Please help with my CO numbers!

[mrfatboy]

To give a little back story my engine has always had the incorrect timing pointer on it.  I was never able to know exactly what timing I had.  It was all done by ear, or diagnostic machine, vac hose method.  Not very accurate for me. It drove me nuts. I have been dealing with that for the last 10 years or so. I finally got the correct timing pointer from JA17 so I could see where I really stood.   When the engine was rebuilt 10 years ago I was getting about 230 miles per tank.  Over the years it  has degraded to about 170 mile per tank.  I am guessing that is mostly attributed to me trying to tune "by ear".  Bad idea.


So 2 weeks ago when I started this whole thing I think I was at 14 BTDC.  Whoa! that led me to a broken distributor vac hose.  Fix'd that and that put me at 4 BTDC.  Then I followed the BBB book and tried setting to 2 ATDC.  This introduced some missing at mid to high range.  I then moved on to Dan's timing numbers and that eliminated the missing  However, I was extremely lean at mid and high range and extremely rich at idle.

The last two days have been experimenting with the IP pump and concluded that I just need an IP rebuild.  I talked to JA17 (Joe) last night and he gave me some more tips by trying to adjust the internal mid/high range (black/white) screws inside the pump.  I figured what the heck,  if I really mess it up the pump is going to be rebuilt anyway

So that brings be today. I decided to set everything at BBB specs as I stated above and tweaked the IP pump to get a good idle CO and prepared to go into the pump to adjust the mid/high range screws full expecting it to run very lean as it has previously done before.  Which brings me to the two pictures of the spark plugs.

I just got back from a 10 mile drive and it drove great.  I am just worried that it's too lean.

 So.. Too Lean or OK?  I don't want to melt anything    If they are considered too lean I then have to start the ugly process of tweaking the internal IP screws.




@twistedtree
The only thing I worked on today was getting the IP idle mixture set correctly.  I just set timing to 2 ATDC. Move the idle adjustment screw on the IP 15 clicks from max lean.Tweaked shims on the BC.  I was fully expecting to get bright white plugs (too lean) at mid/high range but I got the pictures above which I can't tell are still lean or OK.  If they are OK I might be out of the woods

[Benz Dr.]

For the 051, the BBB calls for

2-4 ATDC @ idle w/ vacuum
12-19 BTDC @ 1500
30 BTDC @ 3000

Dan, it sounds like you've found other numbers work better?

That's wrong or at least it's not what works right. The 280SL should be 6 degrees BTDC and the 230SL or 250SL won't be any different when using a 051 distributor. 30 degrees is how much the distributor should advance but it's not your maximum advance. For that, you have to add your initial timing amount at idle because the distributor won't be advancing at idle. It doesn't matter how much you advance the ignition at idle with the 051 distributor because the vacuum portion won't advance until you open the throttle. The mechanical portion will start to advance above 900 RPM but this can be changed by adjusting the spring tension inside of the distributor.
The 30 degrees at 3,000 RPM is what you should have while making this test using a distributor tester and is not what you set your ignition at. MB mechanics would have already known this and would have simply added the initial timing advance to the total distributor advance. The BBB wil give you specs but they have to be understood from the point of view that some are to be taken as a maximum and others as part of a total amount.
Another example of this would be cylinder bores. The maximum bore may be 83.5 mm and when you order pistons you order that size. The piston is actually smaller at maybe 83.46 mm but that is already taken into account and they're machined to that tollerance. 

As I recall, this patricular distributor is advancing 35 degrees which is 5 degrees too much. So, where ever you set idle timing, it's always going to be wrong at full advance. 2 - 4 degrees ATDC is for the late 280SL and should not be used for cars running the 051 unit.

I'm going to try one more time. Set your ignition to 5 degrees BTDC.

 Remove the vacuum cell from your distributor and turn the pull rod in one full turn. This should give you less vacuum cell advance but it will not change the mechanical portion. Install the distributor and set your tinming to 5 degrees and check your maximum advance which should be around 35 to 36 degrees BTDC. If It's more than 36 degrees remove the distributor and do the pull rod adjustment again but only turn it a half turn this time.
Repeat setting the timing and checking what you have for full advance. When you get it to 35 - 36 degrees lock the distributor in place and don't mess with it after you have this amount.

