CAR IS ON THE ROAD! Idle hanging a bit, CIS troubleshooting tips
 

Hey Boys! CAR IS BACK ON THE ROAD! Stoked.

1977 911, CIS still there, engine out refresh, replaced all hoses, gaskets, etc.

The car ran perfectly before I redid everything, and I put 75 miles on it, the only issues I noticed were 3 things:.

1. Idle hang. When I come to a stop the idle is at 1600ish, and slowly goes down to the real idle speed of 950ish. All of my throttle bushings are new, so it isn't that. I've been reading that maybe it's the cold start valve dripping fuel and not turning off right away? Any other tips on what to look for?

2. Noticed breakup around 5k RPM 2 times in over an hour of driving. I do have a pertronix system installed, but some people have had issues? Not even sure where to begin on that one, as it seemed not repeatable.

3. After starting/stopping/off/on and driving 75 miles, I got home and parked in my driveway. 30 minutes later I wanted to pull into the garage, car would crank but wouldn't start. Took like 3 tries and then it came to life. Didn't do that previously.

Not sure if any of this is related, but posting so you have as much info as I do.

Vacuum leaks, wrong basic setup of the CIS.

Don't get me wrong - as lang as you haven't proved (with a smoke generator with pump) that there is no vacuum leak I don't believe your statement ("replaced all hoses, gaskets, etc." and "therefore everything is tight").

1. Check for vacuum leaks with a professional smoke generator and close all other openings of the CIS and pressurize it with the smoke generator. Pressurizing is important because some leaks are too tiny to see smoke coming out of with no pressure.
2. To determine if there too much fuel or air that kept idle high use a starter spray.
3. A proper running CIS engine must start on the first turn, no matter if it's cold or hot. Period.
4. No experience with the Pertronix ignition, but if it's not clear that the mixture is perfect under all conditions (idle and cruising with AFR 14.7; accelerating and WOT at 12.5) I tend to say that the ignition is not the problem.
5.Point #3 might hang together with a wrong control pressure from the WUR (check the pressures in all conditions!) or either the fuel accumulator or the check valve at the fuel pump is bad.

Fun fact alongside: We had in the german forum a case where the oil filler cap seal was the culprit for a temporary vacuum leak, not predictable, but it showed up in general when the engine was warm after a longer drive....

Check out for more info https://jimsbasementworkshop.com/CIS/pages/test_troubleshoot.html and https://jimsbasementworkshop.com/CIS/Troubleshooting%20Guide/Notebook%20Spiral.html

Thomas

Also on point 3 as this just bit me, spread the pins on the fuel pump relay a bit to make sure you are making good contact. I spent like a week tracking down the same sort of symptom and that was it.

Congrats on the successful overhaul. Can’t help with the N/A driveability issues but wishing you a quick resolution. I will say like the other poster that over the years here I’ve noticed that vacuum leaks in those years are often the culprit even when the owner swears it can’t be that. And then it is.
The driving season is upon us. Good luck!

Just find it hard to believe, since all the typical sources of vacuum leaks are either brand new hoses or my sealed/glued/screwed airbox.

3. A proper running CIS engine must start on the first turn, no matter if it's cold or hot. Period.


Thomas,
How do you know this? It does not make sense. The cold start valve is timed so that somewhere between when the cold start injector turns on (key turned) to the mid point of the allotted time it will remain active is the correct number of turns.

Meaning, if the temperature is such that 8 seconds of cold start valve operation is available, then most likely 4 seconds is the correct start time, not the first turn. I think starting on 1 turn is a defect of the aged system. I've moved away from that easy solution (overly rich first crank startup, to several cranks. Takes more detailed work to achieve this.)

Phil

Subbedhttp://forums.pelicanparts.com/suppo...leys/pint1.gif

Along the same lines did you have WUR or FD rebuilt? New fuel filter or accumulator or pump? I did my WUR was good right out of the box (thanks Tony) but my “calibrated” FD was set to the wrong system pressure. I assumed it was correct and never checked it before reinstall. Took me two months to find after the motor was back in the car.

