Cold start problems

[Markymike]

My 82 SC has severe cold start problems. I need to lift the air plate for a few seconds to get gas to it. Then it's rough till it warms up. When the engine warms up, it runs great.

I did an air leak test. I found a cracked air box and replaced it. I found leaks around the injectors and replaced the rubber donuts.

I just did the pressure test. These are the results:

I seem calm but this is driving me nuts

1. Year of engine: 1982
2. US or RoW (Rest of World): US
3. WUR model number: don't know
4. Ambient temperature at time of test (in degrees C): 76F / 25C
5. WUR Resistance (in Ohms): 9.1
6. System Pressure (in bars): 5 bar / 72 psig
7. Cold Control Pressure (in bars): 2.3 bar / 34 psig
8. Warm Control Pressure (in bars): 3.4 bar / 49 psig
9. Time delta for Cold -> Warm Control Pressure (in minutes & seconds): 50 seconds
10. Residual Pressure @ 5 min (in bars): 1.8 bar / 26 psig
11. Residual Pressure @ 15 min (in bars): 1.6 bar / 23.5 psig
12. Residual Pressure @ 30 min (in bars): 1.5 bar / 22 psig
13. Residual Pressure @ 60 min (in bars): 1.45 bar / 21 psig

[tirwin]

System pressure is good.
Cold control pressure is good.
Warm control pressure is good (low end of the range).
Residual pressure is fine.

Tony and I had a discussion about the WUR resistance values I have in the CIS for Dummies thread (which you obviously used! Good on you!). I can't remember the details now but I may have something stated wrong. I do remember that my resistance was about the same as yours and that was one reason I sent it to Tony for a tune-up. That and the cold control pressure was too low.

What are your RPMs at cold start and what are they once the car warms up?

Could be that the AAV is not opening.

When you raise the plunger arm does it feel like it is traveling smoothly? If it feels like it's binding you'd want to check that.

I'd probably have checking the AAV and the injectors (the Tony baby bottle method) on the list but one thing at a time.

[stlrj]

Originally Posted by Markymike

I need to lift the air plate for a few seconds to get gas to it.

You first need to find out why your cold start valve is not working. Is the thermal time switch connected? Is the TTS providing the proper ground for the cold start valve to work? Is the cold start valve connected?

I suggest you resolve this asap since lifting the sensor plate for starting is recipe for a very expensive air box explosion.

Joe

[boyt911sc]

Originally Posted by Markymike

My 82 SC has severe cold start problems. I need to lift the air plate for a few seconds to get gas to it. Then it's rough till it warms up. When the engine warms up, it runs great.

I did an air leak test. I found a cracked air box and replaced it. I found leaks around the injectors and replaced the rubber donuts.

I just did the pressure test. These are the results:

I seem calm but this is driving me nuts

1. Year of engine: 1982
2. US or RoW (Rest of World): US
3. WUR model number: don't know
4. Ambient temperature at time of test (in degrees C): 76F / 25C
5. WUR Resistance (in Ohms): 9.1
6. System Pressure (in bars): 5 bar / 72 psig
7. Cold Control Pressure (in bars): 2.3 bar / 34 psig
8. Warm Control Pressure (in bars): 3.4 bar / 49 psig
9. Time delta for Cold -> Warm Control Pressure (in minutes & seconds): 50 seconds
10. Residual Pressure @ 5 min (in bars): 1.8 bar / 26 psig
11. Residual Pressure @ 15 min (in bars): 1.6 bar / 23.5 psig
12. Residual Pressure @ 30 min (in bars): 1.5 bar / 22 psig
13. Residual Pressure @ 60 min (in bars): 1.45 bar / 21 psig

Mark,

Item #5: With a 9.1 ohms reading when cold, your WUR is most likely a -090 (correct WUR). Unfortunately, it is out of spec and would need some work. This was exactly what Tim had when he sent his WUR for test (free).

Your cold control pressure is high and WCP on the low side. But it should not prevent you from starting the engine with the above conditions. If I were in your shoes, I would check and test:
1). CSV operation during cranking. I doubt it is the culprit but better to test it.
2). Test and confirm the absence of a significant source of vacuum leak. This is the most critical test but overlooked by many troubleshooters. Use the low pressure test method. Much better and efficient than the conventional carb cleaner or propane method.

Keep us posted.

Tony

[T77911S]

CSV is keeping it from starting.

other problems making it run rough.
make sure the intake bolts are tight.

