CIS Troubleshooting for Dummies

[Sicklyscott]

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.

[xjoegtix]

This is a great help thank you

[snbush67]

[lespaul]

Subscribed.

[Topgun63]

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???

[Topgun63]

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??

[snbush67]

Originally Posted by Topgun63

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???

Have you verified that your spark plugs are not fouled?

[Topgun63]

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

[snbush67]

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.

[tirwin]

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

[rwest]

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.

[Jay Laifman]

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.

[Steve F]

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!

[tirwin]

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!

[Steve F]

Thank you Tim,


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


Thanks again,

[Steve F]

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

[RarlyL8]

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.

[Steve F]

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!

[RarlyL8]

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.

[Steve F]

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!