W111 220SE Cab 1963 with M127.984 Motor - very high fuel consumption

[hansr433]

I posted earlier under the topic W111 Throttle Linkage, and I am trying to narrow down the causes of these symptoms:

1.  High fuel consumption - 20l/100km
2.  Very Sooty plugs

Car starts easily cold or hot.

Done already:

1.  Changed plugs to NGK BP6ES from Bosch WR 7 DC
2.  Adjusted throttle linkage according to Linkage tour.
3.  New Mahle air filter

Yesterday, I tried to check the Cold start valve as follows:

1.  Removed the small air filter on FIP.
2.  Started engine and heard strong sucking sound.
3.  Placed a piece of paper over air filter socket.
4.  Experienced strong engine surging (hunting) to the point of engine almost stopping.
5.  After ca 10 Minuten, the paper was still stuck to the air filter socket but the sucking vacuum was less.

Videos are here:

Video MB 220SE Coldstart 1 Link1
https://www.dropbox.com/s/mzgj…%20Coldstart%201.MOV?dl=0

At the exhaust:
Video MB 220SE Coldstart Exhaust Link2
https://www.dropbox.com/s/pw97…dstart%20exhaust.MOV?dl=0

Video MB 220SE Warm 1 Link3
https://www.dropbox.com/s/z9eb…220SE%20Warm%201.MOV?dl=0

and Video MB 220SE Warm2 Link4
https://www.dropbox.com/s/1ybw…220SE%20Warm%202.MOV?dl=0

What do the gurus think might be the cause?  Thank you for your advice.

[gcw206]

I had the exact same problem; sooty exhaust and terrible gas mileage.
Turned out the PO had replaced the Fuel Injection Pump Thermostat, but left the old collar.
The new FIP T-Stats have a larger diameter, and do not fit into the old collar.
The T-Stat was never seated correctly, and therefore never operated as it should.
The result was that the FIP Pump always ran rich.
I bought a new t-stat and the correct collar from Authentic Classics.
That solved the problem.

[hansr433]

I had the exact same problem; sooty exhaust and terrible gas mileage.
Turned out the PO had replaced the Fuel Injection Pump Thermostat, but left the old collar.
The new FIP T-Stats have a larger diameter, and do not fit into the old collar.
The T-Stat was never seated correctly, and therefore never operated as it should.
The result was that the FIP Pump always ran rich.
I bought a new t-stat and the correct collar from Authentic Classics.
That solved the problem.

Interesting, and definitely worth exploring.  The engine and FIP were totally rebuilt 5000km ago, and perhaps the wrong parts were used.  Against this theory is the fact that the car ran reasonably well with OK fuel consumption for the first 2500km.  Something changed suddenly and I am at a loss where to look.

[col320ce]

Have you tried driving it to warm it up?Have you replaced the thermostat on the fip?
The sucking completely stops in my cars but some report a tiny bit of air flow.

[PeterPortugal]

Hans,

When people talk about the cold start valve it is the part on the inlet manifold. This dumps additional fuel into the inlet for a few seconds when cranking.

The part you are referring to is the warm running device "WRD". The strong sucking is correct with the engine cold and this sucking should lessen as the coolant warms up and the thermostat pin closes off the opening. If the sucking was not too strong after 10 mins then it is working and may just require a minot adjustment to optimise it.

I think if other posters have suggested checking the cold start valve they mean the other part. If this is leaking it will always be adding additional fuel into your inlet.

Regards

Peter

[PeterPortugal]

Hans,

On your car this is located at the end of the manifold near to the wiper motor. You will note a fuel line is routed across the bulkhead to it. It is a solenoid valve.

Regards

Peter

[wwheeler]

Peter is correct in that there are two cold devices and I think you might be mixing them up.

The thermostat (WRD) on the IP is like a choke on a carbureted engine. It richens the mixture until the engine warms up and then shuts off. The vacuum at the small air filter port should be completely off or very much near so when the engine reaches 165*F or so. Just a bit before normal operating temperature. If the vacuum doesn't completely shut off, you have to find out why. Could be wrong shims are installed, stuck air valve or bad Thermostat. Or maybe the wrong spacer as was posted earlier.

The Cold start valve (CSV) is on the side of the intake manifold and squirts fuel into the manifold when the engine is starting. While this can leak, it is usually not enough to mess up the fuel mixture at higher speeds. Yes, it will mess the idle mixture up. Test this by removing the small hex bolt on the side. With the ignition on and fuel pump running (engine NOT running), no fuel should come out this hole. A VERY small amount is allowed, but not like drips.

Once you test these, we can move on from there. 

