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-   -   CIS rebuild threads? (http://forums.pelicanparts.com/porsche-911-technical-forum/379458-cis-rebuild-threads.html)

HarryD 11-27-2007 06:41 PM
Quote:
Originally Posted by v8_ranch (Post 3610729)
All,

Thanks for the reponses. The reasons for my thoughts about doing this are more than one:

1. I do have what I suspect to be a slight vacuum leak somewhere, as I have a slight hunting idle (am I right to suspect vac leaks here?)

2. I have recently started having a problem with the idle turning way low (like 250-400 rpm). It will stay running barely and then it will clear up after I drive it a bit. But, as I stated on an earlier thread, it seemed to really stand out after a hot restart. And the weird thing kindof, was that Jay Freels(also and SC with CIS) started having a very similar problem during the same trip we all made to Arkansas for the Porsche Palooza.

3. As someone else stated, it would be nice to replace the 25 year old rubber components, and as a side benefit to this, the vacuum lines would be all nice a purty again!

4. The car smells like it is running rich, which sounds to me after reading here awhile is better than running lean. I would just like to make sure it is all optimal.

5. And finally, I would just like to clean up the whole area - very thoroughly.

That all said, I work in the gas turbine industry, and believe me, I know there is a fine line between "don't fix it if it ain't broke" and "and ounce of prevention...". I just wasn't sure about the specifics of what I had in mind, hence the question. I would like to make it as minimal invasion as possible but still clean and replace 25 year old rubber.

Perhaps I should get it operating at optimum first, and then do the clean and replace work? my gage set has not yet arrived, so I cannot really start any detailed checks yet. I DO have a coupe of books that look to have good and pertinent info:

1. "Solving Bosch CIS Problems" by James Weber
2. "How to Tune and Modify Bosch Fuel Injection" by Ben Watson

From reading the earlier posts, it sounds as though to do part of this work, it might be easier or necessary to drop the engine? I guess that would be an excuse to get the first one out of the way. I have a friend close by that is building an RSR and he has dropped his numerous times, so I have a good resource for help there.

John - I missed your thread as well. Don't know why I could not get when searching the last couple fo days. But thank you for the link. I will look at it next.

Gunter - (I ask this seriously) are there more than one type of CIS (besides euro and US) that would be found on an 83 car? I ask just because I have my car labelled in my sig. Maybe I need to add more info to it. Thanks for poining it out.

Thanks again everyone. Looks like I have some more research and thought to put into this. Hopefully my gage set will get here soon.
I also am not a CIS expert. At it's most basic, CIS is a simple system that relies on air flow and fuel pressure meter fuel into the cylinders. The air flow adjusts a metering valve that inturn control the flow of fuel to the cylinders.

Two things to check before you fiddle with the other components are vacuum leaks (use carb cleaner or UNLIT propane to find) or your mixture is off (have someone with a CO tester adjust your mixture once you are sure you have no vacuum leaks).

You should also remember this old saw about CIS:

"There are three types of CIS Owners:
1) The guys with working CIS systems are probably out driving their cars so they won't reply.
2) The guys that tinker with their CIS systems and have them royally screwed up will keep you running in circles with suggestions.
3) The guys that have spent a fortune on Webers (or PMOs or Megasquirt etc) will tell you they're great to justify their expenditure to themselves.

Your choice."

RarlyL8 11-27-2007 07:43 PM
I went through every component of the CIS system on my car during the rebuild process.
If the part wasn't needed to run the engine I tossed it. Figured I could put it back later if need be. Every hose was replaced and every component cleaned and checked (including the fuel distributor). You'll feel a lot more confident about your car once you do this.

SCWDP911 11-27-2007 10:22 PM
Quote:
Originally Posted by RarlyL8 (Post 3611688)
I went through every component of the CIS system on my car during the rebuild process.
If the part wasn't needed to run the engine I tossed it. Figured I could put it back later if need be. Every hose was replaced and every component cleaned and checked (including the fuel distributor). You'll feel a lot more confident about your car once you do this.

Brian, did you have a chance to look at that pic I sent you?

