CIS troubles - two problems, related?

[7783911]

Sorry to Jump in on someone else thread

Tony

is there a simple way to test the decel valve on my 77targa/83 sc engine? I have always had a strong burble on decel, thought i solved when i found a loose vacuum hose at the decel valve but the burble remains. I am not sure if that is the decel valve or the exhaust (maybe a baffle within has let go, its a 2 in 1 out sport muffler). No Vacuum leaks, all exhaust components sealed up tight...so leads me to decel valve or muffler.

Nice box of decel vales...wanna sell one or trade for a new targa rear bar seal I have as a spare?)

[AndrewCologne]

Your decel. Valve is closed per default. One metod for testing is when idling, unplug its vacuum hose and connect a simple vacuum tester like this one or similair:
https://www.amazon.com/Amdirect-Bleeder-Vacuum-Pistol-Tester/dp/B015IP5060
When applying vacuum at a specific point with a given inHg the valve should open and the idle rises.

Regarding your burbles, ... pops and burbels occur mainly cause of a too lean air fuel mixture which won't be ignited in the combustion chamber / cylinder but afterwards in the exhaust systems due to an arbitary self combustion as of of hundreds of degrees clesius at the exhaust manifold.
Or also cause of a correct mixture but a too late ocurring ignition at the spark which rises the possibility of a non proper/full combustion of the mixture, where still parts of fuel or the combustion itself get into the outtake.
"Sudden" lean mixtures occure mainly on fast Throttle closings at higher rpms as of by this a huge rise of vacuum in the maniold happens, which lets the mixture lean out.
Or, ... cause your initial CO is simply set to lean.

Does your 83 SC got its second vacuum hose properly connected to the orginal dizzys second vacuum can?
What is your initial ignition timing with all vacuum hoses unpluged from the vacumm can of the dizzy?

[7783911]

I dont have a second vacuum on the dizzy, where would it connect? I do have a vacuum test gun so will try that this weekend if it ever warms up ... spring is a little late in Canada!

re timing, i will have to ask my mechanic to test when it goes in for spring tune..but i can say they tested for the burble and confirmed the fuel mixture is spot on, they were the ones suggesting it was the actual muffler baffle. The burble is definitely on decel (ie going down a hill in second gear)

I will bring your points up with them...especially since the muffler i want is crazy expensive (in Cdn $)

Thanks

[AndrewCologne]

If you have a vacuum test gun, then ... you should consider buying a test light as well, so you can check your timings by yourself :-)

So if no second vacuum connection is present on your dizzy, your 83 model is actually a ROW one?

Greets to Canada

EDIT: Now I got it, a 77 Targa with a (US or ROW) engine.

[boyt911sc]

Your decel valve should be closed below 22” Hg. I like to set the valve opening between 21.5”~22.0” Hg. The older decel valve (pear shape) is much easier to calibrate than the saucer-like shape found in the ‘80~’83 US CIS.

Tony

Originally Posted by 7783911

Sorry to Jump in on someone else thread

Tony

is there a simple way to test the decel valve on my 77targa/83 sc engine? I have always had a strong burble on decel, thought i solved when i found a loose vacuum hose at the decel valve but the burble remains. I am not sure if that is the decel valve or the exhaust (maybe a baffle within has let go, its a 2 in 1 out sport muffler). No Vacuum leaks, all exhaust components sealed up tight...so leads me to decel valve or muffler.

Nice box of decel vales...wanna sell one or trade for a new targa rear bar seal I have as a spare?)

[mikesarge]

Sorry y’all, I gotta reclaim my thread

Today I went to try and start the 911. Started fine, but was majorly lean on the cold start. Took a solid 2-3 minutes to warm up and enrich enough to not backfire like crazy out of the intake when touching the throttle.