My point is unfortunately because something is new or redone it can still cause an issue.

Back to the basics: When you turn on the key, do you hear the CDI box whine? Does the fuel pump run? I don't remember if the 77's have the airflow switch that controls the relay to the fuel pump. If so, raise the air metering plate and see if the pump runs, and listen for the injectors squeaking.

At the risk of beating the dead horse… cis pressure test is the only way to find out what part of the system isn’t working. It could be something stupid simple but you’ll never know without data.

Guys, I put 100 miles on the car in the past 2 days. It runs pretty good. It starts up on the first crank every time except for last night. Prior to the refresh, it ran awesome so I didn't adjust the WUR or FD, I did not change any of the CIS system components, just cleaned them, redid the airbox and all the hoses/gaskets.. Yes, I get CDI box whine, again, the car runs and drives pretty great.

Personal experience. I replaced the bad TTS on my SC with a new original from Porsche.

The CSV is nothing else than squirting start spray additionally into the airbox to make the engine start easier and quicker.
If the CSV doesn't work, the engine will also start, but not that quick and reliable. The TTS controls the CSV. The TTS (and therefore the CSV) is connected in parallel to the starter motor. While you crank the engine, the CSV squirts a bit extra fuel into the bottom area of the airbox (later SC have the "spider" pipes therefore in which the CSV injects the fuel). The CSV / TTS works only when the starter motor is engaging! When engine starts and you let snap the key back to ignition=on the CSV/TTS also stops as the starter motor does!
The max. time the TTS let the CSV squirt fuel is 8sec to prevent flooding the engine with fuel in the case of longer cranking if necesssary.

The old (electromechanic) version of the TTS only squirts up to 35°C / 95°F engine temp, the newer TTS version is fully electronic and squirts at any temperature half a second to easier and quicker start the engine.

This, in combination with other things like a correct control pressure giving WUR, a new fuel accumulator (the old FA was still tight, but worn and it often hanged anywhere so that free diaphragm movement wasn't sure anymore) and a new Bosch fuel pump with a new check valve brought a huge improvement on starting and operating the engine. Alongside I let overhaul the fuel distributor (I measured differing outputs far more then 10% which is too much to balance them with the screws) and put in new fuel injectors. All the named parts either were bad or not appropriate to the car. Surprinsingly the engine ran with the old / wrong stuff anyway, but it was harder to start, the engine consumed a lot more fuel (also due to a bad basic setup) and the performance was not that what I expected from a light and small 180HP sports car of the 80ies...

Thomas

i did not read the whole post....
did you try to adjust the deceleration valve? 7mm open wrench and 13mm
take a picture of it if i could see it how do you have it?

Ivan

this one
[/url]http://forums.pelicanparts.com/uploa...1294687096.jpg

Update: so previously, I just marked where my distributor was and installed it in the same location, but i snagged a timing light and timed the car yesterday over lunch, and..... low and behold, breakup above 4k rpm is gone. Pulls good. Still a little idle hang, but less?

Biggest issue now is hot start. Sometimes no problem, other times I need to crank and it sounds like it runs on one cylinder, pumping the gas doesn't help, eventually it will slowly run and I pump the gas a bit and then BAM it wakes up and idles/runs fine. Not sure what that is about, because sometimes it doesn't do that at all.

Look at the residual fuel pressure. Check it with the gauges and you might find that it's dropping too quickly before the WUR resets.

There's a small O ring that if cracked or knicked will result in a rapid drop in fuel pressure. You also might need to shim the spring. All really easy fixes but you NEED to have gauges to set the pressure correctly.

thanks for the tips! I'll look into gauges now, not sure if I can rent them or what.

