Its time again!
 

Why not revive this thread for another year?

I have a CIS question for Souk (or whoever wants to answer).

First let me state that I'm aware that the CIS is a SYSTEM and that there is a proper procedure for trouble shooting, ie. control pressure testing etc. I also have the Bentley manual and I intend to go about this in a systematic way.

That being said, I'd like to describe my problem and benefit from any wisdom that comes my way. Here goes:

I have a 78 SC engine that came from a warmer climate. I'm in Eastern Canada and spring and fall temps in which I still drive the car can be a little below freezing once in a while and very often in the 40 - 50 range. It seldom ever gets above 85 F here in the hottest part of the summer.

Firstly, the car runs very well when warmed up, idle is right at 1000 and smooth, performance is great. I don't know how the mixture is but there is a fair exhaust odor. I'd say its a little rich if anything but I'm guessing here.

Secondly, warm starts are also fine. Starts with a bump of the starter, idles fast for a few moments 1300 - 1500 and then settles back down to 1000 or so.

My problem is with cold starts and warm up:

With a cold engine, it takes a fair bit of cranking to start the engine. It may cough a few times and take 3 or 4 attempts before it catches. It will run very roughly for a few moments (10 seconds or so) while missing and popping (pop-off valve is a good thing!) at about 600 - 700 RPM, then very suddenly it will smooth right out as if all cylinders suddenly came on line and it roars up to 3800 RPM. It will run at this speed for approx 1 minute and then very suddenly it drops to about 1300 and then slowly settles to 1000. Its just as if you were holding the throttle open to run it at 3800 and then took your foot off the pedal. Its very sudden.
During the rough start up phase before the high rpms kick in, applying throttle has little effect. While in the high rpm phase, thottle works normally, ie. if you push down on the pedal, the rpms will increase past 3800, (not that I do this). Exhaust smells very rich while this is going on.

It seems to me that something is a bit out of whack here. While this does warm the car up quickly, 3800 rpm is just a little harsh on a cold engine and it takes too much cranking before it starts. (At least its already built up oil pressure from all the cranking before it soars to 3800).

On a partially cooled down engine (sitting for an hour or so) I'll get a less extreme version of this. That is, it starts first try, stumbles a bit and then revs up to maybe 2500 or so.
A few times when the ambient temp was 80 ish, it cold started like you would want it to, high idle of about 1300 - 1500 and then dropped to 1000.

Its seems obvious that one of the CIS components is controlling this very high warm up idle and needs to be adjusted or repaired, but which one? Is this most likely a WUR adjustment issue?

Any info much appreciated.

I should mention that plugs, wires, cap and rotor are new and valve lash is correct. The problem was the same before and after.

Sorry for the novel.

Check the cold control pressure to see if the WUR is whacked, which it sounds like it may be; they can be made adjustable if so. You may also want to check the wiring\operation of the thermotime switch\cold start valve. HTH,

ianc

Thanks Ianc.

Anybody on the nightshift have some input?

I switched over to Webers last December and haven't looked back. I have a bin of CIS parts from my two '74 2.7L engines if anybody needs any replacement parts.

I also have a Gunson tester, CIS pressure tester, CIS books and Bosch tools for adjusting the CIS that I won't need anymore...

Hi Andy,

I'm sorry I haven't had a chance to reply to your post or e-mail. Work has me in 4 places at the same time.

There are two concurrent events during start up, the WUR will run rich at initial cold start then start to increase the control pressure to lean out the mixture. The other even is the AAR will go from wide open to close. When these two events don’t synchronize to the design range of ratio, you start getting high idle and erratic cold running. The snap action like behavior you are reporting may be attributed to a sticky AAR, which over time can gum up from oil and contaminates from the case gases. You can remove it and clean it out without a major hassle.

Checking your control pressure from cold to warm will also give a little insight into your problem. If the WUR is not gradually increasing control pressure it needs to be checked for a plug screen or just proper operation.

Your idle mixture should be checked when you are at operating temperature. You can use the “field method” in the thread linked in my signature. This will get you close to determine if you are not just running too rich or too lean. When the idle goes high like you described, more times than not, you’re getting more air than you need for a low idle. But since you are seeing normal startup when warm, your idle mixture may not be too far off. Read the first paragraph.

The most important thing to keep in mind here (I know you said you’re going to take a systematic approach toward fixing this, good!) is to understand what the affects of any change you make will have on the system. It’s highly recommended that you keep a note of what changes you make (e.g. ¼ turn CCW of the mixture screw, two turns of the idle bypass valve, etc.)

Buy a CIS pressure test gauge from Pelican or anyone of the online vendors. You won’t need a gas analyzer yet. The analyzer will help you fine tune the system, but there is enough troubleshooting without it that you can perform to get your CIS to a good state. Then fine tune it.

Do a search for the CIS fuel P-T chart for your car. But keep in mind that it’s a range. So don’t get hung up on any exact pressure versus temperature.


Report back...but start with cleaning the AAR.

