My SL55 is at the dealers in lots of bits after refusing to start and they seem to be at a dead end after several days of "Diagnosis" so I thought I would defer to the experts...

I went to start it 12 months ago about 2 hours after driving it and all I got was a "click" and "Visit Workshop"

A new MB battery sorted it and it has been perfect till last Thursday.

Drove it to breakfast with my son, parked it and returned after about 30 minutes and had the dreaded "click" from somewhere under the bonnet and "Visit Workshop" message.

Numerous attempts to start it resulted in the same thing happening.

Called Roadside assistance who arrived and tested the starter battery (under the bonnet (hood)) ... 13 volts

Roadside insisted on testing the consumers battery which was a bit low at 11.5 volts.
He wasn't much interested in my suggestion that the little one at the front was the starting battery. Numerous attempts to start it with jumper leads on the consumers battery failed.

The consumers battery (1 year old) tends to gradually lose voltage (doesn't everybodies?) but I usually put it on charge overnight about once each month to sort that out. The delaer blames that on the fact that it is not an MB battery

We tried jumping the start battery and got nothing.

I suggested disconnecting the terminals to the battery and just connecting his battery to the car the engine turned over slowly. Getting a better connection saw it start perfectly

When I stopped the engine it refused to start again...

I am thinking solenoid here.

It refused to start with the car's battery despite it reading 13 volts and eventually started with the car's battery jumped a few attempts later.

He suggested taking it to the dealer.

The dealer has had it since then and, from the service manager's explanation, have spent hours diagnosing things and pulling things to bits, eventually trying to check continuity in various critical wires. They have checked the battery control module amongst other things.The starter has been removed and checked by a local auto electrician who gave it the all clear. It appears that the solenoid is not getting '"a signal"

The next step, on MB Australia's advice is to check the engine computer's connections.

Does anybody here have any insight into the likely solution?

I am still thinking solenoid or the "starter relay" mentioned eleswhere in other threads.

Thanks in advance

Peter
Sydney

 

Have you checked the fuel pump?

 

Also look at the Crank Position Sensor. Very common failure on these cars. Although, the symptoms are a little different than yours, the end result is the car won't start.

It's a cheap, quick Remove/Replace

 

if the motor does not turn over it is not cps or fuel pump

my vote is for lousy wire-to-terminal battery contact or bad ground somewhere. in other words - bad voltage. could be also a bad battery. merc batteries are abused a lot.

remove starting battery. clear terminals. clear "plus" and ground wire "loops" that plug into the battery. recheck and tighten connections to battery. there is a very high draw from the battery on start and if wires are not tight you will get the "click".

if not that check all major grounds. they are shown in sds schematics

speaking of sds - any codes?

just in case- replace battery in remote too...

on battery discharge over time- you should drive your car more often those cars do not like to sit. abc is particularly evil if you dont exercise it on a regular basis

 

I know you said the starter battery read 13V but I have seen batteries do VERY WEIRD things... Exactly like what you describe!

ie:
After sitting for 5 days my SL65 started one cold morning with no issues.... I drove it for 20 minutes turned it off went inside got my cell phone came back and then the FAMOUS CLICK! and nothing else...

We tried jumping with a small jumper and still nothing... Finally got it started with a big battery and I went directly to the dealer who replaced only the Starter Battery. They said it was a common problem...

 

A dead battery can have a surface charge of 13 volts, but when a load is applied, voltage can drop to almost zero. A quick check is to clean your connections, then using a voltmeter, watch the voltage while attemting to crank the engine. If the voltage drops below 12 during this test, replace the battery.

 

This.

 

Thanks for your advice so far.

Sorry not to have not got back sooner but I forgot to hit the instant email notification and for some reason couldn't log onto the site yesterday.

A few days down the track and...

The dealer has replaced the starter relay and had the starter out and bench checked by an auto electrician... all OK

They had another SL 55 in the shop and they tried its starter motor on my car... same problem... click and no go.

The solenoid is only getting 4 volts instead of 12

They are currently searching for wire continuity.

Any ideas please?

Thanks

Peter

 

Thanks for the replies.

It seems that the dealer has identified the problem and, although I haven't got the car back yet it's looking good (apart from the 23 hours labour problem solving!)

Here's the explanation:

We have checked & found no trouble codes. Checked & found reduced power supply at starter motor solenoid. Tested front battery – ok. Removed boot trims & tested rear battery – ok. Tested battery control module – ok. Removed NSF false floor & checked main fuse – ok. Checked battery lead connections under false floor – ok. Swapped starter relay – no better. Removed N/S of exhaust & removed starter motor & sent for bench test – ok. As a precaution, swapped starter motor with known good one – no better. Ran jump wire from battery straight to starter solenoid to give it 12 volts – no better. Followed wiring diagram & checked ALL relevant connections at wiring junctions – ok. Checked all relevant earth points – ok. Tested inputs & outputs from ECU – ok. Removed fuse box under bonnet, removed signal acquisition module (SAM) from fuse box & found corrosion from water present at connection between SAM & fuse box. Cleaned up all corrosion on connectors & reconnected SAM to fuse box – now starting correctly.

Hopefully this is not a common problem and that this post might help someone else in the same shoes.

The source of the corrosion has still not been identified

Peter

 

Bad news, I am afraid...

Perfect for four weeks then it failed to start again.

Same problem... solenoid clicks but engine does not turn over.

After a few attempts it started and gave no problems for one week then it did it again, same resolution.

It sat for two weeks while I was away and started perfectly when I returned for the first week then failed to start in the garage.

I removed the fuse box and cleaned the connections to the signal acquisition module, reassembled it and it started perfectly five times. Put the fuse box cover on, put the tools away, tried to start it and nothing. Checked both batteries: 14.2 on the start battery, 12.8 on the consumers battery. Charged both anyway and it started.

Went shopping, unloaded the boot, tried to start it and nothing. Did the dismantle and clean and spray with contact cleaner, reassembled and it started.

Went to drive to work yesterday... Nothing.

Beginning to get a bit cranky now!

Called the dealer who told me that the corrosion was between the SAM and the fusebox.

Came home from work and pulled it all to bits again and pried the SAM from the fusebox as instructed on the sticker attached.

There were no signs of corrosion but faint signs of scraping.

I sanded all of the terminals with fine sandpaper (the male side only, te female side looked clean and was not cleanable), used contact cleaner and reassembled everything...

Nothing.

Spoke to the dealer today who said to have it towed up there.

When asked what were they going to look for he replied that they would start at the beginning again.

The "Beginning" cost me AUD$2000 although the dealer said they spent $4000 on it so I am a bit reluctant if they haven't got a clue.

The "beginning" also caused me a headache when the car decided to sag at the front while it was at the dealers for the two weeks. It had never happened before and they said that the pump was faulty and was going to cost AUD$7000 + labour to replace.

When I said that I would source the pump myself the car miraculously lifted itself up and hasn't misbehaved since. The genuine benz pump I sourced from the USA for AUD$1100 is sitting in its box in the garage waiting for the day the current one actually fails.

I've attached a few pictures of the fusebox and SAM just in case anyone wanted to know where they were... there's nothing else out there.

Anybody got an idea where I should start looking?

Thanks

Peter

 

Two more photos

Thanks

 

Have you resolved the problem yet