Troubleshooting CIS

[Alan L]

Actually, a second thought - maxing out from Cold pressure - around 2.5 bar, to hot pressure 3.5 bar in about 20 seconds from cold sounds very quick. The warm up phase should take a few minutes. This may be prematurely leaning out.
Brian may have some words of wisdom here - but this does not sound quite right, and would produce the symptoms you describe.
Alan

[boyt911sc]

Originally Posted by Alan L

We've all been there and done that.
I pulled an engine/g/box once, and stripped the gearbox right down to find why I had lost two gears. After no luck in the g/box and reassembling engine (g/box integral in engine), I found a stone in the linkage tray.
You have a way to go yet to catch up.
Vacuum leaks would be a good follow up - as previously suggested - run engine and spray hydrocarbon around all joints, rubber intake runners etc - if the engine note changes try and locate source of intake.
Alan

You don't need a running engine to do the following tests:

1). Control, system, and residual pressures. Just a running FP.
2). WUR's could be inspected and evaluated by simply running the FP.
3). Looking for these mysterious air leaks does not require a running engine.

There are very simple procedures to do these tests and if a guy like me who have been called "hopeless" could find them, what more about the rest of the community.

Tony

[RarlyL8]

At 75F the WUR will warm up quick and achieve near spec warm fuel pressure in 30 seconds.

Do you have a safety valve in the air filter housing? Has it blown before? Check to see that it is seated properly.

What happens if you try to start the engine cold holding at part throttle? (only attempt this if you have a safety valve in place)

Have you done the vac leak tests and are confident in the results?

Have you pulled the spark plugs on a cold engine? What did they look like? Were any wet?

[tirwin]

Originally Posted by Alan L

Actually, a second thought - maxing out from Cold pressure - around 2.5 bar, to hot pressure 3.5 bar in about 20 seconds from cold sounds very quick. The warm up phase should take a few minutes. This may be prematurely leaning out.
Brian may have some words of wisdom here - but this does not sound quite right, and would produce the symptoms you describe.
Alan

Alan,

I ran the test again and this time I did a better job of watching the clock. It took ~40s instead of the 20s I previously said. I don't know that it makes that much difference -- it sounds like you're thinking it should be happening on the order of minutes.

I took a video and posted it on YouTube.

YouTube - ‪Porsche 911 CIS Cold and Warm Control Pressure Test‬‏

[tirwin]

Originally Posted by boyt911sc

You don't need a running engine to do the following tests:

1). Control, system, and residual pressures. Just a running FP.
2). WUR's could be inspected and evaluated by simply running the FP.
3). Looking for these mysterious air leaks does not require a running engine.

There are very simple procedures to do these tests and if a guy like me who have been called "hopeless" could find them, what more about the rest of the community.

Tony

Tony,

Done 1 & 2. 3 is next on my list.

[tirwin]

Originally Posted by RarlyL8

At 75F the WUR will warm up quick and achieve near spec warm fuel pressure in 30 seconds.

Do you have a safety valve in the air filter housing? Has it blown before? Check to see that it is seated properly.

What happens if you try to start the engine cold holding at part throttle? (only attempt this if you have a safety valve in place)

Have you done the vac leak tests and are confident in the results?

Have you pulled the spark plugs on a cold engine? What did they look like? Were any wet?

Pop-off valve is installed in the air box, yes. As the car is new to me I can't say for sure what happened in the past. Maybe the pop-off valve was installed after an incident. I suppose their could be a crack or it could be loose.

I haven't tried cranking with the accelerator depressed -- I was under the impression that was a no-no with these cars. What I have noticed is that sometimes when I cold start the engine I can hear a little backfire and the pop-off valve opening.

I think tomorrow morning I will record a video of me starting the car and post it so some of you can get a better sense for what I'm saying.

I haven't done a vac leak test. That is my next course of action. A couple of people have suggested using 5-10psi of air. If anyone could outline a procedure for that I'd be very grateful.

[tirwin]

Originally Posted by RarlyL8

Have you pulled the spark plugs on a cold engine? What did they look like? Were any wet?