Seems to drive fine once it’s warm, still a tad rich at idle (12.8) and a bit lean on part throttle and decel (15-16 part throttle, 17 decel, seemed to backfire out of the intake a bit in-gear no throttle decel)

Would a thermotime valve fix this cold start issue? All pressures looked good so I removed my gauge. Now I’m just using the AFR to dial in the mixture, since I’m not adjusting FD or WUR

I am going to nudge it a bit richer and try again tomorrow on the cold engine. Any other tips?

Thanks
Mike

[AndrewCologne]

Originally Posted by mikesarge

Sorry y’all, I gotta reclaim my thread
Today I went to try and start the 911. Started fine, but was majorly lean on the cold start. Took a solid 2-3 minutes to warm up and enrich enough to not backfire like crazy out of the intake when touching the throttle.

a) from where do you know that the mixture is actually too lean on cold start?
b) if that is prooven, then, ... did you check the termo valve on the left keychain housing?

Seems to drive fine once it’s warm, still a tad rich at idle (12.8) and a bit lean on part throttle and decel (15-16 part throttle, 17 decel, seemed to backfire out of the intake a bit in-gear no throttle decel)

At idle your AFR should end up around between 14:1 and 15:1, once you partly accelerate it should go down and on bigger accel. it should even end up between 12:1 and 13:1.
Your results above are too lean and even with a not working deaccel. valve but in a closed state AFR should not rise that much.
Btw, ... did you check your sensor plate adjustment?

In my case with an active lambda control and wathcing my external display from my didgital ECU I can clearly see how the ECU compensates "a getting richer beyond idle" state. Means with a duty cycle at idle at approx. 55-60% when accelerating and driving/crusing at mid revs its duty cycle drops down to 30%, means the k-jet itself would let result the mixture even too rich if lambda control would not work or if being removed.
So in your case ... the AFR should drop when driving and shurely when accelerating

[mikesarge]

Originally Posted by AndrewCologne

a) from where do you know that the mixture is actually too lean on cold start?
b) if that is prooven, then, ... did you check the termo valve on the left keychain housing?


At idle your AFR should end up around between 14:1 and 15:1, once you partly accelerate it should go down and on bigger accel. it should even end up between 12:1 and 13:1.
Your results above are too lean and even with a not working deaccel. valve but in a closed state AFR should not rise that much.
Btw, ... did you check your sensor plate adjustment?

In my case with an active lambda control and wathcing my external display from my didgital ECU I can clearly see how the ECU compensates "a getting richer beyond idle" state. Means with a duty cycle at idle at approx. 55-60% when accelerating and driving/crusing at mid revs its duty cycle drops down to 30%, means the k-jet itself would let result the mixture even too rich if lambda control would not work or if being removed.
So in your case ... the AFR should drop when driving and shurely when accelerating

a) because it starts hard with fuel pressure as read on the gauge, and when the throttle is applied, it backfires out of the intake, and the revs do not increase. AFR gauge reads about 14.8, but there's no way the sensor is warmed up that quickly, so I do not trust it on cold start.

b) I do not have a thermotime valve, though I do have the two-pin plug for it. I may try to track one down, but I am not convinced that would cure my issues, as it only runs on the coldest days for a very brief period. There is a thermotime switch on my car, and I have found the procedure to test it as follows, from an old post:

Originally Posted by T77911S

i am sure there are lots of ways to test this circuit. so i assume it is hard to start. if so, i would not worry about the 12v to the heater side of the TTS for now. i would pull the wire form the CSV and check the resistance on the TTS to ground. if that is good, while someone cranks the car, i would check the voltage on the wire from the CSV, with it removed. if you so desire, when you have it running, you can pull the CSV wire off the TTS and check the resistance to ground, it should be open.

if that is all good, i would check for air leaks and then my cold control pressure, assuming plugs and all the basic tune up stuff has been replaced.

I also plan to do a smoke test, hopefully this weekend, when I get a chance to spend a couple of hours in the garage before I leave for a bit

[AndrewCologne]

Originally Posted by mikesarge

... There is a thermotime switch on my car ...

