yet another CIS hard start.

[67flat4]

So I'm new to the CIS and and the board. I have read up on it and I've learned a lot and still learning.
On to the car 1981 911 SC ROW, I made a smoke machine to check for vacuum leaks and have found the injector seals leaking, while I was there I have found 3 bad injectors. So once I get the new injectors and seals I will retest for vacuum leaks again.
My issue is that during the fuel pressure tests the injectors keep dumping fuel. The Air plate seems to be in the correct position. If I slightly pull the lever down I can get the injectors to stop.
So I know I need to start with fuel pressures but I need to be able to perform the tests. The car does run just hard to start.
I have a feeling the mixture screw is set too rich?
I know diagnosis over the internet is tough so let me know what other infor you need to help me.

[ossiblue]

You've already found a key problem--the injectors are spraying when they shouldn't. The fact you can stop the spraying by pulling down on the plunger is significant because it likely means the plunger arm is getting stuck, or the pin in the fuel distributor is getting stuck, or the stop adjustment for the arm is out of adjustment. The spraying of fuel could also contribute to your hard start situation.

Before worrying about the mixture screw, solve the situation of the spraying injectors. Clean and inspect the plunger in the intake, and check the free movement of the mechanism. Find out why the plunger can be "pulled down" to make the injectors stop spraying. Once that is resolved, proceed with your pressure tests.

[Vereeken]

Look at my fight with CIS by doing a search on my username.

Although I not recommend it as a first step follow this procedure out of the Bosch manual (I also did that when I revised my CIS system).

With 1 injector out and connected to the fuel line (injector in a small container, engine dead cold).

Jump the fuel pump in the relay box upfront so that the FP runs when key in position 2.

Put your allen key in the mixture adjustment screw and turn clockwise until the injector starts to spray (not drip). When it sprays a nice pattern turn the mixture adjustment screw half a turn counterclockwise. The injector should stop spraying .This gives you the base setting.
If you have a 81 SC CIS you have a 089 WUR and the opening bar for your injectors is 2,5bar.

Leave the car for a while as you have dumped quite a lot of fuel in the intake chambers by doing this procedure. Best is to remove all injectors but that is a drag with hard fuel lines.

Michel

[67flat4]

Originally Posted by ossiblue

You've already found a key problem--the injectors are spraying when they shouldn't. The fact you can stop the spraying by pulling down on the plunger is significant because it likely means the plunger arm is getting stuck, or the pin in the fuel distributor is getting stuck, or the stop adjustment for the arm is out of adjustment. The spraying of fuel could also contribute to your hard start situation.

Before worrying about the mixture screw, solve the situation of the spraying injectors. Clean and inspect the plunger in the intake, and check the free movement of the mechanism. Find out why the plunger can be "pulled down" to make the injectors stop spraying. Once that is resolved, proceed with your pressure tests.

I think this is it took another look when I got home. It's ever-so slightly that it needs to move to stop. The plate moves free through the whole stroke and bottoms out (too soon I think). I took pics but its so minute that it doesn't show.
I'll adjust it, clean it up and install the new injector seals and injectors, do another smoke test. and give you guys an update.
Thanks

[timmy2]

Replace your injector sleeves and o-rings while you're in there.
Porsche 911 & Turbo CIS Fuel Injection - Page 4

[boyt911sc]

Originally Posted by 67flat4

So I'm new to the CIS and and the board. I have read up on it and I've learned a lot and still learning.
On to the car 1981 911 SC ROW, I made a smoke machine to check for vacuum leaks and have found the injector seals leaking, while I was there I have found 3 bad injectors. So once I get the new injectors and seals I will retest for vacuum leaks again.
My issue is that during the fuel pressure tests the injectors keep dumping fuel. The Air plate seems to be in the correct position. If I slightly pull the lever down I can get the injectors to stop.
So I know I need to start with fuel pressures but I need to be able to perform the tests. The car does run just hard to start.
I have a feeling the mixture screw is set too rich?
I know diagnosis over the internet is tough so let me know what other infor you need to help me.

67flat4,

My only advise to you at this point is be careful and listen only to the people who knows about CIS. Focus on Ossiblue's advise and you'll be in good hands. Others are offering you advises while they could not even fix their CIS own problem/s. So be wise and use your good judgment. Just my two-cents.

Tony

[67flat4]

Thanks Tony, and I want to thank you already, I've read many of your posts and have learned a lot about the CIS design and function. Sometimes I forget to KISS (keep it simple stupid) I'm a big fan of that philosophy but am very forgetful. You seem to always remind people of this.

