FP. Inspect all six (6) points for any sign of fuel drips while the FP is running (engine off). Share your test results.

Tony

Back to this thread...Preformed a smoke vacuum test:
A few leaks were identified:
- between the upper and lower part of the air box
- the axle of butterfly on the throttle body (residual)

Regarding injectors drip:
- injectors are wet all the time. All of them. This is the third set on the car!

Decided to pull out the injection from the car to sort the vacuum leaks.
First thing I found after taking it out:

http://forums.pelicanparts.com/uploa...1615399207.jpg

All six injectors with signs of fuel and all the closed head valves retained a large amount of fuel .

CIS troubleshooting....
 

Alex,

Pull out all the fuel injectors and test run the FP. There should be no fuel delivery at this point. Or fuel drips. If they exhibit fuel drips or premature fuel delivery, you got a problem like you are having now.

Adjust your fuel mixture LEANER until you eliminate the fuel drips. You may have adjusted the fuel mixture too RICH to compensate for the vacuum leak. Keep us posted.

Tony

Tony,
Before I took off the hole injection, I have done that test. With or without fuel pump test running, the injectors were dripping. Obviously less frequently when the fuel pressure was off.

Regarding the fuel mixture screw, I will test it when I assemble the injection back on the engine. But it makes sense... if there is a vacuum leak, AFR has to be compensated.

BTW, have you shared a full picture of the car? Always nice to see what’s being brought back to life.

If you have not seen this, here is the procedure you should be using for the fuel distributor default setting:
http://forums.pelicanparts.com/uploa...1615474034.jpg

Hi,
Car looks like this one. I just have some technical photos to help my work.

http://forums.pelicanparts.com/uploa...1615491421.jpg

.... and this is some work preformed on the car...


http://forums.pelicanparts.com/uploa...1615491528.jpg

http://forums.pelicanparts.com/uploa...1615491528.jpg

http://forums.pelicanparts.com/uploa...1615491528.jpg

http://forums.pelicanparts.com/uploa...1615491528.jpg

http://forums.pelicanparts.com/uploa...1615491528.jpg

http://forums.pelicanparts.com/uploa...1615491528.jpg

http://forums.pelicanparts.com/uploa...1615491528.jpg

Thanks eastbay for your help.
I am planning to put the engine back on car tomorrow and I will use that procedure.
Thanks!

Well... back to this never ending story...

- engine out to repair air box, while I was there, new intake boots, new vacuum hoses, etc.
- all fuel lines cleaned, all injectors cleaned through the back flush process

Before I started the car, I blended the fuel lines, and run the fuel pump for a while to check any signs of dripping, assuming the screw was way too far!
No signs of dripping with the fuel pump running (relay jumped).

Started the car, and results of a detailed oriented refresh on a CIS, starting to show up!
The warm up cycle much more evident, very smooth idle... looking good.
When for a ride, reaching the operating temperature and the for 115th time, the 20 minute test.

Remebrering that when I decided to pull out the engine for better check on the air leaks, I found the intakes completely flooded on the cylinders with the valves closed.
Many of you have suggested, logically, that probably the mixture screw was way too far.

At first it looked like that was not the case for the first checking I did before starting the engine.

After the 20 minute test, the problem persists! Rough start for a few seconds (flooded again?) and after that runs normal. Waited another 20 minutes and it was even worse, flooding two spark plugs.

From what I see, I can conclude, injectors are allowing fuel out.
Injectors were new... but after all of this, that does not mean nothing...

Today I decided to try and set up the piston position in the fuel distributor following the procedure suggested by eastbay.

Pulled out all the injectors, fuel pump running, started to turn the mixture screw down (clockwise) until the injectors barely spray. Turned half a turn back.

Started the car and once again it was a perfect cold start. Very smooth.
Drove up to the running temperature and when I stoped, pulled out two of the injectors into small containers to check how much they drip during the 20 minutes after a running temperature stop.

Nothing! 1 or 2 drops in 20 minutes...

