CIS Troubleshooting for Dummies

[AndrewCologne]

For testing the fuel pressures just only disconnect the electrical plug from the WUR.
And ... later when pressure have been read ... as the plug is disconnected, ... do test the voltage at the terminals of the plug which will be plugged to the WUR, .... here 13 volts are mandatory when engine is running. Lower voltages will make the bimetal strip move slower and so the warm up phase will result longer.

The AAR is only needed for providing a bypassed metered air to the manifold air flow so the idle is higher while warming up a cold engine.

[mike sampsel]

Originally Posted by AndrewCologne

For testing the fuel pressures just only disconnect the electrical plug from the WUR.
And ... later when pressure have been read ... as the plug is disconnected, ... do test the voltage at the terminals of the plug which will be plugged to the WUR, .... here 13 volts are mandatory when engine is running. Lower voltages will make the bimetal strip move slower and so the warm up phase will result longer.

The AAR is only needed for providing a bypassed metered air to the manifold air flow so the idle is higher while warming up a cold engine.

Thanks,

it makes sense to me, as it was odd statement in a text on the subject, an unmissed error, I expect.

Cheers

[Jay Laifman]

What happened to Jim's website on CIS? I used to use that all the time.

[andino]

Originally Posted by Jay Laifman

What happened to Jim's website on CIS? I used to use that all the time.

It got moved and is maintained by Rarlyl8. Content is still the same though but URL a bit harder to find

https://cis911primer.com/home.html

[Jay Laifman]

Thanks!

[Jay Laifman]

Adding something I learned in separate threads on solving my problems, but is good for troubleshooting. I fully agree with the multiple comments above that this thread should not be for solving peoples' individual problems, but to provide answers and solutions. With that in mind, here is a problem and solution I found that differed from the specification testing.

I had a hot start problem - would start ok when cold. Would start great for 4 minutes after shut off, but starting 5 minutes and more after shut off, it would spin with the starter but not start. After lots of experimenting out of desperation, I did find that if I first tried to start without the cold start valve going, it would spin for a while, and when I got any type of flutter attempt at ignition (usually after a second try), if I then lifted the throttle engaging the CSV, it would start.

My injectors did leak a little bit of fuel after shut off. But, I tested for leak down, and my car absolutely tested to specification, holding the spec pressure after 20 min. So I figured the little bit of fuel was acceptable. I also read that leaking injectors are not leaks because of the injectors, but because of the fuel distributor.

Both turned out wrong. The injectors absolutely leak on their own, regardless of the fuel distributor. And, even though the leak down is to spec, the leak was still enough to make a hard start problem.

I just put in all new injectors, no more leak and my hard start problem went away completely. It now starts immediately like it used to. (And my other thought that "new gas" might be to blame was also unfounded)

So I thought it important to post here that testing to spec doesn't eliminate all problems for 50 year old parts.

[Phony930]

I've just found this thread and am pouring over the info now -- is the CIS Primer for 911s also applicable to the CIS system on turbo models? It only references 73-83 models from what I can see. I have a Carrera that was swapped with a 3.3T and CIS system and I am trying to soak in all of the info I can about this new-to-me fuel system.
I believe my Fuel Distributor is a 145 and WUR is a 153, just trying to get past the "I don't know what I don't know" phase and get into the much easier "I know what I don't know" phase.

[Schulisco]

Originally Posted by Phony930

I've just found this thread and am pouring over the info now -- is the CIS Primer for 911s also applicable to the CIS system on turbo models? It only references 73-83 models from what I can see. I have a Carrera that was swapped with a 3.3T and CIS system

CIS was still used up to the 964 3,3 turbo...I personally have no experience with a 930. But
I would say yes that you still can use the CIS primer for troubleshooting on a 930 for the basic things. The principle is pretty the same, but some of the details will differ for sure. Most problems on CIS are related to engine start cold and warm and running culture, performance and fuel economy and the components here are mostly the same ones as on naturaly aspirated cars.

