CIS Cold Start Problem Did Pressure Tests Now What?
 

I'm new to working on CIS and have done a bunch of reading. Did the fuel pressure tests with results below. Symptoms after.

1983 911 SC with 105k miles stock motor
WUR 090

4.7 bar System Pressure

Ambient air 67 degrees
1.0 bar Cold Pressure
1.25 bar @ 1 minute
2 bar @ 1:30
2.75 bar at 2:00
3 bar at 2:30
3.5 bar at 3:00 and holds steady there

1.7 bar 10:00 residual pressure and holds for over an hour

Problem is the car is either extremely hard to start or won't start when ambient air is less than about 70 degrees. When it gets into the 50s it usually wont start cold. It will crank and crank and sometimes sputter just a bit as I let off the key. Crank too much and smell fuel. If it does finally catch and run it will idle a little low for about 30 seconds. If I give it some revs it runs just fine. After running for a minute or so the car runs excellent. Revs great, idles great and then comes back to idle great. Once its been running even for as little as say 30 seconds if I turn it off it will immediately fire back up and run well at first turn of the key. All of this goes away if the ambient air is in the mid 70s and above with the exception of maybe a bit of a low idle when first started.

So looking at the charts in my Bentley it looks like system pressure is within spec of 4.5-5.2 bar. Residual Pressure is good being over 1.1 bar. Control Pressure warm is within spec of 3.4-3.8 bar. So looks like the problem is the cold pressree. Looking at the graph it says I should be at about 2-2.4 bar.

So where do I go from here knowing I have low cold pressure? What do I need to do to get it to start when its cold and cold outside?

Is your cold start valve connected?

I had a similar problem with my car until I discovered the power connector for the cold start valve had fallen off. Plugged the cable back in and all is well.

If it is connected, are you getting power to it when you crank? It is powered by the same power feed to the starter motor and switched by the thermotime sensor on your timing chain cover. Is your thermo time sensor working?

If you are getting power, is the valve working? Not sure how to test.

Wiring diagram:
http://forums.pelicanparts.com/uploa...1544236396.jpg

Where is the cold start valve, mine does this occasionally.

On my 1973.5 it is behind the throttle body.


This thread may be helpful to the OP: http://forums.pelicanparts.com/porsche-911-technical-forum/386478-76-cold-start-valve-troubleshooting-need-help.html

http://forums.pelicanparts.com/porsche-911-technical-forum/382249-testing-cold-start-valve-removal-replacement.html

Jim Sims posted this info for a 1973.5 911 and "should" be similar to your car.

Wur.....
 

Wyatt,

What is the heater resistance (Ohms) of the WUR-090 when the engine is cold? Keep us posted. Thanks.

Tony

calling pmax and ADDvanced! this is a formal CIS string band request for you guys to hum your tune some. where ya?

Hahaha. They say carbs are too complex...

http://forums.pelicanparts.com/uploa...1544243669.jpg

Wyatt,

I’m not near the Bentley book but your numbers seem normal. Even if they were slightly off, it is doubtful the car would be as hard to start as you describe.

Tony asked a question. It would be good to follow up.

Good thought on the CSV. The cold start valve is the “7th injector”. It provides extra fuel on cold starts. It’s located on the back side of the throttle body. It looks like this:

https://www.pelicanparts.com/More_Info/91160610701.htm?pn=911-606-107-01-OEM&gclid=EAIaIQobChMItKOh4LaP3wIVlFmGCh23wQIyEAQY AiABEgLdWvD_BwE

After CSV, I would start thinking ignition. When was the last time plugs, plug wires, cap & rotor were replaced?

If you pull the coil wire and you ground it (being careful not to get electrocuted) while a helper cranks the car, is there a strong blue spark? How does the car drive once warmed up?

I did not test the resistance cold because apparently I am not smart enough to get the electrical connector off and didnt want to break it. Any tips on removal? I can make out a little metal clip that I can see on the drivers side of the plug but couldn't figure out how to release.

Seems pretty far off at cold. Bentley chart says it should be at about 2.2 bar where as I am seeing only 1 bar. ????????

