CL203 C180K M271 long cranking time before start
10-08-2020, 12:27 PM
#1
CL203 C180K M271 long cranking time before start
Hi guys,
recently I started having a really strange problem with my car (M271 engine) - the thing is that it cranks a really really long time before it starts and right after it starts the revs go crazy going from 400 to 1200 and this continues for like 4-5 seconds and then disappears (the rev go to normal 800 rpm). After this the car runs fine, no CEL, I can't tell any difference in the behaviour of the car as when it is working "normally". The problem appears when the engine is either cold or hot. One things I noticed is that if I stop and turn off the engine and then try to start it right away - I have no problems with the long cranks and hard start, but if I wait, for example 20 seconds, then the car struggles to start and the long cranking appears again.
so far what I've done on the car (somehow related to the problem IMO):
- replaced starter
- checked the voltage of the battery (12.7V, so no problem from it)
- changed oil, cabin, air and fuel filter
- changed spark plugs
assumptions what might be causing the problem IMO:
- bad crankshaft position sensor
- dirty MAF ? (a bit unlikely as I would suspect engine hesitations during driving and that's not the case)
- dirty throttle body (a bit unlikely as I would assume that the car would have rough idle during neutral and that's not the case...)
- probably problem with some fuel hoses (bad o-rings or something) that introduces air to the system and thus - a hard start
- bad pre-cat o2 sensor ?
Any suggestions ?
Thanks!
recently I started having a really strange problem with my car (M271 engine) - the thing is that it cranks a really really long time before it starts and right after it starts the revs go crazy going from 400 to 1200 and this continues for like 4-5 seconds and then disappears (the rev go to normal 800 rpm). After this the car runs fine, no CEL, I can't tell any difference in the behaviour of the car as when it is working "normally". The problem appears when the engine is either cold or hot. One things I noticed is that if I stop and turn off the engine and then try to start it right away - I have no problems with the long cranks and hard start, but if I wait, for example 20 seconds, then the car struggles to start and the long cranking appears again.
so far what I've done on the car (somehow related to the problem IMO):
- replaced starter
- checked the voltage of the battery (12.7V, so no problem from it)
- changed oil, cabin, air and fuel filter
- changed spark plugs
assumptions what might be causing the problem IMO:
- bad crankshaft position sensor
- dirty MAF ? (a bit unlikely as I would suspect engine hesitations during driving and that's not the case)
- dirty throttle body (a bit unlikely as I would assume that the car would have rough idle during neutral and that's not the case...)
- probably problem with some fuel hoses (bad o-rings or something) that introduces air to the system and thus - a hard start
- bad pre-cat o2 sensor ?
Any suggestions ?
Thanks!
Last edited by ststav01; 10-08-2020 at 12:29 PM.
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gobiz (10-08-2020)
10-08-2020, 08:32 PM
#2
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Join Date: Mar 2005
Location: Kuala Lumpur, Malaysia
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2002 C32 AMG
Hi guys,
recently I started having a really strange problem with my car (M271 engine) - the thing is that it cranks a really really long time before it starts and right after it starts the revs go crazy going from 400 to 1200 and this continues for like 4-5 seconds and then disappears (the rev go to normal 800 rpm). After this the car runs fine, no CEL, I can't tell any difference in the behaviour of the car as when it is working "normally". The problem appears when the engine is either cold or hot. One things I noticed is that if I stop and turn off the engine and then try to start it right away - I have no problems with the long cranks and hard start, but if I wait, for example 20 seconds, then the car struggles to start and the long cranking appears again.
so far what I've done on the car (somehow related to the problem IMO):
- replaced starter
- checked the voltage of the battery (12.7V, so no problem from it)
- changed oil, cabin, air and fuel filter
- changed spark plugs
assumptions what might be causing the problem IMO:
- bad crankshaft position sensor
- dirty MAF ? (a bit unlikely as I would suspect engine hesitations during driving and that's not the case)
- dirty throttle body (a bit unlikely as I would assume that the car would have rough idle during neutral and that's not the case...)
- probably problem with some fuel hoses (bad o-rings or something) that introduces air to the system and thus - a hard start
- bad pre-cat o2 sensor ?
Any suggestions ?
Thanks!
recently I started having a really strange problem with my car (M271 engine) - the thing is that it cranks a really really long time before it starts and right after it starts the revs go crazy going from 400 to 1200 and this continues for like 4-5 seconds and then disappears (the rev go to normal 800 rpm). After this the car runs fine, no CEL, I can't tell any difference in the behaviour of the car as when it is working "normally". The problem appears when the engine is either cold or hot. One things I noticed is that if I stop and turn off the engine and then try to start it right away - I have no problems with the long cranks and hard start, but if I wait, for example 20 seconds, then the car struggles to start and the long cranking appears again.
so far what I've done on the car (somehow related to the problem IMO):
- replaced starter
- checked the voltage of the battery (12.7V, so no problem from it)
- changed oil, cabin, air and fuel filter
- changed spark plugs
assumptions what might be causing the problem IMO:
- bad crankshaft position sensor
- dirty MAF ? (a bit unlikely as I would suspect engine hesitations during driving and that's not the case)
- dirty throttle body (a bit unlikely as I would assume that the car would have rough idle during neutral and that's not the case...)
- probably problem with some fuel hoses (bad o-rings or something) that introduces air to the system and thus - a hard start
- bad pre-cat o2 sensor ?
Any suggestions ?
Thanks!
Funnily enough (and thankfully) it always starts though and drives absolutely fine, no misfiring or rough idling.
The previous owner has changed everything on the spark side and I've recently replaced the fuel filter.
I have a hunch it's actually the fuel pump, apparently it has an inbuilt valve that wears down as it gets older, so doesn't pressurize the fuel system enough to start first thing. I'm planning to replace the fuel pump assembly soon and will update.
10-09-2020, 06:21 AM
#3
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Join Date: Jan 2007
Location: Malaysia
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W203 (2007), W120 (1962)
If the fuel pump is good, you should hear a hissing sound for a second or two to indicate the fuel system is priming when you move the key to position 2, especially in the morning if you left the car overnight. No?
