CIS Issues SOLVED!!!! NO Carbs for Me.

[Jay Laifman]

I just wanted to say that my 73.5 911 is now singing nicely. I think I can still dial it in some. But, I'm pretty confident that it's fixed. I'd like to thank most enthusiastically Art Zasadny, Jim Williams and Pete Zimmerman. I wouldn't have fixed it without them. I've seen so many guys come through here with CIS problems, showing their desperation. I felt just like them. I'm glad I did not give up hope. I'm amazed how much patience and help Jim and Pete provide. I look back at my posts and see how silly I looked. I think, "wow, that guy (me) should give up and take it to a shop that knows CIS." But, I'm so glad that these guys came through. I learned so much about my CIS and I'm so empowered to know that I fixed it (or THEY fixed it with my hands doing their bidding!)

Here are some details of what I had and what I learned for those of you who may be in similar situations. My car was running rough. It was hard to tell if it was fuel, electric or an off balance engine. It started fine, hot or cold (though previously the $12 return valve contributed to a decade of hard starts). It couldn't both idle and run well, it was really one or the other. Also, it really pretty much maxed out to a slow acceleration at about 5,000 rpms, though it used to happily spin past redline. I took it to a smog place and got a CO reading which was way too high.

I bought a CIS fuel pressure pump from Performance Products. It was about $200. I later learned that JC Whitney had one for $60, which seems just as good. One thing to know is that the Performance Products one is made by Baum and is an excellent tool. But, you have to hit the pressure release valve between readings, much like an tire pressure gauge. The JC Whitney one apparently drops with the pressure.

Many of you probably already know this. But, I learned that the system builds up a certain amount of pressure. It is then *reduced* when the Warm Up Regulator and Throttle Position Regulator releases some gas out of the system, which drops the pressure. The released gas then circulates back to the tank.

I initially misdiagnosed my Throttle Position Regulator as the problem because it did not allow enough change when I rotated the throttle. But, I later learned that it was fine. It was that the WUR was letting out too much gas at all times. So, even if the TPR in it's closed position at partial throttle, the pressure was too low. The TPR releases more fuel at idle and WOT.

I found that my system pressure was too high. I think this is odd because as far as I know, the pressure only drops when the spring in the valve in the fuel distributor weakens. I took out two of the discs in the valve and lowered the pressure to the exact right spot. This still didn't resolve anything.

I installed a new WUR and the car was better, though still not right. I kept driving around town adjusting the richness, an 1/8 of a time. But, I couldn't find a sweet spot. On the other hand, the 5,000 rpm max was gone. It kept pulling and even got a kick about then. So, obviously, with the WUR leaking out too much gas, keeping pressure down, it just wasn't working.

Finally, per Pete's insistence, I checked the air flow sensor. To my knowledge, this has never been touched by hands since the factory, like the pressure setting. But, the plate was about 1mm below the line it is supposed to be. After a lot of trial and error in bending the spring, I got it right on. The side gaps were all good. I thought it would be difficult to take of the top to get at it. But, it was easy.

A little more adjusting of the fuel ratio after that, and it's running very nicely. I'm still going to go to the smog place to get a CO reading and get it perfect. But, that's it.

Thanks again to Art, Jim and Pete.

[azasadny]

Jay,
I'm very glad to hear that you persevered and got that CIS fixed! I recommend that you keep a "spare" WUR and a few other CIS "spares" so you can swap parts in and troubleshoot. You approached the problem in a methodical way and performed troubleshooting with the pressure gauge, which is much smarter (and cheaper) then simply replacing each and every CIS component, hoping you'll eventually fix the problem, like I did!

I would also recommend that you replace all the vacuum and fuel lines to avoid the typical vacuum leaks and potentially disastrous fuel leaks. A spare CIS fuel pump, fuel accumulator, intake couplers, fuel hoses, etc... are also good to have.

I'm very happy for you, you're on the road to becoming the "CIS guru"!!

[Paulporsche]

Congrats! Another example of just how good this BB is!

[SCWDP911]

good info... as a side, what CIS parts are no longer available as new parts?

Thanks

[azasadny]

I know the fuel distributor for the '74 is NLA. Most of the parts are available, they are just very expensive (WUR, CIS fuel pump, etc...).

[Jay Laifman]

The '73-'75 throttle position regulator is NLA. It cannot be obtained new or rebuilt. That said, mine turned out to be fine.

The 73 fuel distributor is also NLA new, but can be obtained rebuilt - but only from Bosch.

[SCWDP911]

What about the other years? I know I am showing my nubian ways here, but mine is the 83 vintage CIS. It would be nice to have a comprehensive list of both parts that are no longer available, and if they are, where you can source them. If it already exists, let me know. If it does not. Let me know that as well, and I will start a new thread to cellect the info. We can ask contributors to submit using a standard format to make it easy to pick out the right info. I do minid compiling the list if there is an interest in it...