Thanks for the reply Souk, I understand about being busy at work!

I tried the field method this morning after my drive in (40 minutes - so thoroughly warmed up).

Car at idle - 1000 RPM

Pulling down on the air plate yielded an immediate drop in rpm. The further down I went the slower it got. I didn't take it to a stall. Actual distance I moved the plate was very small.

Pushing up yielded an immediate increase in rpm. Continuing up resulted in more RPM up to about 2000 - 2500 (couldn't see the tach) then it would begin to die. Again, very little actual movement.

I read on Jim Williams primer that a slight increase followed by roughness while pushing up is likely about right. This would be more than what I would call a slight increase. Does this sound like its close enough for now and I should get on with fixing the cold start and idle problems or does it sound a bit lean based on the above?

So, assuming adjustment is warranted, if I now richen the mixture screw, Idle should increase but the mixture will be closer to where it should be. I should then adjust the bypass screw to bring the idle back down and then try the 'lift test' again, and so on. How am I doing?

Will do re. cleaning WUR and AAR and pressure testing. I will definitely report back.

Thanks again, much appreciated.

Leave the idle mixture alone for now....cleant he AAR with carb cleaner and let it dry before installing it. Make sure to clean the mating surface of the AAR and the engine (intake) where it sites. There needs to be good heat transfer there....same goes for the WUR.

the AAR will not open enough to reach 3800 RPM. the AAV (aux air valve) will, if you have one. it is a big round disk mounted behind the FD. sounds like it is slow to close, maybe due to a vacuum leak or just leaking itself. if it has a leak, that will also make it run lean causing it to pop and ahard to start. the AAV is plumbed in with the AAR. the AAV is only for starting.

Good point.

You can remove the AAV and plug the hoses going to it then see what happens when you try to start it cold.

here is how you can check the AAV.

get a vacuum pump (like one from advance) and put the large adapter on it. plug it into the outer fitting. place your hand over the center connection ( the vacuum pump does not have enough air volume to close the valve) pump up the pump to around "20" , remove your hand and see if it holds.
if not, reverse connections, i may have them backwords.

Couple of other points...On a cold engine when you crank the starter there are a few things taking place. The cold start injector injects fuel while you crank and if the thermotime switch is below a set point[113 degrees f or so]. If that system is not working then you will have a hard start issue. The thermotime switch, thermovalve, WUR and the AAR need 12 volts at their connectors. While the engine is cranking and sucking air, the air sensor plate is lifting and allowing the fuel pump to turn on and pressurize the system also important. Once the car starts the heating elements in the WUR, AAR and thermovalve begin to heat up {the AAV, thermotime switch and cold start injector are now out of the picture}. The heating element in the thermo valve opens after about 10 secs and allows vacuum to be appled to the WUR. The lack of vacuum allows the WUR to run a bit rich during start up. Once the vacuum is applied the WUR begins to lean the mixture at the same time the heating element in the AAR is closes off the opening and begins to slow the idle speed, should take 2 to 4 mins or so.
As Souk states above the proper procedure to sorting the system out is to adjust the mixture, idle speed and timing with the engine at operating temp. Since it sounds like your system is operating properly at temp you might as well jump to the pressure testing. The cold pressures, warm pressures, system pressures and bleed down will really help nail the problem. The Pelican Test kit is nice, well made and comes with a case and fittings...a little pricey but if you are going to be married to CIS {happily married to it myself} then it becomes a very useful tool.
Souk will set you straight.

This thread is golden.

Thanks for the advice guys. I hope to dig right into this on the weekend and discover the problem(s).

A question re. the AAV (if I have one - will check): Can you get at this thing behind the fuel distributor without major disassembly? I might try a cold start tomorrow morning with it disconnected and plugged. Can I just take the AAR out of the loop and connect vaccuum directly to the WUR?

I should have my pressure testing setup by the weekend so I'll go about checking pressures then.

Mystery Train: Is what you are calling the Thermotime valve the same thing that others are calling the Auxiliary Air Valve (AAR), behind the FD?

Thanks again.

I can get to my AAV (item 39 in the CIS diagram in my signature) without removing anything. There are two 10mm nuts that hold it to it's bracket. Y0u can't see it, but you can feel it. Be careful you don't drop the nuts. It won't be terrible, but I hate loosing my nuts in my engine compartment :) You should be able to see it on the right side of the CIS just above and behind cylinder #6.

(I have a '78 SC engine in my "mid-year" too.)

The thermotime switch (17A in the CIS diagram in my signature) looks like a connector with a round portion about the size of a US quarter. It has two wires (in a connector) connected to it with vacuum hose (8 or 10 mm hoses) going to and from it. It should be bolted to a bracket on the left side on the number 3 runner.

I pretty sure my thermo valve is crapped out. My CIS is alittle bastardized, so I have compensated for it. I haven't noticed that it makes a huge affect on the start up or running of the engine.