Looking at your spark plug pictures they look about right and maybe a tiny bit rich which is OK for now. You will need to drive the car for a while while checking the plugs but frankly, a pump rebuild would be your best option here. You may be able to get it close by working on it but I've never been a big advocate of playing around with such a delicate piece of machinery.   

[66andBlue]

.... 2 - 4 degrees ATDC is for the late 280SL and should not be used for cars running the 051 unit. ....   

.... or perhaps he says - they say. 
The 1969 Mercedes Technical Data Book clearly specifies 2° +/- 1° after TDC with vacuum even when installed in a 230SL.
Obviously "late 280SL" did not yet exist in 1969.
So, who is right?   

[Benz Dr.]

I know what the book says and I'm not following it because it's 40+ years later. 5 degrees is where the engine will make power. It will run at TDC just fine but it will use more fuel and won't pull as hard.

I run my own car at 36 degrees. I had it at 30 degrees and it never seemed to have very good throtttle response.
 After studying ignition systems on these old cars for about 20 years now I hope I've got some of it figured out. There's a sweet spot where every engine runs really good and it isn't TDC or anything after that unless it's a late 280SL. Clearly, if you hear pinging, you have it advanced too much or you need higher octaine.
I use regular in my car and it never pings at 36 degrees. I haven't checked my compression in a while but the last time I did it was up around 175 PSI. I set the advance springs in my distributor a bit tigher than stock so it would advance slower which is why I can run regular. The car gets a consistant 26 MPG ( IMP ) every tank.

The car is a '66 230SL with the ZF 5 speed. I used a distributor from a 300SE that's dual point - dwell angle is 52 degrees. Each set of points runs three cylinders - throws a wicked spark with the red coil and ballast resistor set up. I'm running a 230SL cam shaft advanced to 12 degrees BTDC.
Last year I changed out the 4.08 rear axle to 3.92 LSD and I picked up a bit more mileage. 

[mrfatboy]

Well.... I guess I have come full circle as far as I know.  Last night I put the car away knowing that it was idling (warm) with a nice 4.0% CO.  Today I wanted to see what it would do completely cold.  It started right up and quickly went lean to about 2.0% CO and stumbled as it got warm.  After the engine was completely warm (no air sucked into the WRD) the CO  was still 2%.  Mind you, I have not touched anything since the night before when everything was running perfect at a CO 4%.

I then clicked the IP idle mixture screw (CW) one click to enrich the mixture. Boom! the CO% is not back up to 4%.  Everything runs nice 

Now it gets stranger.  I let the car sit for a couple of hours and get completely cold again. Start it up and the CO is back down to 2%.  Again, I clicked it one more time (CW) to enrich it.  This is +2 clicks rich from last night.  The CO% popped back up to 4%.  It seems like I'm just chasing it now.

All this leads to the conclusion (like we didn't know already) that the IP has something really funky going on with the idle mixture and needs to be rebuilt.   The IP mixture seems to float or get readjusted after the car engine turns off.  It's almost like something in the pump is broken, loose, or bouncing around, or stuck spring. 

Other than pulling the pump and getting it rebuilt can anybody explain what it going on or seen this type of behavior?

[ja17]

Hello,

Things take time to settle in after radical adjustments. Moving parts are getting to know each other and new locations. Fuel varnish build-ups are worn away as parts settle in new locations.

[Benz Dr.]

Hello,

Things take time to settle in after radical adjustments. Moving parts are getting to know each other and new locations. Fuel varnish build-ups are worn away as parts settle in new locations.

I think I'll start using that answer from now on.

 '' Yep, them there new parts is gettin' to know each other. It'll improve once they get better aquainted. '' 

[mrfatboy]

After 43 years, I think those parts are very well acquainted and they just don't like each other anymore 

[wwheeler]

After you make those adjustments, are you driving the car for several mnutes? I have always found that when changing the idle mixture screw, the engine wants to be driven before the final results are to be seen.

[mrfatboy]

Yes and no.  It really does not seem to matter.  I have discovered a pattern but it really does not make sense to me.

Start car stone cold (starts right up)
 - CO is about 4%

As car gets warmer the CO% gets leaner to 2%

Turn the FIP idle mixture screw +1 click CW to enrich

CO% is now back up to 4% and everything is good.

