cold start problems

[nh911]

Hello

hoping that someone can describe the cold start process. Any how, my car takes 12-15 starts before it will finally stay running(not well till warm up) .

If someone can finish the statement or correct

turn ignition on, fuel pump gets power, thermo valve determines cold engine which powers WUR which sends add'l fuel to the injection system.

electrical diagram shows WUR has red/white and brown wire. I have a connector that goes nowhere and after research in forum it appear it should not be connected.

Any procedure on telling me where to start checking voltage to see if the system is juicing properly. Thanks, Michael

[john walker's workshop]

the WUR just allows the fuel distributor to run the engine richer. it doesn't by itself add any fuel. it needs no voltage to allow a cold start. the voltage just warms it up so it increases control pressure and leans the system out over about 3 minutes. a good state of tune and a fast cranking speed make starting easier. year of the car would be helpful. the cold start injector is probably what you're thinking of.

[nh911]

Thanks and sorry about the year. I have an 83 911sc. I guess cold start is probably the direction but I have no idea how the system works. What energizes the cold start valve(+ where is it located), does it get powered from the fuel pump relay. Any detail is really appreciated

[Paulporsche]

I see you are new to this forum. Welcome, and when you get a chance, post some pics of your car.

You should use the search fn of this site. There is a lot of info on CIS cold start/warmup problems.

Generally speaking, you should first make sure all your ignition components are operating to spec.

Then check for vac leaks.

Get a CIS fuel pressure gauge to check pressures. The cold control pressure is particularly important. Other local Pelicans may have one they can loan you.

Jim Williams' website on CIS is very informative. So is the Bentley Manual for SCs.

You don't say where you are, but I'm guessing it has recently turned colder there and this is a recent problem.

Most of the time, this happens because the WUR is out of spec, w/ a cold control pressure that is too high, resulting in a mixture that is too lean @ startup. Sometimes the mixture is simply set too lean.

The AAR and AAV sometimes are out of spec or not getting power. The AAV helps the sensor plate rise by giving the system extra air @ startup. The AAR keeps revs up during warmup to prevent stalling.

[boyt911sc]

When I first saw the title 'cold start problems', my first reaction was this must be one with a CIS engine. This topic had been discussed again and again. This particular question about cold start usually get asked when the fall season starts to cool the prevailing climate. And as the weather gets really cold, the problem is agravated.

First thing you should do is determine your fuel delivery pressures (control and system). Based from your explanation, I would check the CSV (cold start valve) and TTS (thermotime switch). Both these CIS components have been discussed intensively in the last 60 days in this forum.

After your search, you'll probably notice the same group of guys responding or giving some suggestionss how to remedy the problem/s. I've not encountered a CIS problem that could not be diagnosed correctly by these people. These guys are good!!!!

Tony

[Gunter]

nh911:
Get the Bentley SC Repair Manual; you'll love it!
It'll show you how the CIS works and explains what happens during cold-start.
The CSV gets power through the TTS (situated on the left chain cover)
The TTS gets power from the Starter Solenoid during cranking.
There could also be a problem with the AAR not opening fully when cold or the WUR acting up.
I assume that your engine has been maintained properly and all ignition components like plugs, rotor, cap, wires etc. are good?

[nh911]

thanks for the response. As I was waiting I did some researching on the forum and found many guys have asked along with many items to check.

Long story short, bought the car not running, motor has been in/out 4 times for several reasons, want to check power to CSV but haven't got a clue where to start. I will need to order the Bentley manual as suggested because I have not seen any good diagrams of where to find the items to check.

Car runs good once warm but 15 tries to start is gonna wear out the 2nd new starter and 2nd new ring gear(I have a good mechanic to NOT recommend).

This is my second 911 but my first time at DIY repair so I am trying to associate myself with all parts and locations. If there is a search text you can recommend for the most detail on this issue please let me know.

[Gunter]

On the Starter Solenoid are 2 yellow wires: One is coming from the ignition lock and the other goes to the TTS located on the left rear chain cover.
Both these wires get power during cranking.
So, climb under and make sure the 2 yellow wires are connected on the Solenoid.
Next, have someone crank the engine while you check the power supply to the TTS; it should have power during cranking but be aware that the TTS cuts out the CSV after a few seconds during cold-start.
The CSV is situated behind the throttle body and hard to reach; in fact, it's a PITA to get to.
The reason why the TTS cuts off power to the CSV is that it should only energize for a few seconds during cold-start. When the engine is warm, the CSV doesn't get energized.