Probably it makes sense to start a new thread describing the issue(s) and your car to support you.

Thomas

[HarryD]

Originally Posted by Phony930

I've just found this thread and am pouring over the info now -- is the CIS Primer for 911s also applicable to the CIS system on turbo models? It only references 73-83 models from what I can see. I have a Carrera that was swapped with a 3.3T and CIS system and I am trying to soak in all of the info I can about this new-to-me fuel system.
I believe my Fuel Distributor is a 145 and WUR is a 153, just trying to get past the "I don't know what I don't know" phase and get into the much easier "I know what I don't know" phase.

Conventional wisdom with any CIS system is that everything outside the CIS components need to be spot on. We are talking Valve adjust, timing, dwell, plugs, wires, etc. Vacuum leaks are a common problem. Once these are resolved, you may find your CIS is ok and merely needing a sight mixture adjustment.

What exactly is the issue you are trying to address?

[Phony930]

Thanks guys, haven't put the car through its paces yet -- bought it with some unknowns and some modifications and just trying to shake it down and go over everything to feel confident its good to go. I plan to install a Wideband soon so I can start there.
In speaking with RarlyL8 previously, he advised that my fuel setup with the 145 distributor and 153 WUR was not going to support the modifications and boost level of the car, so just looking to understand and navigate that as the previous owner seemingly ran it this way for years. Previous owner said "the fuel system was set up properly to support the modifications" but he did not know what was done.
Modifications include: K27-7006, Webb/SC cams, Billyboat full exhaust system, manual boost controller set to 1 bar. Engine was refreshed in 2001 and 15k miles ago, likely to stock spec, but some upgrades were at least quoted by the shop so I don't know for sure.
I just like to understand my vehicles fully so I'm on a bit of an exploratory mission to know where I am and then figure out where I should go.

[Schulisco]

Originally Posted by Phony930

I just like to understand my vehicles fully so I'm on a bit of an exploratory mission to know where I am and then figure out where I should go.

Troubleshooting a CIS you've never seen before is a not an easy job. But all in all - if you got the whole picture - basically it's a simple system. The confusing thing is the bunch of vacuum and other lines. But when you understood all components and their purposes it's simple.

Here in this thread you'll find many good sources, although some are no more available over time. Some have been mirrored on other URLs either.
I always recommend a set of resources t get familiar with CIS as follows:
https://forums.pelicanparts.com/porsche-911-technical-forum/1171604-cold-control-pressure-k-jet.html#post12375978

Thomas

[PeteKz]

"Phoney". You are going about learning your car in a good way. Except this: Drive it. Put a fresh tank of gas through it regularly and drive it hard. CIS does not like to sit with old gas in it.

[pmax]

WUR033, adjustment?

Adjusting the WUR

[flyboy182]

Hello folks. Relatively new to the forum and also to the Porsche world. Picked up my first vintage machine, an '83 911SC. Car has not been run much at all in last 20 years but well preserved and busy now trying to get the bugs out of the CIS system. Seems like I have a few things wrong...any guidance would be appreciated and I have a few specific questions. I have completed the tests per this thread at the start...as follows:

YR: 1983
Market: US
WUR #: 090
Test Temp: 21C
WUR resis: 25.3 ohms
System P: 4.75 Bar
Cold P: 0.9 Bar
Warm P: 3.1 Bar
Time to Warm P: 3.5 minutes
Resid Pressure: Drops like a stone to zero

Other tidbits:
I had a brutal warm fast (stuck) idle problem when I first got the car. Took it to a shop that proceeded to disconnect the decel valve, did a few other minor checks and sent me away saying it was running well enough to go put some miles on it and run some good quality injector cleaner thru it. I followed instructions. Still doing that.