[hansr433]

Peter, Wallace, thank you for your concise explanations.  I have removed the inspection bolt of the CSV, turned on the ignition and no fuel at all came out.  Then I removed the thermostat (WRD) and heated it in boiling water to about 80deg C.  The actuator bolt extended about 1.5mm, less than it should according to the manual.  Here is a photo of it.  Does it look familiar to anyone?

@gcw206 - do you still have the part number for the parts you bought?

best

Hans

[larryled]

Please, for us dummies, don’t use acronyms unless it is first identified with the “name”!  I am having the same problem with my 1966 111 Coupe, and find this frustratingly interesting, because I can’t figure what most of them mean, CSV, OK, but!  Thanks, Larryled

[PeterPortugal]

Hans,

I tried the same test with my thermostat and it didn't protrude as much as the BBB recommemded. The same as your situation.

However if I remember correctly the part which the pin acts on is a screw so you could adjust this so that the thermostat does close off the air intake when it is extended fully.

This might give you less air than anticipated when it is cold. I am not sure of the trade off.

The idea of the thermostat is to make starting and running from cold OK and your car is fine for this condition so you could try the adjustment.

Regards

Peter

[wwheeler]

Keep in mind that there are two different thermostats. The early tall one moves very little and 1.5 doesn't sound that far off. The shorter newer version (250/280) moves much more. The below is from the tech manual here on the site:
The pin on the early thermostat should extend about 2 mm when tested in hot water, while the one on the later thermostat extends by about 7 mm. So I don't think you are that far off.

Did you determine that the suction shuts off on the warm up device when warm? It should be either completely off or just a VERY slight amount of suction.

[PeterPortugal]

Hans,

I have not got round to adjusting my mixture yet because there were so many things the BBB suggested had to be verified first.

I have sent you an email with the list I created.

Regards

Peter

[hansr433]

I also posted on the German VDH forum.  Here is what a member who repairs pumps for a living said:  The actuator pin in the large thermostat found in W111 2-piston pumps and also early W113 cars should extend at 20 °C  by 6,1 mm.  At 100 °C, it should extend a further 3.2mm.  It should be firm to pressure.  The pressure test works only for the newer short thermostats.  Thus my thermostat most certainly does not work as it should.  Peter and Larry, this is something for you to check as well.

Tuscany, where I and the car are at the moment, has just gone back to Red, meaning that I basically cannot leave my town.  Once I can go for a drive again, I will go for a nice 100km ride with the thermostat of the WRD disabled to see if my fuel consumption has improved.  I will also go through the checklist Peter sent me (Thank you!!!).  Finally, i might also remove the pump and injectors and send them for repair/calibration to Germany. 

[PeterPortugal]

Hans,

You can see the info in section 00-15 of the BBB. 6mm at 20 DegC and 9mm at 80 DegC. However what you will also notice also is that it suggests the check is made with a load of 3kg on the pin. The advice given on VDH is consistent with this and probably the "firmness test" is used instead of the 3kg weight.

I tested mine in an electric oven rather than in hot water. I used a temp gauge in the oven for a bit more accuracy.

I think mine behaved like yours Hans and moved a further 1.5mm or so between 20DegC and 80 DegC. Check at least the starting point is OK i.e. 6mm.

I also suggest you check job No 07-14 in the BBB "Adjustment of Injection Pump for USA". Could this also be a factor?

Regards

Peter

[PeterPortugal]

Hans,

Further to the last post I return to what I suggested has been done with my car. I think the WRD was adjusted so that with the thermostat fully extended (to say 7.5mm rather than the correct 9mm) it leans out the car fully and closes off the supplementary air. This means it might be less effective at cold starting but my car doesn't seem to have an issue with this.

Peter

[PeterPortugal]

Guys,

Going back to the post by GCW206 is it possible to use the new style thermostat which are cheap and readily available if you can source some other components to do the "conversion"?

The old long thermostats are a ludicrous price if you can still find them i.e. over a thousand in all major currencies. I would certainly be interested in finding out more about this.

Regards

Peter

[wwheeler]

I think gcw has a later car and the later short thermostat and not the early tall one. The spacer he is speaking of from Authentic is for the short thermostat (250/280) and not a conversion. He never specified what model he had.

Looking back at the original post, it has high fuel usage and sooty plugs. So burning very rich when warm. It also says the WRD suction was high when cold and reduced when warm. I don’t it was ever said if it shut off completely. That would be an important point.

I would say the next step is to shut off the WRD function (via bolt) and see what happens when warm. Know it is going to run poorly when cold. If indeed it runs more lean with the thermostat deactivated, then you have isolated the problem. That is why the shut off function is there, to deactivate a bad thermostat.

