More Air valves and washer woes ? :(

[Ben]

I have read about folk with similar but not the same issue and despite searching the various posts I cant find an answer !

My car fires instantly hot or cold, but when cold it will sometimes stall, unless I rev it the instant it fires then it will setttle down to a LOW idle. This is the problem.

When hot I give it a little gas as I spin it on the starter and it fires right up and idles at about 800RPM. But when cold after it fires it only idles at about 700RPM !

Does it need washers between the Air valve housing and the body, and who sells them, I've havent seen any listed ? My timing/dwell and linkages are all spot on and the CO reads 3.5-4.0 at warm idle. The advance seems to work as I can see 30deg at 3000RPM and no more.

Also when I removed the thermostat housing I saw the little spud that stick out, and verified it works, and the air shuts off when warmed up but I didn't see any washers? The spud makes direct contact with a small maybe 6mm bolt which has maybe an 8mm locknut behind it. It looks as though one could undo the lock nut and extend the bolt out so the thermostats spud could press it deeper for longer.

Is this correct for a '64 230SL, or am I looking in the sring place for the washers? I didn't remove the slide valve as there is a little 14mm bolt on the side that has a tiny roll pin pushed on and a spud sticking out preventing the slide valve from popping out once the thermo housing is removed. I know I probably dont need washers here and dont need to touch it but I'd like to know if I have it right?

Any ideas/advice ?

Regards,
Ben in Ireland.
'64 230SL 4sp.
'03 CLK Kompressor

[ja17]

Hello Ben,
Before changing the settings in the warm-up device, find out what the engine needs to raise the cold idle. During the warm-up period disconnect the linkage rod from the injection pump. With the linkages still disconnected, move the linkage going to the intake open slightly. If the rpms increase, then the engine needs more air, if it faulters then it needs more fuel. Next move the linkage open, going to the injection pump slightly, if the engine rpms increase more fuel is needed. If the engine faulters more air is needed.
Need for adjustment at the warm-up device is unusual since this is a factory setting. Realize that shortening the length of the plunger in the warm-up device will allow the air valve to stay open longer and open wider during warm-up, however it will also increase the quantity of fuel injected during and AFTER warm up cycle.
Before changing this do the test as described above and relay the information if you like. Let us know what you find.



Joe Alexander
Blacklick, Ohio

[Ben]

Thanks Joe !

Yes I've done that and when I open the air intake slowly the RPM's rise by only 50-100RPM. I can move the pump lever quite a bit but notice no rise then it will falter !

Sounds like it needs more air. I have replaced the washers under the air valve housing so I am back to the start again.

The car drives perfectly hot or cold, and idles great when hot, its just lumpy and too low when cold!

Where to now, how do I give it more air when cold is it via the other set of compensating washers.....which I havent found yet ?

Regards,
Ben in Ireland.
'64 230SL 4sp.
'03 CLK Kompressor

[ja17]

Hello Ben,
Try giving the injection pump a couple of clicks richer then a little more air at the air adjuster screw  first. If this does not work put the settings back and we will proceed!


Joe Alexander
Blacklick, Ohio

[Ben]

Okay Joe I'll do that and report back !

But wont that make my hot idle very much higher ?

I'll try first and record what I do !

Regards,
Ben in Ireland.
'64 230SL 4sp.
'03 CLK Kompressor

[hands_aus]

Hey Ben,

I have the same situation as you so this is a very interesting thread for me.

A couple of questions?

Was the Temp gauge showing the car running hotter than 180 F ?

Why did you replace the washers/ shims under the air valve housing? Was it because you ran out of inj pump fuel adjustment?

I had to free up my air valve and in doing so the whole air/fuel mixture was out of adjustment. I then added the removed shims ( there were only 2) and still I have run out of adjustment to make the car run richer.
I bought a used set of 3 more shims to use if necessary.

Bob (Brisbane,Australia)
early 250 SL, RHD

[Ben]

Hi Bob, firstly no my car rarely runs hotter than 180deg, only if its a really warm summers day and I'm idling for about 10 minutes it might see 190 ! Dont forget I'm in Ireland !!

My idle and mixture was/is perfect when hot, it reads about 800RPM and the mixture CO is roughly 3.5 -4.0 which I think is correct.

My only problem was/is when I start from cold it idles too low at about 650-700RPM when it should be 800-1000 i.e HIGHER than when fully warmed.

I had made sure everything else was fine so since I had never ever checked the pump thermostat I removed it, checked it, it worked. Then I looked for the famous washers. The only ones I found were beneath the entire valve housing. There were 3, 2 very thin and one noticeably thicker. I removed the two thin ones and drove the car for a day or so. I didn't notice any difference so I put them back as Joe advised ! I freed up the sliding valve too although it wasn't really sticky!

