exessive air to the collector

[ralbani]

Hi,
the engine remains too accelerated (at or above 1000 rpm), in spite of closing entirely the screw that chockes the air. There is no excessive air coming from the power brake and the butterfly valve near the rubber hose of the air collector is well registered. I hope I have expressed myself clearly..
Where could the excessive air come from?
Please help,
Roberto, Rome

[jeffc280sl]

Hello Roberto,

There is an air filter canister is located on the fuel injection pump.  A valve controls the flow of air through this filter into the injection pump.  The valve is open when the car is cold.  When open air is added to fuel to assist warmup of the engine by increasing rpms.  As the engine warms this valve should close and rpms should drop to a normal level.  Your valve may be stuck in the open position.  The air filter can be removed with a thin 17mm? wrench.  When the car is warm no air should be sucked into the opening.  Place a piece of paper near the opening to see if air is sucked into the when the engine is warm. If so you made need a new fuel injector pump thermostat.  Cost is around $25 USD for the part.  Search for information on this part.

Jeff C.
1970 280SL 4-speed

[jeffc280sl]

Look at the post titled "Cold Start Warm Start"  for a good explanation and pics.

Jeff C.
1970 280SL 4-speed

[hands_aus]

22mm spanner needed to remove that air filter

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[ralbani]

Hello Jeff,
do you know of a website that sells online the thermostat you mention, in case i need it? I haven't been able to find it in the usual websites I buy from in Europe.
Another subject entirely. Do you know of any way to relieve the suffering from heat driving the Pagoda during the summer?....
Thanks a lot for your suggestions
R.

quote:Originally posted by jeffc280sl

Hello Roberto,

There is an air filter canister is located on the fuel injection pump.  A valve controls the flow of air through this filter into the injection pump.  The valve is open when the car is cold.  When open air is added to fuel to assist warmup of the engine by increasing rpms.  As the engine warms this valve should close and rpms should drop to a normal level.  Your valve may be stuck in the open position.  The air filter can be removed with a thin 17mm? wrench.  When the car is warm no air should be sucked into the opening.  Place a piece of paper near the opening to see if air is sucked into the when the engine is warm. If so you made need a new fuel injector pump thermostat.  Cost is around $25 USD for the part.  Search for information on this part.

Jeff C.
1970 280SL 4-speed

[ralbani]

Hi Jeff (and everybody else online),
sorry about pestering you with my questions. As you can see I am a "junior" and very little experienced. I have indeed checked the fuel injection air filter. It works well, in the sense that there is no air being sucked in when the engine is warm.
I am wandering if the excessive rpms in the idle phase might have to do with the fact that, when I last filled up, I added a cleaning agent to the fuel...
Any idea anybody?
Thanks again,
Roberto from Rome

quote:Originally posted by jeffc280sl

Hello Roberto,

There is an air filter canister is located on the fuel injection pump.  A valve controls the flow of air through this filter into the injection pump.  The valve is open when the car is cold.  When open air is added to fuel to assist warmup of the engine by increasing rpms.  As the engine warms this valve should close and rpms should drop to a normal level.  Your valve may be stuck in the open position.  The air filter can be removed with a thin 17mm? wrench.  When the car is warm no air should be sucked into the opening.  Place a piece of paper near the opening to see if air is sucked into the when the engine is warm. If so you made need a new fuel injector pump thermostat.  Cost is around $25 USD for the part.  Search for information on this part.

Jeff C.
1970 280SL 4-speed

[A Dalton]

High idle RPM can easily be caused by improper ignition timing OR no vac retard at idle.
 I would check that first with a strobe light.. these cars [except for early .042] use a vac retard ignition at idle and if that is not working [ bad vac line to dist or bad vac control ], the results will be a high idle.
 If you pull the vac line at dist with engine running and there is no RPM increase, that will indicate the retard funtion is not operating..
 I would also check all link adjustments..

 and tell us the model and trans type ..

[ralbani]

Hello,
My car is a 1966 230 sl. Thanks for the suggestion, I will chek on the vac retard and let you know the results.
Roberto

quote:Originally posted by A Dalton

High idle RPM can easily be caused by improper ignition timing OR no vac retard at idle.
 I would check that first with a strobe light.. these cars [except for early .042] use a vac retard ignition at idle and if that is not working [ bad vac line to dist or bad vac control ], the results will be a high idle.
 If you pull the vac line at dist with engine running and there is no RPM increase, that will indicate the retard funtion is not operating..
 I would also check all link adjustments..

 and tell us the model and trans type ..

[Benz Dr.]

I think you might have a vacuum leak. If the cold start thermostat is working properly and you have the throttle valve completely cosed at idle this would be a likely problem.If you can turn the air idle screw all the way in without stalling the engine extra air is coming from somewhere or the engine would die.
 Ignition timing affects idle speed but has no real influence over the idle air screw. Extra air will increase idle far more than maximum timing if there's enough fuel present which in the case of most 113 cars is a very real possibility.
Try pouring a small amount of water along the manifold gasket. If the engine slows down or runs roughly there's your leak. If test the hose going to the brake booster with a vacuum pump. The other vacuum lines affect ignition timing but are not a big enough leak source to increase idle all that much.
 Test all pipes, hoses and areas where a vacuum leak might cause problems. This could be several areas and not just one. After you have all the leaks repasired you will need to reset the idle mixture at the pump and probably the ignition timing. Once you can stall the engine ( or really slow it down ) then you have no vacuum leaks.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[rwmastel]

quote:Originally posted by Benz Dr.

I think you might have a vacuum leak. If the cold start thermostat is working properly and you have the throttle valve completely cosed at idle this would be a likely problem.

Roberto,
Did you check that the throttle body is properly adjusted to be closed all the way, but not binding?  This is very important for many reasons as excessive air can pass through.  Some inexperienced mechanics use this adjustment as an idle adjustment, which is bad practice.

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[Cees Klumper]

Hi Rodd - I suggested this as well, but when re-reading Roberto's original post ("the butterfly valve near the rubber hose of the air collector is well registered") it seems he has covered that base ...

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic

[ted280sl]

Jeff,
  It seems many of the members have given you solid advice on your air leak but, no one has mentioned your heat problem. I had excessive heat and there were two area that eliminated my problem. My first problem was with my exhaust pipe. It was not properly fitted so an exhaust pipe was hitting the frame transmitting noise and heat. Once I replaced and re-positioned the rubber exhaust "O" rings this problem went away. Some of our cars are missing the heat shield between the exhaust pipes and the floor. The second problem I had was that when I turned off my heater I still had heat coming through the heating system. It seems that my heater core shut off valve was frozen. After I repaired the shut off valve my car has been much cooler. In fact it is so cool that I have not used my air conditioner for a few years.