Hello fellow merc heds..

Boog12345

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Jun 11, 2021
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West mids
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E320 coupe
Hello ther..i thought I would join this forum to help me diagnose a problem with my 320 coupe..95plate..I've hadctge car nearly 2 yrs and never missed a beat apart from when it didnt start the once..I phone the rac and after a few checks it was a dodgy fuse..well after 3 days on a car park ir cane back home..but last week I fired it up..started as it usually does and drove around 3 miles..then boom..it just cut out..i thought it was that fuse again..and after numerous fuse twiglin it didnt start.. I was on a duel carriage way and the que was building up nicely.. but managed to get it off the rd..and phoned the rac..he checked the fuses and said they was all good..checked the relay fuse but the euc's .not blown..and looked for a spark and didnt find one 😣 so he towed it back to me drive and it remains ther..he did say he thought it could be a crank sensor..I brought that..ther was a broken piece off the top of it..and the metal piece in the middle was slightly dented..so I brought a new one.. me mate fitted it in..and says it will start now..but still didnt..just lookin on the forum and I'll change the battery today in the fob and try the emoberliser reset..but after that..what else would be good to check?..its had a really damp wet winter with lots ov condensation build up..and quite a lot of water in the doot wells..all dry now but might be part of the problem 🤷‍♂️hope to get it running again soon..
 
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Boog12345

Boog12345

New Member
Joined
Jun 11, 2021
Messages
15
Location
West mids
Car
E320 coupe
Yes it has been..I've checked all the wires for any cracks or breaks but didnt find any..thanks is for the reply William 🙂👍
 
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Boog12345

Boog12345

New Member
Joined
Jun 11, 2021
Messages
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Location
West mids
Car
E320 coupe
:) thank you ,..im still non of the wiser what the fault is,,,would it not spark if one of the coil packs was broke?...because ive only check 2 sparks plugs,.& they didnt spark,.
 
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Boog12345

Boog12345

New Member
Joined
Jun 11, 2021
Messages
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Location
West mids
Car
E320 coupe
Well I'm thinking of buying the diagnostic kit to try and see what the problem is...could anyone recommend one for the job..I've saw this one on ebay recommended for the w124..any help would be appreciated..thanks in advance 🙂👍
 

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jotter22

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Gravesend,Kent.
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CLK 320 Avantgarde convertible
I did have similar symptoms which did end up being the crank position sensor but alas i am no mechanic so probably better to get a better opinion than mine. 👍
By the way the grammar police will have a field day with your post! ;)

Tony.
 
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Boog12345

Boog12345

New Member
Joined
Jun 11, 2021
Messages
15
Location
West mids
Car
E320 coupe
I did have similar symptoms which did end up being the crank position sensor but alas i am no mechanic so probably better to get a better opinion than mine. 👍
By the way the grammar police will have a field day with your post! ;)

Tony.
lol,,thanks for the reply tony,,ill blame this phone for the spelling mistakes :) but my mate says that if theres a little bit of dirt etc on in the hole then it won't read or crank,,he suggested refitting it & hoover out the hole this time to get rid of any unwanted particles... 👍
 
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Boog12345

Boog12345

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West mids
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E320 coupe
well ive hoovered out the crank sensor hole and refiited it,,still dont want to fire,..how deep is the little hole what goes into the block?..ive stuck a cotton bud tied to a stick down it but still isnt long anough,,ill make something longer incase its blocked at the end,,is ther a window ther or will ther be a hole stright into the block?...i highly dought its that now,. were o look next,.🤔
 

Bellow

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C2500 350, 450
:) thank you ,..im still non of the wiser what the fault is,,,would it not spark if one of the coil packs was broke?...because ive only check 2 sparks plugs,.& they didnt spark,.
I'm not familiar with the engine in your car but generally a coil pack will serve two plugs so if no spark on one there wont be on the other either - assuming the two plugs you checked are served by the same coil. It won't hurt to try other plugs but I'd expect it to at least 'offer' to start if only one coil pack went bad and it's unlikely they all failed together. I'm more inclined to think it's somewhere upstream of the coil plugs that the problem is and possibly heat related. Meantimes, check all the engine earths are good. They can bring a motor down.
well ive hoovered out the crank sensor hole and refiited it,,still dont want to fire,..how deep is the little hole what goes into the block?..ive stuck a cotton bud tied to a stick down it but still isnt long anough,,ill make something longer incase its blocked at the end,,is ther a window ther or will ther be a hole stright into the block?...i highly dought its that now,. were o look next,.🤔
Compare old and new. If the part that inserts is the same length on each one it should be fine.
It's end sits next to a toothed reluctor wheel and the 'air gap' has to be correct. A bad CPS shouldn't stop the engine cranking though. Check the earths.
 
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Boog12345

Boog12345

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West mids
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E320 coupe
I'm not familiar with the engine in your car but generally a coil pack will serve two plugs so if no spark on one there wont be on the other either - assuming the two plugs you checked are served by the same coil. It won't hurt to try other plugs but I'd expect it to at least 'offer' to start if only one coil pack went bad and it's unlikely they all failed together. I'm more inclined to think it's somewhere upstream of the coil plugs that the problem is and possibly heat related. Meantimes, check all the engine earths are good. They can bring a motor down.

