3.0 SC takes WAY too many cranks to Start When Cold

[scotricker]

I searched before posting.. rule #1. but anyway...

My 78 SC 3.0 starts fine after an extended period of cranking. 5 to 10 seconds.

That seems too long. Can I fix something so it just cranks right over and starts?

I also need to work on the idle when it's cold. It surges until it gets warm.

So, hence my dilemma...

Extended cranking suggests lean mixture,, but then surging idle suggests too rich..

Or is it a combination of all?

Yikes! tear my hair out?

[ossiblue]

First, Test to see if your Cold Start Valve is working. Regardless of your fuel supply, you should get a quick firing of the engine from the injection of the CSV.

Have your fuel system pressures checked, especially your residual pressure as your symptom hints toward a bad check valve or other leak that allows the fuel to drain out of the system, in combination with an out of spec cold fuel mixture.

You are correct to think the surging is overly rich mixture--something that may show up in the fuel pressure check.

Also, check that your Auxilary Air Regulator is functioning. It should be open when the car is cold, and if not, the car will be hard to start.

[theiceman]

hard to start does NOT mean a lean mixture . it just means conditions aren't ideal for starting .. if it surges while cold I would conclude someone thought as you did and tried richening it up to get it to start ... bad idea ..
some excellent advice above .. start with the basics , get out your bently and start checking , check the thermo time swith, cold start injector, cold system and control pressure. If your not back firing your not to lean .

[psalt]

Hello Scot,

The engine needs a very rich mixture to start, and a rich mixture to run at a stable cold idle. On CIS these things are handled by two different components. The Cold Start Valve supplies the fuel to fire a cold engine, and the lower control pressure from the WUR, the cold running mixture. The CSV is powered only when the key is in the start position (cranking) and is grounded only when the thermotime switch is closed. The CSV is behind the engine and hard to reach, but the TTS is on the left timing chain cover. Test that the red/black wire is grounded when cold. If not, disconnect it and attach it to ground and try a cold start. If there is no difference, you need to get at the CSV to test it.

It is very unlikely that your cold running mixture is too rich, much more likely it is too lean from a combination of possibilites, fuel pressure, lower compression, injectors, vacuum leaks. Cold engine are very comfortable with richness, and very uncomfortable with lean.

This all assumes that you have checked the ignition, that you have a good blue spark and clean plugs.

[Gunter]

Could be a combination of things like psalt says.

Go over the cold-start wiring from Starter Solenoid-Thermo Time Switch (TTS)-Cold Start Valve (CSV)

Check the AAR located on the right side of the engine between 5-6 intake runner.
It's the item that has a small electric plug and a large vacuum hose connected to it.
Open the clamp holding the outside-hose.
Pry it off with the screwdriver just enough to get it out of the way so you can see into the opening.
Don’t worry about the Alu pipe; it’ll move enough.
With the help of a small mirror and a light, peek inside the AAR.
When COLD, you should see an opening in the slide shaped like a half-moon.
When HOT, the opening is completely closed.
If it isn't closed, the AAR is either kaput or doesn't get any power.
You can spray some WD-40 into the valve in case it is just sticky.
To check the power, carefully open the tiny clip on the plug with a very small screwdriver and pull it off.
The wire clip is tricky but necessary; don't yank it off.
Start the engine and check the plug for 12 V.
(One wire is power, the other (brown) is ground)
With power to the AAR, it should close after about 5 minutes.
If all is well, replace the hose and clamp securely.

Does the WUR get power? WUR and AAR only get power with engine running; not just ignition ON.

The WUR has a tiny screen inside the top line. Disconnect the line and clean the screen if necessary.

Be patient.

[scotricker]

I disconnected the leads from the TTS and checked for 12V while cranking, but did not get consistent results, so still unsure of that.

the part in the middle of the TTS is not secure between the contacts. it moves if I wiggle it around. is that normal or is it broken? see pic attached.

Then,, If I remove the TTS., will it leak oil all over ?

And.. my bently says to check the current at the CSV to check if the TTS is working correctly.

But how do I get to the CSV? There is a pic in the Bently, but it doesn't show where it is or how to get to it to check the voltage..

I will work on checking the other things, too, but where is that CSV?

[scotricker]

I checked the AAR, as Gunter suggested, and I saw the little half moon shape just fine. While I had it open, I tooted a little WD-40 in there just in case...

