CIS issues fixed. Thanks Pelican.
 

I managed to get my CIS issues sorted out over the winter. Here are the details for those who might be interested (car is a 1980 Euro SC). This is an update on the thread http://forums.pelicanparts.com/porsche-911-technical-forum/632088-help-cis-test-numbers-new-guy.html

PROBLEM:
After startup, I had about 20 minutes of rough running, hesitation, stalling, backfires, etc. Also low gas mileage and a layer of soot on the back of the car after long drives. With the help of a few CIS gurus here on Pelican - Ossiblue, Tony, Bob Kontak - I adjusted the WUR to set warm control pressure, and replaced seals on the injectors. This had some effect but didn't fix the problem. The most likely scenario seemed to be unmetered air in the system from still-undiscovered vacuum leaks, and a fuel mixture set too rich by the previous owner to compensate. a common situation I'm sure.

FIX:
Over the winter I had the engine out and found a number of serious leaks: a badly cracked breather hose due to a bad install, a blown airbox, and a leaking seal around the pop-off valve (used pressurized air and soapy water to find these). The crankcase breather hose was the wrong size, and was leaking oil into the clutch. So I removed the CIS, disassembled and cleaned it, and rebuilt it with new rubber components and gaskets. I didn't want to spend close to 500$ for a new airbox, so I took apart the old one and reglued it. I used 3M Scotchguard DP8010. After a thousand miles the glue job has held up very well. knock on plastic.

I put the car back together and it ran like a top - really a different animal altogether (I also changed shocks and suspension bushings, shifter and shifter bushings, clutch, engine mounts, and a bunch more WYIT stuff). However it seemed to be running rich, which was good in a way because it confirmed my theory that there were air leaks and a jacked up AFR to compensate. With the leaks fixed, I expected it to run rich.

Last week I brought the car to a shop to put it on a CO meter. Turns out it was running at 4.68%, and this was after I had leaned it out one turn already! The mixture was brought back to spec, and now the car runs nicely. It idles normally, with no hunting or stalling, and the layer of soot on the back of the car is almost gone. Gas mileage is also up.

So I consider the problem solved at this point.


Except...
- Car has a hard time starting now, when cold. It's very rough for the first minute or so, and takes about three tries to get it to catch. I know the AAR is working. It may be the cold control pressure setting on the WUR, but i haven't had time to put a fuel gauge on it to check. once the bimetallic strip kicks in, everything smoothes out and car runs fine. this was not an issue before.

- Now that the leaks are fixed and the AFR is set to spec, I'm starting to see why people replace the CIS with carbs. When the car was running super-rich, it had oodles of power all the way up the tach, from about 3000 to 6000rpm. Now the real power is between 4 and 5000, more or less. The car is more efficient and sounds less raucous, but it's a little less of a kick to drive. I'm beginning to think about PMOs….


Thanks Pelican for all the help. it's a blast to get this thing running the way it was intended. What an amazing car! It wouldn't have been possible without this forum.


Before and after:

http://forums.pelicanparts.com/uploa...1341000998.jpg


http://forums.pelicanparts.com/uploa...1341001112.jpg

On CIS it usually fuel pressure. Beg, borrow, steal or buy a set of gauges.

If it runs better when warm, consider the CHT. I assume you have a Bentley manual? If not, it's a good investment.

Nice clean up! Sure is pretty!

Great work.

You mentioned you reset the warm control pressure, which affected running. Did you check/reset the cold control pressure, which affects cold starting? Did you verify your fuel pressure?

Well done Area Man!!! Sure is a clean powertrain now!

This is an inspiration as I need to do the same thing for nearly the same reason!
It is nice to see what is possible when I finally jump I'm!

I've also noticed the difference in power when the engine isn't set up rich. I switched out my stock muffler for a B&B and had a huge improvement in throttle response as well as power, most obvious when I put the stock muffler back on and dialed in the AFR.
It felt like it was breathing through a straw and had lost half it's power below 4k! :rolleyes:

Anyway, hope you get that last issue dialed in.

+1 on buying the good set of CIS gauges

Cheers. SmileWavy
Jason

Don't give up on the CIS just yet. Get some gauges and a timing light and post your results.
Sounds like it still needs some tweaking. Should pull strong from around 4K right up to red line.

I have a CIS pressure gauge and a Bentley manual, I've just been too lazy to use them. Or maybe I just spent too much time working on it and all I want to do now is drive!

I'll get on it this weekend. I'm thinking the cold control pressure setting might be too low, making the mix too rich at cold startup, which would explain why it gets better when the bimetallic strip activates and raises the pressure. But I'm usually wrong... ;)

Paulporsche - I did reset the cold control pressure when I had the engine out. I took apart the WUR and pushed the 'plug' up with a clamp. I may not have pushed it up far enough. Definitely time for a pressure test to see where things are.

CIS troubleshooting.......
 

Area man,

Good job. However, if you did your troubleshooting without using your fuel pressure gauge kit, you left a wide window to guess-work. It is mandatory to have a fuel pressure gauge for fuel injection troubleshooting regardless which type of system you have.

Since you have checked your vacuum and air mixture, next is to determine your cold control, system, and residual fuel pressures. It would tell you a lot if you would have a starting problem or not at the very beginning.

So your current problem now is about cold start? Keep us posted.

Tony

Just to clarify, I do have the fuel pressure gauges! lol

This whole process started off with a thread about CIS pressure test numbers and how to interpret them (see thread link above).

Thanks everyone for the comments. Next step is definitely to do the fuel pressure test again on a cold start, and see what's going on. I'll post the results. I'm guessing the cold start issue is fairly minor. :cool:

Have you considered sending your WUR to Brian Leask for a rebuild and adjustable features?

Dave - I did think about that at first but I decided it wasn't worth it. It's possible to adjust the WUR as is, just a bit more work. My plan is to do it once, get it right, and then hopefully leave it alone.

Update
 

Did a fuel pressure test this weekend.

Cold control pressure is 3.0 bar at 80F ambient temperature. Too high. It's my own doing - I reset the cold pressure on the WUR when I had the engine out over the winter. It was too low, so I took apart the WUR and pushed the plug upwards with a clamp. Apparently I pushed it up too far. Easy to do! Lesson learned. Next step is to tap the plug down carefully so as to lower the cold pressure at startup.

Nice work!
Tapping the plug with a hammer/punch offers only crude adjustment and can easily overshoot the target. It is better to use a C clamp to press the plug down in a controlled manner while watching the fuel pressure change on the gage.

Thanks RarlyL8 - great idea! I was puzzling over how to tap it down without overshooting the mark and having to take it all apart again.