Clicking the Fuel Adjuster Left

[wwheeler]

I can say with 100% certainty that a very small air bleed is a possibility and not a worry as Stick says. When I noticed the small air bleed on mine, I added round shims until the WRD shut off so early it wasn't then doing its job. And yet, the small air bleed was still there. The air valve piston has no seal other than trace oil that is between it and the housing cylinder. So it makes sense to me that given wear over time, a 100% seal is just not realistic.

Something that gets overlooked on the WRD operation is that the rod that contacts to IP lever, is spring loaded. And in fact, there is a stop down in the pump that will prevent that rod from continuing to lean the pump as the thermostat bulb keeps extending with temperature. JeffC discovered this and is in the tech manual I believe. So if you go beyond the normal engine operating temperature, the WRD will not continue to lean the pump. The spring loaded rod will just compress further. If the stop is adjusted correctly, the air valve should shut off at roughly the same time the rod hits the stop screw in the pump. This just popped into my head when you mentioned that the rod may not be going down far enough.   

Adjusting the BC is just an easier way to adjust the full range on the pump. It does not mean that anything is wrong with it. I prefer that over the screws in the back of the IP which is like a can of worms unless you are very knowledgeable. If you don't have any BC shims, then you may have to mess with the rack screw. On my BC, there is a thick washer and maybe a 1mm thick. You could replace that if you have it, with thinner shims.

Replacing the thermostat may also be a good idea and I do not believe it is very expensive. Good luck.

 

[450sl]

Pawel, I have had my wrd not closing 100% as well and added a small 8mm dia Or so shim of 0.4 mm : now my wrd closes completely. For the overall rich situation I would first think of the oval shims

Mark

[Pawel66]

You added the round one on top of air valve or oval one, below the base? I suppose the round one...
Yes, this would be a solution for me, as I thought, thank you.
But if the thermostat is not working as it should - I think I would just replace it. Then I will take it from there.

[Pawel66]

Wallace, I read those posts from Jeff. That contributes to understanding of how the WRD works, it was very informative.

On the adjustments - yes, the BC seems to be the easiest, but I have no shims there. It may happen, however, that, if someof the theories are right, that I would need to add shims to BC.

I have absolutely no intention to go into the adjustments of the black and white screws under the lid. It is the full range adjustment and idle screw that I would touch if I need to. I think it is manageable even with a primitive Gunsons. We will see.

Thank you for your thoughts!

[mrfatboy]

Pawel

Reread Wallace's #18 post. The oval shims only control mixture during warm up.

Since you are rich over all rpm ranges. I would suggest the following.

1. Put WRD back together
2. Verify that Air slide valve is completely shut (minimal air suction) AFTER the car is completely hot.  Just warming up in garage takes too long or might not get it completely closed.
3. Adjust rack in back of pump leaner. 

[Pawel66]

mrfatboy, yes, thank you. WRD works on warm up (that is when it affects mixture) then shuts off.

The doubt is if the WRD indeed shuts off. If it does not - WRD will cause rich condition across the rpm range. I suspect the thermostat may not extend as long as it should be. I will risk $130 and replace it. If it does not help - yes, I will be back to rod adjustment. I just want to eliminate all the factors that are suspicious. CSV was ok, BC was ok. WRD does not seem to be ok - so I will fix it. I do not know other/further factors, other than adjustments.

[Benz Dr.]

Dan, I have to respectfully disagree.
A small bleed at the auxiliary air slide is just the same as undoing the idle screw half a turn and can be easily compensated for in tune-up.
Obviously a large and unchanging bleed is a different matter but as long as there a big noise at that orifice when cold and a little or no noise when hot I'm satisfied.

Yes, but that's not what I said or at least not what I meant. Full shut off is a reference to fuel shut off. Air, as you indicated, can be compensated for if not too much.

I think Pawel gets how it works which is why we discuss stuff like this - so we can all learn from one another. 

[Pawel66]

I received my new thermostat (picture enclosed).
Then I did the testing, picture with results enclosed (sorry for format). It looks like I found my 2 mm. The temperatures might have varied a bit - it is difficult to hold steady temperature in a kettle... but - old one stps at 5mm travel, the new one goes 7mm travel, then stops.

The air shuts off at ca 80 degree.

I will put it all back together in the car and see what I get in CO results/rich condition.

Do I put sealant between thermostat and its housing only, or also somewhere else? e.g. where the oval shims are?

Is there anything that should be inside the air filter? Any foam? Felt? Mine is empty...

[Pawel66]

I put everything back together and into the car. And I need your kind asdvise.

The new thermostat extends 2mm further than the old one - I think I eliminated thermostat as potential source of additional fuel supply due to not complete additional fuel shut-off after warm up. At least I have to assume this.

Before: fairly steady warm up (rich), revs down at 85deg or close, air shut-off (not really complete) at close to 85, then smooth but rich idle (8-9% CO) and rich higher revs (15-17% CO - but not sure, it took Gunsons long to stabilize).

