CIS Problem?
Burning Brakes
Joined: Oct 2004
Posts: 1,056
Likes: 1
If you're DIY'ing, read, read, read. There are numerous CIS discussions (here and on Pelicanparts.com) and some great books that explain the system in detail.
You have given us very little to work with, which is probably why there are no responses, yet. Has your 911 been well maintained? Has it had a valve adjustment recently? Are the timing, mixture, idle set properly? If not, get these done. Pretty much any diagnostics on the CIS system begins with checking fuel pressures, which you'll learn about in any reading you do.
Brett
You have given us very little to work with, which is probably why there are no responses, yet. Has your 911 been well maintained? Has it had a valve adjustment recently? Are the timing, mixture, idle set properly? If not, get these done. Pretty much any diagnostics on the CIS system begins with checking fuel pressures, which you'll learn about in any reading you do.
Brett
Racer
Joined: May 2007
Posts: 259
Likes: 0
From: San Diego, CA
?? Is it back-firing out the exhaust or back into the air cleaner??? If it backfires out the exhaust do you have any leaks in the exhaust system? Any fresh air mixed with unburned fuels in the exhaust will pop, especially on decelleration/gear shifting.
Otherwise, what Brett said.....
Otherwise, what Brett said.....
Burning Brakes
Joined: Jan 2005
Posts: 863
Likes: 0
CIS Warmup Regulator
I have a 1975 911S that I've owned for 28 years. It's a California car that I just put back together. Engine and gearbox completely rebuilt with SC cams and SSI heat exchangers. The shop who did the work recommended that I go with the Unwired tool unit as an update to the traditional Porsche warmup 
regulator which I did. I am still facing the same problems with the Unwired Tool unit that I used to face with Porsche warmup regulator. Unwired Tool has replaced the unit several times, but the issue still exist when the car has been ran and it's hot, it will not turnover and find myself priming the fuel distributor. Are there any suggestions on solving this problem? My Technician stated that the early version of this unit worked great on a 74 but he has had difficulty with their new unit on my car and a 83SC.:
regulator which I did. I am still facing the same problems with the Unwired Tool unit that I used to face with Porsche warmup regulator. Unwired Tool has replaced the unit several times, but the issue still exist when the car has been ran and it's hot, it will not turnover and find myself priming the fuel distributor. Are there any suggestions on solving this problem? My Technician stated that the early version of this unit worked great on a 74 but he has had difficulty with their new unit on my car and a 83SC.:
Rennlist Member
Joined: Oct 2004
Posts: 20,607
Likes: 16
From: Bakersfield, CA, for now...
FYI: I have no idea what an "Unwired Tool" unit is, can you provide some info...?
Burning Brakes
Joined: Jan 2005
Posts: 863
Likes: 0
CIS
The Unwired Tool unit is a Rest Pressure Kit- it's and replacement upgrade for the OEM CIS Warmup Regulator. It's a software package with mechanical design that permits closed-loop control pressure management, allowing you control of the CIS injected engine. I only have the starting problem after the car has been ran. No problems @ cold start startup, and the fuel accumulator seems to be functioning okay. My Technician is the Retired Service Manager for a Porsche Dealership in Florida, and states he his having the same problem with Unwired Tool new unit on 83 SC.
Rennlist Member
Joined: Oct 2004
Posts: 20,607
Likes: 16
From: Bakersfield, CA, for now...
The Unwired Tool unit is a Rest Pressure Kit- it's and replacement upgrade for the OEM CIS Warmup Regulator. It's a software package with mechanical design that permits closed-loop control pressure management, allowing you control of the CIS injected engine. I only have the starting problem after the car has been ran. No problems @ cold start startup, and the fuel accumulator seems to be functioning okay. My Technician is the Retired Service Manager for a Porsche Dealership in Florida, and states he his having the same problem with Unwired Tool new unit on 83 SC.
My advice is only given based on what I read - which is why I recommended a hard look at the accumulator. It's less expensive than a fuel pump, and your car is not maintaining system pressure for the required time period following shut off.
...which makes me think that you're chasing a different problem on the '83, and are chasing the wrong part (problem unchanged from original WUR to new style) on your car.
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Rennlist Member
Joined: Oct 2004
Posts: 20,607
Likes: 16
From: Bakersfield, CA, for now...
Good luck with it - I know that diagnosing CIS problems can be tricky with the car in front of you, but long distance is even harder! We gotta just keep trying to make the cars the best that they can be!
Burning Brakes
Joined: Oct 2004
Posts: 1,056
Likes: 1
wpriller: Your post is a completely new topic. You should start a completely new thread. It'll help you attract more attention to your cause since your title will be visible on the main board, and it'll help the original poster in this thread maintain discussion of his problem.
The new, modern warm up regulator replacement (or replacements if there is more than one) are interesting and certainly overdue for a long discussion of its merits and demerits on these forums. Real world experiences are going to be very useful to those considering purchasing these devices. Start a new thread to open that kind of discussion.
