Pagoda SL Group
W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: jsandoval on January 03, 2009, 03:37:15
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I have a 1969 280SL 4 Speed. It starts fine but the idle goes up and down from about 500 to 900 rpm. When you just touch the throttle it sounds like it's going to die. When you drive it sputters a little before taking off. It runs fine going down the road. I have changed the plugs, wire, cap, rotor, points, condenser and changed fuel filter to no avail. Any suggestion?
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Hello,
Sounds like you may have a basic fuel mixture problem. You can verify this by a simple test.
With the engine running disconnect the linkage rod at the injection pump, between the injection pump and the "cross over rod" . If you move only the cross over rod linkage going to the intake venturi, and the engine decreases in rpms then the engine may be running too lean. If the engine stays the same or only increases 100 rpms or less, the mixture should be good. If the engine increases over 100 rpms the mixture is to rich.
Verify the information by next just moving the injection pump lever. If you move the lever down and the engine increases in rpms the mixture is too lean. When the mixture is correct, the engine will stay at the same rpm or increase less than 100 rpms. Also when the mixture is correct the engine idle will not increase when the injection pump linkage is moved .
This "linkage mixture analysis" can be conducted at idle and any other throttle position.
Be aware that this will tell you the mixture condition but may not tell the cause of a problem but may verify that you have a mixture problem.
Some posible causes of fuel mixture problems are linkage wear, linkage set-up, incorrect fuel pressure or volume, plugged air or fuel filters, leaking or mal functioning starting devices or warm up devices, mal adjusted or faulty fuel injection pump or injectors, a simple mxture adjustment or a combination of some of the above. Start with the simple test first and hopefully a simple adjustment will do the trick. Get back with us with your findings! The "Linkage Tour" is a good place to start.
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I was told to it could be the injection thermostat so I replaced it and it seems to be better but not perfect. Also I have noticed in the technical section that my car seems to be different in that the cold start valve is not hooked up and I am looking to see if wires are around somewhere and I also have 2 solenoids on the back of the injection pump and neither one of those is hooked up. Is this suppose to be like this or do I need to hunt around for the wire connections? My car is a 1969 280SL 4 Speed Euro could this be why?
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The lower solenoid is the fuel shut-off solenoid. These are frequently disconnect without much consequence. The upper solenoid is a engine starting aid and should be connected. The injection pump starting solenoid (top solenoid) is activated when the starter is engaged.
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Should I hookup the cold start valve on the intake manifold also? I think I found the wires for that. I still can't find the wires for the solenoid on the injection pump but still looking. When I get more time I will go through the linkage just as you suggested. Thank you for your help by the way.
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Yes, I think you should. Check it works properly also. There is a ton of info on the site about how to take it apart and check it. It's a very simple process indeed.
JH
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I am sorry the CSV is connected. It's the idle throttle switch that is not connected. Should it be connected? I found to 2 wires that have been cut and taped up. One is solid red the other is red with a green stripe. Could these be them?