Now:
1. A bit rich warm up ambient to 60 deg (could be normal);
2. 60-80 deg very lean warm up, tendency to stall, stalling sometimes, need to hold throttle a bit to keep it running or hold FIP lever a bit
3. Near 80-85 getting rich again
4. Air still shuts off at 85 or close; feels a bit late... (garage warm up)
5. Then smooth but rich idle, leaner than before (6-7% CO); higher rpm rich as well, a bit leaner than before

In essence:
1. I leaned warm up (not surprising); will have to come back to it, but probably later as the main topic is rich idle and rich high rpm; will
2. Given that the last potential cause of richness was supposedly taken care of (fuel shut off)
a) add a 0.5mm round shim to have the air cut-off a bit earlier?
b) go back to rack adjustment and idle adjustment screws?
C) once this is done, add a, say, 0.5mm oval shim to enrich the warm up?

Please kindly advise.

[mrfatboy]

Hi Pawel,

I have access to a Gunson CO tester also.  Just yesterday we ran a cold start CO test on another member's 250 SL for fun.  He has the European configured pump.  His car was sitting for a while and we just wanted to see what it would do and compare with mine.

Tests 1-5 were done on my 280sl last January.  I ran the tests with experimenting with oval shim thickness and fip idle screw.

Yesterday's test is marked 250 SL. (Orange.  He will be tweaking based on what we found.  I think he will just use idle air screw to lean out as his idle RPM's only hit 900

To run the test I used the Gunson and an iphone.  I downloaded the Fast Camera app that takes a picture every two seconds. Started the car and let the camera do it's thing.  I then copied the results into an excel file.  I could send it to you if you like so you can graph your own data.

You can see by the first high curve is were the CSV injects the fuel, rack is pushed forward and the trough is when the WRD pin hits its stop in the FIP and just the remaining air from the WRD air slide valve is closing up.

You could do the same test and see how yours compares.

But to answer your adjustment question....

If it were me I would adjust the rack to make leaner over all rpms.  I say that because you said you played with it a couple of years ago and might have turned the wrong way.  Also  your BC has no shims left for adjust.  You just slowly have to walk your way back.  Hopefully you can get it to a point to add some shims back into the BC.

[Pawel66]

Thank you! This looks like a very good and hel[ful material!

I di not set the Gunsons for the warm up. My conclusions are based on split linkage tests. I will check it as you did.

Truth is that when I plugged in the probe the engine was after some time of standstill, a little cooled down. and initially for some minutes the reading was 5% - that might have been equivalent of the dip in your graphs after fuel was shut off and some air still coming in. Then the reading on idle went higher, to the level of 7-8% during regular idle and stayed there.

I think I will start the rack leaning then.

Does the rack adjustment affect warm up mixture? Or the warm up is fully controlled by the WRD?

Thanks for sharing!

[mrfatboy]

Adjusting Rack screw clockwise leans pump over all temps and rpms (same as BC adjustment)
Adjusting Rack screw counter clockwise enriches pump over all temps and rpms (same as BC adjustment)

[Pawel66]

Yes, thank you - I remember that, it is opposite to idle screw.

"All temps and rpms" - so it does affect mixture during warm up, I understand.

[Pawel66]

I am a bit lost and need some kind advise again...

I keep turning the rack adjuster clockwise to lean the mixture across the ranges.

What responds so far is the idle - I leaned it dramatically, so for the end of the day I had to enrich idle with idle adjuster, left it at 4% CO for now.

But then when i press the pedal, observing the time intervals Gunsons require, practically no matter after how many clickds I have 8% CO at 1500rpm and 10-11 at 2500rpm.

I lost count of clicks. Not because I cannot add, but because I lost a feeling of what a rack adjuster click is. Sometimes it feels like half of turn, sometimes like quarter of a turn, sometimes is pronounced, somtimes less pronounced - I am lost there.

It is logical - I was leaning idle in the past, so overall leaning "cought up" with leaned idle. But what worries me is that at medium rpm I see no reaction. I think I turned the adjuster ca 1.5-2 turns. I do not seem to be hitting the threshold that is visible on CO meter...

Should I continue? Or the culprit is somewhere else?

I looked at my notes and confirmed today: I have both the throttle lever and FIP lever starting from the stops and returning to the stops at the same time. But when the FIP reaches max position, the throttle lever still has about 10mm travel to its stop. I disregarded it in the past (also not knowing how to fix it because linkage was set as per instructions, I have a hole in the shaft pedestal) thinking that this difference may not be critical (BBB says at least 1 mm extra travel for throttle). But maybe it is important?

[Benz Dr.]

