83 911 sc cold start issue

[GaryDG]

This '83 is difficult to start in moderate to cold temperatures. Repeated starting of car ultimately starts it but it may take 25 attempts. Once started it's oscillating between (my guess) 250-600 rpm. Then it slowly, say 5-10 minutes, (as it warms up (I guess)) the rpms increase to the point where the idle is smooth and I would estimate the rpms at ~ 850-900. If I turned the engine off at this point it would immediately restart and idle smoothly at the same rpm rate. Similarly, if I drove it, it would immediately restart after having been parked for an hour or so.

So, looking at the shop manual it appears that the culprit is (are) the cold start solenoid(s) which look difficult to get to.

What are your thoughts? Thanks!

[Scott R]

The CSV only operates during cranking, and it's controlled by a thermo-time switch on the drivers side chain cover. Hard to tell when its dead really, but not terribly difficult to change out, just need to remove a few things like the rubber air boot.

However, it sounds more like the cold control pressure is out of spec. You're going to need CIS gauges to go any further.

[Paulporsche]

If you try a search of these items: WUR, AAR and Pelicans Souk and Jim Williams, who also has a Rennlist site, you will find out there is a lot of info on these very common symptoms.

As Scott said, the CIS gauge, which you can get from JC Whitney for about $60, will tell you your fuel and control pressures. If you get figures for those, get back to us and we can help.

Very likely causes are vacuum leaks and/or a high cold control pressure resulting in a too lean mixture during start and warmup, but knowing the control pressures really helps in diagnosing this.

[boyt911sc]

GaryDG,

Scott and Paul got you in the right direction in figuring what do. But both of them inadvertently forgot to mention that it is customary for new members to post the picture of their cars. Welcome to the board. There will be plenty of help available in this forum.

Tony

[GaryDG]

Originally Posted by Paulporsche

If you try a search of these items: WUR, AAR and Pelicans Souk and Jim Williams, who also has a Rennlist site, you will find out there is a lot of info on these very common symptoms.

As Scott said, the CIS gauge, which you can get from JC Whitney for about $60, will tell you your fuel and control pressures. If you get figures for those, get back to us and we can help.

Very likely causes are vacuum leaks and/or a high cold control pressure resulting in a too lean mixture during start and warmup, but knowing the control pressures really helps in diagnosing this.

Thanks those searches provide a lot of info on my problem. JC Whitney is out of stock on their CIS guage, is there another source people use for this type of tool?

Thanks again!

[Scott R]

Originally Posted by GaryDG

Thanks those searches provide a lot of info on my problem. JC Whitney is out of stock on their CIS guage, is there another source people use for this type of tool?

Thanks again!

Our host sells one, listed at 219.00 though. Or you can try making one, I forget who posted this link in the past, however here are the instructions:

http://www.geocities.com/jonnyguru/vw/fpressure.html

[GaryDG]

Again for 911 sc

My CIS pressure guage is now on the way. I am reading Bentley to get prepared to do the tests outlined above. Which, according to Bentley, are System Pressure and Control Pressure. I'll check Residual Pressure but I don't believe it is involved in my situation since once the engine warms up restarting is immediate.

The book refers to "Operating fuel pump for tests". In that section it describes testing the fuel pump while not operating the engine. This implies that the fuel pump dosen't operate without the engine running. In my car, the fuel pump does operate with the ignition on, the engine not on or not invoking the starter. Is my situation normal?

Any special tricks while performing the tests outlined in Bentley?

System Pressure
If shims are needed to adjust pressure regulator, I presume Pelican has them.

Control Pressure
The test is performed with engine off, and pump on but the pressure specifications call for warm or cold engine and engine running? Don't understand what they're saying.

[boyt911sc]

Originally Posted by GaryDG

Again for 911 sc

My CIS pressure guage is now on the way. I am reading Bentley to get prepared to do the tests outlined above. Which, according to Bentley, are System Pressure and Control Pressure. I'll check Residual Pressure but I don't believe it is involved in my situation since once the engine warms up restarting is immediate.

The book refers to "Operating fuel pump for tests". In that section it describes testing the fuel pump while not operating the engine. This implies that the fuel pump dosen't operate without the engine running. In my car, the fuel pump does operate with the ignition on, the engine not on or not invoking the starter. Is my situation normal?
Any special tricks while performing the tests outlined in Bentley?

System Pressure
If shims are needed to adjust pressure regulator, I presume Pelican has them.

Control Pressure
The test is performed with engine off, and pump on but the pressure specifications call for warm or cold engine and engine running? Don't understand what they're saying.

Gary,

All SC's including ''76-'77 US models should not have the FP running when the ignition switch @ ON position. If the FP is running, one of the following could be the culprit:
1). The air sensor plate is slightly OPEN.
2). The FP relay is defective. The Normally Closed (87a-30) remained closed even after the relay coil is energized.
3). The wiring has been altered or jumper wire installed.

You can test the FP without running the motor.
1). Remove the FP relay.
2). Use a jumper with in-line fuse and connect terminals 87a & 30.
3). Turn ignition switch.

Since your FP is already running when the ignition switch is turned to ON position, the above procedure is not necessary in your case.

Lastly, it is not normal for SC motors to have a FP running unless the motor itself is running. The safety feature of the 'air meter' has been compromised in your situation. You need a CIS fuel pressure gauge to effectively troubleshoot your problem/s.

Tony

[GaryDG]

Thanks for the reply on the fuel pump issue with the ignition switch in "ACC" Mode. I'll look into why that's occuring. Based on my interpretation of the electical diagrams in Bentley, there must be feedback from another "system" to provide the power.


My secondary post included another facet of the issue I will be attacking concerning my startup issues. These are:

Any special tricks while performing the tests outlined in Bentley?

System Pressure
If shims are needed to adjust pressure regulator, I presume Pelican has them.

Control Pressure
The test is performed with engine off, and pump on but the pressure specifications call for warm or cold engine and engine running? These instructions appear contradicting. That is, we can't have engine on and off at same time. Maybe I won't have a problem in this test but if I do I would like to address it while I'm there.

[boyt911sc]

Originally Posted by GaryDG

This '83 is difficult to start in moderate to cold temperatures. Repeated starting of car ultimately starts it but it may take 25 attempts. Once started it's oscillating between (my guess) 250-600 rpm. Then it slowly, say 5-10 minutes, (as it warms up (I guess)) the rpms increase to the point where the idle is smooth and I would estimate the rpms at ~ 850-900. If I turned the engine off at this point it would immediately restart and idle smoothly at the same rpm rate. Similarly, if I drove it, it would immediately restart after having been parked for an hour or so.

So, looking at the shop manual it appears that the culprit is (are) the cold start solenoid(s) which look difficult to get to.

What are your thoughts? Thanks!

Gary,

Check the cold start valve (CSV) for power and flow pattern when you crank the starter. It is a very awkward and tight location when you do the test. Check if the TTS (thermotime switch) is grounded when the engine is cold. Lastly, it is good to know your (cold) system and control fuel pressures.

Since you didn't have problem starting (warm), CSV and TTS were not needed for warm start up, testing these CIS components must be done to determine what causes your cold start woes. At this point, I would also check your WUR & AAR because they are critical components for cold start.

PM me if you need some clarification about the procedure. Keep us posted.

Tony