SCWDP911 11-27-2007 10:28 PM
Quote:
Originally Posted by HarryD (Post 3611588)
Two things to check before you fiddle with the other components are vacuum leaks (use carb cleaner or UNLIT propane to find) or your mixture is off (have someone with a CO tester adjust your mixture once you are sure you have no vacuum leaks).
Agreed, at least one of the two books I have (I think number 1 above) says in teh opening page that ALL vacuum leaks AND ignition problems should be corrected before further troubleshooting of the CIS.

So for those of you who have done it, are all the vac lines accessible enough to replace without an engine drop?

RarlyL8 11-28-2007 05:23 AM
I didn't get any pictures. Please re-send.

It's a lot easier to do CIS work on an SC with the engine out of the car, but I wouldn't drop the engine for that purpose alone. Take lots of pictures and start removing from front to back enough to get the intake out of the car. R&R the entire assembly on the bench, disassemble what is needed to get it back in the car, then button it up. Check and tune your WUR. If you had any CIS issues before they will now be gone.
The one reason I did mine all at once is because you can chase your tail trying to fix an old worn out system with several potential issues.

boyt911sc 11-28-2007 05:44 AM
Quote:
Originally Posted by v8_ranch (Post 3611822)
So for those of you who have done it, are all the vac lines accessible enough to replace without an engine drop?
Nope!!! Why? Take a look at these pictures and decide for yourself.

http://forums.pelicanparts.com/uploa...1196260085.jpg

http://forums.pelicanparts.com/uploa...1196260117.jpg

Take a look at the AAR hose near the CSV and imagine working on it with the motor installed. A partial engine drop might help. Having been able to test run a motor before installation is a great convenience but that's another story.

Tony

dtw 11-28-2007 06:06 AM
Quote:
Originally Posted by v8_ranch (Post 3611822)
Agreed, at least one of the two books I have (I think number 1 above) says in teh opening page that ALL vacuum leaks AND ignition problems should be corrected before further troubleshooting of the CIS.

So for those of you who have done it, are all the vac lines accessible enough to replace without an engine drop?
I think this is really important, and a fact that is really ignored or glossed over by shadetree mechanics. It is either too time-consuming, costly, difficult, or we lack the correct tools, so we might just have a tendency to say 'ehh everything is probably fine' and we move on. I know I have been guilty of that with MFI.

Many of the vacuum lines face the back of the engine bay and are difficult to access. I had a weird idle problem once after doing some work. By doing some blind groping around, I was able to figure out I had knocked a vacuum line loose while installing a fuel line. Re-installed it blind, but I got lucky.

I don't think I am up to date on all your issues, but it sounds like you might benefit from a drop. This will allow you to get really familiar with your CIS and engine, and take care of any oil leaks and other maintenance items. If you don't feel like that's needed, it is also a relatively simple matter to pull the CIS off the engine. From memory - so I might forget something:

-disconnect fuel supply and return lines
-disconnect both breather hoses
-disconnect throttle linkage
-disconnect wiring harnesses - including main 14-pin and ancillaries
-remove 12 M8 nuts and washers on the intake runners - make sure to account for all washers so you don't lose any in the intake - magnet-on-a-stick helps here
-remove throttle linkage plate nuts - three I think - or disconnect throttle linkage plate from CIS setup - one nut but hard to access in-situ

The CIS is bulky and a bit heavy, and is in an awkward position to remove while still in the engine bay. It may be a good idea to have a helper for the removal, at least the first time through.

I'd lean toward pulling the engine, but I'm the guy who also is known to say "Hmmm time for an oil change, guess I'd better rebuild my engine". I tend toward overkill :).

SCWDP911 11-28-2007 06:42 AM
Thanks again everyone. A lot more to ponder. Looks like an engine drop might be the easier route to go as far as the vac lines are concerned. With that in mind, without a drop, how on earth do you get the propane or carb cleaner isolated enough to a particular hose to tell if there is a leak or not, as opposed to somewhere else in the vicinity? Are you really good at using inspection mirrors?

Luckily, my car does not drip a drop of oil, at least nothing hits the ground anyway... now where is my piece of wood to knock on?

RarlyL8 11-28-2007 09:21 AM
What is it you're doing? Fixing a problem or restoring you CIS?
If you are restoring your CIS then you are wasting effort chasing problems. The entire system will be removed, disassembled and restored. Any vacuum leaks or component issues will be cured.

SCWDP911 11-28-2007 09:44 AM
Brian,

Yes, good point. I am just weighing it all out before making the final decision. I have the problems I noted earlier. I also just experienced this 2 days ago.

