Cold Start Issue - Video

[mca]

The dizzy seems to be working fine. Correct advance at 6K rmp.

I tested the retard vacuum line again. When disconnected and plugged, it DOES change the timing by about 3 degrees. I can't clearly distinguish a change in idle though - maybe my hearing sucks.

So, all seems fine with dizzy which certainly makes me happy considering replacement costs.

On to other things.

[Scott R]

Originally Posted by mca

The dizzy seems to be working fine. Correct advance at 6K rmp.

I tested the retard vacuum line again. When disconnected and plugged, it DOES change the timing by about 3 degrees. I can't clearly distinguish a change in idle though - maybe my hearing sucks.

So, all seems fine with dizzy which certainly makes me happy considering replacement costs.

On to other things.

Thats still not correct, if I pull the blue retard line off my SC distributor the idle speed jumps up to 1200 right away, why because retarding the timing drops the idle. Still sounds like something is up with the advance plate. I had issues like this and it turned out to be a broken spring retainer on the plate.

[mca]

Originally Posted by Scott R

Thats still not correct, if I pull the blue retard line off my SC distributor the idle speed jumps up to 1200 right away, why because retarding the timing drops the idle. Still sounds like something is up with the advance plate. I had issues like this and it turned out to be a broken spring retainer on the plate.

Ok i understand the idle thing.

So your idle jumps to 1200 - how much does your timing change when you pull and plug the retard line?

When you had the broken spring retainer on the plate, what symptoms did your engine display?

I would think that an advance issue would lead to a poor running condition. I have no issues whatsoever with engine performance at any rpm. Wouldn't I be having some apparent problems?

[Scott R]

Originally Posted by mca

Ok i understand the idle thing.

So your idle jumps to 1200 - how much does your timing change when you pull and plug the retard line?

When you had the broken spring retainer on the plate, what symptoms did your engine display?

I would think that an advance issue would lead to a poor running condition. I have no issues whatsoever with engine performance at any rpm. Wouldn't I be having some apparent problems?

I get a 5 deg change with the line off, it's very noticeable. Prior to the rebuild I did the engine was laggy, my mechanic described it like this: "It feels like the accelerator pedal and the engine are disconnected." Kind of a weird reference, but if you think about it it makes sense. Lagyy, in that the fuel system is working, but the timing and electrical system is out of whack.

I would have also said that I didn't think I had any performance issues either, however if you look up my dyno threads the machine told otherwise. And when I finally fixed the distributor it was like I woke the car up from a long sleep.

[mca]

Scott R -

Thanks for the info. Maybe I can swap a distributor into mine and see what happens. Now you got me curious. I need to drive a local stock SC in order to draw a comparison.

My engine is due for a rebuild - so I don't expect her to be running like new. The funny thing is that it is running and tuned better now than 3 years ago when I got it. I still get great pulls and she still comes alive after 3500 rmps.

Anyhow, thanks again for the help and I will keep searching.

[mca]

What do you all make of this?

Because everything else has tested correctly, as a last ditch effort I richened my mixture a tad - turned clockwise about 1/16 of a turn.

Since richening, I have not had any cold start problems. She fires right up and idles high and then settles at 950 rpms after a few minutes. I can drive away immediately with no hesitation, backfiring, etc.

Could a slight richening be masking the real issue or is it possible that my old, tired engine likes to run slightly richer? Could it possibly mask a small vacuum leak?

Although I have not completed a thorough hunt for leaks, when I check my oil I get a nice big drop in rmps. Not sure if this really indicates a solid, closed system or not.

[mca]

Edit my last comment. Making it slightly richer only works half of the time. The other half of the time it continues to show the same symptoms.

I am now looking at the thermo-time switch and cold start valve operations.

Question: Does the thermo-time switch dictate HOW LONG the cold start valve provides extra fuel at start up?

I ask this because I always get a big rush (meaning fuel and high rmp jump) during cold starts. The rmps jump up really nice and strong but will die down quickly and struggle to hang on. Is it possible that the cold start valve is not providing fuel long enough?

On the second cold start attempt she gets another big rush and then hangs around 1200-1400 rmps until warm ... and settles to 950.

