I have a question regarding the 1980 only CIS setup. I (obviously) have a 1980 911 SC that is a US car. From what I understand the '79-'79 cars do not have an 02 sensor. They started adding them in 1980 but I've heard the system doesn't adjust much (if at all) for the O2 until the '81-'83 CIS version. Can anyone shed some more light on this? My car is currently running very rich, does not have the O2 hooked up, and the idle seems to creep up to 1100 rpms when warm. I'm wondering if the troubleshooting process is any different.

This is a great help thank you

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I have followed every direction in this thread to the letter, but my car still won't start. I have rebuild the entire fuel system from new parts and a rebuilt FD and WUR from Larry Fletcher at CIS Tech. The pressures are in line at 72 lbs with pump running and 22lbs cold with WUR power disconnected and 42 lbs within 2.5 minutes with WUR power. The car was running before I got a stuck FD and flooded the engine. I have a clean gas tank with fresh gas, recent fuel pump, new lines through the tunnel, new filter and accumulator and the injectors were tested and cleaned by CIS Tech. I have spark, as verified with an inductive timing light, the engine wants to start, but doesn't...what am I missing???

I am also concerned about the possibility of air in the lines to the fuel injectors, i figured they would bleed quickly, am I wrong about that??

Have you verified that your spark plugs are not fouled?

Yes, they are clean and dry...all 6...

Have you verified that the injectors are spraying fuel?

If you have good spark and are getting the right amount of fuel, it could be timing. Verify that your timing is set correctly.

Recheck the order of your spark plug wires, make sure they are correct, often it is something as silly as that. Also check the cap and rotor make sure they are seated properly.

Topgun63,

I agree with Shane. It sounds like maybe something simple is being overlooked like plug wires out of order. You've taken things apart -- most likely the culprit at this point is something didn't go back the right way if you've replaced everything and the engine isn't firing up and everything checks out independently.

If I could make a suggestion regarding this thread -- I've noticed a few people are posting their specific issues in this thread. In an effort to make this thread a clear "reference" it would be better if folks would start their own. 1) It will get more attention 2) I
It will allow people to get a discussion going specific to YOUR vehicle and problems and 3) it will a avoid confusion created by separating information and procedures from troubleshooting

Great thread Tim,

just about to dig into mine for some refreshing and thought I would read through it and also get the thread back up near the top for others who didn't realize it existed.

I did not see this reference above: http://www.renntech.info/SharedData/Manuals/911/911%201972-1983%20Workshop%20manual%20Deel%202%20Brandstofsys teem.pdf

It's a workshop manual on most of the CIS years. I had never seen this before until recently.

I found it recently in searching on how to install the 1975 009 WUR into my 1973.5, and use the vacuum line.

I am almost ready to embark on this procedure and had question about 1 thing ( to start with that is) Tim, you mentioned a 8 amp fuse in the fuel pump relay cheater switch, and while reading in the Bentley manual, he mentions a 25 amp fuse. Which is the safer bet please? The car is a 1981 911 SC stock 3.0 . The WUR #0-438-120-149 with 141 stamped below those numbers.

Engine # 6591383
Vin# WPOEAO916BS160860

Thanks so much for your write up!http://forums.pelicanparts.com/uploa...1458155557.jpg

Sorry for the delay in responding. I just got back from a business trip to ol' Mexico.

I'll have to go double check what size fuse is in my bypass circuit. Fuse #18 is usually the fuel pump circuit so just check to see what that fuse is rated for and match it as close as you can.

Good luck!

Thank you Tim,


I will check fuse #18. I'm also looking for the graph for the above mentioned WUR.


Thanks again,SmileWavy

Sorry, more confusion....I have the fuse worked out, 25 amp seems to the ticket. Just found out that the engine is a 1979 930/06 with 1981 CSI on it, with o2 sensor, hard fuel lines. dist# 0237306001 AAV # 0280160-02 FD# 0 438 100 077, but the kicker is the WUR. It has the number 0 438 120 149 with 141 stamped below. Shouldn't it be an 090 model and where can I find a chart for it when I do the fuel pressure test? Not in the Bentley manual, searched with no luck. What does the WUR belong to?

Thanks much,Steve

0 438 120 xxx is not a WUR part number (typo?), 0 438 140 149 may be a Mercedes part number in the 147/148 series.

Thanks for your response, perhaps I'm looking at something else. this a brass badge just below the FD on the alum . body, that the FD bolts to, is that the correct area for the number? Just behind the air filter housing. That is the number on it.

