87 300E starting problems
 

Hey guys,
I have a 1987 300E. I can go out in the morning and she starts right up. But after the engine reaches operating temp. and i stop to say run in the store for coffee when I return I have to hold the gas pedal to the floor for 3-8 seconds to get her to start. when she is running she idles smooth and behaves as it should. It actually drives and runs as well as my e320. yet she just won't start right up. I have replaced plugs,wires,distributor,and rotor. cleaned the fuel system and she still will not start when stopping around town running errands. I have taken it to several shops and they seem to not have an answer, yet they want to all tell me that it could be the fuel distributor and that it would be less expensive to just buy another car. I am very fond of this car as it was the first mercedes I ever owned and it has done me well for the last 299000 miles. I have always thought that the fuel dist. would cause more problems than just not starting right up. Any information as to anything else I can do would be greatly appreciated.

What grade fuel are you using, reg, mid grade or premium?
Are you using the CORRECT plugs for the car, or something else? Should be using just the normal Bosch "Super" plugs, non-resistor plugs. The platinum tipped or split-fire or other fancy plugs don't work as well as the regular ol copper core Bosch plugs.
Also you could pull the plugs to check for deposits, possibly could be valve stem seals, or at 300,000 miles could need valve guides.
Gilly

I am running bosch super and only use premium fuel. I have checked the plugs and they look really good. I had the valves worked over about 60000 miles ago. Like I said the car runs fine once cranked. It is just so hard to start after stopping to run errands. Could it possibly be the injectors need replacing?

It could be alot of things. The ideas I gave were my first thoughts. On the fuel side the fuel distributor could be checked, or it could be the EHA. Ultimately, at startup the mixture is determined by the coolant temp sensor, that could be checked too. On the ignition, it sounds like you have all the bases covered, except maybe the coil, usually they will fail at high temps, but a possiblity. I'd try getting things tested on it, just trying to repair it by throwing parts at it can get expensive, especially on weird problems like this. "Repair" isn't like doing maintenance where you are replacing parts because their time or mileage is up.
Gilly

A bad accumulator or a minor fuel leak on the supply side will cause this problem, although it will usually cause hard cold starts as well.

Requires a system pressure check to diagnose.

I've also seen a hard hot start problem caused by bad idle control valve hoses -- instant stall when releasing the key from the start position. Check for vacuum leaks -- an overlean condition will cause hard starts but will run OK once the computer is controlling fuel mixuture.

Peter