Drive or Sit for a bit. Park. Wait a hour or so for stone cold.

Start the whole process over.   




I started at 15 clicks from max lean at the beginning of this process.  Now I am at 20 clicks CW from max lean.  It seems like something is resetting internally in the pump.

I don't know how it can go lean as the car warms up either.  The WRD shuts off the air. It should go richer, right?  And I certainly don't know why the FIP idle has to be turned one turn CW each time I do a cold start.  I can't imagine what funky thing is going on inside the pump to make that happen.

[twistedtree]

Think how happy you would be if your rebuilt FIP arrived today ready to install :-)

[ctaylor738]

Last fall I spent a lot of time on a 230SL getting the warm-up right.  When I finished it had a very good warm idle at around 4.5%.  The next day I started it and it was around 3%.  I varied from time to time between 2.5% and 5.5%.

I asked Gernold about this, and his answer was a worn throttle body will allow slightly different amounts of air past it when it is closed.  It takes only tiny amount of air to change the idle CO.

Also, if you are using a Gunson Gastester, they are only accurate to .5% even when calibrated.

[mrfatboy]

Here is an update to my magical mystery FIP 

I will start off by answering a question that I asked in a couple of posts above.  After taking a break it came to me that the FIP does lean out as it gets warmer (not richer).  I was thinking it was getting richer do to less air getting sucked in from the WRD but I forgot that the WRD also pushes down on the FIP rack as the engine warms leaning the CO%.

As a result, the partial behavior I described does seem consistent with how the FIP should work.

I started from scratch yesterday and have come up with better result albeit not perfect.

From a cold stone start in the morning.

-15 second fuel pump prime
-Turn on engine (fires immediately) and idles on it's own
-CO% 6
-As the engine warms the WRD slowly stops sucking air until completely shut off.  At the same time, the CO% slowly drops from 6.0% to 2.1% and engine dies (of being too lean i guess)
-I then try to restart the engine (rough idle) and it needs a lot throttle help to keep it going.
-I use high revs for about 10-15 seconds before the engine starts idling on it's own at CO 4.0%
-I then take it for a 10 mile spin going to thru all the gears and getting the final warm up at 180 degrees
-I come back home and retest the CO% ant it's back at 6.0%


For some reason it really likes to go down to 2.1% when it's cold no matter where I set the idle CO%.  I'm not sure what that really means. I can understand it dropping down a relative amount from the starting CO% but it likes 2.1%.

Is it possible that the WRD is shutting off it's air intake and leaning out the FIP way too soon before the engine gets at the required operating temp thereby getting this funky behavior?  I know that the internal shims in the WRD can control WHEN it shuts down the air and how much it really leans out the pump when thermostat pin fully extends.

@ctaylor
Thanks.  That is an interesting explanation.  It certainly is a possibility.

@wwheeler
Thanks. I took your suggestion about driving after every adjustment of the FIP.  It seemed to help and got me to where I am at today

[wwheeler]

There is another recent WRD thread on this site that talks about the condition where the engine is warm but not hot. There were about three people from what I recall had this issue although each acted differently. While I haven't had a chance to break out my Gunson tester, I used the spilt linkage method to determine lean or rich.

My cold engine starts rich as expected and as it slowly warms and the RPMs drop, the mixture gets closer to balanced. In the time between "fully" warmed up and somewhat warm, the engine runs lean. Not to the point where it dies, but lean enough to run rough and slower. If I rev the engine enough, after a while it will warm so the mixture will richen and then it is balanced and runs great.

What I normally do when starting the cold engine is let it idle until the RPMs drop for the first time usually around 130*F or so. I then take the car and drive it. The engine does lean and slow at idle for just a bit while sitting at idle, but the throttle solenoid (automatic) keeps the RPMs up enough. After that brief time, it runs fine. So the lean period is much shorter then when letting it idle in the driveway.

I have lessened the lean effect by adding .003" oval shims to the WRD. If I add too many though, it runs way too rich when very cold and the fast idle isn't very fast. Maybe I am being too picky (I have been accused of that before ), but it would be nice to have it right. The gunson tester should help me fine tune it, but for now it is as close as I can get it by feel. 