How this can be? If I don’t pulll out the injectors, after the 20 minutes the engine will start like it is flooded.... but if I pull out the injectors during the 20 minutes it does not drip any fuel... ????

Should I order the third set of injectors?

These were completely clean and doing a good spray after that. I did not check the opening pressure but they were spraying nice when pressure was applied.

is there anything else I can do with them?
Is there a separation between the sealing function of the injector and the spray function? Meaning, It can be spraying well but not sealing the fuel correctly when the engine is off?

CIS fuel injectors........
 

Alex,

Were you using brand new or refurbished CIS fuel injectors? You need to know the cracking pressures of the used or refurbished injectors. Even new ones, I test them before installation.

All these CIS tests should have been performed while the motor was out. And I test run the motor before I install the engine in the car. It saves me a lot of time and less aggravation fixing any problem that might prevent the engine from running well.

How long have you been doing the start-up? Either we have communication problem or you are having trouble understanding the suggestions presented to you. As a professional mechanic we have no business telling you how to do your job. The irony is that I have successes helping others but failed miserably with a trained mechanic. I feel frustrated and disappointed at this moment because of my failure to assist you.

Tony

Hi Tony,
The injectors were brand new before I started to share this subject here. These were the second set after I assumed (wrongly because I did not test them), pressure was being lost through them. I cannot find here on the Island the proper bench test for CIS injectors. I think I might build one... to test them even when new.

I didn’t do more tests with the engine on the bench because I felt the remaining ones (injectors dripping) could easily be done with the engine on car... specially the mixture screw setup.
And also because all this situation has been creating a big frustration and sometimes I see myself speeding up things, unconsciously...

Regarding the startups, after all the improvements done, they have been reducing significantly. Before, an hot start would take 3+ seconds, now in half time. The actual time would be acceptable if the car would run properly after that... but not. I suspect it does not work properly until the excess of gas is present on the chambers.

Tony, being a mechanic or not, I think if I am here, it is because I recognize my lack of knowledge and was humble enough to search. That is my posture. That is why I have the opportunity to listen to so many experienced guys here and on other platforms - and I am very grateful for that!

I have been searching older posts and I don’t see where I contradict or misleads the tests you and others have suggested.
Maybe I am not able to explain the results or I don’t do it correctly... but I don’t see where... could you please be more specific...?
I really want to share the information clearly so others can help.... but if you could point out where, it would be of a great help.

Don't feel bad. Tony made an engine test stand. I'd love to have one, but I'd only use it every other year at most, and don't have space to store it. Tony loves a challenge, because he wrestles these engines down to his basement and back up!

I keep thinking of using some old brake MCs I have to make an injector pressure tester. Gauges are cheap. But I've not had issues with new injectors, and wouldn't use it often, so it doesn't get done.

I agree there ought not to be raw fuel sitting there on the back of closed valves (and thus probably in the combustion chamber of the open ones). And if I understand things correctly, there ought not to be any significant residual pressure to the injectors with the engine stopped. Because the FD plunger should be down far enough that no fuel can get from the lower to the upper chamber except for the control pressure system, which only gets to the top of the plunger, and also over to the WUR. It shouldn't get to the the injector lines.

I see two protocols for the emissions screw setting system - the one you used involved watching for the injectors to spray, then resetting the screw. The other one involves either removing an injector or - to make things simpler - loosening one of the injector lines at the FD. Adjust until some fuel emerges, then reset the screw. I would expect this second approach would result in a lower position for the plunger, but maybe not. Much easier and quicker than pulling an injector, and not dependent on the injectors. If you get the mixture screw too lean, I'd expect you would see the engine start when cold (on the cold start valve fuel), then stall due to an over lean mixture. Fine tuning of the mixture typically involves an exhaust gas measuring instrument, and checking that at idle when it is running might also be informative.

You can delay the warm up feature of the WUR significantly by pulling the electrical heater plug from the WUR, if that might help.