Thanks,
Shane

[azasadny]

Shane,

If you go through Pelican's CIS parts list that has pricing, you'll see the items marked as "NLA". You may still be able to get the parts from the "used parts" forum or a Porsche salvage lot, but you can't get the parts new. Sometimes a NOS part will pop up on eBay, but you never know. I'd recommend building up a stash of spare parts "just in case"... I bought an engine that came with the CIS last summer and I removed it as well as the CIS setup on my old engine, so I had 2 "almost complete" systems. I have 2 fuel distributors that need to be rebuilt...

[OZCarrera3]

Hi Jay,

I have been having similar problems with my C3 for some 10 months now and have had it to 5 specialists, including Porsche who have been unable to diagnose the problem. My car is currently with another guy and he has provided me with this data:

1) CO levels are out the window at around 7%, should be 1.8 - 2.0%.
2) Control pressure is ok (not great, but not really an issue - not know previously).
3) When at operating temps, the line pressure is 4.8 bar (should be 5.2 bar).
4) When cold, the line pressure is 2.5 bar (should be 1.8 - 2.0 bar).

I have had the fuel distributor and WUR rebuilt (both had the diaphragms reset), as well as getting the air flow sensor checked (apparently ok). The mechanic has stated that whenever he adjsuts the CO2 levels to where they should be, the hydrocarbon levels then go out the window. He is at a loss at the moment is basically going back to check everything.

For you and the guys who helped you out, should I ask my mechanic to replace the WUR and recheck the air flow sensor? Is there anything else I should suggest to him?

[Jay Laifman]

Well, like I said, I'm no expert. I've only been learning from others. So, with that big caveat, here are my $.02 suggestions:

1. If I've learned anything, if something is not right, fix that first before moving on. And all these things relate to each other. For what it's worth, I had similarly high CO numbers.

2. You have indicated your pressures are not right. So, fix those before doing anything else. The first thing would be the system pressure. That said, I seem to recall that the system pressure for my car had an acceptable range and it was like 4.8 to 5.2. Mine was at 5.7. I was able to drop it to 5.1. I don't know how to adjust your system. If it's the same as mine, all you have to do is add little round shims or washers. But, then those are probably impossible to find. I think I saw somewhere about stretching the spring. But, I'd be worried about that advice and wouldn't follow it unless you got comfort somewhere else on it.

2. So, once you have the pressure right, check the control pressure. There are four readings you should have: idle cold, idle hot, part throttle hot, and full throttle hot. Whoops, that said, that's for my 73.5 with a throttle control. I don't know about your year. So, again, you got to keep my advice in its place! Bottom line, get the full measurements. If yours is too high, it could be that the WUR is not letting out enough gas, or there is a plug in the lines leading from the WUR to the gas tank. I have no idea how to check for blockage. But, what I did is that I took the outlet hose off and put on a new hose and ran it into a jar. So, I knew there was no restrictions. I got the same reading doing that as I did when it was attached. So, I knew there was no blockage. But, for all I know, in your system there may naturally be some back pressure getting back to the tank that the WUR is designed for.

3. I'm told that the Fuel Distributor cannot be properly rebuilt by anyone other than Bosch. I don't know about the WUR, but assume that is true too. Around here anyway, the only way to get one rebuilt is to buy a rebuilt one and turn in your as a core. No one offers to send yours in to be rebuilt. Your language suggested you did have yours rebuilt. If that means they did not go to Bosch, you many want to question the quality of what you got - or if you got anything at all other than a nice cleaning!

4. On the Sensor Plate, like I said, mine was 1 mm too low. That's a pretty small number. For all I know, your mechanic may look at it and think "it's good enough." But, my opinion is that the Germans don't go for "good enough." They go for "Perfection was Expected." That said, the sensor plate won't fix your bad pressures.

The Porsche Handbook I have on the CIS system also lists to be sure all the following are to spec before trying to "fix" the CIS system:
valves adjusted properly,
coil hooked up properly,
ignition system as a whole in order,
accelerator linkage working properly without binding.

Oh, this book was printed in 1978. There are different stats per year. There is no '76 3.0 Carrera identified. Here are the stats that are there:
System pressure (this is before the WUR lets gas leak out reducing the pressure) 4.5-5.2 Bar. So, yours seems good.
Control Pressure (that is, when it is controlled and reduced by the WUR):
Idle position (car off) 2.9-3.1
1/2 throttle 3.5-3.9 (Europa 3.4-3.9)
WOT 2.7-3.1

Cars fitted with vacuum WURs
Engine off: 2.9+/- .2
Idle, running: 3.6 +/- .2

CO
This is tough because it lists years, but not 76
77 is 1.0 to 1.5% for Europa

Again, I'm the blind leading the blind here. Please do not rely too heavily on what I have here.

Hope some of this helps.

[OZCarrera3]

Thanks Jay, a very detailed review and comment.

I'll print this out and fax it to my mechanic today. Will let you know the outcome.

Cheers,

Sheldon

[ianc]

Glad you gave up on the carb idea. CIS is really a reliable system once it's setup properly. Good luck to you,

ianc