Very cold day here (30's). Started car up (cold start) and the idle was up at about 2000 for the first 10 minutes I figure. It did start dropping to like 12-15 and then back to around 950-1000 (after that 10-15 minutes had passed of city stop and go driving.

SCWDP911 11-28-2007 09:52 AM
Since it is my thread, I won't consider this hijacking:

I have never had a good feel for the mixture adjustment screw. I have tried to find it with my wrench, but I just have never felt it really seat inot the hex cap screw. I and in trying to find it, I guess I am applying some pressure to the "flapper" in the airbox in the process, adn it will usually kill the car unless I let up on it right away. I had done this just to give the Souk "no meter adjustment method" a try. I am pretty sure my car is running rich, as it usually has a fairly gassy smell to it. Also, I have never gotten better than 22-23mpg, and it is usually more like 20-21 max. This again is on a basically unmodded 3.0 SC engine.

Sorry to ramble, just throwing out more while trying to take it all in before I decide the best course of action. As I said earlier, I would like to restore the system, but despite RarlyL8's and some other's encouragement, I am still a little timid about rebuilding the whole enchilada right now - kind of the "first do no harm" thing I guess.

SCWDP911 11-28-2007 07:18 PM
I went for a drive tonight after not driving car for 3 days. It is about 45-50 degrees out tonight. I started up and car was idling 2000 rpm. Drove 5 minutes away to a gas station and filled up. Started car and still idling high at 2000. About 1 minute later, it is down to about 1500 rpm. Drove 5 minutes away to O'Reily's Auto Parts. Pull in and park and idle back to normal at 950. Stopped car and went into store to buy some carb cleaner to do some vacuum leak checks tomorrow (my stupid test gage kit still hasn't shown up yet). Come out of store 5 minutes later and start up car. Rough lopey idle down at 500. Drive car for 5 minutes and idle back to normal again at 950. This is mostly the condition that I am fighting. I will start checking for vac leaks tomorrow. I also have a new set of wires, cap, rotor, on the way. When I change all of that, I will also replace plugs. As a side note, my plug wires are only a couple of months old, but the company (High Performance Wires) that reps for Kingsbourne is replacing them - just heard back from them tonight.

Then, after I have made sure there are no vacuum leaks at that point. I will decide to pull off the whole unit and refurbish, or repair only what is necessary. Either way, I want to go through the logical steps to get the hands-on out of the way at least once.

Walter_Middie 11-29-2007 04:30 AM
Quote:
I and in trying to find it, I guess I am applying some pressure to the "flapper" in the airbox in the process, adn it will usually kill the car unless I let up on it right away
I wouldn't try adjusting the mixture while the car is running - you're asking for an expensive backfire. The mixture screw is turned very little, and with the car off.

Porsche_monkey 11-29-2007 04:34 AM
Well there is no shortage of CIS guru's on this site. My advice, from someone who's pulled few engines: do all the basic checks, namely fuel pressure, vacuum leaks, timing verification, injectors, mixture, etc.

If you still can't solve it then start taking stuff off and inspecting what you can without pulling the engine. Last option: pull the engine.

I would start a new thread dedicated to the CIS problems, now that I've told you how you're going to proceed. :)

SCWDP911 11-29-2007 05:00 AM
Quote:
Originally Posted by Walter_Middie (Post 3614388)
I wouldn't try adjusting the mixture while the car is running - you're asking for an expensive backfire. The mixture screw is turned very little, and with the car off.
Is this true? I thought Souk's "quickie" method had you doing this with car running so you could hear the change in the engine. Did I misread that?

On another side note:

I drove the car into work this morning: It again is about 40-45 outside. Started car up, backed out of garage, and idle was high and rough, by the end of my 1/8 mile driveway, idle had stabilized, and was sitting at 1500. Drove to co-worker's house to pick him up (about 7-8 minute ride through town) and when I got there, idle had kicked down to about 1000. Ran smooth all the way into the town close to our plant (45 miles). We stopped at Sonic for a burrito, car shut off. Started right up, idle smooth at 1000. Drove into work another 5 miles, and car ran smooth at idle when I pulled into parking lot.

OldTee 11-29-2007 06:35 AM
Quote:
Originally Posted by v8_ranch (Post 3614447)
Is this true? I thought Souk's "quickie" method had you doing this with car running so you could hear the change in the engine. Did I misread that?

