Cold Start Problem with 1987 300E
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Joined: Nov 2004
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Cold Start Problem with 1987 300E
New to me 1987 300E. Runs beautifully when it finally gets going.
Misearable to start when motor is cold.
When cold, I can eventually get it started by repeated cranking attempts
without touching the gas pedal. This morning, it took about 20 times
cranking before the motor caught and continued to run. On the first
crank the motor caught after about 4 seconds, sputtered and died. Over
the next 18 cranks, it would catch and sputter from between not at all
to 10 seconds. Finally, it caught and stumbled and shuddered itself
into a sustained idle at about 500 rpms. It feels like the motor is
missing after it gets going. After I get in and drive it a couple of
seconds, the motor is fine and the idle is smooth.
I have tried to start it up by depressing the gas pedal to various
depths but this seems to only make it worse. Even a single push and release before starting seems to make things worse.
On two occasions over the past couple of days, during cold start
cranking attempts, the motor has caught, revved up to almost 1,000 rpms
and run perfectly. This did not happen on the first cranking attempt
but happened after maybe 5 or 6 attempts. On these occasions, it
feels like the cold start system has kicked in. This is making me think
it could be an intermittent electrical problem rather than fuel
pressure.
I have replaced the plugs with Bosch Super as specified in the owner's
manual gapped to .032" I have filled the tank with premium and added
Techron fuel system cleaner. I checked the fuse on the over voltage relay and it was fine on visual inspection.
Where do I start diagnosing this problem?
Thank you,
Robert
Misearable to start when motor is cold.
When cold, I can eventually get it started by repeated cranking attempts
without touching the gas pedal. This morning, it took about 20 times
cranking before the motor caught and continued to run. On the first
crank the motor caught after about 4 seconds, sputtered and died. Over
the next 18 cranks, it would catch and sputter from between not at all
to 10 seconds. Finally, it caught and stumbled and shuddered itself
into a sustained idle at about 500 rpms. It feels like the motor is
missing after it gets going. After I get in and drive it a couple of
seconds, the motor is fine and the idle is smooth.
I have tried to start it up by depressing the gas pedal to various
depths but this seems to only make it worse. Even a single push and release before starting seems to make things worse.
On two occasions over the past couple of days, during cold start
cranking attempts, the motor has caught, revved up to almost 1,000 rpms
and run perfectly. This did not happen on the first cranking attempt
but happened after maybe 5 or 6 attempts. On these occasions, it
feels like the cold start system has kicked in. This is making me think
it could be an intermittent electrical problem rather than fuel
pressure.
I have replaced the plugs with Bosch Super as specified in the owner's
manual gapped to .032" I have filled the tank with premium and added
Techron fuel system cleaner. I checked the fuse on the over voltage relay and it was fine on visual inspection.
Where do I start diagnosing this problem?
Thank you,
Robert
Super Member
Joined: Jun 2003
Posts: 595
Likes: 0
From: Middlefield, CT
1994 E320
You will want to check the cold start valve. It is screwed into the intake manifold. Remove the valve, hold it over a cup, and start the engine. It should open and fuel will pass. If not, that could be your problem.