See how such a pressure gauge can be built by yourself or purchased:

https://jimsbasementworkshop.com/CIS/pages/test_pressures.html

https://toolaid.com/product/33800

https://cis-jetronic.com/index.php?rt=product/product&product_id=309

https://www.vwvortex.com/threads/diy-fuel-pressure-tester.6060634/#post-82272967

https://www.klassikats.com/2021/08/21/how-to-fix-your-porsche-c-i-s-fuel-injection-system/

Thomas

thank you!

Welcome.

I heavily recommend to watch the YT Channel of KlassikATS and his series about the 2,7 CIS 911: https://www.youtube.com/playlist?list=PLkWFofpgz2OgF9FdliKnlzuY0pygqRkMj

Thomas

Interesting.
Thanks,
Phil

Thomas
I compared the wiring diagrams for the 1977 and the 1982 cars. In both the CSV (called a start valve in the diagram) is only activated when the ignition is in the start position. In addition, the TTS circuit looks to be the same for both per the diagrams - when the switch opens, the CSV loses its ground instead of only its positive. The positive for the heater element in the TTS also comes from the start position wiring (so it can heat up only with the key in start, or the engine's heat from some amount of running opens that switch). But no matter what the position of the TTS switch, the CSV can't squirt fuel without the key in the start position.

I don't see anything in this system which would cause the CSV to squirt for any amount of time once the key returns to the run position. Nothing which could cause the CSV to keep squirting unless you kept the key in start after the engine started. What am I missing?

Walt,

please reread my posting #12.

I didn't claim otherwise...

The only difference between the old electro-mechanic TTS and the newer electronic version is - that the newer version now always squirts fuel for roughly 1/2 second while the cranking the engine, no matter which temperature the engine has.

Thomas

Thomas,
Does the electronic version stay on for longer than 1/2 second when it's cold out as the original, up to 9 seconds at -20C? Near freezing they would have targeted around 3 seconds of crank time as nominal so as not to flood or run to lean with +/- 3 seconds of margin.

I would say that the original design would not on average have started on first crank at this temperature. If it did, there was something wrong. Now 40 years later, who can really say. Every wur has had it's bimetal strip warped with age (so even if we buy a brand new one, they were produced a long time ago and they would be warped as well one would assume having the spring work against it for so many years) resulting in non-linear characterisitics that we tune out with rich mixtures at low temperatures to compensate for lean mixtures at high to try and balance things out. Hence the 1/2 second at higher temperatures electronic version to boost up the mixture is one solution.

I would love to see a video of a morning start of one of these in 1983. I'm guessing 4 compression cycles (ar ar ar ar brmmmmm :)) at all temps in the morning was the goal, would be nice to hear from people who bought the car new and remember specifically the first few years.

Phil

http://forums.pelicanparts.com/uploa...1681869948.JPG

TTS part #s etc
 

Well, yes I read that. I see that Pelican says the 911.617.117.00 has been superseded by the .01 version. Externally identical in appearance. The .00 version has a white plastic insulator visible. From what one can see in vendor information, the .01 has black plastic. Both have the same two size round connectors (so you can't wire them up backward). The old version, whose operation has been often explained, relies on a bimetalic switch - when it gets hot enough it opens a contact. A vendor listed its specs as "12V 3W 45*C 8 Sec." I take the 8 seconds as the time it takes the heating coil inside the device to open the switch from some starting temperature. Others report similar specs, though 40W (seems high). So a warm engine would take somewhat less time to open, all of which made sense. It seems VDO made this device with a variety of specifications, as vehicle manufacturers other than Porsche used temperature switches like this. Here is a drawing of the inside of the original version - it isn't the exact one for our Porsches, as it has a different connector. But the internals are as we all imagined.
http://forums.pelicanparts.com/uploa...1681933944.jpg

But perhaps Porsche decided, many years after these models were build, that there was a better approach, or VDO had a reason to make a change. Was there a technical service bulletin out on this? My copy is from 1984, so hardly complete.

