911SC Hot Start Issues

[boyt911sc]

Originally Posted by kiwiokie

From what I understand the bottom chamber of the FA on my car should always be dry. After replacing the check valve and cleaning the tank etc I set the control pressure but still had the hot start issue. The FA had been replaced by the previous owner so I thought it would be good. Pulled the bottom hose and fuel gushed out. Once replaced runs perfect.

Kiwiokie,

The bottom chamber of a fuel accumulator should not be dry unless you have the two-port fuel accumulator with no bottom drain port used in early CIS. But if you have the three-port FA used in SC's, the bottom chamber would be always wet with fuel. If you don't agree with this, check it yourself. Detach the bottom connection for the fuel accumulator after the FP has ran and fuel would be draining out from the fuel line and FA. A fuel accumulator could be tested and would take only several seconds to confirm whether it is good or bad.

Tony

[DanielDudley]

Have you pulled the plugs ?

[kiwiokie]

Tony, I am certainly not claiming to be an expert on this issue which is why I phrased my reply "I understand that". I had read a couple of posts that said remove the bottom hose and if there is fuel there the FA is bad. Replacing the FA in my situation fixed the problem. Maybe it was just dumb luck!

Originally Posted by boyt911sc

Kiwiokie,

The bottom chamber of a fuel accumulator should not be dry unless you have the two-port fuel accumulator with no bottom drain port used in early CIS. But if you have the three-port FA used in SC's, the bottom chamber would be always wet with fuel. If you don't agree with this, check it yourself. Detach the bottom connection for the fuel accumulator after the FP has ran and fuel would be draining out from the fuel line and FA. A fuel accumulator could be tested and would take only several seconds to confirm whether it is good or bad.

Tony

[ossiblue]

Originally Posted by kiwiokie

Tony, I am certainly not claiming to be an expert on this issue which is why I phrased my reply "I understand that". I had read a couple of posts that said remove the bottom hose and if there is fuel there the FA is bad. Replacing the FA in my situation fixed the problem. Maybe it was just dumb luck!

I don't believe Tony was criticizing your post directly, only trying to point out and reemphasize the "danger" of assuming that if fuel comes from the FA when the hose is removed that the FA is bad.

There was quite a thread a few years back where Tony clearly demonstrated that the bottom hose and bottom of the FA will contain fuel due to the flow of fuel through the common return lines back to the tank. It was an attempt to convince people not to just replace an expensive part without properly testing it. Simply removing the bottom hose and witnessing fuel running out is not a definitive test.

Yes, you were lucky but you had already eliminated the other obvious suspects so your FA was now at the forefront, even though it had been replaced by the PO. Your takeaway, IMO, should be that the FA needs to be properly tested before replacement and that simply removing the hose and observing fuel is not the test to use. Remember, all these threads help future users and someone who, like you, isn't quite clear after reading other threads, may come across this one and have more clarity.

[Coloradocurt]

As the OP, I was posting this question/issue for a friend whose SC has been in a shop for 3 months and he still has doubts about the effectiveness of the "supposed" solution. My friend believes that an important factor is the ambient temperature, as the problem first appeared during the Summer and after he had a new AC system installed.
Can anyone suggest an Indy shop in Texas/Arizona who might be willing to provide some expert troubleshooting advice?

[kiwiokie]

I have heard good things about Ed Mayo at Home but have never used him myself.

[Easy Tiger]

Love the banter! Good to see some passion

Let me jump on this discussion, because I have a similar problem: Cold start, good, but engine surges after 15 seconds. Warm start-up is a no-go without some 'encouragement' from lifting the pressure plate manually or spraying ether into the airbox. Problem: Lean mix (confirmed by plate not raising and color of the exhaust pipe).

Here's all the things I have done so far:
- New Fuel Accumulator
- Checked ignition switch
- Fixed excessive play in distributor
- New fuel filter
- New fuel pump
- Emptied and checked fuel tank (clean as a whistle)
- Checked cylinder bolts
- Valve adjustment done
- Timing done
- Air filter checked
- Spark plugs checked (look good)
- Swapped WUR with another (may also be defective)
- Fuel pressures checked and ok
- Airbox checked for leaks and ok
- Rebuilt CDI Unit and installed.

Next on my list:
- Confirm correct distributor for engine (not original to car)
- Rebuild old WUR and install
- Install a check valve in fuel pump (may not have one)
- Check the fuel plunger in fuel distributor for movement
- Pressure test fuel again

Good plan?

[theiceman]

Hey Tony

Was reading this with great interest . Do you know how the car is wired. I thought I read somewhere that the cold start injector was wired to the starter motor. iS this via the thermo time switch

I am strying to understand how it works .. so if you crank the motor for 2 seconds and it starts how long does the cold start injector fire for ? is it a MAXIMUM of 8 seconds as the engine cranks then the TTS switch cuts it off ?

[boyt911sc]

Originally Posted by theiceman

Hey Tony

Was reading this with great interest . Do you know how the car is wired. I thought I read somewhere that the cold start injector was wired to the starter motor. iS this via the thermo time switch

I am strying to understand how it works .. so if you crank the motor for 2 seconds and it starts how long does the cold start injector fire for ? is it a MAXIMUM of 8 seconds as the engine cranks then the TTS switch cuts it off ?

Theiceman,

There are several wiring connection configurations for the CSV in CIS (911). The early one has a direct connection to the CSV and the later passing through the starter. If you look closely to the factory wiring diagrams, they are basically the same. To complete the circuit, the CSV depends on the TTS (thermotime switch) for ground contact. Below 113°F, the TTS is grounded. Above 113°F, the TTS is not grounded (open switch/contact). To prevent prolong operation of the CSV that could flood the engine with fuel, the TTS has a built-in heater that limits the operation to 8 sec. (+|-).