[scotricker]

Is it this dealie-bobber? Is this the CSV? It is located between the 1 & 2 intake runners..

[psalt]

Hello Scot,

That is the WUR, the CSV is on the other side of the engine in the middle of the airbox. You need to remove the heater blower and use a mirror to see it. The TTS is the ground for the CSV. Do you understand how it works ? There are two terminals, one is the ground for the CSV, when you turn the key on a cold engine, power goes to the CSV and it sprays. It is dumb, so it will continue to spray fuel into the engine if the engine does not start and you keep cranking. To prevent damage from flooding, the other terminal is for a heater, the same yellow wire that powers the CSV powers the heater to disconnect the ground connection if the engine does not start in around 7 seconds. Yes, a broken TTS insulator can be a problem. The test you want to do is disconnect both leads, tape off the yellow wire, ground the red/black with a test lead and try a cold start. Forget about the AAR it has nothing to do with this issue.

[scotricker]

I will try a test start in the morning as wired up with a test lead.

I looked up a new thermo time switch from Pelican and it is genuine Porsche and almost $200.00. Mine might be broken, because the middle part moves/wiggles.

The picture of the new one makes it look like that center section is insulation, and I guess that might be important.....

[boyt911sc]

Originally Posted by psalt

Hello Scot,

That is the WUR, the CSV is on the other side of the engine in the middle of the airbox. You need to remove the heater blower and use a mirror to see it. The TTS is the ground for the CSV. Do you understand how it works ? There are two terminals, one is the ground for the CSV, when you turn the key on a cold engine, power goes to the CSV and it sprays. It is dumb, so it will continue to spray fuel into the engine if the engine does not start and you keep cranking. To prevent damage from flooding, the other terminal is for a heater, the same yellow wire that powers the CSV powers the heater to disconnect the ground connection if the engine does not start in around 7 seconds. Yes, a broken TTS insulator can be a problem. The test you want to do is disconnect both leads, tape off the yellow wire, ground the red/black with a test lead and try a cold start. Forget about the AAR it has nothing to do with this issue.

Scot,

Follow the above instructions. And if you want to test the TTS check the following:
1). The large terminal (for red/blk wire) is the ground contact for the CSV. It is grounded to the body (TTS) when cold. The internal contact switch inside the TTS will open after a few seconds when energized (cold) due to the built-in heater or will stay open when TTS body is warm (due to engine temp).
2). The smaller terminal (for yellow wire) is the power supply line for the heater. Depending on what type of wiring set-up and starter you have, the heater is energized either directly from the ignition switch ('76-'77) or via the starter solenoid (SC's).
3). Check the heater resistance between the two (2) terminals at cold condition.

In summary, the TTS serves as ground source for CSV. When the red/black wire is grounded, the CSV will inject fuel when energized. But with an open ground (red/black), CSV will be dormant.

Inspite of the above suggestions, a sure way to verify the condition of the CSV's is to physically inspect it when energized (FP running). Removing and installing the CSV is very cumbersome with engine in place. But once you're able to dismount the CSV, the tests are easy. If you decide to follow this route, I still have the fuel hose and electrical socket used to do this test. PM me.

Tony

[Gunter]

All good stuff, scotricker.

Glad the AAR checked out, it doesn't hurt to check everything to do with cold-start.

Your picture shows the WUR. I would check the tiny screen in the line because when it is clogged, it can screw up your fuel pressures.
Checking is easy. Use 2 open end wrenches: One to counter-hold the fitting, and one to open the cap-nut. You'll see the screen inside.

Getting to the CSV and removing it is such a PITA that I would first check the wiring and power going to it before proceeding.

The CSV has a seal that can be damaged; PITA, is held in by 2 screws; PITA, has a large hose attached to it with a clamp; PITA, has an electrical plug secured with a tiny wire clip that you cannot see; PITA, and everything is very hard to reach.
The electrical plug cannot be disconnected unless you remove the tiny wire clip; PITA.

You can get a used one here on Pelican.

I'll take a look at mine later to see how loose the center is.

I found the center of the TTS is solid.

[LarryHughes]

As I understand the original problem, he's having difficulty starting. Otherwise performance is okay. I suggest that you simply ground the red/black wire from the Thermoswitch. This completes the Cold Start Valve's circuit by providing a constant ground. Power to the CSV is provided by the ignition key on the crank position only. This means the CSV will squirt every time you hit the starter, regardless of engine temp. If this solves your problem, spend the $200 TTS replacement cost on beer and drive on. If you find a tendancy to flood on warn or hot starts, then replace the TTS.