The fuel pressure specs have a range. You can adjust the fuel pressure with the washers on the pressure setting screw. I wonder if reducing system pressure to Porsche/Bosch's minimum would help, if it is at the higher end of the range? Long shot, as shouldn't matter.

What about the fuel in contact with MC’s seals? Will they handle it?

Maybe a dumb question: your description a couple posts back says “two spark plugs” have fuel. Is it 2 or all 6? So is it 2 injectors that leak or all 6? Did you save all the injectors you bought recently. If only two are misbehaving, you try 2 from your prior set you thought were bad?

“After the 20 minute test, the problem persists! Rough start for a few seconds (flooded again?) and after that runs normal. Waited another 20 minutes and it was even worse, flooding two spark plugs.”

Main reason I am asking is it seems possible to have 2 bad in a new batch of 6 and very unlikely to have all 6 be bad. Somebody may chime in with an “all 6 were bad” experience by it seems worth considering if you have not already, especially if you can’t test their cracking pressure individually.

Answering your question: when I disassembled the air box to repair the crack I noticed that all 6 cylinders had signs of fuel. More evident on those with the valves closed.
Because of this, and because I had already tested Tony’s suggestion about having the fuel pump running with all injectors out in 6 containers, I assumed they were behaving the same. No dripping.
After I drove the car to the running temperature, I stoped and pulled out only two injectors, as a reference, because this engine has hard lines and it is difficult to pull out all 6 injectors without bending the lines. Only two as a reference to stay out over night in the containers to check the amount released.

Today, there were no signs of fuel in the containers.

I am starting to believe that our problem was due to a temporary contamination of the injectors (or the system), and after we recently clean all the components and lines, injectors, fuel tank, pressure accumulator, etc. it is now starting to “stabilize”... (???)...

What is a fact is that many things had improved since starting all the tests and checkings- cold start is much better, running smoothly, etc.

I personally really like have an AFR gauge in my car. You may want to consider if you don’t have easy access to a tailpipe testing unit. It helps ensure your setting, after you have confirmed all your pressures, etc are correct and let’s you know ongoing if things start to go astray. It’s one of the few continuous data providers on these old cars.

yes, you are right! I will consider that

Alex - I wouldn't worry about seal compatibility using a spare brake MC as a pump to test injectors. Brake fluid and gasoline are both hydrocarbons, so that ought to help even if one would use a different seal formulation for a fuel pump. If the seals deteriorate, you'll soon find out with leaks you can easily deal with. I wouldn't expect that to happen in the short time you'd be doing this. If concerned, you could flush the system after you were done with it with brake fluid, or motor oil. Maybe google "seal fluid compatibility" to get some idea of what sources say. But it isn't like this is a part going into your car.

Yes, I will consider that. I have it almost ready. Lack of time is pulling me to other areas...
Meanwhile my mechanic tested the injectors using a different approach.
Please feel free to leave your insight about the conclusion of this test - if there is any!
He connected a fuel pump with a pressure switch, through a gauge, to an injector.
Pressed the switch until the injector opens and right after, release it.

All 6 injectors hold the pressure between 2,4 and 2,5 bar...
Can I assume they open at the same pressure as they hold pressure- close?
Or, closing at this pressure, higher pressure will be needed to open them?

Any ideas?

Fuel injector’s cracking pressure test.......
 

Alex,

You need to test the fuel injectors individually to determine its cracking pressure. All you need is a fuel pump and supply tank to do the test. Or use the CIS in your motor. Below is the picture of my tester for testing the opening pressures of a fuel injector or a oil piston squirter.

http://forums.pelicanparts.com/uploa...1617075155.jpg

You could use air or fluid to do the test. I tend to like to use fluid because you could observe better watching the fluid (water, gasoline, kerosene, etc.) than compressed air.

Tony

Thanks Tony,
I have written “all 6 injectors were holding pressure between 2,4 and 2,5 bar” but when tested individually. This process I described on the previous post, only allows to test one at at time.