The thermo time switch is mounted on the left chain housing. You'll see it sticking out of the chain housing with two wires on spade connectors on it. I don't think it is part of your problem since you have good warm start. But then again if it is faulty, it will prevent your coldstart valve from spraying on cold start which is not need during warm start (see it in the wiring diagram in my signature). You can test it for resistance. I don't recall of the top of my head what it should be cold or warm. I think the Bentley has those numbers, otherwise we have discussed it before.

T77911S may have got it right, so concentrate on the AAV. The high RPM leads me to believe that you have an internal air leak, via the AAV or AAR. So check the AAV and you might as well clean the AAR. The AAR closes by action of a bi-metal, so heat from the electric heater or the engine will cause it to close.

The Bentley does a good job of describing how these some of these things work, so check it. Print out the electric diagram in my signature (in color) and keep it in your glove box. It is a great tech reference to have. Make notes on it for the resistance of the components (thermo time switch and AAR...hmm maybe I should have done that on my :D)

I once had a high rpm at start-up problem that was caused by the AAR opening being too large at start up. Actually, I was the cause of this problem because I had opened the unit up in an attempt to alter the time it would take for the opening to close. I adjusted the bimetal arm to create a larger opening when cold. It turned out that the opening was to large and the engine raced.
Another thought...since your car idles and runs fine after it is warm how would one explain the problem as the AAV? That device is open until pulled shut under vacuum and is technically out of the picture after start up.
The Jim Williams CIS page explains the various components pretty well.
The AAV is the cad plated flying saucer that is behind the air box on the right side of the engine.
The AAR is an aluminum device with large vacuum lines going in and out and an electric connector. The AAR is located between the number 5 and 6 intake runners on the right side of the engine.
The cold start valve is on the back of the air box.
The thermotime switch is located in the left chain housing cover.
The thermovalve is located near the number 3 intake runner. A small black bottle cap sized device with small vacuum lines going in and out and an electrical connector.
The WUR is mounted between the number 1 and number 2 intake runner.
In the picture below the thermovalve is 17a
the WUR is 54
and the cold start is 30

http://forums.pelicanparts.com/uploa...1178806203.jpg

I just tried something....
 

Just went out and cold started it, it revved up as usual. Ambient temp about 65.

On a whim while thinking about unmetered air I blocked the intake horn as completely as I could with my hand and it slowed down to 2000 and stayed there. I'm not sure however if it was just warming up and would have done this anyway or if it was because of the change in airflow. It usually doesn't pause at 2000 though. Maybe blocking the airflow caused whatever component is sticking (AAR maybe) to move a bit before it usually does.

I then went for a drive and warmed it up. (The car is running just freakin' great when warmed up btw) Idling at 1000, I blocked the intake horn again and it revved UP a bit. Should it stall if I completely block the intake horn? I suppose it can still get air through the breather hose from the oil tank and maybe other places. Is this indicative of a massive air leak such as a cracked box? Where do I look for the cracks? I couldn't see anything wrong with the cover off and while flexing the plastic around and looking for cracks. Is it the plastic that cracks or the rubbery part behind? A pop off valve is installed and working and one would hope that the box was checked for cracks when it was installed, right?

Thanks.

You need to step back and think about what you just said. A massive air leak will be a massive air leak all the time. I suppose if you could get the car running and at operating temperature you could adjust the mixture and the idle so that it would run well. I doubt it would restart. You state that its hard to start, when it does start it idles high and runs well when warm. You really need to look at what is suppose to be happening when the engine is cold and transitioning to operating temp.

Yeah, starts well when warm too. So I guess no big deal re. blocking the intake and having it continue to run. I didn't think about it very long before making the post....

Good then, I will focus on the problem and stop trying to invent new ones.

This weekend I will attack.

Thanks

mysterytrain- nice descriptin of thermo time valve, most people get it confused with the TTS. my TTV drops my pressure down to .7 bar from 1.7 bar with it bypassed. if you dont live where it is extremely cold (up north or canada) you can live without it.

the reason i said the AAV is because it has such big connections, about 1/2 or 3/4 of an inch, big enough to allow the engine to rev to 3800 RPM, which i think is the key to the problem. if the AAV has a hole in it, or there is a leak in the connecting hoses back there, it would take a few extra seconds to close, which would cause the 3800RPM thing. once closed, the RPM's are dropping to the range where the AAR takes over. also, if it is popping, that is another sign of a posible air leak. there is a metal vacuum line back there that could have a hole in it, mine was rubbbing a hole in it. mine was rubbing on the plastic "scoop" to the oil cooler.

two tone- i am not sure what you mean when you say "Can I just take the AAR out of the loop and connect vaccuum directly to the WUR?"

if you take the AAV out, you will have to plug the lines so it will run.

Yeah, I was thinking they were plumbed together on the same vacuum circuit when I wrote that. Please ignore that question.

Well, work interfered this weekend and I was unable to spend time with the car. I will update as soon as I get at this. I should have time this week. Stay tuned folks.