Larry
'79 911 SC

[K9Torro]

Listen don't do this simple test first because my car must be messed up from what people are telling me.

(1) get in car
(2) put key in ignition
(3) turn key to "on" position
(4) listen for fuel pump to run (I can hear mine it is loud!)
(5) look at watch or clock on wall (must have second hand)
(6) sit and watch clock
(7) when sixty (60) seconds or one (1) minute which ever comes first goes by then proceed
(8) turn ignition to strart position and release when your car starts

I know it sounds simple but give it a try, if this fails see below.

(1) replace WUR
(2) Follow directions above for a great running car.

Todd

[Jim Sims]

"(4) listen for fuel pump to run (I can hear mine it is loud!)"

Unless this car is a 73.5 T or an early mid-year model this means the air flow safety switch is bad or has been disconnected. From '76 on, the fuel pump should only run when air is being inducted into the engine: i.e. during starter cranking or when the engine is running.

[K9Torro]

Hi Jim

I have owned my car (79 ROW) for years and I have always been able to hear the fuel pump on the car, it is quite loud from inside the car (unless the engine is running then you cant hear it). I use the above method to start my car which sometimes sits for several weeks between starts and have never had a problem

Todd

[boyt911sc]

Originally Posted by K9Torro

Listen do this simple test first ok , in this order.

(1) get in car
(2) put key in ignition
(3) turn key to "on" position
(4) listen for fuel pump to run (I can hear mine it is loud!)
(5) look at watch or clock on wall (must have second hand)
(6) sit and watch clock
(7) when sixty (60) seconds or one (1) minute which ever comes first goes by then proceed
(8) turn ignition to strart position and release when your car starts

I know it sounds simple but give it a try, if this fails see below.

(1) replace WUR
(2) Follow directions above for a great running car.
Todd

Todd,

Fuel pumps for '76-'83 (911) CIS cars do not run when your turn the ignition switch to ON position. Unless it is wired incorrectly or have a defective AFS switch. However, for earlier CIS like '73.5-'75, FP does run at 'ON' position. And never replace a CIS component unless verified defective.

Tony

[Jim Sims]

K9Torro,

The air flow safety switch was installed to stop fuel flow into the engine in the event of a rollover or other incident that jams the the air flow meter plate open. It also prevents filling a cylinder with gasoline due to a leaking CIS fuel injector. There were instances with the early CIS cars without this safety switch that resulted in raw gasoline filling a cylinder and then proceeding through the exhaust all the way to the tail pipe! The '79 ROW had such an air flow safety switch. Yours may be disconnected; this was sometimes done to mask a problem with a fuel pump check valve or the accumulator instead of actually fixing the problem. A noisy fuel pump can mean the pump is near the end of its life or that the fuel pump rubber mounting bushings have failed or become excessively hard.


Jim

[boyt911sc]

Originally Posted by K9Torro

Hi Jim

I have owned my car (79 ROW) for years and I have always been able to hear the fuel pump on the car, it is quite loud from inside the car (unless the engine is running then you cant hear it). I use the above method to start my car which sometimes sits for several weeks between starts and have never had a problem

Todd

Todd,

If your '79SC (RoW) exhibits what you described above, the AFS (safety device) is probably not working as Jim Sims mentioned or worse, incorrectly wired. Unless you know and understand the wiring set-ups for '76-'83 CIS cars, having a FP running @ ON position is an anomaly. BTW, are you familiar with AFS (air flow sensor/switch) in your car? HTH.

Tony

[K9Torro]

Tony

I have never even heard of an AFS until now, as I stated above I have owned the car for years and the fuel pump has always turned on with the ignition in the on position. As this was the first air cooled 911 I owned I always thought that it was normal and never mentioned it or asked about it before.

I have replaced the WUR at one point several years ago when I could not get the car to stay running when the engine was cold, this has been the only CIS component that has ever been changed on the car.

I think I will check the rubber bushings to see what they look like on the fuel pump, I had never actually thought about doing that to see what they look like, if they are still in decent shape I guess I will wait until the pump fails before replacing it if it is the pump itself making the noise.

Where is the AFS located and how should it be wired ?

Here is a couple of pic's of my engine bay if that will help,

Todd