     

[Benz Dr.]

In most cases you will probably sart your car and drive away shortly after. Getting it close is usually all you need because your main objective it to get the engine to start, right? As long as it continues to run the engine should be fully warmed in a few miles or less.

Starting is important of course, but driving impression while fully warmed should be your main goal. Once you have that, then maybe you can try a couple of diffrent settings to improve cold start idle and warm up. I wouldn't fixate too much on this brief running peroid unless your engine stalls or is belching black smoke.

[ctaylor738]

Maybe you are getting a small amount of air past the valve during your driveway idle warm-up.  Then with full warm-up. the valve is pushed down far enough to completely close off the air.

If you look at the diagram on 07-14/13 in the BBB and also in the Haynes manual at p. 72, you can add a compensating washer to move the slide valve down a little further and shut off the air earlier.

[ja17]

You may notice brown varnish deposits on the back side of the camshaft lobes. This varnish build up happens in areas not in use. The high points of the camshaft lobes are bright and polished. These areas are in contact with the rocker arms. Making radical adjustments to the IP moves internal parts to areas not normally used. These areas most often have varnish build up like the camshaft. When I mention that "the parts need to get to know each other" I am referring to the varnish situation. A short test drive as Wallace suggests allows the parts and new settings a chance to "get to know each other" in other words, wear the varnish off.

Drive the car a bit then get back to the fine adjustments.

[mrfatboy]

A very good update!  

I would like to first thank everybody that has offered suggestions.  I could have not done it without you guys    I know that sometimes it gets tedious dealing with the same old problems but it's definitely great to talk them through.

After I kept getting no where with the FIP I decided to follow WWheeler's advice and focus on the WRD a bit.  I found this thread which I think he was referring to:

http://www.sl113.org/forums/index.php?topic=9244.0

Mind you I had always ASSUMED (yup, you know what's coming) that the WRD was working fine based on the air suction stopping as the car got warmer.  After reading the WRD thread I decided to take it apart to see what was really going on if anything.  I wanted to see how many "round shims" were there.  When I first opened up the WRD I could see an original round shim at the top just underneath the retaining clip.  Upon removing the retaining clip and removing all the shims I found 3 additional homemade shims  .  There was a total of 4mm of shims in there which if I understand correctly is too much.  I then put back 3 original shims totaling ~1.30 mm. (1mm, .1mm, .2mm)

I then started from a stone cold start.  The air being sucked into the WRD seemed louder now. The other thing I noticed is that it took much longer for WRD to shut off air intake from before.  Also, the WRD air intake did not completely shut off when just idling as it did before. The engine really had to be warm.  I took the car for a quick spin and by the time I came back the WRD air intake was completely off.

While I was doing all of this I was monitoring the CO% with the Gunson.  At the cold start, it fired immediately, and the CO% rose to 11% over 50 seconds.  After 20 more seconds the CO% started dropping.  Over the next 2 minutes the CO steadily declined to 1.5%. As it declined you could hear the WRD air intake slowing closing to the point of just shy of completely closed.  This is where I decided to take the car out and get it 100% warmed up.  Upon returning the WRD air intake was completely closed.

I now decided to move back to the FIP tuning.  The adjustments I was using were shims under the BC and the FIP idle mixture screw.  This was quite the iterative process but satisfying because things starting working as they are supposed to do.  I started with a 2mm shim (original?)under the BC and ended up with adding an additional 1.5mm for a total of 3.5mm.  I added a 0.15 shim each time in conjunction with dialing down the FIP idle mixture screw.

After doing all the adjustments (and driving in between) I settled on a CO of 4%    I think I that took me to almost MAX Lean on the FIP idle screw.  

When I started all of the adjustments this morning the car would slightly miss every once in awhile and ONLY on hard acceleration.  I diagnosed this (correctly I think?) being too lean in the mid and upper ranges.  As I added shims under the BC(more rich) each time the missing slowly disappeared. The missing is 99.9% gone now.  Now, I could add more shims under the BC to enrich the FIP over all ranges to possibly make it 100% but as I stated above I think I'm all out of FIP lean clicks. I would like to avoid going into the pump. I will drive for a bit and let everything settle.  Overall, I am extremely happy with the results.  


