Cold Start Issue - Video

[Paulporsche]

Your warm cp w/ the engine warmed up and running should be about 3.4 to about 3.8 bar. bar (50 to 55 psi) according to Bentley, although the graph is more like 3.25 to about 4.1 or so. It's probably best to get the cold cp @ the coldest temp you can. Let us know what you get.

[mca]

New Videos Added:

Video of system, cold, and warm pressures >
http://www.reactionplus.com/pcar/pressures.html
I turned system off before warm control reached 57psi (consistently reaches 57psi and stays there).

Video of pressure gauge connected while cold starting car >
http://www.reactionplus.com/pcar/coldstart_guage.html
I start the car twice. First time shows same old same old - but a little backfire this time. Second try is perfect - rpms around 1250.


TEST ONE - 71F
System Pressure
67 psi - 4.62 bar

WUR Electrical Unplugged (cold control)
44 psi - 3.03 bar

WUR Electrical Plugged (warm control)
57 psi - 3.93 bar


TEST TWO - 68F
System Pressure
66 psi - 4.55 bar

WUR Electrical Unplugged (cold control)
43 psi - 2.96 bar

WUR Electrical Plugged (warm control)
57 psi - 3.93 bar


Seems like the cold control pressure is too high. Anyone else believe this to be the case? I am hoping that the video showing the gauge hooked up during a cold start will provide some insight.

Many thanks,
Craig

[psalt]

Craig,

No one can tell you without the ambient temperatures. I still think you are fishing in the wrong pond. That initial stumble is not the WUR or the CSV. What is your FV duty cycle at cold start and what is the ignition timing at idle ?

Paul

[mca]

Originally Posted by psalt

Craig,

No one can tell you without the ambient temperatures. I still think you are fishing in the wrong pond. That initial stumble is not the WUR or the CSV. What is your FV duty cycle at cold start and what is the ignition timing at idle ?

Paul

Paul,

Thank you for the feedback.

Ambient temps are posted next to the test number - 71F and 68F. Even if it was 100F my numbers seem too high.

Don't know the FV duty cycle at cold start. I did buy a dwell meter last week but failed to find the test plug near my CDI. I would love to see a picture of someone with a dwell meter hooked up - the Bentley picture is a joke.

Ignition timing at idle is 7 BTDC with vacuum lines disconnected and capped.

[psalt]

Craig,

If you have 140.090 WUR, cold control pressure should be closer to 2.5 bar.

The test plug is at a loose end of three wires taped together with a rubber boot on the end. It is usually tucked under the electric panel under the plastic cover on the left side of the engine compartment. You must remove the wings nuts and panel to find it. The hook up is dwell sense (coil) wire to the green/white stripe terminal inside the plug, positive to the blower fan fuse block and negative to the engine ground. The O2 sensor is a big help in understanding what is going on, I would consider fitting a $4 bung and a universal Bosch sensor.

The distributor is often ignored, it often needs to be cleaned and lubricated, a few drops of oil under the pad and snapping the rotor against the springs can give you an idea about its condition. Worn springs can give a false reading at idle, but if idle and 3000 rpm are at spec, it is working. Leave the vacuum retard disconnected.

Your audio is very familar to me, I have solved this problem on several cars, and it was never the WUR , AAR or AAV. Usually the combination of fixing injector sleeve leaks, mixture and timing adjustments will solve it. Believe it or not, a swap from platnium to normal Bosch plugs makes a difference .

Paul

[mca]

Originally Posted by psalt

Your audio is very familar to me, I have solved this problem on several cars, and it was never the WUR , AAR or AAV. Usually the combination of fixing injector sleeve leaks, mixture and timing adjustments will solve it. Believe it or not, a swap from platnium to normal Bosch plugs makes a difference .

I changed the plugs a couple of weeks ago. They are the standard stock Bosch plugs - same as what was in there before changing them.

I will get the dwell meter hooked up and report back.

Essentially you are saying that a high cold control pressure can be caused by things other than a faulty WUR.

[psalt]

Essentially you are saying that a high cold control pressure can be caused by things other than a faulty WUR.


No, I am saying, that my experience is that if you were to swap in a new $700 WUR, you would have the same first crank cold start stumble. You either live with it, or tune it out with subtle changes to timing, idle speed and mixture (after you fix the vacuum leaks).

[mca]

I am tracking with you. I certainly don't want to buy a new/rebuilt WUR at this stage ... especially since I recently spent $1200 on new oil lines and an oil cooler.