[safe]

Originally Posted by mca;3640550
Question: [B

Does the thermo-time switch dictate HOW LONG the cold start valve provides extra fuel at start up? [/B]

Yes, its electrically heated during the cranking, so the engine doesn't even have to start for the CSV to stop supplying extra fuel.
I don't know the exact time it's active, but its only seconds.
EDIT: To be more clear, it's not active when the engine is running.

I don't think thats your problem, more fuel does not make the rpm rise, if it does you have an air leak somewhere.
It's just a Cold Start Valve, it supplies more fuel during cranking, the "more fuel when cold" function, is regulated by the WUR.

[mca]

Originally Posted by safe

Yes, its electrically heated during the cranking, so the engine doesn't even have to start for the CSV to stop supplying extra fuel.
I don't know the exact time it's active, but its only seconds.
EDIT: To be more clear, it's not active when the engine is running.

Thanks, that is what I thought. The Bentley isn't terribly clear about how long the CSV is initiated by the thermo-time switch.

I still don't see how the WUR could be my problem when she runs great after the initial starting problem. All of my fuel pressures seem to be within spec.

I suppose I will check these again.

[safe]

Originally Posted by mca

Thanks, that is what I thought. The Bentley isn't terribly clear about how long the CSV is initiated by the thermo-time switch.

I still don't see how the WUR could be my problem when she runs great after the initial starting problem. All of my fuel pressures seem to be within spec.

I suppose I will check these again.

It was a while since I read this thread, but:

Have you checked both cold and warm pressure?

Have you checked the AAV and AAR function?

[mca]

I checked the cold system and cold control pressures ... both seem to be in spec. I calculated the cold control pressure with the fuel pump running only. The Bentley only has values for the cold control pressure with the engine running - don't imagine this makes a difference though as the readings would be the same... right?

I never took a warm pressure as she operates fine when warm. Do I get her up to operating temps and then hook up the CIS gauge and then crank her back up? Should I be cautious about the fuel pressure at the distributor when I hook up the gauge? (btw ... warm starts are fine)

The AAR opens and closes properly. Once I get her started (second try when cold) I get a nice high idle.

Don't know how to test the AAV. Been searching and searching for info on the AAV but it seems to be lacking. Actually, the AAV is my guess but I am not sure what symptoms would be shown if the AAV begins to fail. Does it fail completely or does it slowly begin to fail? If it is the culprit, can it be fixed similarly to how I fixed my decel valve (using a vice and compressing slightly)?

[safe]

From Jims site:

Auxiliary Air Valve:
Provides bypass air around the throttle when the engine is first started. When the intake manifold vacuum reaches 5 - 6 inches, the valve closes. The closing is independent of engine heat. Part number 0 280 160 400 pulls in at ~8" vacuum. This regulator supplies air to the intake manifold during warm and hot starts when the auxiliary air regulator is closed. This was added in '76.

Failure mode: When not closing properly, can cause high idle speed , or idle speed to oscillate.



I tested mine with a vacuum meter.
If you remove it, it should be open and you could blow air through it. Then if you put your thumb on one of the connections you can suck a vacuum in the other connection with just your mouth, connect a vacuum meter so you see how many inches of hg. When you reach the specified vacuum you should hear a click that closes the valve. Then you can remove your thumb and it will still hold the vacuum.
If you have a vacuum pump its easier.

[Jim Williams]

Originally Posted by mca

I am now looking at the thermo-time switch and cold start valve operations.

Question: Does the thermo-time switch dictate HOW LONG the cold start valve provides extra fuel at start up?

Yes. It's good for 2 - 3 seconds before the internal switch interrupts the ground path for the CSV, and it is powered off.

[Jim Williams]

Originally Posted by mca

I checked the cold system and cold control pressures ... both seem to be in spec. I calculated the cold control pressure with the fuel pump running only. The Bentley only has values for the cold control pressure with the engine running - don't imagine this makes a difference though as the readings would be the same... right?

I never took a warm pressure as she operates fine when warm. Do I get her up to operating temps and then hook up the CIS gauge and then crank her back up? Should I be cautious about the fuel pressure at the distributor when I hook up the gauge? (btw ... warm starts are fine)

The AAR opens and closes properly. Once I get her started (second try when cold) I get a nice high idle.