IP lever should move to full stop and go back to idle at full stop. The throttle valve can be adjusted and should just grab a little bit indicating that it's fully closed. When fully opened it should be maybe 3 -5 mm from the full stop screw. If your full stop screw is adjustable someone may have moved it back. Do this adjustment on a cold engine!

The correlation between the IP and and the throttle valve is not a one to one ratio. Placed on a graph, the IP would appear as a straight line on a 45 degree plane. The throttle valve would look more like a bell curve with the beginning and ending touching the IP line. Both the throttle valve and the IP have to open at exactly the same time or you will have a stumble ( too rich ) or a flat spot ( too lean ) right off idle speed. This is not an easy thing to do by watching both levers and is in fact just about impossible to do that way. I place my finger on the IP lever and then I move the throttle linkage. When I feel the IP lever moving and see the throttle lever moving I know they perfectly synchronized.   

[Pawel66]

Dan, thank you.

I think I made pretty sure and correct syncronisation between the IP stop (which is given) and the throttle stop in closed position, then the legths of the rods, etc. Did it by the book. So when closed they rest at stops and raise from stops in the same moments.

Then when fully open, where you say throttle still has 3-5mm to full open stop, I have close to 10mm there. I do not know how to decrease it, actually..

I am not sure if this is can be the cause of the rich condition of 10% CO at 2500rpm...

[Pawel66]

I thought I had it, but I do not...

I managed to bring the CO level to between 3 and 4.5 (not sure how accurate measurements are with Gunsons) for higher rpm, up to 2500rpm. Idle at 4% CO. I was happy at the moment.

Then I took the car for a ride.

She seriously hesitates on acceleration from standstill or from low speed. Then I noticed she hesitates also when idling and revving up - but slightly, under load she hesitates seriously. I replaced the plugs, did not help.

She does not like this low CO level.

What do I do next? How rich is acceptable?

Make the idle richer? Will help to ca1200rpm...

[hkollan]

I was not happy with the Gunson CO meter at all. Not sure how much it can be trusted.
I never got confident with and was very happy when replaced it  with perfectly working Ex-Bundeswehr Bosch unit that I got off eBay. That still works as it should after more than 15 years in use here.
At least I would run the gunson against a verified pro unit to make sure the readings
are good.

Hans K

[Pawel66]

I agree, I do not treat it as a precise tool, and I will verify the readings. But it should be reading at least an approximate level, i.e. will differentiate betwen 10% and 5%.

What worries me is that when I got closer to where I should be, the engine hesitates when I press the pedal...

Tail pipes went from deep black to dark grey, spark plugs from soothey black to medium brown. This looks like leaner than it used to be, but not super lean yet... but I get a hesitation..

Not sure what to do next.

[mrfatboy]

It sounds like you need to start enrichening your Overall CO a bit by adding shims back into your BC. 

Then you will have to compensate your idle CO by going leaner a turn.

It's a balancing act. It will take multiple iterations.

[Pawel66]

That I think is one of the very likely ways...

What woud you say is a relatively safe level of CO at higher rpms (safe from the engine oil diluting standpoint, put aside legal and fuel consumption aspects)?

[Pawel66]

I followed the advise of one of the Members, put 2mm shims under the BC, leaned it back again with the rack adjuster and tuned the idle. Still warm up mixture to be fixed as per Mfb scientific approach.
I arrived at
5% CO at idle
5% CO at1500 rpm (this one is way above the norm)
3.5% at 2500 rpm

The car runs great and it starts when warm.

I hope these levels will not ruin the engine with frequent oil changes. I need to verify one more topic before attempting leaning it a bit further.

[Tom in seattle]

Are the WRD shims available?  I have no legal shims, just those I cut out of various materials and I don't know what thicknesses may be required. 

Thanks
Tom

[Pawel66]

Not to my knowledge. I saw many posts where Members were cutting their own. I also do not know what I need to adjust - doing some tests now.

I equipped myself with tools to cut the shims myself. Some say it is fairly easy if you use e.g. soda tins sheet metal.

[Cees Klumper]

I was just tinkering with this myself this morning. I have about 10 FI pumps sitting here in France and from 3 (the one in my car and two of the spares) I collected the shims, and I visually checked 9 more pumps. All have it seems between 2 and 4 shims. The ones I have in hand are of the following thickness: .5 mm, .3 mm and .1 mm. So it seems the stock ones vary in thickness in increments of .1 mm. Then there was one more that someone clearly made by hand, as it has a somewhat irregular shape, and it measures 1.3 mm. The pump on my car seems to warm up ok on 1.3 mm total shims. When I reduced it to .8 mm, it clearly was not happy and would not keep running from cold without constantly presssing the throttle just a bit (but not too mic or the engine would stall). I added back the .5 thickness and it was fine again. So the WRD is quite sensitive to the shim thickness. Which I guess was already clear from the fact that they are made in .1 mm for finetuning. It reminds me of the sensitivity of AC compressor clutches to differences of tenths of millimeters in their free play.