I just wanted to make sure that cold control pressure is not solely controlled by the WUR ... especially since I have the option of tapping the WUR plug in order to adjust cold control pressure. I don't want to do this if the WUR is not the problem.

Now, regarding vacuum leaks. I have a propane torch that I used around the injectors - found no change in idle. That isn't to say that there may not be a small leak as I am not terribly comfortable dumping propane gas in the engine compartment - I have never seen it done so I am very hesitant.

[Paulporsche]

Try tapping the plug in. It works. @70F your ccp should be about 2.1 to 2.5 bar.

Your fuel pressure is on the low end of the range. It should be 65 to 75 psi, although I don't think this is causing you a problem.

[mca]

Originally Posted by Paulporsche

Try tapping the plug in. It works. @70F your ccp should be about 2.1 to 2.5 bar

Paul ... sent you a PM about this.

[mca]

Connected a dwell meter to my test connector - wanted to be sure that mixture was within range. It should be b/c I had a quailty sniffer on it a couple of months ago and I only recently richened it a bit by turning 1/16 of a turn clockwise.

The 02 sensor is disconnected and the retard vacuum is disconnected and plugged. I checked timing - with retard disconnected I am at 7 BTDC.

Not sure how to interpret the results. Here is a pic of the meter reading. The needle is stationary - no fluctuation.



Here is a pic of the dwell meter connected to the test connector. Green clip is on green/white pin and black clip (ground) is on brown pin. Those with sharp eyes will see a little dampness at the WUR connection - this is residual fuel from some pressure tests. It is not leaking.



Here is a pic of my interior gauges. RMPS near 1000 and temp is within warm range.



Any help would be appreciated.

I still have not messed with the WUR as I am waiting for some wise advise from Paulporsche. He suggested I "knock the pin" on the WUR in order to decrease cold control pressure.

Thanks,
Craig

[Jim Williams]

Craig,

I'm not familiar with that dwell meter, and what other switches are on it. If you are using the 4 cylinder scale, with a maximum reading of 45, then multiply the reading you have by the factor of 2.22. This makes the reading equate to a max reading of 100% max if that were a duty cycle meter. This all follows from your meter, being used as a dwell meter, measuring the percent of time your ignition points would be closed during the rotation of your point-type distributor.

Anyway, to cut to the chase, you can use the meter as a duty cycle meter if the max voltage seen at the O2 measuring connector you are using is in fact 12 volts, which I am pretty sure is the case.

Multiplying your reading of 10 by 2.22 would give a 22% duty cycle, equivalent to the ECU driving the frequency valve lean. But since your O2 sensor is not connected, the reading should be 45*0.5 or about 22.5 on the 45 scale.

A further check on your Lambda system (closed loop) operation would be to ground the O2 sensor lead after the engine is warmed up, and see if the duty cycle approaches 90% (approx), then substitute a 1.5 volt penlight cell (- to ground, + to the O2 sensor lead to the ECU), and see if the duty cycle is driven to about 15% (I forget these exact numbers).

In open loop (cold engine) the duty cycle should read about 65%.

[James Brown]

time for me to switch to a EFI system like the Bitz unit, a lot easer to tune, less components, more reliable, more power, and just cool!!

[TibetanT]

Subscribing for information purposes.

[psalt]

Craig wrote,

Connected a dwell meter to my test connector - wanted to be sure that mixture was within range. It should be b/c I had a quailty sniffer on it a couple of months ago and I only recently richened it a bit by turning 1/16 of a turn clockwise. The 02 sensor is disconnected and the retard vacuum is disconnected and plugged. I checked timing - with retard disconnected I am at 7 BTDC. Not sure how to interpret the results. Here is a pic of the meter reading. The needle is stationary - no fluctuation.


Hello Craig,

First you need to understand that you cannot get an idea about the mixture without the O2 sensor connected and operating. You are only testing that the default duty cycle of the FV is within range. The cold open loop spec is 58% dwell on a 4 cyl range. Your meter is reading 20. What does this mean? The FV bleeds off lower chamber pressure to richen the mixture, the higher the duty cycle (open longer) the lower the pressure and the richer the mixture. Your reading means the system is out of range, creating a lean condition which you are trying to compensate by adjusting the mixture screw. I would check all the connections on the lambda box and use the engine as a ground and see if the reading changes. Swapping in a known good lambda box would be helpful.