This isn't a huge problem but I'd like to get to thye bottom of it as I am the only one who can start the car easily from cold. I feel if my wife was able to start it easily she'd use it and enjoy it more !

Regards,
Ben in Ireland.
'64 230SL 4sp.
'03 CLK Kompressor

[bayleif]

Hello Ben,
Having spent the better part of a year trying to get my warm-up device working correctly I can sympathize, and relate that it may not be any of the obvious or probable causes. So let me ask the less obvious question.
It almost sounds like the warm-up device is not open when the engine is cold. Have you verified that it is? This is usually done by removing the air filter on the warm-up device and verifying that it is "sucking wind". However to do this (on a 280 at least) you need a very thin 19mm wrench only available in limited quantities from I don't know where. I could never find one. But I did find that I could hear the sucking wind sound easily using a short piece of garden hose. I could also verify that my warm-up device was open by pinching the short hose that goes from the device to the ridged pipe connected to the manifold. When cold, the engine slows down, but when warm there is no difference.
If you find that the device does not seem to be open or open enough when cold, I would ask the next not so obvious question. Are you sure that all of the parts are correct? I understand that the thermostat in the 230 is different and a lot more expensive then in the 280. I don't know what the differences are or how having the wrong one could effect things (or even if its possible to have a 280 thermostat fit in a 230 housing) But I do know from experience that sometimes the wrong part finds its way into our cars. Then we can drive ourselves nuts by replacing what we think may be not working with the same wrong part.


Chuck Bartlett
1969 Signal Red 4 Speed

[hands_aus]

Hey Ben,
Did you do the "Linkage Off Test" of Joe Alexander both COLD and HOT?
I reckon that test would reveal your adjustments to be perfect when HOT but needing more air when COLD.
This would indicate that the air valve is not fully open.
I remember reading on the Yahoo site ages ago that the Inj Pump Thermostats often get "lazy" as they get older, meaning that they fully expand when Hot but don't fully retract when Cold.
I did the test on my car and this seems to be the situation.
There are two different types of thermostats for the inj pumps. The early 230sl had a different type to the later 230-280 sl. Accordingly there is a huge price difference also.
The later model is cheap and the earlier model is very expensive.
This may be a condition that you will learn to live with.

Joe supplied some pictures of the later style Inj Pump thermostat/air valve housing in this topic

" MOTOR RUNS ONE SECOND ONLY "

I intend to replace my thermostat at about $45.00 AUD.

A question: How do you test your CO level?

Please keep us informed of your progress.

Bob (Brisbane,Australia)
early 250 SL, RHD

[Ben]

Hi guys, I have tried and verified that the warm up device opens and shuts off completely !

I did the linkage test as indicated below and as Joe recently suggested I richened it a couple of clicks and opened the air screw. This seems to have improved thing a fraction !

I will start the car later today and see how it idles, then drive it and see what the idle speed is.

I will report my findings !

Regards,
Ben in Ireland.
'64 230SL 4sp.
'03 CLK Kompressor

[hands_aus]

Hey Ben,
I was having a look at the listings and saw this thread again.

Did you eventually sort out this problem of low idle speed when cold?

I had a similar problem. Recently I had to replace the points because the cam rubbing block had worn which affected the dwell angle, timing and general running.

As soon as I started the car, the cold start revs were sky high, hence further adjustment needed.

You said your points, dwell and timing were spot on but if the points were slightly worn it may have affected the timing and possibly the cold idle speed.

Also when you adjusted the COLD fuel/air mix did you notice any major change in the HOT running exhaust CO level?

Bob (Brisbane,Australia)
early 250 SL, RHD

[jeffc280sl]

I don't know if the 230SL was setup the same as my 1970 280SL but I would also check the low temperature switch.  When colder that 17 dgrees C it should be closed.  When closed the two way valve is energized and atmospheric pressure is supplied to the distributor which causes the idle to increase. You can test it by grounding the lead to this switch. I have looked everywhere online to no avail to find this switch.  Anyone know where to find one?  Mine has failed in the open position so  it fails to advance the idle when cold.

Jeff C.
1970 280SL 4-speed

[Ben]

I havent actually checked the CO settings since but my timing and dwell are still spot on !

The cold idle is still not noticibly different to whenit hot, possibly 50RPM but since the adjustement the car starts within 5 seconds hot or cold so I am happy to leave it 'till I ahve time !

Regards,
Ben in Ireland.
'64 230SL 4sp.
'03 CLK Kompressor

[hands_aus]

Thanks Ben

I agree, you should leave it alone if you are happy with the way it is running.



Bob (Brisbane,Australia)
early 250 SL, RHD