CSV looks just about impossible to get off without an engine drop any tips on this?

Car run excellent after it warms up. Zero issues. Pulls strong idles smooth.

Plugs, wires, cap and rotor were replaced about three years ago and only have about 2k miles on them.

Sounding more and more like something that is just starting related. The WUR pressures are only going to really come into play in the moments right after starting when the engine transitions from start to run state. You’re not getting past starting. It sounds like you’re fuel starved when cold. Cold air is more dense than hot air, so when the ambient air is colder you need more fuel to compensate for the fact that there is more air per unit of volume. Hence the reason for the CSV.

Once the engine has started, and the engine is cold, you are in the warm-up state. The WUR adds more fuel during this time and gradually backs off to normal running state once the engine is warmed up.

A lower cold control pressure means you’re getting a richer mixture on cold start. If everything else is functioning correctly you would just have some white smoke on startup and the smell of unburnt fuel in the exhaust. What you are describing is hard starting so while the cold control pressure is off, it is likely not the source of your problem. I would make adjusting the CCP a second priority at this point.

Getting to the CSV can be a pain. But the first thing to do is check the easy stuff. Someone already suggested making sure the connector on the back side is connected. Next step would be to verify power and ground. The CSV fires when certain conditions are met. Engine is cranking AND engine is cold. Do you have the Bentley? If so, do the diagnostics associated with the Thermotime Switch. If the TTS has failed the CSV won’t fire. The tests aren’t hard and the TTS is easier to access. The TTS is located on the left side chain cover housing in the far left corner. It has two wires going to it. If the TTS is good then it’s pointing back to CSV and you’ll have to verify CSV is firing when cold and cranking.

Getting to the CSV may require a partial engine drop. You may need just enough clearance to remove the “pope’s hat” and have some room to work.

To remove the electrical connector on the WUR just grab it by the base and pull straight up.

Yes I have the Bentley manual. I saw the instructions on testing both the Thermotime switch and the CSV. I will get my hand back there and double check that the plug is on the CSV first and then run the test on the thermotime switch. Going to be a day or two before I can get to the tests and will report back.

Isn't there a spring type clip around it? I never did understand those things and am always in there with a scriber type tool trying to remove the clip.

Check your thermo time switch and make sure it is connected. Next, check the red/black terminal to make sure it is grounded. If all checks out, it should fire up!


Cheers,

Joe

There is but I’ve never had difficulty disconnecting mine. It’s a statistical sample of one though so take it for whatever that’s worth.

Maybe WyattEarp could test.

It's just a spring clip, folks.

LOL, there are at least half a dozen regulars here who understand this inside out. Just sit back and watch them work.

I do want to add though that the resistance of the WUR does not affect the initial startup, it comes into play only after the engine springs to life.

You call it a spring clip. What does that imply? Just pull as Tim suggests? I have seen BMW spring clips that have a little press thingie to allow removal of the connector.

Disengage, release, pry out ... the metal clip on the sides then pull.


Here ... it's Saturday morning, why not :)

http://forums.pelicanparts.com/uploa...1544303315.jpg

+1 The car could start with injector fuel lines removed with a functioning cold start system. (Then stall shortly after starter disengaged)

OK. This what I have been doing. I was hoping it would have been like Tim's experience.

Thanks.

His probably has a broken connector, like the one in mine !

Mine seems to not be broken and trying to keep it that way. Always very afraid of pulling too hard on 30+ year old plastic that has been heat cycled over 105k miles.

I was always prying out the spring clips and I ended up chewing up and breaking a couple of the plugs. They actually just pull straight off without removing then spring clip. If you use a little thin screwdriver and just very lightly insert the blade and twist under the plug it just pops right off. If I had of known this when I was disassembling my CIS it would have probably saved me a couple of hours sheesh.

Remove clip with one of those bent tool dental tool, scriber things.

Easy to lose. Too much tension and it will fly and disappear.

15 years ago you could go the the bone yard and snag all the clips and connectors you needed off of 1980's VW's.

They are thinning out.