The on-line parts catalog for the SC, dated in 2006, doesn't show any update. The very helpful Parts and Technical Reference Catalog from 1995 shows the original .00 part number. It also shows a 930.617.118.00 temperature sensor (which could cover single pole sensors without an internal switching function) for the 1986-89 Turbo, which makes sense since those turbos continued to use the CIS. The 3.2 on line catalog shows the 911.617.117.00 for the 930.66 Turbo, and the 911.617.118.00 for the 930.68 Turbo. All shown in the same left chain housing cover position.

To complicate matters, VDO is now owned by Continental. I could not find a current VDO catalog of the kind I was used to, so I couldn't do any checking there. What I found was not useful at all.

I suppose some kind of solid state device with two terminals could, when powered, create a ground for one second. And externally it could look just like the .00 in its configuration. What is its part number, when did it supersede the older electro-mechanical version, and what are its specs?

As an aside, the cost for the .01 version is a bit mind boggling for what seems a simple part. These are also advertised used at hefty prices. I'll have to check out an old one I have to see if I can sell it. If a guy had one which demonstrably had failed (resistance heater burned out, or contacts no longer able to carry current, or something), it might be worth rigging up a switch on the dash so you could manually operate the CSV.

I also note, from the many past posts on the TTS, that actual failures are said to be rare. Makes sense, as it is only called upon to close on a cold engine, and transmit current only during starting. Not the same as, say, the points in older distributors. Because it is part of the system for starting a cold engine, it is a logical device to check. And the bimetal part could change its characteristics with use and age. Same with the CSV injector itself, though, in terms of the infrequency that it is called upon to squirt fuel. Hence the admonishment to all with CIS issues to start with the pressure checks.

Phil,

wow - lot's of effort!

Yes, for sure. Otherwise the TTS/CSV would make no sense, wouldn't it? The max. time of 3secs when being cold seems to be correct. Never measured it as I didn't drove in the past at that temperatures because of salty roads.

Here's a PDF from Bosch out of 2017 with a little more tech. details about the TTS and a comparison list of the TTS they offer, I found it years ago on the net. This will hopefully answer some of your questions (only 7days available)
https://we.tl/t-u5uKzI7Vo4

It says on page 2:
The re-manufactured thermo-time switch is fitted with electronics and is therefore most wear resistant.


Unfortunately the list does not contain the TTS for the 911! I guess this hangs together with it special contact form (round contacts instead of Faston connectors as the rest of cars uses) and that Porschr probabaly wants to control the number of purchases on this part, who knows. Depending on the type they vary from 8s at -20°C / -4°F up to 12secs max squirting time.
The fact that the new electronic version squirts on any start is my personal observation (LED lamp in parallel to the CSV for testing purposes). I read this in advance somewhere on the net before, then I proved it afterwards by myself because of curiosity and even while I was troubleshooting my engine. I cannot say if it still squirts when engine is rather hot and not only jsut warm. But it will definitely squirt when engine is warmer than 40°C/104°F. And this definitely helps the engine start. Don't know if the additional 1/2 sec prolongs the max. squirting time. If so it doesn't matter from my side. The new electronic version looks exactly the same, also the insulator is white as the old was. I suppose this makes no difference. The electrical power switching capability is exactly the same.

I have a 911 PET parts catalogue from 2017 (you can download the latest version from Porsche and it names also the 911.617.117.00 still as the actual version. Don't know if Porsche itself has superseeded it by a newer version, but they will anser this for sure. I'll look if I can find the old package or the bill I got from Porsche when I purchased it.

Yes, VDO has been acquired by Continental. There is a lot of movement in the automotive market not only since the decision of sorting out combustion engines as you cannot register new ones with a combustion engine any more starting from 2035 in Europe excluding those operated only with E-Fuels...
But I never saw a TTS from VDO. Afaik they have been all manufactured by Bosch as the rest of the CIS system and they will still I guess.

Thomas

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While the TTS shown in that Bosch catalog is certainly Bosch (and shaped differently with a different plug for the two wires), the parts in Porsche's catalogs were made by VDO - it's stamped on them.