Thank You!

Ah, you are looking at the air meter assembly. The fuel distributor has a similar tag directly on it that may be hidden from view. The WUR part number is cast into the housing on the top side with the last 3 digits stamped into the metal. In your case the cast-in numbers are 0 438 140 and the stamped number 090.

Is that your '81SC? I have a '78SC that is IDENTICAL. I forget the paint color/code but really like the color.

Thank you much Brian! I thought I had a Frankenstein engine:) Yes, that is our 81SC and we love the color too, it won't fit my sig line:)
You made my day!http://forums.pelicanparts.com/support/smileys/wat6.gif

Pros - cons on removing or bypassing the Decel Valve? Mine is showing all the signs of improper operation (high idle, slow return to idle). My guess is the over rich condition when lifting would cause backfire - is that all? Is it a serviceble part?
Thx.
-C

Everything I've read on this decel valve condition is that you have to squish the valve by 1mm with a pair of channel lock pliers or similar. There was a Porsche bulletin on it too.

I'd like to learn more about this. Is there an online version of the service bulletin?
Thx

My decel valve has always been bypassed.

I'll give it a go. Thanks.

Also interested :)

Yep here it is - it's a one page tech bulletin. I have not tried this.

http://forums.pelicanparts.com/uploa...1458601318.jpg

thank you!

Looks like a later generation (3.0) CIS than my '74 has. Interesting read nonetheless.
-C

Hi Charles - I *think* there is a screw on the top that you can use to adjust the older style valve.

Hello, I'm stuck at your 1st point!

Can anyone point to a store that sells these gauges? I am in the U.K and it's not obvious what to buy, thanks.

But this book and read it with extreme enthusiasm. Especially the k-jet chapters.

https://www.amazon.com/Bosch-Fuel-Injection-Engine-Management/dp/0837603005/ref=sr_1_fkmr0_1?ie=UTF8&qid=1495568727&sr=8-1-fkmr0&keywords=charles+probst+Bosch+continuous+inj ection+systems

I am assuming you don't know how to use the gauges, correct? Read the book. You will ask better questions.

Here is an Amazon UK link to a pressure tester that will work fine with CIS.

https://www.amazon.co.uk/Jago-BZDP01-Steel-Pressure-Tester/dp/B00A78CCHY/ref=sr_1_1?ie=UTF8&qid=1495569045&sr=8-1&keywords=CIS+fuel+pressure+tester

Thanks Bob, that looks like the right set. Ordering now!

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Decel valve ('74~'79).......
 

Charles,

You have the earlier type decel valve which is adjustable. Use a hand held vacuum pump to adjust and calibrate the valve's opening pressure (15"~ 22" Hg). I like the old one better than the newer version.

Tony

I had high idle problems, slow rpm drop off and many other poor driveability issues. It made the car unpleasant to be in, when the revs climbed to 2000 while sitting in traffic, or gear shifts were botched because the revs didn't fall.

I disconnected the decel valve and put a golf tee in the vacuum line, as recommended here. Instantly fixed all these woes. PO had spent bulk cash with clueless mechanics trying to sort out the issue.
The only thing I'm planning to do further is to make up a proper dead plug for visual purposes rather than having a golf tee hanging off the side of the engine. I'll never reconnect the valve, and won't bother trying the crush method above.

It is a pollution control measure and does nothing to improve the driveability of the car, even when working properly it deadens throttle response. The only downside is the occasional pop and crackle in the exhaust on long throttle-closed downward descents. The same as you would get in a carb equipped car, because the high vacuum, fuel rich mixture is igniting in the exhaust.

Great reference thread Tim, thanks for doing the hard work.

Just thought I would share a couple pictures of the switch I made and the hookup at the fuse panel since I don't think I've ever seen the actual hookup and you know, the whole thousand word deal!

I made my switch with a very long length of fairly heavy gauge speaker wire (had it handy) so that I could operate it from the engine compartment- seems to me if something went wrong I could immediately shut the pump off as well as not knowing if something was going wrong as I made my way to the back of the car.

http://forums.pelicanparts.com/uploa...1499618333.jpg


http://forums.pelicanparts.com/uploa...1499618355.jpg

Outstanding, rwest.

Subscribed!!!

Collecting the charts here

http://forums.pelicanparts.com/uploa...1449098242.jpg
http://forums.pelicanparts.com/porsche-911-technical-forum/893455-1981-sc-cis-low-idle-wrong-wur-5.html


http://forums.pelicanparts.com/uploa...1218170716.jpg