It either will be the thermostat is bad or the adjustment is off. You can go from there.

[hansr433]

I think gcw has a later car and the later short thermostat and not the early tall one. The spacer he is speaking of from Authentic is for the short thermostat (250/280) and not a conversion. He never specified what model he had.

Looking back at the original post, it has high fuel usage and sooty plugs. So burning very rich when warm. It also says the WRD suction was high when cold and reduced when warm. I don’t it was ever said if it shut off completely. That would be an important point.

I would say the next step is to shut off the WRD function (via bolt) and see what happens when warm. Know it is going to run poorly when cold. If indeed it runs more lean with the thermostat deactivated, then you have isolated the problem. That is why the shut off function is there, to deactivate a bad thermostat.

It either will be the thermostat is bad or the adjustment is off. You can go from there.

I read somewhere that in order to use the new, short thermostat you also have to change the part (collar) it mounts into.  As Peter has said, the price of the older thermostat is insane, so this is an exercise worth doing.

In order to shut the WRD off completely, do I need to push the pin in the photo down while turning the bolt 90 degrees? Does it make a difference if turning the bolt left left or right?  Right now I can push the bolt inwards a few mm.  Is that normal when it is set in the working position?  Looking at the attached photo again, why is there this half-moon cutout in the brass?  If I were to turn that brass assembly clockwise to 7 o'clock to clear the blocking pin, then would the whole assembly pop up?  I also found out that I am missing an aluminium washer between the thermostat and the upper housing.  The spec for the washer is 20x24 DIN 7603Al.  Thus I am getting some drips of coolant.  Hoping to find one at our local farm supply store.

[wwheeler]

Regarding the bolt, this what I wrote in another thread:
Yes, that is the bolt I am talking about. My understanding is that you press the bolt in and then rotate the bolt to the right 90*. The pin is offset and will move the plunger down far enough so the pump is locked in full warm mode. If the pin is in the upper position then it allows the thermostat to act on it. This is described in the workshop manual for Passenger cars starting 1959. It is on page 07-10/12. The bolt is #59 in that illustration.

I have never completely torn my WRD down on this this car like I have the later 280SE. So I am not as familiar with the internals. Not sure I am aware of the notch in the brass piece.

As I stated, I have never moved the bolt, I just know that it can be done and the purpose for it. The BBB seems to state that you turn it to the right. Hopefully you can get it to work. I really don't know the purpose of that cutout. Maybe others do.

In regards to the thermostat conversion, I am 99% sure you cannot convert the tall thermostats to the short later version. The strokes alone of the two thermostats are different. I saw in another thread that GCW206 posted and has a '69 280SE W111 and uses the later short thermostat. The spacer he is talking about is for minor differences between original shot thermostats an newly produced short thermostats. See link to Authentic -  https://www.authenticclassics.com/Seal-Ring-250SL-280SL-Injection-Pump-Thermostat-OS-p/auth-007310.htm

Note: this spacer is for 250/280 short thermostats only and the small differences in the diameter of their mounting bases. Not for the 220/230 early tall thermostats. Hopefully that clears that up and please correct me if I am wrong. I also would love to use the less expensive thermostat.

[hansr433]

I can report some baby steps, but not really progress.  I found the correct washer 20x24 DIN 7603Al at a motorcycle repair shop.  Photo of new and old washer is attached.  Of interest is the other attached photo of the thermostat taken a few days ago before I tested it.  Can you see the alu washer on the thermostat?  It is the wrong dimension, 20x26 DIN 7603Al, and had been installed on the wrong side of the thermostat by the rebuilder.  It had also been attached with a sealant and thus was stuck to the thermostat, making me think that it was part of the assembly.  Moving on.

I pushed the plunger down by hand and turned the blocking bolt 180 deg., closed the WRD up and tried to start the car.  It would not run at all, so i turned the bolt by hand to the right again 180 deg with the WRD assembled and the car does a proper cold start like it should.  The thermostat protrudes 1.5mm more than before since the washer is now where it should be, behind it and not on top.  I also remeasured the length of the pin at room temperature and at 90 deg C and this time I measured 4.4mm and 7.1mm, more in line what it should be, I believe.  Can someone please confirm?  As soon as I can make a decent run, I will report back on how the car runs now.

Thank you everybody for your advice and patience with a noobie.

[PeterPortugal]

Hans,

I recommend you repeat the test of seeing if the air is closed off when the coolant is getting warm.

If it is then you have made some  progress.

Peter

[wwheeler]

Hans,

I recommend you repeat the test of seeing if the air is closed off when the coolant is getting warm.

If it is then you have made some  progress.

Peter

I agree. Not sure that was ever determined.