Looking at that interesting spec list, it seems only two things are different: 40 Watts (quite an increase), and a >35*C of 1 second. Below that temperature the duration, as before, the switch would appear to be a ground from 8 seconds (really cold) to 2 seconds (@34*C?).

If there are two ground paths in parallel inside the TTS, one always closed for the 1sec circuit, and one closed based on lower temperatures, then it would work basically as before, other than the hot engine squirt. I'm not electronically savvy enough to know just what parts, transistors, NTC resistors, whatnot, could by inside that small tube. But don't doubt it could be done.

Thomas - how did you deal with the different plugs? Your car's wiring came from the factory with the wider and narrower Faston type female plugs. The one for the Bosch look like the kind of two connector in one plug used by the WUR, CSV, and safety switch on our SCs.

Walt,

The Bosch catalogue shows all the known variants of the Bosch TTS available, also for some Porsches (928, 924, 914) but not for the 911. I've personally never seen such a TTS of the 924, 928 & 944, but following the catalogue says the have the Faston plug. Taht's why I had to purchase the TTS for my 911SC directly at Porsche. Those have round contact plates for flat connectors:

This version was mounted in my SC. And it's again mounted. The plugs in the car are flat connectors as they're widely used on cars.

https://i.imgur.com/7qzwPW8.png

https://www.pelicanparts.com/More_Info/91161711701.htm?pn=911-617-117-01-OEM

This will work plug'n'play in the 911. Be aware: There is a bigger (8mm) and a smaller (6,3mm) plug used! They allow to rotate a bit because the cable comes rectangular to the TTS. The round contact plate allows the cable to move.
(By the way - here on the pic from Pelican the TTS is stamped from VDO indeed...never seen before!)

https://i.imgur.com/Xpb1YZm.png

As I said - never measured. I suppose it will be no less than 1 second at 35°C / 95°F and above, as the catalogue is saying. If it won't spray at higher temperatures, then this would be mentioned there...

Don't get me wrong - but you're thinking in dimensions of discrete electromechanics. In the electronic version there is a temperature sensor, and a tiny IC to control on which temperature it will switch on the CSV via a transistor. Pretty easy to realize for a big vendor as Bosch or VDO / Continental. Highly integrated in a tiny circuit board...even when they produce in large numbers...

The old electrmechanic version was not able to realize the functionality of squirting for 1 sec at 35°C/95°F and above. It only switched the CSV on on lower temps up to 8secs in maximum.

Thomas

Need Some Clarification………..
 

Thomas,

When I read some of your posts, I just scratched my head. Where did you get this information? Did you actually have a first hand experience or just read them in the Internet? The TTS used in 911 CIS is 911.617.117.00. There is no electronic TTS ever used in 911 CIS. The TTS used 911 CIS operates @ 45°C/113°F.

What 911 CIS is using a TTS with 35°C/95°F? What newer TTS electronic version used in 911 CIS are you talking about?

Tony

Tony,

I watched the TTS at my car again and grabbed the box of the new one now:

The new one has a black insulator, Porsche brand sign (triangle with P), part no. 911 617 117 01, currently I have no pic from the important stamp numbers on it, but here's a picture from the box:

https://i.imgur.com/acg0bxW.png

If you don't believe me, I have to take it out of the car at the weekend.

The old one : white insulator, stamped with VDO indeed, 45°C, 12V, 40W, part no. 911 617 117 00. Date stamp from 2008.

Conclusion: Earlier VDO branded, now Porsche. Purchased directly at Porsche.

I suppose that Bosch is the only vendor for them now, and that those available from Porsche are as well manufactured by Bosch. And so I think they will be all electronic now. No clue if VDO produced them by themself earlier or just rebranded them.

Did you read the Bosch TTS catalogue I posted in #25? Here's the relevant section of the catalog:

https://i.imgur.com/3dGWSev.png

The TTS in the catalog squirt for a minimal delay of 1sec at temps higher than 15/35°C. See the overview chart of the catalogue:

https://i.imgur.com/MJrTXWt.png

Conclusion: The 911 one from Porsche now squirts longer than 1sec on temperatures below 45°C depending on the temperature (the lower, the longer, up to 8sec in maximum), at 45°C and higher temps just only one 1sec.