Symptoms at present:
- Seems to run decent once I get it started and warm...emphasis on "once I get it started". Idle is relatively stable. Good throttle response and power.
- Cold start crank is about 3-4 seconds. Starts consistently. Seems to waver in idle at first then climbs up to about 1400 and comes down in a minute or two. If I drive off too quick (I tried this as a test) the car chugs and lurches and isn't happy. If I sit and wait and let it warm a bit and settle it seems fine and happy and settles in as noted above.
- Hot starts are another matter (from above now I guess we know why...). Immediate start or say within 30 seconds to a minute...No issue, starts right back up.
- Any amount of sitting and it cranks and cranks and eventually fires, sometimes stalls and can be slowly coaxed into keeping running if you feather the throttle a bit and then it settles down and is good again. Its a slow process to get it running again when warm.

From the above, it seems for sure an issue with resid pressure. I have read this long thread and a few other resources (I have Bentley in hand and a Bosch Workshop manual...doesn't cover my specific year but at least explains CIS and testing etc). So...Fuel Accumulator, Check Valve at the pump, or Pressure Regulator at the FD. Any opinions on which one to buy and change first? I have limited skill and tools but trying my best to not just throw money at the local shop and rather try to figure this out myself.

If this isn't the right thread as this one started as more of a "Knowledge Base" thread then, please, long time users please advise me and I will start a new thread or attach to another and ask admin to remove this mis-placed post. Many thanks in advance and great to be part of this community of assistance with these awesome machines.

[Funracer]

I have an 83 US as well. From what you have posted:
WUR 090 is correct model
25.3 ohms is good
System P 4.75 bar is ok
Cold P .9 Bar seems way low. This will effect cold running. See chart in Benson
Warm 3.1 is low as well. 83 spec is 3.4-3.8 bar from memory.
Time to warm is ok
Residual press zero, as you know, is a problem for warm start.

You said car was not run much for 20 years. I would check fuel pump/check valve, fuel filter and have the WUR tested and rebuilt as needed, and converted to adjustable as well.

As for hot start you are on the right track. Accumulator, Fuel pressure regulator and FP check valve are the usual suspects.

Yours is the US version. Is the Lambda oxygen sensor relay plugged in underneath the pax seat?

Lots to look at but lots of help here as well.

Congrats on your new car!

[flyboy182]

Thanks Funracer. To answer your questions and to add a few more details I perhaps should have noted initially...
- I had a PPI done at the shop that worked on the car thru pretty much its whole life (have all records). Multiple owners but all in the same locale and consistent service at this one shop. Shop seemed reputable and everyone I asked to take it there for air cooled service.
- That shop had done some service just before sale and that included installing a "rebuilt" WUR...perhaps they didn't use a good shop to do the rebuild??, as it seems like I am out of spec here.
- this work order also says "replaced Lambda relay". I just checked and indeed it is plugged in under the seat.

As you said, lots to look at here and it seems I certainly have multiple things going on.

Lastly I should mention that despite my efforts to be diligent here (as I said I am new to air cooled Porsche) the PPI shop apparently did miss a few things. Once I got the car home and had the super high warm idle problem..the local shop that did some initial recon work for me on the CIS and disconnected the decel valve also found that I don't have a "pop off valve" in the airbox and that some of the screws were loose. They smoke tested it and said it is not leaking and tightened down the screws...but they said I got lucky that it didn't fully blow and that I should have a valve installed...which I plan to do.

Thanks.

[boyt911sc]

Flyboy,

A quick look at your control fuel pressures data shows that your WUR needs some work. At this point, without correcting your WUR, it will always have erratic cold and warm idle. And will always suffer warm up start due to residual fuel loss. The airbox is questionable at this point. Have it tested. If the screws of the air box had popped out, your CIS could had been compromised.

Tony

[flyboy182]

Thanks Tony;
No missing screws so nothing went deeper into the CIS system or the engine, they were just loose. Agree on the WUR, the "rebuilt" one the last shop recently installed clearly wasn't set up right or done right or both. I am wondering about taking it out and doing the mod I read about to make it adjustable...then see if I can get it set to be in spec. Question for you though, WUR aside for the moment...with my resid pressure dropping like a stone when the pump is shut off would you agree I have one of the three things noted that has failed (ie pump check valve, accumulator, or PPV on the FD)....or not necessarily and I should focus on the WUR first, period?

