crank no start

chisel

New Member
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Aug 2, 2020
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16
Location
Tunbridge wells uk
Car
300e 1993 w124
Hi all, hope someone can guide me in the right area...
father inlaw has 300e 93 w124 mb
there has been a succession of firing issues with her:
last year she would crank but not fire- finally found a tiny amount of oil/fuel- (dark and oily looking) pooling out of one of the fuel pipes on top of the distributor, it started and ran.
Then had a problem with the distributor cap replaced it- it ran.
then he started going for a run in it, it would heat up and then cut out, after cooling it would start and he got it home, afterwards it stopped running and now just cranks very healthy mind!
i’ve checked the spark plugs all sparking two fuel pumps audible
changed the cps (the original was ok but didn’t really know to trust my test properly)
bought 2nd hand ecu- still same problem
so i’ve got a multimeter with duty cycle. going to probe no. 3 in the 9 pin diagnostic port os of engine but i can’t find anything to help me interpret what i find.
can anyone help or suggest...
many thanks
 

horatio

Active Member
Joined
Apr 11, 2011
Messages
800
Location
herts
Car
CLK, 190E
Are you getting spark from the coil?

Don’t get into guessing at parts. Taking it to a good Indy who know these cars well might be the best bet. It might be something really silly.
 

Gbrowncls55

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Sep 11, 2016
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951
Location
Surrey
Car
CLS55 AMG 06, SL350 06, 996 cab, all current. Gone : E500 W211, 2x M5s and far,far too many 911s
As above its a classic crankshaft positioning sensor diagnosis. about £120 fitted.Every mercedes I have had(6) has had it fail at some time.
 
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chisel

New Member
Joined
Aug 2, 2020
Messages
16
Location
Tunbridge wells uk
Car
300e 1993 w124
Are you getting spark from the coil?

Don’t get into guessing at parts. Taking it to a good Indy who know these cars well might be the best bet. It might be something really silly.
i know what you mean, i don’t want to through parts at it but they were pretty cheap and I was stuck...i’m still stuck but a bit poorer :). Good spark from plugs distributor and coil, is it possible to by pass the ovp to see if it’s at fault?
 

grober

MB Master
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Jun 22, 2003
Messages
28,470
Location
Perth, Scotland
Car
W204 C200CDI Estate
If its a single cam distributor M103 its probably the EZL ignition unit. Classic symptoms--- the unit is heat-sinked to the inner wing with conductive paste which dries out and the unit overheats intermittantly then finally fails completely- lots of posts on here if you search EZL
scrap that if you have a decent spark. :oops:
 
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horatio

Active Member
Joined
Apr 11, 2011
Messages
800
Location
herts
Car
CLK, 190E
So when you crank the engine when the car is warm there is no/very weak spark from the coil?

I would test the values of part such as the cps, coil cold v warm

I had an intermittent cutting out at idle problem when my coil went bad.
 

grober

MB Master
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Jun 22, 2003
Messages
28,470
Location
Perth, Scotland
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W204 C200CDI Estate
oh bugger is there a bypass or a way of testing the dreaded ezl?
Not really --they can't be repaired-- best plan is to pick up a working one second hand -warning they are not all the same= different advance curves dependent on part no.
testing best achieved by temporary substitution if you can borrow one.
 

optimusprime

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Dec 29, 2013
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3,553
Location
Kidderminster Worcestershire UK
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Mercedes W124 260E M103
Pull out the OVP and give it a shake . Noise will tell you its fullty inside .By the way dont just fit parts if the number is not the same .
Also clean all the fuses in the fuse box,, check for cracks in the fuse material .
Another is make sure the battery terminals are clean with a little vaseline on them before refitting .
Also the earth ponts will need looking at for corossion ,these are the large earth cable from engine to chassis ,,clean up and grease them .
These are general maintenance items ,,do it now and look at them again in 3 years time .
I know my cousin had this same problem .He had the garage look in to it ,this was back in 1999....They ended up removing the head , only to find out it was still the same after all the work they did .I have the problem part in the garage . It was the OVP relay ,and that car is the one that i now own .
 
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chisel

New Member
Joined
Aug 2, 2020
Messages
16
Location
Tunbridge wells uk
Car
300e 1993 w124
So when you crank the engine when the car is warm there is no/very weak spark from the coil?

I would test the values of part such as the cps, coil cold v warm

I had an intermittent cutting out at idle problem when my coil went bad.
car hasn’t been able to run for months, just cranks very healthily, good spark from plugs distributor. lead from coil has a good spark too.
 
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chisel

New Member
Joined
Aug 2, 2020
Messages
16
Location
Tunbridge wells uk
Car
300e 1993 w124
Pull out the OVP and give it a shake . Noise will tell you its fullty inside .By the way dont just fit parts if the number is not the same .
Also clean all the fuses in the fuse box,, check for cracks in the fuse material .
Another is make sure the battery terminals are clean with a little vaseline on them before refitting .
Also the earth ponts will need looking at for corossion ,these are the large earth cable from engine to chassis ,,clean up and grease them .
These are general maintenance items ,,do it now and look at them again in 3 years time .
I know my cousin had this same problem .He had the garage look in to it ,this was back in 1999....They ended up removing the head , only to find out it was still the same after all the work they did .I have the problem part in the garage . It was the OVP relay ,and that car is the one that i now own .
the car has been fine running then it started cutting out when warm now it won’t run, it seems like something simple, it doesn’t feel like a dodgy earth, battery is giving loads of power it’s just not firing, ezl then?!
 

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