Brett
The new, modern warm up regulator replacement (or replacements if there is more than one) are interesting and certainly overdue for a long discussion of its merits and demerits on these forums. Real world experiences are going to be very useful to those considering purchasing these devices. Start a new thread to open that kind of discussion.
Brett
Thread Starter
5th Gear
Joined: Mar 2007
Posts: 5
Likes: 0
Hi All,
Thanks for adding these additional threads to my note. My problem is that it is backfiring out of the exhaust. I adjusted the valves two years ago. I did a chain tensioner update last year but that also meant I have not driven the car much over the last two years. This year my car has been in for repaint that has taken it down to bare metal. It has been nine months and I almost ready to take it back. The backfiring was present for awhile but because of the two major repair items the car has stood mostly over the last two years.
If there is a manual or book that would allow me to understand air mixture settings I would like to do this. I have the old heat exchangers on my car and the hoses that go from them to the heating intakes are not tight. Would this make a difference? As far as the exhaust goes, when I did the chain tensioner update I put new gaskets on the muffler to heat exchanger last year. I will tighten down the bolts to make sure it is tight. Because I have not driven the car much I was going to put in a new gas filter when I get it back. All your responses are very much appreciated.
I know a great porsche mechanic who I will most likely try and set-up a time to take it in. He is a couple of hours away and I wanted to learn as much as I can about these is a porsche
Thanks for adding these additional threads to my note. My problem is that it is backfiring out of the exhaust. I adjusted the valves two years ago. I did a chain tensioner update last year but that also meant I have not driven the car much over the last two years. This year my car has been in for repaint that has taken it down to bare metal. It has been nine months and I almost ready to take it back. The backfiring was present for awhile but because of the two major repair items the car has stood mostly over the last two years.
If there is a manual or book that would allow me to understand air mixture settings I would like to do this. I have the old heat exchangers on my car and the hoses that go from them to the heating intakes are not tight. Would this make a difference? As far as the exhaust goes, when I did the chain tensioner update I put new gaskets on the muffler to heat exchanger last year. I will tighten down the bolts to make sure it is tight. Because I have not driven the car much I was going to put in a new gas filter when I get it back. All your responses are very much appreciated.
I know a great porsche mechanic who I will most likely try and set-up a time to take it in. He is a couple of hours away and I wanted to learn as much as I can about these is a porsche
Burning Brakes
Joined: Oct 2004
Posts: 1,056
Likes: 1
Hi All,
Thanks for adding these additional threads to my note. My problem is that it is backfiring out of the exhaust. I adjusted the valves two years ago. I did a chain tensioner update last year but that also meant I have not driven the car much over the last two years. This year my car has been in for repaint that has taken it down to bare metal. It has been nine months and I almost ready to take it back. The backfiring was present for awhile but because of the two major repair items the car has stood mostly over the last two years.
If there is a manual or book that would allow me to understand air mixture settings I would like to do this. I have the old heat exchangers on my car and the hoses that go from them to the heating intakes are not tight. Would this make a difference? As far as the exhaust goes, when I did the chain tensioner update I put new gaskets on the muffler to heat exchanger last year. I will tighten down the bolts to make sure it is tight. Because I have not driven the car much I was going to put in a new gas filter when I get it back. All your responses are very much appreciated.
I know a great porsche mechanic who I will most likely try and set-up a time to take it in. He is a couple of hours away and I wanted to learn as much as I can about these is a porsche
Thanks for adding these additional threads to my note. My problem is that it is backfiring out of the exhaust. I adjusted the valves two years ago. I did a chain tensioner update last year but that also meant I have not driven the car much over the last two years. This year my car has been in for repaint that has taken it down to bare metal. It has been nine months and I almost ready to take it back. The backfiring was present for awhile but because of the two major repair items the car has stood mostly over the last two years.
If there is a manual or book that would allow me to understand air mixture settings I would like to do this. I have the old heat exchangers on my car and the hoses that go from them to the heating intakes are not tight. Would this make a difference? As far as the exhaust goes, when I did the chain tensioner update I put new gaskets on the muffler to heat exchanger last year. I will tighten down the bolts to make sure it is tight. Because I have not driven the car much I was going to put in a new gas filter when I get it back. All your responses are very much appreciated.
I know a great porsche mechanic who I will most likely try and set-up a time to take it in. He is a couple of hours away and I wanted to learn as much as I can about these is a porsche
Once you have established that all parameters are within spec, the problem may simply disappear... or it may not. If it doesn't, at least you will know that it isn't or should not be an issue with the fuel management system. But... there are other parts to worry about too, injectors for example. At this time in your car's life, and at a point when it has been sitting for a long time, it may be time to flow test the injectors to ensure that they are all flowing equally. One scenario that I can think of is that one or more injectors could be dumping much more fuel than the others giving a rich cylinder (or two) resulting in extra fuel in the exhaust to fuel backfires.
Brett