WyattEarp:

All very interesting discussion, but back to you. Your original post said it was hard to start but once running, seemed ok. That, to me, clearly indicates a problem with the cold start system (Thermotime switch or CSV).

Have you been able to verify all is connected properly?

Have you been able to verify all is working?

Inquiring minds want to know.

Where is it that this thread deviated into off topic?

Hi Bob:

I guess it was the tangential discussion on how to remove a clip. Interesting, somewhat on topic, but the "not the main event".

+1

By no means the main event but pertinent, however small.

Functioning CSV will start the car every time. OP ain't got that going on.

My thoughts exactly.

It is pull/push plug.........
 

Pmax,

You don’t need to pry and remove the spring to unlock or remove the WUR plug. How often do you work with this push/pull type square electrical plug lately? The WUR’s used in CIS have this type of plug on them. The spring is used to secure and lock plug in place. The plug will not come off easily without applying sufficient side to side pulling motion (wiggle) to unlock this spring.

Look very closely on the locking tabs on the sides of the plug. For installation, outer angle of the tabs is approximately 45° and the inner tabs have greater than 45° slope. So you would need a much greater effort to remove or pull out the plug compared to installation.

If is mandatory to use a pick for removal, how on earth would you be able to remove the AFS switch plug, CSV plug, or FV plug with the engine in situ? I will give you several hours to remove this spring with engine in situ. The key to removing this type of plug is to exert a side to side pull (wiggling) to get the locking spring slide over the the locking tabs. Go over the garage and practice removing it. I’ve been working with Bosch WUR’s for many years now and I could not recall exactly how many times I’ve done this maybe several hundreds or thousand times (?).

People been doing a lot of reading and that is good. But they lack hands on experience. This a very good example how people think and understand how CIS works. And this is just the “spring”. Wait till it comes to actually doing the CSV and fuel injectors tests and evaluation.

Tony

Test and confirm.......
 

Bob,

If you have not checked or tested the CSV, how would you know it is good or bad? You can not evaluate the CSV nor the fuel injectors without dismounting them from the engine.

What the OP needs now is to know and understand how to remove and test the CSV and injectors to evaluate them. I intentionally avoided earlier getting involve in this post to allow others to participate and offer his/her advices. The more people participate in a given thread the better.

A good working CSV does not guarantee you that you could start and run the car. A CSV is a very robust and dependable CIS component and it hardly fails at all. But the key is how to test and evaluate CSV if you are able to dismount it from the engine. The removal is easy but cumbersome or tedious with the car installed.

BTW, have you completed the restoration of your SC after the accident? Happy Holidays my friend.

Tony

I have used the pick method for 22 years.

However, I assumed that was the way to do it. It worked, but a pain in the ass. I was wrong.

OK, it can be literally pulled off. Which is awesome.

What does that have to do with not being able to understand other CIS testing methodology?

One of the easiest things I did on my top end rebuild in the 90's was cam timing from a genuine work perspective.

It was easy. Girl work. Set up indicator. Overlap TDC. Shift the pins as needed Snoozer stuff.

The subject is a simple mechanical discussion about how to remove a connector. NOT a dissertation on mental capability wrt CIS.

I just started moving on it. I am serious.

I have one car pal left as two died in the last year. The remaining is a sheet metal wizard. Thankfully. How selfish is that?

I bought all the exterior parts from a car in Canada. Hood, fenders, bumpers, etc. $2,500 which was probably a bargain.

The front tub is the rub. Tree hit drivers headlight spot on and supports moved things around.

I can expound upon this but not the place. Suspect $2,500 in straightening then the $2,500 of parts can be hung.

I did this engine in situ. It was awful but doable, as long as a large caliber hand gun was not close by.

A good working CSV will start the car. Full stop.

No running was referenced.

poor silly pnut! your team is turning on you!! :confused:

Just focus of these........
 

Wyatt,

Ignore the other distractions. Simply focus your effort on what Harry is asking you. If you have any problem, simply ask. Keep us posted.

Tony

Awesome.

Will practise that wiggling technique on my spare harness connector.

Back to the OP's issue ...