Car won't start after accidentally sparking starter
Thread Starter
Junior Member
Joined: Feb 2016
Posts: 23
Likes: 5
2004 SL500
Car won't start after accidentally sparking starter
Hey there everyone, first time poster after lurking a bit.
I just finished replacing the motor and trans mounts in my E320 and in the process of breaking the bolt loose on top of the passenger mount, the wrench popped off the bolt and caused a couple sparks to fly when it hit the unprotected contacts of the starter/solenoid.
I tried to do some digging about what fuses/relays might be affected, but the info is nebulous at best. When I turn the key to start, there's a click (not from the start) and nothing happens. It seems that a lot of people point towards the K40 module being fried in an event like this, but I can't figure out where to look for it. I've checked in the engine bay fuse box (driver's side firewall) and in the ECU compartment (passenger side firewall) and under the rear seat. I didn't see anything that looks like the pictures, so I must be looking for the wrong thing.
Any information you guys have that could point me in the right direction would be stellar, I'd love to have this thing back on the road sooner than later. I've only had the car a few weeks, so my familiarity with its technical details is still somewhat lacking.
I just finished replacing the motor and trans mounts in my E320 and in the process of breaking the bolt loose on top of the passenger mount, the wrench popped off the bolt and caused a couple sparks to fly when it hit the unprotected contacts of the starter/solenoid.
I tried to do some digging about what fuses/relays might be affected, but the info is nebulous at best. When I turn the key to start, there's a click (not from the start) and nothing happens. It seems that a lot of people point towards the K40 module being fried in an event like this, but I can't figure out where to look for it. I've checked in the engine bay fuse box (driver's side firewall) and in the ECU compartment (passenger side firewall) and under the rear seat. I didn't see anything that looks like the pictures, so I must be looking for the wrong thing.
Any information you guys have that could point me in the right direction would be stellar, I'd love to have this thing back on the road sooner than later. I've only had the car a few weeks, so my familiarity with its technical details is still somewhat lacking.
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Joined: Sep 2013
Posts: 1,185
Likes: 42
'15 T&C & '14 SL63
Sounds like a fuse for sure.
IF it's a fuse, the there should be two, a low amp one for the ignition circuit (which is not blown if you hear the solenoid clicking) and a high amp one for the power before the solenoid.
If you can't find the fuse, use a voltmeter and see if you're getting +12v at the starter. Then check if you're getting +12v at the hot side of the solenoid (that should get +12 w/o activation the start circuit).
IF it's a fuse, the there should be two, a low amp one for the ignition circuit (which is not blown if you hear the solenoid clicking) and a high amp one for the power before the solenoid.
If you can't find the fuse, use a voltmeter and see if you're getting +12v at the starter. Then check if you're getting +12v at the hot side of the solenoid (that should get +12 w/o activation the start circuit).
Thread Starter
Junior Member
Joined: Feb 2016
Posts: 23
Likes: 5
2004 SL500
Sounds like a fuse for sure.
IF it's a fuse, the there should be two, a low amp one for the ignition circuit (which is not blown if you hear the solenoid clicking) and a high amp one for the power before the solenoid.
If you can't find the fuse, use a voltmeter and see if you're getting +12v at the starter. Then check if you're getting +12v at the hot side of the solenoid (that should get +12 w/o activation the start circuit).
IF it's a fuse, the there should be two, a low amp one for the ignition circuit (which is not blown if you hear the solenoid clicking) and a high amp one for the power before the solenoid.
If you can't find the fuse, use a voltmeter and see if you're getting +12v at the starter. Then check if you're getting +12v at the hot side of the solenoid (that should get +12 w/o activation the start circuit).
Thread Starter
Junior Member
Joined: Feb 2016
Posts: 23
Likes: 5
2004 SL500
The plot thickens! It turns out the guy I bought it from had NOT replaced the battery like he said he did, so it appears that in addition to being quite old, the shorting killed a cell. I put it on the battery tester and it would only charge to 70%.
So, new battery and all is well. Almost. Now there are two malfunction codes in regards to the ABS and BAS systems. Guess I have a bit more digging to get it back to 100%, but nowhere near what I thought I was going to have to go through before.
Back to researching!
So, new battery and all is well. Almost. Now there are two malfunction codes in regards to the ABS and BAS systems. Guess I have a bit more digging to get it back to 100%, but nowhere near what I thought I was going to have to go through before.
Back to researching!
Thread Starter
Junior Member
Joined: Feb 2016
Posts: 23
Likes: 5
2004 SL500
Yup! Got it all cleared up after poking around the forums a bit. Idles smooth as glass now and no more thunking when making sharp turns. Both mounts were totally collapsed and the driver's side was in two pieces. Next up is flex discs since the one at the transmission was showing a few small cracks. Thankfully that's a much easier job than the motor mounts, dropping the passenger side midpipe was ridiculous, the engineer who designed that flange angle needs a stern talking to!