Compare old and new. If the part that inserts is the same length on each one it should be fine.
It's end sits next to a toothed reluctor wheel and the 'air gap' has to be correct. A bad CPS shouldn't stop the engine cranking though. Check the earths.
hi ther & thanks for the reply,..its cranking as in turning over but no firing,.yes the new one is the same size as the old one,.& it fits into the hole without any issues,,but theres a little hole going into the block i was just wondering if theres anything in the little hole,..well the day it stopped working it strated up fine,,drove around 3 miles then all the lights on the dash come on & it hasn't started since,..were are the earths points i should check?..ive saw a few but ther might be some hiding,..would be good to see wwere all the earths points am & ill check them all,,thanks aagin for the reply :)
 

Bellow

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C2500 350, 450
hi ther & thanks for the reply,..its cranking as in turning over but no firing,.yes the new one is the same size as the old one,.& it fits into the hole without any issues,,but theres a little hole going into the block i was just wondering if theres anything in the little hole,..well the day it stopped working it strated up fine,,drove around 3 miles then all the lights on the dash come on & it hasn't started since,.
Crank PS should be fine - but possibly there is a camshaft position sensor also and almost certainly required for starting.
Symttom of a failed crankPS is usually engine dying when warm and idling and will usually restart after a few minutes of cooling down. Cam sensor needed for starting but not sure if needed for actual running.
.were are the earths points i should check?..ive saw a few but ther might be some hiding,..would be good to see wwere all the earths points am & ill check them all,,thanks aagin for the reply :)
Braided steel cables and/or sheathed in black plastic is what you are looking for. There will probably be a few in different thicknesses. Some will disappear into the wiring loom, some (the heavier ones) will bolt straight to the chassis. Have a good look around and you'll find them. They are invariably bolted to bare metal on the engine, frequently tagged onto a stud holding something with an additional nut. There's usually a heavy one in the vicinity of the starter motor.
 
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Boog12345

Boog12345

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Jun 11, 2021
Messages
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West mids
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E320 coupe
Crank PS should be fine - but possibly there is a camshaft position sensor also and almost certainly required for starting.
Symttom of a failed crankPS is usually engine dying when warm and idling and will usually restart after a few minutes of cooling down. Cam sensor needed for starting but not sure if needed for actual running.

Braided steel cables and/or sheathed in black plastic is what you are looking for. There will probably be a few in different thicknesses. Some will disappear into the wiring loom, some (the heavier ones) will bolt straight to the chassis. Have a good look around and you'll find them. They are invariably bolted to bare metal on the engine, frequently tagged onto a stud holding something with an additional nut. There's usually a heavy one in the vicinity of the starter motor.
thank you for the reply,..im thnking its not the cps now,..i have checked the cam sensor as its easy to get to but all looks good,..how would i check the voltage of this?..what vots should it be reading,,i will mearsure the cam & crank sensor to elliminate there working correctly,..& then ill check for the earths on the engine & in the car,..there was wires in the passenger side which was full off water from the heavy rain,,think ity was coming from the loom into the car,,mybe its done some damage in ther,.ill take the covering off & see if its in ther,..ill keep you posted,,thanka again for your help :)
 
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Boog12345

Boog12345

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E320 coupe
i would like to addd that the day of the break down the rpm needle was bouncing around upto say 4 rpm when i was turning it over,..is that cps related?
 

Bellow

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C2500 350, 450
thank you for the reply,..im thnking its not the cps now,..i have checked the cam sensor as its easy to get to but all looks good,..how would i check the voltage of this?..what vots should it be reading,,
There's probably a resistance measurement in Ohms in a manual somewhere - if you can find it. If not, compare it to the new crank one - chances are they are similar.
Usually they have three wires. Ones an earth - check for continuity back to a known earth. One will be a live in run (ie, ign on) 12V supply - check for that on the wire. The other wire is the output. It's across its and the live 12V's terminals that the resistance value can be measured. It will have some value between open circuit and short circuit. If there's no reading there, check between the output and the earth tag. Do a dummy run on the old crank sensor first. If it wasn't goosed it should show you what to expect and where.
i will mearsure the cam & crank sensor to elliminate there working correctly,..& then ill check for the earths on the engine & in the car,
You're looking for clean and firm (no slackness) in the earth connections. Any doubts, detach, clean and re-bolt tightly. Pay particular attention to any earths in the vicinity of ignition components. Another check is to use jumper leads between engine and chassis. If you get spark like that but not when its detached - definitely missing an earth. Probably one as per previous sentence. A robust earth is required for cranking - or a world of pain awaits!

..there was wires in the passenger side which was full off water from the heavy rain,,think ity was coming from the loom into the car,,mybe its done some damage in ther,.ill take the covering off & see if its in ther,..ill keep you posted,,thanka again for your help :)
I don't know the car well enough to know if there are electrics there that could create a problem. Water and electrics are usually a bad mix though - not least for corroding terminals.
Just systematically work through things until you find what stopped it running.
 

Bellow

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i would like to addd that the day of the break down the rpm needle was bouncing around upto say 4 rpm when i was turning it over,..is that cps related?
Hard to say. I'd go more with ignition.
Typically, the crank position sensor is the trigger for the spark and the cam position sensor is used during starting to ascertain which stroke a cylinder is on (the crank sensor can't tell compression stroke from exhaust stroke - only that the piston is close to TDC) so it fires the correct plug - but double ended coils don't need this. Once it's running the crank sensor is usually enough as the system doesn't lose the synch the cam sensor gave it.
The cam sensor though is sometimes required to keep the engine running if the fuel injection is sequential. As far as I know, some do, some don't.
Generally, the cam sensor is needed for timing but not necessarily spark generation.
 

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