Any Porsche Mechanic should be able to find the problem; try someone else.
Wait for the Bentley; one big error in it is the direction of rotation for the distributor: It is ccw, NOT cw; make a note of that.

[boyt911sc]

Each time you crank the starter, the yellow wire from the solenoid (starter) supplies power to both CSV and TTS (refer to SC wiring diagram). The TTS does not supply power to CSV but rather supplies the ground connection. The CSV depends on the TTS for ground connection only. Without any grounding, the CSV will have an open line and becomes inoperative during the start phase. TTS as the name describes it is temperature and time dependent during its operation. Open when warm and close when cold. The internal heater in the TTS controls or limits the duration of the contact point (grounding).

To test for the operation of your CSV (detached from engine), have the fuel pump running and supply 12 volts to the CSV. A uniform spray pattern should be observed when energized. A defective CSV will cause cold start problem.

Tony

[Gunter]

boyt911sc:
Good heads-up on the power supply to the CSV; I edited my reply accordingly.
The TTS actually provides ground on or off depending on temperature.

The TTS may show power during cranking if the connection from the Solenoid is good but, that doesn't mean that the CSV is also getting 12V.

He would have to remove the CSV, disconnect the plug, provide 12V plus ground and have the pump running for the test.
Or, leave the plug on if it's cold enough, have someone crank and observe if the CSV sprays.
The CSV is hard to reach behind the TB but the test would confirm if it's working.

[psalt]

Hello Michael,

Can you be a bit more specific ? If it fires and stalls 12-15 times before running, it is probably not the CSV. It is also probably not the WUR connection. If it fire and stalls, the CSV is working, but the initial mixture is too lean to make the transition to cold running. On CIS lambda, there are a few tests you should do. First make sure the relay is working and the system pulses the FV at the cold default value. Check the temperature switch on the right chain case. If OK, disconnect and plug the grey hose behind the distributor, start the engine and check the ignition timing and the FV duty cycle.

Paul

[boyt911sc]

Originally Posted by Gunter

boyt911sc:
Good heads-up on the power supply to the CSV; I edited my reply accordingly.
The TTS actually provides ground on or off depending on temperature.

The TTS may show power during cranking if the connection from the Solenoid is good but, that doesn't mean that the CSV is also getting 12V.

He would have to remove the CSV, disconnect the plug, provide 12V plus ground and have the pump running for the test.
Or, leave the plug on if it's cold enough, have someone crank and observe if the CSV sprays.
The CSV is hard to reach behind the TB but the test would confirm if it's working.

Gunter,

Please accept my apology for posting a contradiction about the subject. My intention was to explain or show how the system is set up. I have saved and bookmarked your work about distributor re-furbishing and considered it as one of best reference work in this forum. Let's consider this as a forum for ideas.

Not too long ago, I posted a contraction (different thinking) in one of MCA's posts. It turned out that he was correct and acknowledged publicly my blunder. Your contributions to this forum is very much appreciated by many including myself. Thanks.

Tony

[nh911]

Exceptionally thankful for the responses. I am struggling a bit with the acronyms and references so hoping I can get on board with these as I read thru several posts. The relay you reference is..... fuel pump relay? FV = fuel valve?? and where?

Bear with me, I am sure by the time I am done chasing this 83 SC I will be of some benefit to the forum!

[Gunter]

FV = Frequency valve.
I'll come back to that one later.
Do the easy stuff first.
Did you get power to the TTS when cranking?
Have you tried to open the fast-ide screw for an easier start?
It's a large slotted screw on the left side of the throttle body. (TB)
Open it ccw 1/2 turn by hand and see where the idle ends up: ~950 RPM

[nh911]

Good Morning,

I tried a 1/2 ccw turn on the screw from its current position and it actually stopped firing, perhaps too much fuel. I then bottomed out the screw and brought it out 1/2 ccw turn to no avail. I currently have it set at 2 1/2 turns out from bottom which is where the mechanic left it. Car cranks and fires but still need to turn the key 12 plus cranks before it begans to sputter and finally catch(rough).

I have power at the TTS. TTS is ground with key in the on position without cranking. Do I need to wait for my son to crank while I check the ground? Any other steps you could suggest? Thanks, Mike

[Paulporsche]

Have you gone through the other various things mentioned, incl your igniton components, vacuum leaks and your control pressures? How about the frequency valve? The fuel mixture?

