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Registered
2004 ML500 Inspiration Edition
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91 Posts
Discussion Starter #1
2004 ML500
127,775 miles

Yesterday morning I drove to a store and all was well. Come back to the car in the parking lot 15 minutes later and try to start it, cranks but no start. I tried several times and no dice. A friendly bystander suggested I disconnect the battery to reset the security system. I was skeptical because the red light would flash as usual when I put the key in ignition but I thought I didn't have much to lose. While the battery was disconnected I swapped in replacement fuses for the fuel pump and ignition system even though they looked fine. A few minutes pass, I reconnect the battery and it starts right up which honestly surprised me. I got home and thought it must have been one of the fuses but I checked both and they tested fine. I know in hindsight I should have been more scientific, i.e. disconnect and reconnect the battery, try to start it, then replace one fuse at a time and try to start it to isolate the issue. But at the time I was pretty sure it wouldn't start and would need to be towed, and I just really wanted to get out of that parking lot.:)

Other info:
  • NO "start error" message displayed.
  • NO codes found with iCarsoft i980. But I've only owned that thing for a few months so I plan to reread the instructions and check again to make sure I didn't miss anything.
  • Truck has started without issue twice since then but hasn't left the driveway. I was just testing it.
  • I think I could hear the fuel pump come on when key was in second position but not certain. There was definitely some kind of noise from something...
  • In late November I had an incident where it stalled at a red light for no apparent reason. I shifted it into park and it immediately started back up without incident. Has not occurred since then. I think this might be related???

Before anyone tells me to use the search bar, I already did and bookmarked some relevant info. Considering the previous random stall and then yesterday's problem adventure, I'm thinking maybe the CPS is on the fritz. Unfortunately I wasn't paying attention to whether the rev counter needle moved or not when it wouldn't start yesterday. I don't usually like throwing parts at a problem but a new Bosch CPS is 25 dollars from FCP so I'll probably order one regardless. But at this point I'm wondering how disconnecting and reconnecting the battery "fixed" this, or was that most likely coincidental? I can't understand how it would crank but not start if the battery was the issue. I'll probably go buy a fuel pressure gauge and spark tester to keep in the car and hopefully do some diagnosing when and if the issue reemerges. Open to ideas. Thanks.
 

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Registered
Dallas, Texas
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8,585 Posts
Have you scanned it right after no start event? Crank sensors fail when hot. If you have waited same time it took to fiddle around disconnecting battery it would have started.
 

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Premium Member
2000 ML55 sold? 2013 ML500,? 2017 C43 AMG,1929 Victory 6 roadster, 1927 Dodge 4 sedan, 1929 Dodge
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5,485 Posts
Sounds suspiciously like your crank angle sensor.
Unlikely it had anything to do with your battery disconnect.
 

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Registered
Joined
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329 Posts
2004 ML500
127,775 miles

Yesterday morning I drove to a store and all was well. Come back to the car in the parking lot 15 minutes later and try to start it, cranks but no start. I tried several times and no dice. A friendly bystander suggested I disconnect the battery to reset the security system. I was skeptical because the red light would flash as usual when I put the key in ignition but I thought I didn't have much to lose. While the battery was disconnected I swapped in replacement fuses for the fuel pump and ignition system even though they looked fine. A few minutes pass, I reconnect the battery and it starts right up which honestly surprised me. I got home and thought it must have been one of the fuses but I checked both and they tested fine. I know in hindsight I should have been more scientific, i.e. disconnect and reconnect the battery, try to start it, then replace one fuse at a time and try to start it to isolate the issue. But at the time I was pretty sure it wouldn't start and would need to be towed, and I just really wanted to get out of that parking lot.:)

Other info:
  • NO "start error" message displayed.
  • NO codes found with iCarsoft i980. But I've only owned that thing for a few months so I plan to reread the instructions and check again to make sure I didn't miss anything.
  • Truck has started without issue twice since then but hasn't left the driveway. I was just testing it.
  • I think I could hear the fuel pump come on when key was in second position but not certain. There was definitely some kind of noise from something...
  • In late November I had an incident where it stalled at a red light for no apparent reason. I shifted it into park and it immediately started back up without incident. Has not occurred since then. I think this might be related???

Before anyone tells me to use the search bar, I already did and bookmarked some relevant info. Considering the previous random stall and then yesterday's problem adventure, I'm thinking maybe the CPS is on the fritz. Unfortunately I wasn't paying attention to whether the rev counter needle moved or not when it wouldn't start yesterday. I don't usually like throwing parts at a problem but a new Bosch CPS is 25 dollars from FCP so I'll probably order one regardless. But at this point I'm wondering how disconnecting and reconnecting the battery "fixed" this, or was that most likely coincidental? I can't understand how it would crank but not start if the battery was the issue. I'll probably go buy a fuel pressure gauge and spark tester to keep in the car and hopefully do some diagnosing when and if the issue reemerges. Open to ideas. Thanks.
typical crank angle sensor .when this happen you just open hood wait 20 or so minutes to cool it down and it goes until next time .the way you diagnose this when it happen , you connect your OBD2 tester , crank engine and see if in live data you see a rpm count . you know what is ironic about this , my daughter drive a KIA sedona 10 yr old , and still get recall notice , the last one about the brake light switch , this keep you from moving gear shift , sound familiar . before that about some relays .you wont see MB doing that .it is sad that the crank angle sensor keeps going and the brake light switch .they had plenty of time to come out with something durable .
 