[67flat4]

So all 6 injectors,sleeves and o-rings replaced. It's a little better. I adjusted the air plate took 1.5 to 2 turns out and the injectors no longer run constantly. on to the pressures. all at 65*F

cold is 2.2 bar this might be off I'm going to retest again. I think i may have had the wur hooked up to power before I did the test.
warm is 3.3
system is 4.5

I think I need to retest for air leaks first. but while getting the fuel pressures I noticed once the car was turned off I instantly loose 1bar then loose another .5 in another 30-60 secs. It does hold at 1.5 for whats been 10 min now. Not sure what normal is just noticed it.

WUR pressures change when hooked up to 12v.
AAV moves when hooked up to 12v.

I did search on the fuel accumulator. no leaks from bottom port with the air plate lifted. however the hose that is connected to the bottom port spewed with the air plate lifted I think this normal as it appears to be hooked to the return line?

After replacing the injectors I did have to bump the idle up. It wouldn't stay running.
I am going to double check the pressures. but what do you guys think so far.
once the car is running it does run good.
thanks.

[kerthunk]

This should help...

[67flat4]

59*F
cold 1.95

[67flat4]

So cracked air box has been found. Not what I was hoping for. I guess my next step is to pull the intake and look for additional leaks.
Is it likely that this is the only leak or is the intake going to be leaking elsewhere?
it was so small I wouldn't have caught this leak without the bubbles.

[manbridge 74]

Is it cracked or is it at the rubber boot?

These boxes are made in two pieces. It is likely leaking at the seam. I like the soap test, but has anyone tried a vacuum test? Pulling some vacuum and seeing if it holds might replicate engine running conditions a bit closer. Plus it would allow one to know if back of the airbox is cracked where one can't see bubbles. Just a thought.....

[boyt911sc]

Originally Posted by 67flat4

So cracked air box has been found. Not what I was hoping for. I guess my next step is to pull the intake and look for additional leaks.
Is it likely that this is the only leak or is the intake going to be leaking elsewhere?
it was so small I wouldn't have caught this leak without the bubbles.

You are moving in the right direction. Air leak is the Achilles heel of CIS and if you could minimize any significant source of air leak in the system, the rest of the troubleshooting would be easier. The reason why your fuel mixture was set too rich in the beginning was due to this unmetered air. Someone had adjusted the mixture to compensate for the unknown lean condition.

I've been trying my best to tell people that adjusting the fuel mixture without verifying the absence of air leak/s in CIS would make a bad situation worst!!!!!! After you have corrected the vacuum/air leak in the system, proceed checking the fuel pressures. Keep us posted.

Tony

[timmy2]

Once you pull everything off, do a leak test on each component. Hoses, vacuum lines, devices etc. If there are more, you'll find them. Replace the injector sleeves and o-rings too.

[67flat4]

OK so I'm going to bull the air box. I found a leak on the underside on the rt that i can't get to.what all parts need replacement. so far I've got
6 intake gaskets
6 intake boots
throttle body gasket
FD gasket

already replaced the injectors,sleeves and o-rings.
I remember seeing a thread on this but have searched again and can't seem to locate it again.

Thanks again for all your help.

[manbridge 74]

Consider the need for a new or used airbox.

Unless you are really, really good at solvent welding ABS type plastic plus being able to pressure test it.

[timmy2]

Partial engine drop and lots of patience. Long arms and a good assortment of swivels and extensions. Did I mention lots of patience?

[rching]

67flat4 Where on the system did you add pressure? I was thinking of doing the smoke machine thing, carb spray has yielded no results, but pressure and soap solution seems a good alternate. TIA

[67flat4]

Originally Posted by rching

67flat4 Where on the system did you add pressure? I was thinking of doing the smoke machine thing, carb spray has yielded no results, but pressure and soap solution seems a good alternate. TIA

hose at the split in the brake booster. I did make a smoke machine and the only thing that showed with it was the leak at the injectors. I then switched to the soapy water and found one crack. Then found another leak with the carb cleaner. I wasn't able to get the soapy water to the bottom on the rt side. So in all a combo of all 3. you can skip the smoke machine the bubbles work a lot better.

[rching]

Is there another place to hook up pressure if I have no Brake Booster? I saw where someone ran a hose into the throttle body and taped it all up. Is there a better option? This is on a 73.5 T. Thanks