Thomas

Discussions…….
 

Thomas,

This is where your understanding of the operation of TTS particularly a 911.617.117.00 is FLAWED. At temperatures 45°C/113°F and above, there is no CSV operation. NADA. WHY? The circuit is open and you don’t need FUEL ENRICHMENT with a fully warmed up motor. Do some investigative work to confirm and verify the FACTS. There is a very big difference between FACTS and OPINIONS. Why would the CSV injects fuel when the engine is @ 220°F?

Since we are discussing this subject in the Technical Forum, we need facts and less on opinions. Thanks for the discussions.

Tony

Thomas points us to an interesting Bosch catalog, which has this picture, and gives specifications which support ordinary TTS functioning, but also the one second squirt at all temperatures above the usual cutoff. The catalog gives part numbers for 924s and some other Porsches, but not for any 911s.

While I can't imagine a one second squirt will harm a hot start, and the pictured device would require a change in the connectors, it is not clear why one would use it, since the .01 version of the .117 appears still to be available, and hot start issues are usually supposed to result from a lack of residual pressure, not from too lean a mixture. However, since the usual way of resolving hot start problems in the field is to raise the air flow detector flap with a finger after taking the air filter off, maybe a one second squirt might bypass whatever heat related obstacle to normal fuel flow may [img]http://forums.pelicanparts.com/uploads26/bosch_tts1682104478.JPG[/img

But it appears that the .01, indeed, has a black insulator? So it is what comes from Porsche, and would plug right into the existing connectors?

Ehhh, I'm somewhat agnostic. I agree with Tony that a 1-sec squirt into a warm engine to start is not necessary. But, agree with Walt that it won't hurt either. If so, it might work well enough to be a substitute part if the original part goes NLA or gets too freaking expensive ($253!). And, I wouldn't mind changing over to a more protected plug connector--those two spade terminals hangin' out in the breeze always seemed kinda sketchy to me.

So, Thomas, add to the corporate knowledge here by installing one in your car and tell us how well it works!

I would welcome a 1 second shot into a 50C warm engine. Clearly Bosch found a reason for doing this and it makes sense to me given the aged characteristics of the wur, hopefully we don't think that just tapping down an arc (wur strip) won't have other consequences, such as the miracle instant start (overly rich) that every car by now will have, Bosch gives a rudimentary way to help out that is universal. The lambda SC gives alternatives with the duty cycle adjustment, but ideally also requires some electronics to increase the fuel delivery at the ~50C start.

Phil

I'm still interested in a current draw change from 3 Watts (0.25 Amps) and 40 Watts (3.3 Amps). But only out of pure curiosity.

Well Thomas,

My car with wur set optimally and residual pressure holding strong would start very nicely at all times except after sitting for 2 hours. Then it would take 5 seconds to start. I can take the wur out of spec and force rapid agressive starts that will fix this, but then it smells like sick rich at startup, rev's high when cold at startup (1800) and can surge for first minute of drive sometimes, so no, that's no good.

Yesterday I've implemented a ~1.5 second CSV injection over all temperature. It's a very simple circuit that hooks externally to the TTS switch. The original tts still works but this is in parallel, so it does not affect cold durations. I have to run it through the tests over several days.

Edit May26-2023
Can't really say that the one second extra shot even at ~ 50C was helpful with my car. Tried it with a 3 second shot again at around 50C, it didn't seem too happy with that either. I've removed this circuit, which did work well and transferred it over to the cold 15C switch, turning the key then gives ~3sec of 65% duty cycle and only while the key is in start. It's the exact same circuit just the drain of the power mosfet is hooked to the cold temp switch, another experiment.

Phil

Could this be two separate issues of hanging idle of decel valve ( easily checked by disconnecting and plugging vac line with golf tee)
hard start being accumulator (check w/fuel gauges)