280SL W113 : Air Fuel Mixture - Mercedes-Benz Forum

 
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post #1 of 7 (permalink) Old 12-03-2015, 08:06 AM Thread Starter
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280SL W113 : Air Fuel Mixture

Hello,

I finally got my car to run, so far:

I have installed brand new injectors (all 6)

New Spark Plugs

Tested the WRW - seems to work, pulling no air from the filter at the WRD once it is hot.

Cold Injector is not leaking and air tight

Checked all gaskets, no air leaks.

Car starts right up cold and hot condition, and runs smooth, however, when I accelerate the engine from idle, it blows out black smoke (overly rich). I can also smell it.

Is this normal for this engine or do I have some other problem?

Thank you.

R107
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post #2 of 7 (permalink) Old 12-03-2015, 07:12 PM
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Well if it's running well, the last thing you want to touch is the pump ( timing, regulating linkages are correct) you will probably need to adjust the fuel injection pump using a CO meter.(on ebay for less than $200) Make sure the engine is off when you adjust the screw or you will strip the threads. Something below 5% like 3-5%, I think, more knowlegable minds will chime in. Even at that percentage you will still probablely smell gas. (and I like it).
Will
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post #3 of 7 (permalink) Old 12-04-2015, 09:34 AM Thread Starter
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Originally Posted by Baybear View Post
Well if it's running well, the last thing you want to touch is the pump ( timing, regulating linkages are correct) you will probably need to adjust the fuel injection pump using a CO meter.(on ebay for less than $200) Make sure the engine is off when you adjust the screw or you will strip the threads. Something below 5% like 3-5%, I think, more knowlegable minds will chime in. Even at that percentage you will still probablely smell gas. (and I like it).
Will
Great, thanks.

But as far as I understand, the adjustment screw will only affect mixture at idle, is this correct?

I read somewhere that there is a way to check for "richness" by disconnecting the linkages at the throttle body and then opening the butterfly, the engine rpm should not increase by more than 50 rpm.

This is correct?

R107
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post #4 of 7 (permalink) Old 12-04-2015, 10:19 AM
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That is correct, that has only effect for idling and few more rpm's ...

Have you adjusted the linkages between the throttle and FIP ( by using a centrepoint or degree-messurements ?? )

Aditional : the linkage may not be pushing or pulling !!!
Best is you unhook the linkages first. Then use the "centrepoint" to get the right angle and hook all the linkages on without pulling/pushing.
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post #5 of 7 (permalink) Old 12-05-2015, 01:07 AM Thread Starter
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Originally Posted by paul-NL View Post
That is correct, that has only effect for idling and few more rpm's ...

Have you adjusted the linkages between the throttle and FIP ( by using a centrepoint or degree-messurements ?? )

Aditional : the linkage may not be pushing or pulling !!!
Best is you unhook the linkages first. Then use the "centrepoint" to get the right angle and hook all the linkages on without pulling/pushing.
Hello,

the engine accelerates very well and very strong - just a "black puff" of smoke when I "rev" it up.

I do not notice any play between the different linkages, could you explain what you mean by "centerpoint"? A picture would be great

Thank you

R107
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post #6 of 7 (permalink) Old 12-05-2015, 08:13 AM Thread Starter
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Ok - did the followings tests today:

1. Disconnected the linkage at the throttle body, and slowly opened the butterfly - engine stalled and turned off (just went up 50/100 rpm) - CHECK OK

2. I disconnected the linkage at the injection pump - and verified it is at the fully closed position - CHECK OK

3. Removed the WRD air filter (after the engine was fully warmed up) - and put my finger to check for vacuum, CHECK NOT OK. Even after the engine was very hot, it was still pulling air from the WRD.

This means the thermostat is not pushing down the plunger all the way - and at the same time not pressing on the internals of the injection pump to "lean out" upon hot engine condition.

The entire WRD is very simple, so the only part that can go wrong is the thermostat.

Any other thoughts?

Thank you

R107
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post #7 of 7 (permalink) Old 12-12-2015, 09:53 AM
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Yes, that is indicative of a failing thermostat that's not closing the air slide, and not pushing far enough on the lever in the pump.

The other thing you can check is for play in the throttle linkage. With the engine off, open the throttle with the cross bar and look closely at the ball ends at the throttle body and the pump. It may be that they are worn or slightly mis-adjusted. In such a case, the pump lever can move before the throttle plate, supplying some extra fuel and puff of back smoke.

Chuck Taylor
Falls Church VA
1998 SL500
1959 220S
1970 280SL
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