Hello folks, I need a little help:

I have a 97 E420 with 77,000 miles. A week ago I started to experience troubles starting. At first it would take 2-3 seconds of cranking to get the engine to fire up. The engine does turn over fine though, and it seems there is plenty of power to the starter. Once it was running the engine idles rough, to the point sometimes that it seems like it is going to die but it catches itself and continues running. The hard starting and rough idling occur regardless of whether this is the first start in the morning or after the engine has been operating for 30 minutes. Today it took about 5 seconds of cranking to start. I have tried leaving the igntion key to on for 10 seconds and then cranking to see if the fuel system needed to be charged. This didn't help. My car does run good on the road and shows no hesitation when accelerating, I just see these problems during starting and idling. I have pulled the air-filter housing and cover and looked for any loose electrical connections or vacuum lines. I haven't seen anything that appears out of the ordinary (at least out of the ordinary too me, I am a novice). Can someone point me in a direction at things to check out? Fuel filter, pump, plugs, electrical system... What should I look at first? Any suggestions for additional tests I can perform to help isolate the problems? The check engine light has not come on and I have not seen any other warning lights.

Thanks!

-Chris

I have 1995 E420 with same problem. It had hard starting problem, I took it to the mechanic and he replaced my battery. But the problem didnt go away. I have replaced by distributor caps and rotors, and spark plugs. still the problem doesn't go away. I have also replace my fuel pump check valve after diagonsing the the fuel pressure. The check valve were bad I replaced them it had improved the starting but there are some other factor affecting the starting I am still working on fault. My mechanic said it is normal for the car with this much mileage to start in 4 to 8 secs. If it goes beyond that then there is serious problem. My car also runs smooth after it starts.

Things to check for :

1. Check battery voltage with the car off.
2. Check Fuel pressure with fuel gauage. I will give u test procedure later on. this will tell if any fuel pressure is leaking.
3. also check ur distributor and rotor conditions (watch for traces and broken distributor cap)
4. check ur spark plug wire.

I am researching one more thing that is electronic throttle control. If i find anything i will update you.

good luck.
Kamal

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The 1997 E420 does not have caps/rotors. It uses coil on plug ignition. It should not crank for more than 2-3 seconds before starting. If so, there is a problem. There may be a faulty
engine coolant temp sensor or mass air flow sensor giving you
grief. The fuel pressure should be checked. The regulator was updated on those things. You may have plugged filters.
I would suggest taking it to the dealer to have the adaptation
of the fuel trim and the sensor values examined.
You may have a obvious value that is throwing the whole system off.
That may be smarter than shot-gunning parts at it.
Good luck
DR.D