Forgot to answer this question. No I haven't pulled the plugs. I was about to do a full tune-up so I'll have a maintenance checkpoint but I'm still waiting on the valve cover gasket kit to arrive. I'm also considering new plug wires but I can't make up my mind which ones to use yet. Anyway, I was putting that on the back burner until I got this resolved, but I see your point.

[tirwin]

Originally Posted by Ron.G

Did you try removing the oil cap? It should drop your RPM's to about 750 frm 900.
If it makes little change I would start looking for air leaks.
Don't know if this was already suggested.

Ron,

This wasn't suggested yet. I was trying to focus on the fuel pressure tests before I started looking elsewhere. Since they seem to be normal, I think vac leaks are next on the list. I'll try this.

[tirwin]

Originally Posted by boyt911sc

There's nothing wrong with your WUR!!!!
1). The control pressure won't change or increase if there was no power to it.
2). WUR gets power at the same time as the FP.
3). You have unmetered air in your system.

It takes only a few minutes to set-up the test and 10 seconds later you're done. Avoid the guesswork and you'll find this air/vacuum leak/s in your system. All you need is a continuous supply of low air pressure between 5 - 10 psi. And PRESTO!!!! They will be right in front of your nose where you least unexpected to find. There are too many possible sources of air leaks in a CIS and some people get lucky by using carb cleaner to find them. But you cannot rely on luck all the time. The test will tell you whether it is leaking or not. No if's or but's.

Tony

Yes, I think we have established the WUR is operating properly. So it's on to air/vac leaks. I'd much rather run air through the system and find all the leaks rather than guess. I've never done this test before so I would appreciate it if you could describe how to set it up.

[edgarcia737]

Send it to Fuel Injection Corp. for rebuild. Goggle them. Call them. Bob rebuilt my WUR and haven't had a problem since. Plus he's a great resource for troubleshooting..

Good Luck and keep us posted.

Ed

[wichitaguy57]

Tony,

Could you please explain how to setup this test?

Originally Posted by boyt911sc View Post
There's nothing wrong with your WUR!!!!
1). The control pressure won't change or increase if there was no power to it.
2). WUR gets power at the same time as the FP.
3). You have unmetered air in your system.

It takes only a few minutes to set-up the test and 10 seconds later you're done. Avoid the guesswork and you'll find this air/vacuum leak/s in your system. All you need is a continuous supply of low air pressure between 5 - 10 psi. And PRESTO!!!! They will be right in front of your nose where you least unexpected to find. There are too many possible sources of air leaks in a CIS and some people get lucky by using carb cleaner to find them. But you cannot rely on luck all the time. The test will tell you whether it is leaking or not. No if's or but's.

Tony

[Ron.G]

There are a few screws inside your air box. remove the air filter and look to see if they look as though they are not screwed in all the way. This is a tell tail sign that you have a cracked air box from a back fire.

They usually crack on the bottom side seam of the box next to the passenger side intake runners (were they tie in the the air box).
sometimes you will see a crack along the drivers side seam.

I just replaced my air box for the same symptoms that you are experiencing.
If it is running a little rich it is probably tuned that way to compensate for a vacuum leak.
Hope this helps.

[tirwin]

I was tracing out the vacuum lines so I could start checking for leaks and I discovered that the vac line going to the "vacuum limiter" is disconnected. I believe this is what's called the Auxiliary Air Valve (AAV). Or is this the decel valve? It is right under the FD and has two big hoses on the left side and the vac connection on the right.

I also jiggled the injectors and the ones connected to #4 & #6 cylinder seem to have a lot of play in them compared to the others. #4 is by far the worst. Maybe I need to replace the o-rings on the injectors?

Summary of what I know so far:
- CIS pressures are good
- PO states engine set to run rich
- O2 sensor disconnected
- vac line to AAR/devel valve(?) disconnected & plugged
- airbox looks to be in good shape

Maybe AAV/decel valve is bad and was disconnected at some point. Definitely sounds like the richness is to compensate for a vac leak or other issues. If I find a vac leak, it sounds like I'll need to take this someplace that can check the exhaust gases.

