2001 ML320 Cranks but doesn't start after battery change -not key related-
02-18-2011, 01:01 AM
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2001 ML320 Cranks but doesn't start after battery change -not key related-
I'm doing what I can to fix a retired friends' 2001 ML320 for them since they can't afford to have Mercedes diagnose it. It cranks and cranks but doesn't catch at all.
The back story:
It used to run fine but the battery started failing. They asked me where the best place to get a battery for it was and I immediately told them to call Mercedes and have them come out and replace the battery, which they did. According to them, this is what happened with the tech:
The Mercedes tech came out, removed the old battery, halfway put the new battery in and made sure it would start, which it did. The tech then finished installing the battery and suddenly it wouldn't start anymore. It would crank over just fine without any errors, but never catch, sputter, or anything. Just turn over like it wasn't getting fuel or spark. The tech told them the DAS (Drive Authorizing System) just failed and there wasn't much he could do, and left. (They're nice, old retired folks that aren't big on confrontation).
So they told me what happened and I started researching the DAS and other possible causes. So far this is what I've ruled out:
1. DAS is fine. I've tried both of their keys and they work without any error on the dash. The little red LED near the radio blinks fine.
2. Fuel pressure is a healthy ~52 psi.
3. I don't have any noid lights, but I have a portable O-scope I hooked up to a few injectors and they appeared to be getting injector pulse.
4. Checked all the fuses and swapped pertinent relays.
I've tried to hook the o-scope up to a few of the coil harnesses, but I can't tell if it's getting a decent ignition pulse. Does anyone have any ideas on what else to check? I've thought about the crank position sensor, but it didn't show any signs of failure before this. Plus, it doesn't run then die... it hasn't started once since the tech replaced the battery. It will crank away for as long as you hold the key in the start position (in fact, it stuck once).
Any help or suggestions would be greatly appreciated. Again, it's an '01 ML320 with about 130k on the clock.
The back story:
It used to run fine but the battery started failing. They asked me where the best place to get a battery for it was and I immediately told them to call Mercedes and have them come out and replace the battery, which they did. According to them, this is what happened with the tech:
The Mercedes tech came out, removed the old battery, halfway put the new battery in and made sure it would start, which it did. The tech then finished installing the battery and suddenly it wouldn't start anymore. It would crank over just fine without any errors, but never catch, sputter, or anything. Just turn over like it wasn't getting fuel or spark. The tech told them the DAS (Drive Authorizing System) just failed and there wasn't much he could do, and left. (They're nice, old retired folks that aren't big on confrontation).
So they told me what happened and I started researching the DAS and other possible causes. So far this is what I've ruled out:
1. DAS is fine. I've tried both of their keys and they work without any error on the dash. The little red LED near the radio blinks fine.
2. Fuel pressure is a healthy ~52 psi.
3. I don't have any noid lights, but I have a portable O-scope I hooked up to a few injectors and they appeared to be getting injector pulse.
4. Checked all the fuses and swapped pertinent relays.
I've tried to hook the o-scope up to a few of the coil harnesses, but I can't tell if it's getting a decent ignition pulse. Does anyone have any ideas on what else to check? I've thought about the crank position sensor, but it didn't show any signs of failure before this. Plus, it doesn't run then die... it hasn't started once since the tech replaced the battery. It will crank away for as long as you hold the key in the start position (in fact, it stuck once).
Any help or suggestions would be greatly appreciated. Again, it's an '01 ML320 with about 130k on the clock.
03-14-2011, 03:06 AM
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ML320
Agree. Try and get the OBD codes scanned, they should start pointing you in the direction. Yes the crank postion sensor can cause this, the car cranks by itself for approx 30 secs with no fire. replacement is easy and affordable
03-17-2011, 10:12 PM
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2003 ml 350
replace the crank sensor . that has happened to my 2003 ml350.the car was running fine and later would not start.finally i got it running but ck light comes on. I tookto mb dealer .the diagnosis was the crank sensor.I have heard that is a common failure.I hope i could help you more