[Markymike]

Thanks for the help. Thermotime switch was not connected properly. Now engine starts and runs smoothly. Cold idle is too low, maybe 500. That points to the AAV?

[T77911S]

no. the aux air valve (AAV) only opens when starting. it lets air in like putting your foot on the gas. as soon as it starts, vacuum closes it.

the aux air regulator(AAR) raises the idle afgter is starts and while it is cold. the AAR has the electrical plug. peope do confuse the name with the AAV.

you really have to start from the begining with CIS and go thru the system
start with a new ignition. new plugs cap rotor and if needed wires. check timing and advance.
then make sure you have no air leaks.
check pressures. system, cold and warm.
then check the mixture setting and idle.

the AAR could be stuck. you can try to clean it and make sure it works.
but the reason you need to go thru it is other things can make it idle low too. bad mixture, air leaks making mixture wrong. ignition.

[paul.911]

I had the exact same symptoms as you last fall. After spending weeks reading and testing, I gave up and just sent my WUR off to be refurbished and that solved everything.

[tirwin]

At cold start the engine should idle at around 1200rpm and then settle down to 850-900rpm after it is warmed up. Is your idle normal after the engine is warmed up? At 500 rpm it is barely running.

As T77911S, it is a good idea to be thorough and methodical. There are a lot of possible contributing factors and sometimes previous owners (or even the wrong mechanic) will change this or that in an attempt to put a bandaid on the underlying problem.

There is a link to the test procedure for the AAR in the CIS for Dummies thread. I generally like to do the easy/accessible things first. Example: Take the oil fill cap off with the car warmed up and engine idling. Do the RPMs change? If no, you know you have a vac leak somewhere. If yes, well... It doesn't mean you still don't have one so check for cracked or loose vac lines, intake runner boots and the fuel injector o-rings.

There is a procedure to test just about every CIS component. You can tackle each one systematically, but make sure you've done all the easy stuff first.

When was the last time the plugs, cap, rotor, etc were changed? If it's been a long time or you don't know, go ahead and do that stuff and you'll have some basic maintenance knocked off. Do you have a timing light? That's also easy to check.

[T77911S]

BTW, to the OP.
great job posting. i wish everybody had that detail and was that clear and we didnt have to read about what they had for breakfast just to get to the problem. oh im going to hear for that one.

[stlrj]

Originally Posted by Markymike

Cold idle is too low, maybe 500. That points to the AAV?

Forget the AAV, try backing off the idle speed bypass screw until you get the right rpm.

Over analyzing will only confuse us armchair mechanical geniuses.


Cheers,

Joe

[boyt911sc]

Originally Posted by Markymike

My 82 SC has severe cold start problems. I need to lift the air plate for a few seconds to get gas to it. Then it's rough till it warms up. When the engine warms up, it runs great.

I did an air leak test. I found a cracked air box and replaced it. I found leaks around the injectors and replaced the rubber donuts.

I just did the pressure test. These are the results:

I seem calm but this is driving me nuts

1. Year of engine: 1982
2. US or RoW (Rest of World): US
3. WUR model number: don't know
4. Ambient temperature at time of test (in degrees C): 76F / 25C
5. WUR Resistance (in Ohms): 9.1
6. System Pressure (in bars): 5 bar / 72 psig
7. Cold Control Pressure (in bars): 2.3 bar / 34 psig
8. Warm Control Pressure (in bars): 3.4 bar / 49 psig
9. Time delta for Cold -> Warm Control Pressure (in minutes & seconds): 50 seconds
10. Residual Pressure @ 5 min (in bars): 1.8 bar / 26 psig
11. Residual Pressure @ 15 min (in bars): 1.6 bar / 23.5 psig
12. Residual Pressure @ 30 min (in bars): 1.5 bar / 22 psig
13. Residual Pressure @ 60 min (in bars): 1.45 bar / 21 psig

Mike,

The package containing your WUR-090 arrived today. I was able to test it for the evening run. Here are my test results:

CCP = 31 psi. @ 65°F
WCP = 51 psi.

Time (delta) between start to WCP = 60 sec.
Resistance reading = 9.4 (Ohms).

The results from my test and yours are very similar. This WUR has basically no cold idle phase. The control fuel pressure shoots up from 31 psi. to 51 psi in 60 sec. and this transition is too quick. Your cold idle would be erratic for several minutes until you get the engine warmed up. This was some what similar to Tim Irwin's WUR behavior before I did the calibration.

Tony