Am I on a fool's errand here?

[911GT2]

Subscribed

[47silver]

i think the ohms across the wur heater should be 34? if you get an open ciruit then it needs repaired.

[tirwin]

Ok, folks -

First let me say thanks to all those that have offered advice and insights. It is definitely helping me understand the idiosyncrasies of these engines. This is my first Porsche and I'm just trying to take the time to learn everything I can.

If anyone is still paying attention to this thread, I posted a video on YouTube showing exactly what the car is doing from cold start. The car sat overnight.

YouTube - ‪1983 Porsche 911 SC with Cold Running Problem‬‏

Cranks #1 & 2 I just turned the ignition. As you can see, it starts but then wheezes and sputters until it dies.

Crank #3 I gave a little gas after it started, but didn't keep the RPMs up (on purpose). It dies again.

Crank #4 I gave a little gas after start again, but this time I kept the RPMs above 2k. What you can see is the RPMs bouncing around a bit under and over 2k. What you can't see is that I'm trying to keep the accelerator constant. It seems like there is a slight delay between what I'm doing with my foot and what the RPMs are doing. I only need to keep the RPMs up for a few seconds and then it settles in at a normal idle.

If any of you gurus out there can tell me anything insightful, I would appreciate it.

Here's where I'm at:

1) Still need to figure out whether it is the AAV or decel valve that has it's vac line disconnected.

2) Why would it be disconnected?

3) Going to search for vac leaks next. If I can figure out how to used the compressed air method, I will do that. If I can't, I'm waiting on a halotron fire extinguisher to arrive and then I'll use the carb cleaner method.

[tirwin]

There seems to be a great deal of confusion in other threads on this forum as to what this thing is. It is labeled "vacuum limiter" on the vac diagram on the underside of the rear decklid. Is this is AAV or decel valve? Why would the vac line be disconnected?

[5String43]

As I mentioned in an earlier response, my car does/did pretty much the same thing yours was/is doing. But earlier in this thread is a response that says the responder has been able to tune this behavior out of cars. One of his tips is to remove and plug the vacuum retard line, which my car has, and retime it. I did that and it's made the car much easier to start.
Now, my wrench wants that line connected, so I'm in a bit of a quandry. What seems plain, though, is that without it, the car starts better and off-idle throttle response is a whole lot improved.

[tirwin]

As I mentioned in an earlier response, my car does/did pretty much the same thing yours was/is doing. But earlier in this thread is a response that says the responder has been able to tune this behavior out of cars. One of his tips is to remove and plug the vacuum retard line, which my car has, and retime it. I did that and it's made the car much easier to start.

Now, my wrench wants that line connected, so I'm in a bit of a quandry. What seems plain, though, is that without it, the car starts better and off-idle throttle response is a whole lot improved.

5String43,

Thanks for the post. I'm still trying to sort out what has been done before I bought the car and why. The AAV/decel is the latest puzzler. I have a feeling some things were done for a reason - either it was to improve performance or it was to fix another issue.

Perfect example is your wrench. Why does he suggest leaving it disconnected? I'm not arguing. I just want to understand.

[boyt911sc]

Originally Posted by wichitaguy57

Tony,

Could you please explain how to setup this test?

Originally Posted by boyt911sc View Post
There's nothing wrong with your WUR!!!!
1). The control pressure won't change or increase if there was no power to it.
2). WUR gets power at the same time as the FP.
3). You have unmetered air in your system.

It takes only a few minutes to set-up the test and 10 seconds later you're done. Avoid the guesswork and you'll find this air/vacuum leak/s in your system. All you need is a continuous supply of low air pressure between 5 - 10 psi. And PRESTO!!!! They will be right in front of your nose where you least unexpected to find. There are too many possible sources of air leaks in a CIS and some people get lucky by using carb cleaner to find them. But you cannot rely on luck all the time. The test will tell you whether it is leaking or not. No if's or but's.

Tony

Wichitaguy,

PM me your email and will forward a detail description of the process including some pictures.

Tony