W202 Cold start problem
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Joined: Jan 2010
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1999 c280
W202 Cold start problem
Just recently my 1999 C280 has been hard to start cold. It cranks fast, but sometimes doesn't fire until the second crank period (following the time-out of the first crank period).
I changed plugs (it has almost 100,000 miles on it), and mechanic friend suggests it may be the ambient temperature sensor at fault: if it is malfunctioning the engine computer does not sent a cold-start enrichment signal to the fuel delivery system, as he says.
Can anyone confirm this and, if it seems to be the case, tell me (my mechanic) where to find the sensor and test it?
New observation. I now note that if I turn on the ignition, i.e., so all the dashboard lights come on, and wait (long enough to fasten my seat belt) and then turn the key to 'start,' it starts without trouble. This suggests that fuel delivery is faulty on immediate cold start but that leaving the key on (and presumably starting up the fuel pump) allows for fuel pressure to rise to starting level and give no trouble. Any comments? Suggested remedies?
I changed plugs (it has almost 100,000 miles on it), and mechanic friend suggests it may be the ambient temperature sensor at fault: if it is malfunctioning the engine computer does not sent a cold-start enrichment signal to the fuel delivery system, as he says.
Can anyone confirm this and, if it seems to be the case, tell me (my mechanic) where to find the sensor and test it?
New observation. I now note that if I turn on the ignition, i.e., so all the dashboard lights come on, and wait (long enough to fasten my seat belt) and then turn the key to 'start,' it starts without trouble. This suggests that fuel delivery is faulty on immediate cold start but that leaving the key on (and presumably starting up the fuel pump) allows for fuel pressure to rise to starting level and give no trouble. Any comments? Suggested remedies?
Last edited by dickinmd; Jan 16, 2010 at 09:29 AM. Reason: New observation
Member
Joined: Jan 2010
Posts: 131
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2006 ml350
Start with the basics. The new observation suggests a potential fuel restriction. Replace the fuel filter 1st. If no improvement, then potential fuel pump issue or fuel pressure regulator issue.
he cold start sensor should not be affected by the wait time while you are buckling up, but fuel pressure can.
he cold start sensor should not be affected by the wait time while you are buckling up, but fuel pressure can.
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Joined: Mar 2009
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2000 c230 Kompressor
Glad this is solved, but just wanted to mention what i do with my car. First off, even if it's a hot day out, i always drive my car like a grandma till it warms up (on the first drive of the day). Then if it's an especially cold day, i'll let it run in neutral for a minute before I go, this way the oil and such has time to thin out and circulate better. Be nice to your car, and it'll usually be nice to you back... though cars can be like people, some are nice and some are a-holes 