You could bench test a TTS by applying 12 volts to it and monitor the ground contact of the body to the chassis. Approximately after 8 sec., the ground contact to the chassis will open. Thus preventing the CSV from further operation. Contrary to the myth that a CSV will operate above 113°F as long as the TTS is good is false. If it did, there is a wiring anomaly in the system.

To answer your question, power to the CSV comes from the ignition switch @ terminal 50 (#1 @ 14-pin connector) and this is the yellow wire. The yellow wire goes to:

'74~'75.............from 14/1 to throttle valve switch (F25) then to TTS & CSV.
'76~'76.............from 14/1 directly to TTS & CSV.
'78~'83.............from 14/1 directly to starter solenoid @#50 to #16 (different starter connections from previous years) to TTS & CSV.

Tony

[theiceman]

ah thanks Tony I think I understand , so its a maximum of 8 seconds, yeah that gy posted on rennlist too I think stating the CSV would fire after 20 minutes . im like wtf .. I know it has to be a lot colder in 20 minutes, even in February in Canada but did not have enough info to dispute his claim.

Im gonna test my TTS just for giggles

Thanks again.

[leonardo911sc]

Good day to All

Is this thread still active?

I have some very specific questions to CIS experts and i would appreciate your kind assistance

Boy911sc Mr Tony. Are you still here?

[boyt911sc]

Originally Posted by leonardo911sc

Good day to All

Is this thread still active?

I have some very specific questions to CIS experts and i would appreciate your kind assistance

Boy911sc Mr Tony. Are you still here?

Mr. George,

What specific CIS question/s you need help? First post and you got a very tricky question. What model/year is your car and what specific problem are you having? Thanks.

Tony

[leonardo911sc]

Good day!

Thank you for your reply.

911 SC euro 1982 no lambda

Will fire up at when cold but when hot after 1 hour will need about 10 sec of cranking. Next morning when engine is ambient temperature will start first crack.

1. New fuel pump and check valve
2. New accumulator genuine
3. Rebuild WUR 089
4. Cold pressure 1.7 Bar @ 18C, warm pressure 2.8 bar and 3.5 bar with engine running. System pressure 5.2 bar
5. Residual pressure 1.5 bar after 30 min. Will keep above 1 bar for more than 4 hours.
6. Tested TTS with battery and test light. below 45C will light for about 2 sec. Above 45C no light. Working as it should. No problem with cold start.
7. CO% level @ idle adjusted to 2.8. Will reduce to 0.6 @ 3000 rpm. HC below 60 at idle
8. Ordered new FD fuel relief valve. I dont think this will solve the problem though since residual pressure is within spec.
9. Will install new injectors, but i have no symptoms that confirm it is required. Steady idle, no Knock during full acceleration.
10. Total Ignition timing adjusted to 25 degrees (pulley notch) with vacuum disconnected.
11. New spark plugs Bosch W3CC
11. Engine runs very well.

I have all symptoms of residual pressure loss but my gauges prove otherwise

Is there anything i forget?

[boyt911sc]

George,

I would suggest that you test for unmetered air going into the system using a low-pressure smoke generator. Verify and confirm that the the six (6) fuel injectors have uniformed mist-like spray patterns. Keep us posted. Thanks.

Tony

[Matt at Pelican Parts]

Using the search function i see that this topic has come up a few times.
I have this more recent thread that although doesnt have a solution, other forum members listed off a few culprits to check for.

On this older one, it was found that the starter motor ended up being the cause.

-Matt

[Zuffenwerker]

Leonardo911sc I'm very interested to see what you find. I hope you get it nailed! I had an sc do this one time where everything was in spec and checked but had long crank on hot start like it had no residual fuel pressure. Almost like it had a small amount of vapor in the lines despite the residual pressure.
I never figured it out. It's hard to believe it would be an ignition issue. On the next hot start put a spark checker in line and have someone watch just to verify. Ignition components can fail in strange ways. Kind of a long shot. Good luck and please share if you find a good solution.

Daniel

[leonardo911sc]

Thank you All for your input

When i open the oil cap with engine running idle drops slighly as it should. Isnt this a simple way to understand that vacuum circuit is ok?
Also connected a vacuum gauge between intake and WUR to check the enrichment function. Idle pulled a steady 300 mm hg

Will follow Tony's advise and search for air leakages also.

Daniel i have the same exact symptoms.

This Sunday will test the injectors ballance and spray pattern and replace FD relief valve.

Do you think that 0.6 CO% at 3000 rpm is within spec? Car parked. Only engine revving
WUR 089 uses vacuum to lean the mixture for part throttle. Since US engines had O2 sensor to keep theoretically 0 CO% idle and part throttle i think mine is ok.

But This is my first CIS engine so have to ask the experienced people.

[boyt911sc]

Originally Posted by Matt at Pelican Parts

Using the search function i see that this topic has come up a few times.
I have this more recent thread that although doesnt have a solution, other forum members listed off a few culprits to check for.

On this older one, it was found that the starter motor ended up being the cause.

-Matt

Matt,

Are you sure it was the STARTER? Where did you get that information? There was nothing mentioned to believe it was the culprit. Keep us posted. Thanks.

Tony

[917_Langheck]

Under this hot start condition did you verify that you actually have spark during that 10 seconds of cranking? It would be weird if you didn't, but it not on the eliminated list of possible a either.

[leonardo911sc]

Will check spark also.