Don't know how to test the AAV. Been searching and searching for info on the AAV but it seems to be lacking. Actually, the AAV is my guess but I am not sure what symptoms would be shown if the AAV begins to fail. Does it fail completely or does it slowly begin to fail? If it is the culprit, can it be fixed similarly to how I fixed my decel valve (using a vice and compressing slightly)?

Even if your engine is running OK, it can probably be made to operate "OK" with a warm control pressure that is not at spec. The important thing is that the cold pressure is in spec AND the warm pressure is in spec. The WUR is set up to have the correct pressure for cold starts and transition to the correct pressure for warm running. This means that the pressure needs to be right at both ends, cold and hot. The engine does not have to run at all to get the warm pressure. All the necessary heat to get the WUR "hot" comes from electrical heat inside the WUR, furnished by 12 volts from the battery. I jumper the fuel pump relay to get the fuel pump running, which energizes the WUR heater, and immediately start checking the cold pressure, then watch it rise until it quits rising. This is the warm pressure.

You say you got the cold control pressure with the engine running. If the engine is running, the WUR has 12 volts applied and is not really cold, unless you get the reading in 15 to 20 seconds.

[mca]

Originally Posted by Jim Williams

You say you got the cold control pressure with the engine running. If the engine is running, the WUR has 12 volts applied and is not really cold, unless you get the reading in 15 to 20 seconds.

Thanks for the info Jim.

I did all pressure tests with fuel pump only ... never while running or after running. Always did tests after car had been sitting at least 24 hours.

So, I will perform the tests again.

I have an 82 SC without 02 sensor connected.

What should I expect for cold system pressure?
What should I expect for cold control pressure?
What should I expect for warm control pressure?

Based on your site (http://members.rennlist.com/jimwms/CIS/CIShome.html), all I need to do is:

1)Switch on fuel pump with electrical connection to WUR unplugged. Read system pressure, valve closed.

2)Open valve, read and record WUR control pressure for cold engine.

3)With fuel pump running, plug in electrical connector on WUR. Watch for pressure to increase, valve still open. When pressure stops rising, note reading.


Many thanks ... I really want to get to the bottom of this.

[Jim Williams]

Originally Posted by mca

Thanks for the info Jim.

I did all pressure tests with fuel pump only ... never while running or after running. Always did tests after car had been sitting at least 24 hours.

So, I will perform the tests again.

I have an 82 SC without 02 sensor connected.

What should I expect for cold system pressure?
What should I expect for cold control pressure?
What should I expect for warm control pressure?

Based on your site (http://members.rennlist.com/jimwms/CIS/CIShome.html), all I need to do is:

1)Switch on fuel pump with electrical connection to WUR unplugged. Read system pressure, valve closed.

2)Open valve, read and record WUR control pressure for cold engine.

3)With fuel pump running, plug in electrical connector on WUR. Watch for pressure to increase, valve still open. When pressure stops rising, note reading.


Many thanks ... I really want to get to the bottom of this.

Sorry, looking back on your post, I see I mis-read about the engine running during your test.

At 30 deg C (~68 deg F) expect about 2.2 Bar. Warm pressure about 3.4 Bar. System pressure, warm or cold, about 70 psi.

You note the O2 sensor is disconnected. Any reason? Broken, recommended by someone? Just curious.......

[mca]

Jim ... again, thanks for the info. I will test and post results.

The 02 sensor was non existent when I got the car 3 years ago. The PO had headers installed - never added 02 sensor.

My mechanic at the time suggested installing one (not sure why). When it was connected, I was getting some "trailor hitching" - some surging at constant acceleration. Never pursued the issue - simply disconnected it b/c it was running fine and I didn't have money to spend troubleshooting the issue.

The orange/cream colored 02 plug in the engine bay is cracked - green wire inside is exposed and the copper inside of the wire is also exposed (green wire casing is torn). I am not sure if it was always like this or not.

[Mysterytrain]

http://members.rennlist.com/jimwms/CIS/CIShome.html
From Jim:

O2 sensor (Lambda system):
In 1980, the US CIS system was modified to include an O2 sensor system, also called the Lambda system. It consists of the sensor, the control box, the frequency valve which adjusts the mixture at the fuel distributor, and several input devices to the control box. The input devices include an engine temperature sensor, a throttle switch, and the O2 sensor itself, mounted in the exhaust flow. The basic function of the Lambda system is to adjust the fuel mixture to stoichiometric or 14.7:1 air to fuel ratio. This particular air/fuel ratio enhances the operation of the Catalytic convertor, with which the Lambda system was designed to operate. The Cat operates more efficiently in reducing emissions when the fuel mixture is at stoichiometric.

