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steamboatsykes 02-19-2012 08:47 PM

91 300E M103 - Starting Issues
My wife's 300E has had random starting issues since we purchased the car over a year ago.

Mostly when cold, and it has the feel of lack of fuel. Sometimes after starting the idle can be rough until accelerator pumped, then it runs smooth.

I am about to get it evaluated but would appreciate any ideas and feedback.

dkveuro 02-20-2012 02:05 AM

Check following:

Distributor Cap.


EHA on side of Fuel Distributor for leaking.

EHA should be adjusted per Mercedes Factory
Service procedure.


300E Idle Mix ok, but when revved goes off the scale to rich. - Forums


sptt 02-20-2012 02:45 AM

Don't mess with the EHA valve. Do the dist cap and rotor first. Then, plugs (only copper, non-resistor)and spark plug wires (if not fairly new already). The EHA valve is probably ok. It's also a pretty expensive part ( like $350.00) and the adjustment is very easy to screw up and not be able to get back to starting point (I ended up buying a new one and it wasn't the issue...ouch). Report back after you do the above.

dkveuro 02-20-2012 06:35 PM


Originally Posted by sptt (Post 2887707)
Don't mess with the EHA valve.............................................

AU Contraire MON Ami....if the EHA is leaking, it needs replacing....period. If the c/o % is very low after setting ratio/on-off values to 45 to 50 % then the EHA ratio needs adjusting as per my link above.

If ever you adjust the Allen screw in back of the EHA, then very careful not to lose the original setting as the Allen is quiet loose and easy to turn.

The EHA is everything to smooth engine running, starting, acceleration. ...providing upper to lower pressure is correct.

Cap and rotor are usual suspects, I agree.


steamboatsykes 02-20-2012 09:56 PM

Thanks, I will start with the cap & rotor and move on from there.

whunter 02-20-2012 10:34 PM

The random nature makes me suspect a failing:

Crankshaft Sensor, Rear
MB# 002 153 92 28


Overload Protection Relay
MB# 201 540 37 45


E.H.A. Valve (Electro-Hydraulic Actuator)
MB# 000 070 39 62

Mercedes-Benz Driveability
Evaluating Electronic Engine Controls
by Steve Brotherton, Import Specialist
Published in: ImportCar, February 2001
PeachPartsWiki: Mercedes-Benz Driveability


JamesDean 02-21-2012 06:22 AM

I had some cold starting issues however they were semi-consistent. I bought a fuel pressure tester ($75-90) and verified my system pressure, lower pressure chambers, etc and found they were at spec.

I found my lambda tower was out of adjustment. It was running very rich (low % numbers) I readjusted it to 45-50% at idle.

It worked like a charm no more starting, stalling, and restarting or needing to push the gas down to keep it running.

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