420sel problem

[kwken]

Hi All, I am having a problem with my 1919 420sel. I bought it new and have kept it garaged. It has 27000 miles. The problem I am having is that it will miss about 3 times and then run pretty rough for a couple of minutes. After that it runs like brand new. I am retired and have little better to do then to stress about this tipe of stuff. I have followed the Mercedes book as much as possible with the tool's I have. Replaced fuel filter. Checked fuel pressure to fuel distributor and that was all good. Did all test's on various componet's. I replaced a temp sensor. That turned out to be the wrong one. The one by the cold start valve tested good for resistance. I cleaned out the idle air control valve. Checked the cold start valve and it sprayed good. I can start the car normally some times. That made me think the problem was electrical because it was intermitant. I was looking at the power to the cold start valve and got a large variance to the valve. The book say's to disconnect the green wire from the ignition control on the left front fender and turn the starter. I guessed that was so the motor wouldn't start. I don't have a green wire to mine. I disconnected the coil wire and spun the car over. The cold start valve got only about 1 volt. My question is would disconnecting the coil wire be a proper substitution for the missing green wire? Sorry for the length of this post but I wanted everyone to know what I have tried. Thanks in advance. Ken

[Palolo]

Originally Posted by kwken

Hi All, I am having a problem with my 1919 420sel

This might get moved to the "Antique" Benz section...

Have you checked your coil, vacuum lines and distributor/cap/rotor?

I'm curious what it is... I'd think you might be having a vacuum-related ignition issue since it is intermittent and clears up, and will wait to see what the later model experts chime in with.

[kwken]

Hi Palolo, Thank you for your quick response. I haven't looked into the other issues because except for the first couple of minutes it run's perfect. At this point I may have to go in that direction. I built a little test light to probe the onboard diagnostic and it said that the temp sensor was bad. That was why I changed the wrong sensor. The right one sure seems to test good. Thanks again. Ken

[meltedpanda]

is this a cold and hot start issue or only hot?
easy to check CSV, take it out , put it in something to catch fuel , turn ignition on , ( not to start) should spray ( if cold engine ) and then shut down and not drip

[brandlj]

On my 1985 380se that my Dad drives in Phoenix, when he first starts the car it catches and then stumbles and blows some black smoke for about 10 seconds and then settles down into a smooth idle. He was told by 2 independent shops in the Phoenix area that it is the ethanol in today's gasoline that is doing it. These older CIS injected Benz's do not like Ethanol in their gasoline. The Phoenix area has upwards of 15-17% Ethanol in their gas. When he drives over here in Louisiana, we can fill the tank with Conoco gasoline, that advertises no ethanol and the problem goes away.
I am not sure if this is the problem you are talking about with your car or not.

[kwken]

Hi All, Thanks for the idea's. The problem is only on cold start. After I park for about thirty minutes it stumbles on start and runs rough for a few minutes. I found a fuel pump relay and sent off for it. In the meantime in my ongoing effort to start with the most complicated solution and work towards the obvious I bought some cleaner and cleaned the air flow plate. That made a big differance on the starting. I had previously cleaned the idle air sensor and that seemed to help. The car has been sitting so much that I am not suprised that the fuel had clogged stuff up. I put a can of cleaner in the tank today when I filled up today so I will see what happen's. I will let you know. I use premium gas in the car and I am not sure about ethenol around here. Thanks a lot for your responses. Ken