C240 won't start
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Joined: Nov 2013
Posts: 14
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From: PA
2001 W203, 1997 W210
C240 won't start
M 2001 C240 decided not to start last week. The car was cranking just fine, but there was no fuel pressure.
I checked the fuel pump relay and it works.
Fuse #4 in the trunk looks good.
The fuel pump was not turning on with the key in the "on" position, so I ordered a new fuel pump and installed it. The car ran fine for a few days although the fuel gauge showed 1/2 with a full tank. 2 days later it died again. Fuel pump not turning on again.
I put in a new unit (fuel pump and fuel sending unit) today and its still not starting. the fuel gauge is now stuck on empty as well.
I checked the wiring to the sending unit and it seems to be showing voltage for a split second when I switch the ignition to "on" but then it disappears.
Fuel pump is working when hooked up to a battery.
Running out of ideas.
Greg
I checked the fuel pump relay and it works.
Fuse #4 in the trunk looks good.
The fuel pump was not turning on with the key in the "on" position, so I ordered a new fuel pump and installed it. The car ran fine for a few days although the fuel gauge showed 1/2 with a full tank. 2 days later it died again. Fuel pump not turning on again.
I put in a new unit (fuel pump and fuel sending unit) today and its still not starting. the fuel gauge is now stuck on empty as well.
I checked the wiring to the sending unit and it seems to be showing voltage for a split second when I switch the ignition to "on" but then it disappears.
Fuel pump is working when hooked up to a battery.
Running out of ideas.
Greg
Thread Starter
Newbie
Joined: Nov 2013
Posts: 14
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From: PA
2001 W203, 1997 W210
Thread Starter
Newbie
Joined: Nov 2013
Posts: 14
Likes: 1
From: PA
2001 W203, 1997 W210
Both #4 and #53 are good. The fuel pump relay is working as well when tested with a spare battery.
Unfortunately, my fuse diagram doesn't number relays, so I'm not sure where #87 is.
Would a faulty crank position sensor shut off the fuel supply?
Edit: Circuit 87 relay is in bay K if I'm not mistaken, and it functions properly.
Unfortunately, my fuse diagram doesn't number relays, so I'm not sure where #87 is.
Would a faulty crank position sensor shut off the fuel supply?
Edit: Circuit 87 relay is in bay K if I'm not mistaken, and it functions properly.
Last edited by ChiroW203; Aug 30, 2017 at 07:51 PM.
Thread Starter
Newbie
Joined: Nov 2013
Posts: 14
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From: PA
2001 W203, 1997 W210
Well, I found the problem. The Sam unit in the trunk was actually melted in the back where the wires attach. Something caused the plug to get hot and created a short. I replaced the unit and it started right up. The only issue left is that the gas gauge still shows empty. 
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Joined: Jul 2012
Posts: 68
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c240
Well, I found the problem. The Sam unit in the trunk was actually melted in the back where the wires attach. Something caused the plug to get hot and created a short. I replaced the unit and it started right up. The only issue left is that the gas gauge still shows empty.
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From: Boston, MA
'14 ML350, '13 C220 CDI, '07 C280, '98 ML320
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Joined: Nov 2013
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From: PA
2001 W203, 1997 W210
Unfortunately I have not kept the old pump assembly.
What worries me is that the fuel pump relay is still getting nice and warm when the car is running. Are they normally pretty warm after a drive?
What worries me is that the fuel pump relay is still getting nice and warm when the car is running. Are they normally pretty warm after a drive?
MBWorld Fanatic!
Joined: Mar 2004
Posts: 1,175
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From: Boston, MA
'14 ML350, '13 C220 CDI, '07 C280, '98 ML320
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Joined: Nov 2013
Posts: 14
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From: PA
2001 W203, 1997 W210
My next question is do I have to hunt down an early production unit and install that, or can the computer be reprogrammed to play nicely with the new one?
When I spoke to the dealer, they said they only carry the new style pumps, so they must make them work in the early 2001 production models somehow...
When I spoke to the dealer, they said they only carry the new style pumps, so they must make them work in the early 2001 production models somehow...
