Faulty engine

[Gazoo]

Hello, this is a 280 sl 1969 automatic Made in Germany.
After having many problems with fuel , car was extremely rich  I changed all the inyectors ,rebuilt electric pump, put new sparks ,change distribuitor cap,change contact points and ajust time to 30 ,also put a new coil and did what  the linkage tour says.
Now the car is not rich and sparks look perfect.
But sometimes it runs smooth and nice but suddenly it starts to fail and Also when i change from P to 4 it dies,this happens sometimes
Any ideas?
I feel is am electric issue as the engine sometimes is running perfect and a small fail ie felt.
As I said sometimes runs perfect and can go from P to 4 without any problem
Thank you

[Shvegel]

Speaking as a lifelong mechanic You are at the point where you need to find someone who really knows old Mercedes cars.  There are so many little things like making sure the throttle plate stop is adjusted properly or making sure the throttle switch is adjusted properly.  Even things like the type of spark plug wires can effect how it runs.  If all else fails someone at the local Mercedes dealer knows an old retired mechanic who was a magician in his day.

[Cees Klumper]

Could be that your constant speed solenoid is on its last leg.

[Gazoo]

Thank you
In Mexico is hard to find a Mercedes Mechanic.
The problem is not always when changing from P to 4 or R sometimes i drive perfect and with no reason starts to fault

[Pawel66]

Gazoo, I am not a mechanic, so be careful with what I say.

Gear selection form P to 4 or R and engine stall would suggest your Constant Speed Solenoid is not adjusted properly. You just perhaps need to increase revs a bit when it is engaged - if it is engaged. You need to watch it as gear is selected - does it push the throttle? If yes, perhaps it does it not enough. If not, either it is not connected or connection is faulty or it is shot.

But: this Constant Speed Solenoid adjustment is the last step in tuning. You can do it quickly so that it does not stall, but you would need to determine why it gets faulty while driving.

And this I have no idea what a simple reason can be. I would start from simplest and, having checked ignition timing (assuming vlave adjustment is ok), put in a new set of spark plugs, check the spark, drive a bit and take a look at plugs. My shot form the hip would be you will find them rich. But this is just my supposition, not really relevant.

Maybe someone more experienced will chime in.

[Cees Klumper]

Thanks Pawel. What I was suggesting is that, when the CCS is on its way out, it will sometimes work, and sometimes not be strong enough to push the linkage out. So it can be adjusted properly but, due to it getting weaker and weaker, start failing to actually produce the desired effect. That is what happened to me. After replacing with a new one, everything was fine again. The point being that it starts failing intermittently and it is not an issue of adjustment. I thought of that since that is what Gazoo is experiencing: an intermittent problem.

[Gazoo]

Thank you every one,the faulty engine is not only when changing from P to 4
Some times with no reason starts to fault when driving it ,and. after a while comes black to normal
When driving it it doesnt stop but it feels like it
My feeling is electric but I just change sparks ,cables 1kohm ,contacts,condensator,
The distribuitor is aluminum
And checked the alternator wich charges normaly
I Think is not a problem of the css unless you say so , i believe this would only be a problem for the change from idle to drive ?
Any suggestions?

[Pawel66]

The point being that it starts failing intermittently and it is not an issue of adjustment. I thought of that since that is what Gazoo is experiencing: an intermittent problem.

Cees, yes, thank you. I am not eperienced enough here as those intermittent fails are difficult to diagnose. I can only say I had this kind of intermittent issue twice:
- when I had very rich mixture
- when I had fuel delivery issue (that was combined with hot start issues)

But I also know of cases of really simple things, such as ground nut or wire nut on coil were not tight...

[Cees Klumper]

Based on your symptoms Gazoo, I agree it's unlikely to be the CSS. It could be many different things but if it were my car I would start with all the electricals. Maybe hook up a test light to the ignition to see whether, when it starts to fail, it is due to no spark. Check all the wiring, for loose connections etc. Replace whatever you did not replace yet on the ignition. But if it not an 'on/off' condition then fuel supply could be the issue.

[Pawel66]

On electrical I could add
- lose main coil-distributor lead (may be touching somewhere)
- shot coil
- distribiutor cap not sitting tight
- battery terminal not tight
and probably many other.
Once you check electricals, as Cees is suggesting, and it brings no resolution so that you move to fuel, the simplest test of fuel flow is to disconnect the the return fuel hose from the tank and put into a canister. Switch on the ignition, let the fuel pump run: see if you get close to 1 liter in 15 seconds. If you get 0.6 or less - your fuel system is clogged somewhere. sometimes lets furl through, sometimes blocks.