CIS Trouble / Info Req'd - 75 911 2.7

[Porsche_monkey]

Just finished my rebuild and so far the car runs worse than before. AAV and WUR are wired right and working, as is the cold start injector.

Symptoms:

-hard to start cold (if I depress the air flow plate it starts)
-revs nicely right to about 1,800 rpm, then dies
-won't take any throttle without stalling when cold
-bucks and runs rough when warm

I have set the timing statically, I will do it with the timing light today, but I think it is close enough that timing is not the problem.

Car seems too lean, although mixture hasn't been touched (neither have fuel pressures) and the car ran nicely before my rebuild.

I'm thinking vacuum leak? The car sounds right when it idles and rev's, I am sure the engine itself is fine, this is not a rebuild issue, it is CIS related.

Any suggestions?

PS - I have a fuel pressure gauge, but no manuals for this vintage car seem to show what/where to check/adjust?

I need to get this going, I want to break the engine in properly.

[fintstone]

Here are a couple of links that have helped me in the past.
http://www.dietersmotorsports.com/tech/2002/2-2002.htm
http://members.rennlist.com/jimwms/CIS/CIShome.html

[Porsche_monkey]

Well, it's not a vacuum leak....

[rhaas]

the only way to troubleshoot the injection system is to get the fuel injection pressure tester for CIS injection. This will help diagnose the problem. it sounds like a problem with the WUR. the diaphran may have stuck. But there is no way to check this without the injection tester. without this tester it is a shot in the dark, and replacing parts is REAL expensive.

[Porsche_monkey]

I am going to check some pressures tonight, maybe the WUR is screwed up. I'm in no mood to think rationally right now...

[rhaas]

If the WUR seems to be the problem Take the screens out of the in port to the WUR and clean all of them. Sometimes they get gunked up and do not let the WUR work properly. This is easy and free, it has fixed my problems once with the 911 and many times in my beater rabbit I used to own. If this does not fix the problem you can make the WUR adjustable to get the rifght cold start pressures. The WUR is easily able to be made adjustable. Do a search and you will find the posts on this subject.

[Porsche_monkey]

Still checking on the WUR. Pump pressure is 80 psi but drops immediately to zero when I turn the key off. I guess the the check valve in the fuel pump is gone.

[vash]

pbh, you have to kinda do it in order:
check cold pressure
system pressure
warm pressure and then,
at rest pressure.

do you have the CIS tester gauge? how are you hooking up your gauge to see the 80psi at the pump?

[Porsche_monkey]

My WUR needed a wack. Starts fine now, thanks guys.

[fintstone]

Great! Thanks for the feedback.

[Porsche_monkey]

Thanks for the links, I used both.

PS I hate it when people fix their problems but never close off their thread with an answer!

[fintstone]

Same here. Or even worse, ask for help and fail to answer questions regarding the problem...perhaps they think the question is stupid...but if they knew all..they would not be asking a question or have a malfunction...now would they? Good job, CIS problems are tough.

[klaucke]

PBH, when you say your WUR needed a whack, how exactly did you hit it? My CIS exhibits the same problems.

[Porsche_monkey]

I made mine adjustable (do search). After that you just drive the 1/4" pin in a bit at a time. I would not recommend doing this without the fuel pressure gage on the car.