I drove the car today to try to run some more fresh fuel and injector cleaner thru it...barely got it started after it sat for about 75 minutes after a good run. In fact, I had to jumper the fuel pump at the relay for a bit to pressure things back up...then I got it to fire. Close call avoiding AAA!!

[boyt911sc]

Flyboy,

You need to test to determine the culprit/s for your residual pressure loss. While a defective fuel accumulator is the most common culprit, there are other components that could cause this problem. Getting your WUR to spec is also a priority. If you need help testing your CIS components, I will do it for FREE. Just include a return shipping label and will test the parts within 48 hours from receiving your package. It would take me only a few seconds to do each test and it’s FREE. Your only expense is the shipping cost.

Test and confirm that the part is defective before replacing it. Otherwise, you might end up replacing good working parts.

Tony

[flyboy182]

Hi Tony and thank you for that kind offer and your continued assistance. I may take you up on that but for now I want to see if I can narrow it down some myself with assistance if you are up for that? Since your earlier post I have been trying to do more learning and reading and watching videos etc. I have so much to learn...

Anyway, I found one link posted on central NY PCA site that explains 10 reasons one could have low or non-existent residual pressure and thus hard warm start issues...and here I thought it was only three reasons!

https://cnypca.org/bosch-cis-hot-start-problem/

First Question: I think I see now how the WUR itself could allow leak back and loss of residual pressure. Could I disconnect the two fuel lines to the WUR and test pressure within that line to see if I have immediate leak back? If I do then that would tell me I have something else beyond the WUR possibility that is allowing quick leak back. Please let me know if you agree with that?

Second Question: I watched a video or two discussing adjustment of WUR to get pressures within spec...one explains how Bosch set these at the factory by press fitting down the one end of the bi-metallic strip. So discussion about how you can use a drift to knock this down and adjust DOWN the pressure(s). My issue is the opposite per my initial test...both my cold and warm control pressures are too low. This video talks about taking apart the WUR and bending the bi-metallic slightly to bring them back into spec (I guess either direction). The idea of drilling and tapping and installing a bolt etc on the WUR only seems be for getting the pressure(s) down...but not up. Do you agree with that and short of buying (a second) newly rebuilt WUR and hoping it is within spec, is my only option here to take mine apart and try this to see if I can get it to test within spec? Please let me know what you think on that.

If you are interested here is the video I watched discussing this. I know you don't need any education on this topic, but just in case you want to see what I was watching to either agree or debunk it. Thanks!!

https://www.google.com/search?q=how+to+adjust+bosch+CIS+warm+up+regulator +for+cold+control+pressure&sca_esv=8d061dbbff1738e7&sxsrf=AE3TifO5oQgQGfJKrkiXQzhP9mKpeo-rHQ%3A1758976436025&ei=tNnXaKysAYKW5OMPwKijwAs&ved=0ahUKEwis1ozt-fiPAxUCC3kGHUDUCLgQ4dUDCBA&uact=5&oq=how+to+adjust+bosch+CIS+warm+up+regulator+for+c old+control+pressure&gs_lp=Egxnd3Mtd2l6LXNlcnAiQ2hvdyB0byBhZGp1c3QgYm9z Y2ggQ0lTIHdhcm0gdXAgcmVndWxhdG9yIGZvciBjb2xkIGNvbn Ryb2wgcHJlc3N1cmVIkC5Q3wdYyitwAXgBkAEAmAGUAaABlBWq AQUxMS4xNbgBA8gBAPgBAZgCFKACnBHCAgoQABiwAxjWBBhHwg IFECEYoAHCAgUQIRirApgDAIgGAZAGA5IHBDMuMTegB8h7sgcE Mi4xN7gHkhHCBwcwLjEwLjEwyAc_&sclient=gws-wiz-serp#fpstate=ive&vld=cid:7c8e6dd7,vid:-_7jQFHn0o0,st:0