1983 500sl---seems To Be Missing And Stumped - PeachParts Mercedes-Benz Forum

1983500SL · #1 03-27-2006, 11:44 PM

Seems To Be Missing Badly...engine Is Jumping...strong Smell...wires Are In Correct Location On D-cap...dist Is In Correct Position....

Tested Vaccum And Is Good

I've Replaced:
Plugs, Wires, Capand Rotor...geting Strong Spark From All Plugs..

Could A Clogged Fuel Line On The Injector Cause The Car To Miss And Jump Around So Much At Idle....

Seems To Bogg Down At Initial Pressing Of Pedal But Kicks In And Gets Better But Still Rough.

Please suggest a solution!!!

Richard Wooldridge · #2 03-28-2006, 12:00 AM

It might be running too lean at idle, one thing you could do to check it is to remove the air cleaner top cover, and VERY SLIGHTLY press down on the air plate, say 1/16th to 1/8th of an inch, and see if the idle smooths out. If it does, it is running too lean. If it is, it might be possible to adjust the idle with the idle adjust screw, just to the rear of the air plate - 3mm hex wrench, if memory serves, turn ccw to richen, but only 1/8 turn at a time. If it won't richen with the idle adjust screw you most likely have a defective warm up regulator, a squarish looking aluminum unit just in front of the air cleaner close to the upper radiator hose. It has two smallish metal fuel lines on the top of it as well as a connector.

dkveuro · #3 03-28-2006, 12:16 AM

Quote:

Originally Posted by Richard Wooldridge

.............................................It might be running too rich at idle, one thing you could do to check it is to remove the air cleaner top cover, and VERY SLIGHTLY press down on the air plate, say 1/16th to 1/8th of an inch, and see if the idle smooths out. If it does, it is running too rich.................................................

Richard...doesn't down make it richer...it's a down draft air flap, yes ?
I use a magnet to pull it up on the center nut....

Backfire will sometimes cause flap to change position.
Rich is usually control pressure problem although CPR usually fails lean.

See if cold start injector ( Blue Bosch style connector) is spraying or constantly powered up.

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Strife · #4 03-28-2006, 12:35 AM

Stupid question, but there is no chance that the dist is out of phase (was it removed entirely)? In other words, is the rotor lined up at the line on the distributor AND #1 piston is at TDC AND the timing marks on the balancer is at 0?

I've sworn up and down that I did everything right, slept on it, looked the next day, and found the problem immediately. Take a break, and recheck the wires.

(not applicable in your situation):
Really old ignition wires often don't survive a plug and cap change (happened to me, car ran WORSE after plugs and cap, looked like a fireworks show running the engine in the dark, ran much better after wires were replaced).

Richard Wooldridge · #5 03-28-2006, 01:06 AM

Hi DKVEURO,
If the warm-up compensator is allowing too much control pressure on the top of the timing piston the piston will go down further than it should, allowing the mixture to be too lean. Pressing down on the air plate counter-acts the pressure the warm-up compensator is giving the top of the timing piston by providing a pressure against the bottom of the timing piston.
Keep in mind that at idle, the throttle is closed and virtually NO air is getting into the engine via the throttle. The idle air circuit provides idle air and idle speed control by modulating the air quantity via the idle speed air distributor. So what we are controlling here is the idle FUEL quantity by slightly pushing down on the air plate. When the air plate goes down the timing piston goes up because of the pivot point in the middle of the arm.
This test is an easy way to check out the warm-up compensator. They usually fail by allowing too little pressure at the top of the timing piston.
Hope this explanation clarifies the issue for you!

dkveuro · #6 03-28-2006, 08:45 AM

Sorry to contradict Richard.....The flap moves in response to air flow....futher it moves , the more fuel is delivered.
The air metering flap is connected to the delivery piston by a balance arm and a small adjusting screw sets the basic. Pushing down on metering flap, the fuel is increased.

CPR fails in over lean condition...increases the control pressure on the delivery piston and with this extra pressure system will need more air flow for same movement of air metering flap. ( Wider throttle opening.)

All air entering the engine is known as 'contolled air' or 'metered air'.
...idle volume is also 'metered air' and idle speed is set by restriction of idle control valve, but is still monitored by the metering flap.......any other air is known as 'false air'....or 'unmetered air'......an air leak.

So, if you push down on the metering flap ...on a down draft meter, it richens up the air/fuel ratio.
Now, on an updraft types, such as VW uses, pushing down means your leaning it out.

.

Richard Wooldridge · #7 03-28-2006, 09:32 AM

Hi again DKVEURO,
I edited my reply, see if it is right now... Sorry, it was late last night on first reply. I think we both agree that when the timing piston goes up the mixture goes rich, and pushing down on the air flap makes it go up because of the pivot point in the middle of the arm. When the piston is down the fuel slits are almost closed, when up almost open. So you were correct on your earlier post in that if pushing down on the air flap makes it run better it was running too lean. Sorry for the confusion! Still a warm-up compensator problem if pushing down on the air flap makes it run better and adjusting the idle set point doesn't make a difference.

1983500SL · #8 03-28-2006, 06:01 PM

I Took Off The Aircleaner, Started The Car And Pressed Down Ever So Slightly On The Intake Plunger Doo Hicky Thing...

The Idle Went Up But The Extreme Shaking Was Gone And It Was Smooth....

If I push down too much is sounds like its gasping for air and startes to die...

So...now

When I Adjust The Richness A Bit By Turning The Bolt , Will Then The Same Thing Happen And The Idle Will Go Up. And if so...

Will I Then Will Have To Adjust The Distributor So The Idle Will Go Down Or Will The Richness Change And The Idle Will Remain Good.......

1983500SL · #9 03-28-2006, 07:39 PM

Ok ........

YOU GUYS ROCK!!!!!!!!!!!

ALL IS GREAT AND WE ARE IN BUSINESS!!!!!!!!

THANKS SOOOOO MUCH!!!!!!!

dkveuro · #10 03-28-2006, 10:35 PM

Turn the 3mm adjusting screw for c/o with the idle valve disconnected.....do this disconnecting BEFORE you run the engine. You'll blow the controller if you connect/disconnect with ignition on.

With motor fully warmed...turn the c/o adjustment clockwise 1/8th of a turn and allow the motor to stabilize..... do this again until smoothest idle achieved.
Not sure on yours, but early cars had an air idle adjustment screw to the right of the thermostat housing...yellowish plastic nut headed screw with a screwdriver slot in it.....turn it clockwise to lower idle speed.

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