The readings can get a bit confusing, a low duty cycle during open loop cold running, means the system is "broken", and the resulting mixture will be leaner than the original calibration. Once the system goes closed loop and the needle starts fluctuating based on the O2 sensor, a low reading means the actual mixture is too rich and the system is attempting to bring it back to stoich by lowering the duty cycle of the FV. A high duty cycle reading means the actual mixture is too lean and the system is attempting to richen it up by raising the duty cycle of the FV.

You should also understand that the K basic components themselves cannot produce the factory drivability without the lambda system functioning properly.

[mca]

Gentlemen --

Thanks for the replies. I now understand that I can't adjust mixture using a dwell meter with the 02 sensor unplugged. I think that I was reading too much in too many places and started to get confused. Maybe I will see if I can plug it in - the fitting in the engine bay is broken but I will try.

Regarding the lamda system ... when I pull the relay under the driver's seat, she runs really really crappy. And if the lambda box was faulty, wouldn't she run bad all of the time?

I did the air flow sensor plate test per Jim's CIS Primer site. I lifted the plate slightly and RPMS rose and then fell off as I continued upward.

I also hit my injector sleeves with propane again without any sort of idle increase.

Is it possible that the significant engine wear is causing the problems with the cold start? Here are my unverified numbers from about 16 months ago. I use about 1 quart of oil every 400 miles (altough a ton leaks from my valve cover BOLTS). Maybe the engine condition has worsened.


leakdown >
#1=4%
#2=43% (ouch)
#3=6%
#4=30% (ouch)
#5=4%
#6=15% (hurts some)

compression >
#1=140psi
#2=110psi
#3=140psi
#4=130psi
#5=140psi
#6=140psi

[psalt]

Regarding the lamda system ... when I pull the relay under the driver's seat, she runs really really crappy. And if the lambda box was faulty, wouldn't she run bad all of the time?

Is it possible that the significant engine wear is causing the problems with the cold start?


Hello Craig,

The lambda system is not a light bulb, just because it turns on does not mean it is working properly. Try to verify the duty cycle reading when cold and when hot using the engine block as a ground. Make sure the broken O2 plug is not grounding, it will fool the system. Check the temperature switch on the right chain cover and the throttle switches. If your default duty cycle is really 20 instead of 50, you will never be able to the get the correct fuel curve, even if you replace the WUR, AAR, or FD with new parts.

With those engine numbers, my advice is get to the bottom of the FV duty cycle problem, try to correct the cold control pressure problem and then find the best compromise with the timing and mixture adjustments.

[mca]

Additional Info:

Reconnected the 02 sensor and hooked up the dwell meter. I got the same exact readings on the meter as seen in my previous post. This was done with a warm engine.

I took her for a drive and was reminded why I disconnected the sensor two years ago. Here are the symptoms:

1) Idle begins to fluctuate between 900 and 1000 RPMs. The fluctuation is predictable ... meaning that the changes are equally spaced over a certain amount of seconds.

2) At constant accelleration (say 3000 RMPs in third gear) I get a bit of a push and pull. Similar to the fluctuation at idle, the push and pull is predictable.

At the time that I pulled the sensor I was using a local specialist. I spent so much $$$ the first year of ownership that I could not afford to continue troubleshooting the 02 issue ... so I unplugged it and went on my way.

I will do the other tests as suggested by Jim and Paul later this week.

Cheers,
Craig

[Paulporsche]

Guys,

What do you think about those bad compression and leakdown numbers?

Craig,

Check your pms.

[psalt]

Hello Craig,

That sounds like the lamdba system is working, it dithers the mixture back and forth to average stoich for the cat. If the dwell meter reading did not change, I suspect it is hooked up wrong or the meter is bad. Try cleaning up the terminal and using the engine as the ground. The main switch for closed loop is on the right chain cover. Contrary to what it says in the Bentley manual, this switch is closed when cold and opens when hot. The cold open loop reading should be 58, when the engine reaches 15C, switch opens, the lambda system starts adjusting the mixture. You can also test the throttle switch through this connection. Above 35% throttle, the switch grounds the same terminal, giving you the rich mixture setting for WOT.

The main advantage to leaving the O2 sensor connected, is that you can adjust the open loop mixture slightly richer for cold starts, cold running, WOT, engine wear, etc. and the system will bring the hot closed mixture back to stoich for emissions and economy. The surging at 3000 rpm is probably due to vaccum leaks and/or your lack of compression.