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2004 ML500 Inspiration Edition
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91 Posts
Discussion Starter #5
Have you scanned it right after no start event? Crank sensors fail when hot. If you have waited same time it took to fiddle around disconnecting battery it would have started.
Yes scanned in the shopping center parking lot, scanner always stays in the driver's door cubby.

Part ordered, should arrive Thursday. Will update...

Thanks guys.
 

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'00 ML 430
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262 Posts
Agree on CPS as potential cause. Once you shut down the engine the temperature of the engine case spikes for the next 10 minutes before it cools down to below operating temperature. That causes the CPS to not work. After everything cools down it starts working again.

When my CPS was on its way out it made for several extremely embarrassing moments at the gas station: Stop to get gas, fill up, get into the car and then being unable to drive off for the next 10 minutes (with a line behind me....). After waiting for 10 - 15 minutes it would fire up just fine. And of course no codes were thrown because the ECU simply doesn't see crankshaft movements during cranking when the sensor it out.
 

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Registered
2004 ML500 Inspiration Edition
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91 Posts
Discussion Starter #7
* Update *

The new sensor arrived a few days ago and today was the warmest day in the forecast so I tackled the job. It's a pretty straightforward procedure and I didn't anticipate any issues as long as I didn't drop and lose the bolt. I got the electrical connector unplugged and bolt removed from the old sensor with minimal hassle. The sensor itself wouldn't budge at first but after a lot of pulling and wiggling I finally got it out. Old sensor was Bosch part # 0261210171 manufactured week 28 of 2003. New sensor is Bosch part # 0261210170 which is apparently an updated version of 0261210171. I put the new sensor in and it was a tight fit but that seemed fine because the old one was tight when it was removed. So I got it in place but discovered it was slightly rotated so the bolt wasn't lining up straight. I tried to rotate the sensor slightly and... it won't move at all. I can't rotate it and I can't pull it back out, it's too damn tight🤬. After several hours of messing around with it (while being careful not ruin the threads by cross-threading the bolt) I gave up. So the current situation is the new CPS is installed but not bolted in. Everything else was reassembled and I did start the car for a minute so at least it works.

What I need to know is what would be the consequences of driving around with the CPS tightly in place but not bolted in? If it finally comes loose would the engine just stall or would there be other issues or risk of damage?
 

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Registered
'00 ML 430
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262 Posts
If the sensor backs out the engine would just shut down as if you had pulled the key. Worst-case it comes out all the way and gets mangled when it falls onto the hot exhaust. But chances are it'll stay in there with a gap that is too large to generate the signals for the ECU.
 

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Registered
Dallas, Texas
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8,585 Posts
* Update *



What I need to know is what would be the consequences of driving around with the CPS tightly in place but not bolted in? If it finally comes loose would the engine just stall or would there be other issues or risk of damage?
Only thing that matters is installation depth or gap between sensor tip and reluctor wheel of the flywheel. Once gap becomes too large engine will stall with code P0335.

On the technical note. If something is difficult to remove and then put back don't just ram it up the poop shoot.

 

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2001 ML320 LHD
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739 Posts
How old is your battery?
 

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2004 ML500 Inspiration Edition
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91 Posts
Discussion Starter #11
Mfg. September 2016.
 

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Registered
Joined
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329 Posts
2004 ML500
127,775 miles

Yesterday morning I drove to a store and all was well. Come back to the car in the parking lot 15 minutes later and try to start it, cranks but no start. I tried several times and no dice. A friendly bystander suggested I disconnect the battery to reset the security system. I was skeptical because the red light would flash as usual when I put the key in ignition but I thought I didn't have much to lose. While the battery was disconnected I swapped in replacement fuses for the fuel pump and ignition system even though they looked fine. A few minutes pass, I reconnect the battery and it starts right up which honestly surprised me. I got home and thought it must have been one of the fuses but I checked both and they tested fine. I know in hindsight I should have been more scientific, i.e. disconnect and reconnect the battery, try to start it, then replace one fuse at a time and try to start it to isolate the issue. But at the time I was pretty sure it wouldn't start and would need to be towed, and I just really wanted to get out of that parking lot.:)

Other info:
  • NO "start error" message displayed.
  • NO codes found with iCarsoft i980. But I've only owned that thing for a few months so I plan to reread the instructions and check again to make sure I didn't miss anything.
  • Truck has started without issue twice since then but hasn't left the driveway. I was just testing it.
  • I think I could hear the fuel pump come on when key was in second position but not certain. There was definitely some kind of noise from something...
  • In late November I had an incident where it stalled at a red light for no apparent reason. I shifted it into park and it immediately started back up without incident. Has not occurred since then. I think this might be related???

Before anyone tells me to use the search bar, I already did and bookmarked some relevant info. Considering the previous random stall and then yesterday's problem adventure, I'm thinking maybe the CPS is on the fritz. Unfortunately I wasn't paying attention to whether the rev counter needle moved or not when it wouldn't start yesterday. I don't usually like throwing parts at a problem but a new Bosch CPS is 25 dollars from FCP so I'll probably order one regardless. But at this point I'm wondering how disconnecting and reconnecting the battery "fixed" this, or was that most likely coincidental? I can't understand how it would crank but not start if the battery was the issue. I'll probably go buy a fuel pressure gauge and spark tester to keep in the car and hopefully do some diagnosing when and if the issue reemerges. Open to ideas. Thanks.
typical crank angle sensor , it fail when hot [ junk part ] to diagnose when problem is there , with generic OBD2 tester in live data , when you crank you see no rpm .
 
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