There have been many things that I have learned from this thread. But the two diagnostic tips are

1)  Just because your WRD completely shuts down the air suction as it warms up doesn't mean that it is actually running or calibrated correctly.

2) As most of you stated,  it's extremely important to drive the car after you make FIP & BC shim adjustments to let things "settle" and find their place.  I saw a difference every time.



I did have a question regarding the cold start idle mixture starting at 11%. Is this typical and in spec?   If anybody has a gunson meter and is willing to do a quick test(or if you just happen to know) I would like to know.  I'm just trying to dot the "i"'s and cross the "t"'s so I can close the book on this thing  


This is the plug color I ended up with.  What do you think?

[Garry]

mrfatboy,

That plug looks pretty good and that is what this Group is all about, helping each other and keeping these cars on the road. 
Now if you would like to become a full member and then you can do a write up to go into the Technical Manual

Giving what country you are in and area is good too

[clembeauch63712]

Hj J just read this posting completely and the plugs look good to me , note if you have haynes manual usually there is a photo of spark plugs in the back inside cover & will give you an idea at what shoud be correct.. It is a little Iffy to    know after only a 2 mile drive .. I would run it at speed on the open road for about 10 mile drive to know where you are really at.. and compar the plugs at that time to the pictures in Haynes. and  dont let it idle a lot .. shut it rite off after your drive.   Good luck  Clembeauch 63 712

[Benz Dr.]

If you could take a picture of your spark plug from the side with the ground electrode pointing up, that would be better. I can't tell by looking right at the end of the plug due to shadowing. It's not too lean but I can't tell how rich it is because the shadows are about the same colour as sooty deposits.

 I found that my own WRD wasn't quite shutting of just like yours. It really doesn't take much to create enough of a vaccum leak to make you question what's wrong. 

[wwheeler]

Something else that comes into play with WRD; and that is the cooling system thermostat. Because Texas is very hot in the summer (especially last year), I installed a 167*F (75*C) thermostat to keep the engine cool when driving on the highway and in heavy city traffic. When starting the engine this winter (about 50*F ambient) with the 167* thermostat in my garage, I could not get the engine hot enough to shut off the WRD valve completely. So what ctaylor738 is saying, is correct. The WRD thermostat never completely warms up until it is driven. The only way to REALLY get these engines completely hot is to drive them. It won't happen in the garage alone.

I have made more mixture adjustments than I care to admit, and everytime it will change after a drive.

And as Garry says, become a full member. It is the best investment you will make in your car!

[glenn]

The WRD, as the coolant heats up from ambient to 75 C(in 60 sec or so), simultaneously closes off WRD air and reduces FIP fuel to 'idle' rate.   Hopefully, Bosch and the WRD maker made the fuel/air ratio correct across the range......

[mrfatboy]

Well guys, I went for broke today and tried to tackle my Cold Start idle issue now.  I am very happy with how my warm idle and CO turned out but the my cold idle is about 600-700rpm with my CO at starting 11%.  As I stated above, as the car warms up the CO comes down to 1.5-2% and not it until I drive it and get it completely warmed up does it come back to 4.0%.  I'm assuming the CO dip to 1.5-2% is being caused by the last little air gap in the WRD until it completely closes.  

Rereading the thread I posted above about the WRD I decided to take out the 2 oval shims under the WRD (.12mm & .63mm) in order to minimize(try to get leaner) the 11% CO during warm up and increase the rpms.  If I understand the post,  the oval shims control fuel mixture at warm up.  Removing shims making it leaner and adding richer.  So after removing both shims and doing a cold start as I have been I saw absolutely NO difference in CO% and idle speed. Everything was exactly the same (11% and 600-700rpm idle)

I would have thought removing the oval shims under the WRD would have leaned out the CO by at least some amount during warm up.  How would you interpret no change at all?   The only thing I can think of is to add round shims BELOW the air valve slide in the WRD thus extending the pin further in the FIP leaning out cold start mixture?  Is that really an option?

I see that WWheeler had the exact same problem in this post http://www.sl113.org/forums/index.php?topic=11647.0.

Suggestions on what to do next?



BTW, I copied and pasted the wrong WRD reference thread a couple of posts above.  I have corrected it.

[ja17]

Sounds like your WRD is at its upper limit.