Thats what I actually meant :-) ... on the left chain housing

[SkiVT]

You can test the TTV functioning without having one. It blocks vacuum for 30-45seconds as shown in the video link posted several responses back. You can pinch the vacuum line yourself to hold off vacuum to see how cold start behaves. Let the vacuum happen after a similar period of time to see if it helps “cold idle” in that first minute or so.

[mikesarge]

Alright, one pack of camel blues later, and after some significant wrestling with the peanut, I believe I have diagnosed vacuum leaks coming from injector seals on 1, 4, and 5. What a PITA.

I was also getting smoke out of what I believe is the AAV port on the peanut, but that would be metered, since it’s on the back side (inside?) of the metering plate, right?

Also my pop-off valve would leak some smoke unless I pressed lightly on it. That seems fine, as it’s designed to seal under vacuum, and open under positive pressure (backfire). Again, correct me if I’m wrong.

On further inspection, the injectors on all 6 are pretty loose and can be lifted maybe ~1mm up and down, as well as freely rotate in their seals. I gotta imagine that’s what’s giving me my trouble.

I guess I’ll order seals (and oil ), and plan to pull the engine in a week or two. Unfortunately, my CIS is one of the lucky ones with the injector seals “swaged” into place, so there is zero chance I’ll do this with the CIS in the car.

Anything else you’d put on the list to do while the lump is out?

Edit: top end was done two years ago, so oil leaks have been handled!

Edit 2: I just gave injectors #4 and #5 a good tug and the sleeve and injector popped right out!? Maybe I can get the rest out with a little work with them in the car too, that would save me a some effort!

[7783911]

If its out, you should check the triangle of death at the back and possible refresh some parts once you inspect for leak indications. I ve done it with the engine in the car and its not alot of fun, 5 minute job with the engine out, especially with the CIS removed (thus access to the runners)

Swagged into place, there are numerous posts on this..the key is extracting the sleeves which after many years become brittle, so better to remove the runners to push them out and install new ones with sealing rings + a sealing ring on the fuel line as well which many folks forget to order (ask me how i know)

[Old H2S]

Get some AT-203 at Amazon and put it on the injector O rings.. Not a solution but a good crutch until you are ready to pull and replace.
I am in the same canoe as you, here let me take your paddle.

[boyt911sc]

Mike,

The AFR meter is an excellent tool to monitor your actual fuel mixture during operation. But without properly verifying the absence of unmetered air going into the system your data collection is FLAWED. A smoke generator is a convenient way to locate these hard to find air leak sources in your motor. And use it correctly and you will find these critical air leak spots. Keep us posted.

Tony

[mikesarge]

Originally Posted by boyt911sc

Mike,

The AFR meter is an excellent tool to monitor your actual fuel mixture during operation. But without properly verifying the absence of unmetered air going into the system your data collection is FLAWED. A smoke generator is a convenient way to locate these hard to find air leak sources in your motor. And use it correctly and you will find these critical air leak spots. Keep us posted.

Tony

Hi Tony-

I don’t know if you saw my post above, but I did do a smoke test, albeit a somewhat crude method with a transfer pump and cigarettes. It did verify that the injector seals or sleeves are leaking in at least three cylinders. So, I’ll be pulling the CIS and resealing it soon.

Thanks for all of your help, I hope we can get this car running again soon!

Thanks
Mike

[boyt911sc]

Mike,

Getting the motor out to fix your CIS is a good choice and I strongly recommend it. If you are planning to do more work like replacing the old tunnel fuel lines, your car will be out of commission for a while if you don’t have the part ready.

If I were you, I would drop the motor later when the fuel lines and other parts are available. And do a temporary fix with your air leaks and be able to drive the car while you are getting ready to drop the motor. If you like this idea, PM me and I will let you know how to do it. This is a band aid fix that I have been using to run CIS motors with leaking injector seals or sleeves. Think of McGyver.

Tony