The Lambda system does its job by adjusting the duty cycle of the frequency valve, which is plumbed into the lower portion of the fuel distributor control pressure circuit. If the O2 sensor determines the mixture is too rich, it signals the frequency valve to reduce the duty cycle which leans the mixture determined by the fuel distributor. If it is too lean, it increases the duty cycle. If the mixture is spot on (14.7:1 air-to-fuel), the duty cycle to the frequency valve is 50%. Note that the default mode for a disconnected O2 and warm engine is also 50% duty cycle.

The O2 electronics box also has an enrichment function controlled through the throttle switch. This enrichment task is taken over from the vacuum operated WUR of the earlier CIS engines. The O2 sensor was first installed with the '80 cars, and the vacuum operated WUR was discontinued. In '81, the O2 electronics were slightly changed from '80 but still provided the enrichment function. The electronics box provides cold starting warm up enrichment in addition to the cold engine enrichment provided by the WUR. On a warm engine, this is a closed loop system, continually adjusting the mixture. The system reverts to open loop control in both the start-up and WOT modes.

The cold start enrichment by the Lambda system sets the frequency valve Duty Cycle at 65% , overriding the input from the O2 sensor, until the engine temperature reaches 15 degrees C. At temperatures in excess of 15 degrees C, determined by a thermo-switch, a warmed-up oxygen sensor takes over providing a variable duty cycle. The throttle valve switch also provides enrichment at WOT. There is an idle switch, operated by the throttle valve, which dampens the response of the O2 electronics for a smoother idle.

In '81, the O2 system was modified. A different switch on the throttle valve was added. This modified the system operation in the following way: There are now a total of three switch contacts. The first switch had contacts at 15 degrees and at 75 to 80 degrees. When the second idle switch , at about 1 degree, and the 15 degree switch are closed, acceleration enrichment occurs when the engine is cold (determined by the thermo-switch). The small relay beside the Lambda electronics box was added in '81, which then increased the duty cycle to the frequency valve from 50% to 75% providing acceleration enrichment when the engine is cold, dropping out after about 4 seconds.

Malfunction: Usually the O2 sensor itself. A good one produces about 500 millivolts at 14.7 air/fuel, The sensor actually detects free oxygen in the exhaust gas.


On Disabling O2 sensors:
Disconnecting the O2 sensor electronics box (and not just the O2 Sensor) on CIS engines designed to use them will reduce the cold start enrichment, and the full throttle enrichment. The engine may also probably lose some gas mileage.

Failure mode: The O2 sensor itself usually suffers from a low output over time, and may result in a constant 50% duty cycle during closed loop operation regardless of the actual mixture.

[mca]

The cold start enrichment by the Lambda system sets the frequency valve Duty Cycle at 65% , overriding the input from the O2 sensor, until the engine temperature reaches 15 degrees C.

So a disconnected 02 sensor should have no affect on my cold start since it is overridden by the Lambda system. Correct?

Disconnecting the O2 sensor electronics box (and not just the O2 Sensor) on CIS engines designed to use them will reduce the cold start enrichment, and the full throttle enrichment.

My Lambda box (under passenger seat) is still working/participating even though my 02 sensor is disconnected. When I pull the relay out of the Lambda box, my car won't start.

[mca]

Originally Posted by Jim Williams

Sorry, looking back on your post, I see I mis-read about the engine running during your test.

At 30 deg C (~68 deg F) expect about 2.2 Bar. Warm pressure about 3.4 Bar. System pressure, warm or cold, about 70 psi.

You note the O2 sensor is disconnected. Any reason? Broken, recommended by someone? Just curious.......

Jim,

Back on post #53 (09.14.07) I provided my first pressure test results.

System Pressure
69 psi - 4.7 bar

WUR Electrical Unplugged
38 psi - 2.6 bar

WUR Electrical Plugged
58 psi - 4.0 bar


Assuming that I get the same numbers this coming weekend, would you say that my cold and warm pressures are too high?

You say cold should be 2.2, warm should be 3.4, at 68F. I probably ran those tests when it was close to 85F or higher.