Mercedes: 83 Mercedes 380sec starting problem, fuel pump relay, fuel contamination

Question
Hi, so I was driving to work one morning when the car started to run rough. I pulled over (less than two miles away from cold start at my house), turned it off and tried restarting it and the car would not start.

It cranks, has good spark and fuel pressure (now has a new fuel pump and filter). Car will run for a few seconds (putt-putt-putt) after a few cranks with the gas floored (starts to smell though), but doesn't seem to be able to maintain an idle at all.

I have replaced the fuel pump relay and over voltage relay, fuel lines look good, the press-fit lines fuel lines that go from the fuel tank and to the hard pipe look ok, but haven't been replaced.

I can hear the cold start valve snapping away. Could this be an idle control unit? Could it have jumped the timing chain? Crank position sensor bad, bad connection? The plunger on the throttle body / fuel distributor has good motion and reasonable resistance.  

On a side note, there were some surging issues upon acceleration (intermittent).

I'm at a loss.  

I thought the cold start injector is clogged, because of the louder sound it was making (i didn't notice it before, but haven't been driving the car long)

Tomorrow I plan to stick a fresh battery in and see if it will fire with starting fluid. I will probably also pull the CS injector and test it to see if its at LEAST dribbiling. I'm hoping i can swap the idle control unit out with a mid 80's 560sel that a friend has near by. Or raid a parts yard first. But I don't want to just throw money at it. I have an old bmw that I learned THAT lesson on.

Thanks for any/all help.

Andy

Answer
Andy,
Two issues come to mind. Low voltage or fuel contamination. If the alternator is not providing sufficient amperage to keep the electronic ignition operating properly and to fill the battery charged then these symptoms you describe appear. Or if you have contamination in the fuel it can also cause fuel ignition problems.
When were the fuel filter changed last?
I think you idea about a new battery is also a good idea. Make sure that all fitting are cleaned. Also make sure that the fuses involved are also cleaned or replaced with copper tip.
Corrosion at relay socket points can also create these type of electrical problems.
Good Luck
Robert