On another side note:

I drove the car into work this morning: It again is about 40-45 outside. Started car up, backed out of garage, and idle was high and rough, by the end of my 1/8 mile driveway, idle had stabilized, and was sitting at 1500. Drove to co-worker's house to pick him up (about 7-8 minute ride through town) and when I got there, idle had kicked down to about 1000. Ran smooth all the way into the town close to our plant (45 miles). We stopped at Sonic for a burrito, car shut off. Started right up, idle smooth at 1000. Drove into work another 5 miles, and car ran smooth at idle when I pulled into parking lot.
Except for a little high RPM cold (cold start valve leaking, maybe) and idle about 150 rpm high at hot, it sounds about normal to me.

Gunter 11-29-2007 07:08 AM
Adjusting the mixture by ear with the engine running works pretty good.
To be clear: The adjustment screw is an Allen set-screw, not a hex cap.
It has an internal hex opening for the 3 mm Allen.
The hex can get clogged and cleaning it out with a piece of thin wire works.
I spray a little WD-40 with the long nozzle into the opening.
The best Allen key is a very long regular 3mm Allen key; the expensive factory 3mm tool with the handle doesn't have enough room to work.
It takes a delicate touch to insert the key and it takes very little movement to affect the mixture.
Remove the key when revving.
Remember that adjusting the mixture is the last thing done during a tune-up; Valves and ignition timing has to be adjusted first and all vacuum leaks fixed.

SCWDP911 11-29-2007 07:12 AM
Quote:
Originally Posted by Gunter (Post 3614683)
Adjusting the mixture by ear with the engine running works pretty good.
To be clear: The adjustment screw is an Allen set-screw, not a hex cap.
It has an internal hex opening for the 3 mm Allen.
The hex can get clogged and cleaning it out with a piece of thin wire works.
I spray a little WD-40 with the long nozzle into the opening.
The best Allen key is a very long regular 3mm Allen key; the expensive factory 3mm tool with the handle doesn't have enough room to work.
It takes a delicate touch to insert the key and it takes very little movement to affect the mixture.
Remove the key when revving.
Remember that adjusting the mixture is the last thing done during a tune-up; Valves and ignition timing has to be adjusted first and all vacuum leaks fixed.
Thanks Gunter. So the screw is actually a set screw then. A-ha.... I am working on the other things you mentioned, but when ready, I may try this method again. I will look at cleaning my screw head out first. If I have time today, I might pop my filter off and reach around there with a borescope to see the condition of the head.

Thanks

Scott R 11-29-2007 07:16 AM
Quote:
Originally Posted by HarryD (Post 3611588)
I also am not a CIS expert. At it's most basic, CIS is a simple system that relies on air flow and fuel pressure meter fuel into the cylinders. The air flow adjusts a metering valve that inturn control the flow of fuel to the cylinders.

Two things to check before you fiddle with the other components are vacuum leaks (use carb cleaner or UNLIT propane to find) or your mixture is off (have someone with a CO tester adjust your mixture once you are sure you have no vacuum leaks).

You should also remember this old saw about CIS:

"There are three types of CIS Owners:
1) The guys with working CIS systems are probably out driving their cars so they won't reply.
2) The guys that tinker with their CIS systems and have them royally screwed up will keep you running in circles with suggestions.
3) The guys that have spent a fortune on Webers (or PMOs or Megasquirt etc) will tell you they're great to justify their expenditure to themselves.

Your choice."
4) Spent a lot of money on EFI, realized that I would always have issues, and went back to CIS and love it. Tune it with the correct gas analyzers, and fuel pressure gauges. Drive it, dyno it, and love the results.

JK-81SC 11-29-2007 07:49 AM
I'll throw in another thing to check on your high idle problem. My car had a high idle problem before my CIS rebuild. When the CIS was out of the car I also rebuilt the distributor. When I took the distributor apart, the mechanical weights were gunked up with sludge and dirt. I cleaned up everything and oiled the moving parts with 3 in 1 oil.

The high idle problem was gone, but I don't know if the CIS rebuild or the distributor rebuild fixed the problem. My high idle problem was intermittent, so I'm guessing the mechanical advance in the distributor was sticking sometimes, instead of moving freely.


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