crank no start

[chisel]

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

 

[optimusprime]

Engine m104 or m103 ?

 

[Deleted member 149005]

Crank position sensor?

 

[horatio]

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]

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.

 

[optimusprime]

Check the rev counter as you spin the engine over can you see any movement .

 

[chisel]

Engine m104 or m103 ?

not sure how can i check?

 

[chisel]

Crank position sensor?

replaced and tested both, getting 800-1000 ohms on the meter, so they were both good.I had a real mare changing it though.

 

[chisel]

Check the rev counter as you spin the engine over can you see any movement .

yep it’s ok

 

[chisel]

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]

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.

 

[chisel]

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.

changed and tested, they were both ok, dam and blast

 

[chisel]

If its a single cam distributor M103 its probably the EZL ignition unit

oh bugger is there a bypass or a way of testing the dreaded ezl?

 

[chisel]

it’s an M103 looking at internet pics

 

[grober]

deleted

 

[horatio]

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]

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]

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 .

 

[chisel]

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.

 

[chisel]

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?!