BTW I still don't see where you are located.

It is very common, once temps drop, that CIS cars fail to start /warmup easily because the cold control pressure is too high and/or the mixture is set too lean.

[Gunter]

It is my understanding that the TTS and CSV only get power during cranking.
There are 2 connections on the TTS, one smaller than the other.
I don't remember which is the one coming from the Solenoid.
One connection is getting power from the Solenoid, the other is coming from the CSV to become ground provided the TTS is cold enough.
There should be no power on it with ignition ON because then the CSV would be spraying already when it shouldn't.
Easy test for the FV by removing the relay from the ECU under the passenger seat.
Start the engine. Push the seat back all the way.
Carefully remove the square black relay from the ECU. The idle should become very rough.
Re-install the relay. The idle should improve.
If there is no change, check the fuse.
The fuse for the relay is the same one for interior light, glove compartment, clock.
The inside of the cover for the fuses tells you where it is.
The ECU gets neglected over the years and becomes dirty and rusty.
Clean the pins on the relay and use dielectric grease to install.
You should be able to feel the relay click when installing. (Engine running)
Tell us what you find.

[boyt911sc]

Originally Posted by nh911

Good Morning,

I tried a 1/2 ccw turn on the screw from its current position and it actually stopped firing, perhaps too much fuel. I then bottomed out the screw and brought it out 1/2 ccw turn to no avail. I currently have it set at 2 1/2 turns out from bottom which is where the mechanic left it. Car cranks and fires but still need to turn the key 12 plus cranks before it begans to sputter and finally catch(rough).

I have power at the TTS. TTS is ground with key in the on position without cranking. Do I need to wait for my son to crank while I check the ground? Any other steps you could suggest? Thanks, Mike

nh911,

If I were you, I would do the basic tests like these guys suggested. But I'll do these first:
1). Hook up a CIS fuel pressure gauge and measure your fuel pressures. This includes the residual pressure too.
2). Inspect the CSV for spray pattern while it's energized.

If you don't have a gauge, PM me and will make arragement by shipping one to you. The kit is a loaner and expect it back in similar condition after a month or so. BTW, where are you located? New Hampshire?

Tony

[psalt]

Hello Mike,

I suggest you get a manual and search the archives for some basics on CIS. You have to understand what each component does before you can proceed. The Cold Start Valve ( CSV) only operates when you have the key in the Start position and has nothing to do with cold running. If your problem occurs after the engine fires and the key is in the ON position, forget the CSV and move on. After the engine fires, it needs a very rich mixture to establish a cold idle. CIS lambda does this by using a cold default duty cycle for the Frequency Valve combined with the normal lower control pressure created by the WUR. If you don't have good fuel pressure, a pulsing FV, the correct control pressure and no vacuum leaks, it will not idle cold. The system is pressure dependent, vacuum sensitive and you will need to check the pressures and the switches that could shut off the fuel pump when the key is in the ON position.

Before starting I would turn the key to ON, remove the air filter and lift up the air flow sensor to see if the fuel pump runs for a second,(no more you will flood it). While you are there, disconnect and plug the grey hose at the back of the distributor. If you have a dwell meter hook it up to the green white wire in the test port under the plastic cover on the left.
If you can get it running and warmed up, you should check the timing and check the FV duty cycle open and closed loop. Set the warm idle speed to 950 rpm and the timing to 5 BTDC. If the timing is correct, the idle speed 950, vac retard disconnected, and the FV dwell is 58 (4 cyl scale) and you still have this COLD RUNNING PROBLEM, you need to have the system and control pressure checked with a gauge.

[boyt911sc]

Originally Posted by nh911

Hello

hoping that someone can describe the cold start process. Any how, my car takes 12-15 starts before it will finally stay running(not well till warm up).

Thanks, Michael

Paul,

This is the information about his cold start problem. The're might be more than a couple of culprits affecting the cold start so the best way to do is NOT assuming everything is OK. Not until I could confirm the CSV's operation, I would not discount it.

Secondly, the're other things to be checked too. The FV, fuel pressures, WUR, vacuum leak, etc. I wouldn't be surprised if this was caused by a bad WUR. But without the information like fuel pressures and actual inspection, we are all doing guess work. My two-cents.

Tony