W126 300se wont start

[300seman]

Changed spark plugs put new fuel pump and plenty petrol in. Fan is spinning when trying to start. Please any ideas

 

[ray_hennig]

I have the M104.980 engine that's of similar technology to yours. The only time I've had total non-start is because of burned out ignition controller (referred to - wrongly - as the EZL).

Basically, the EZL receives a signal from the crank position sensor (CPS) before it fires the coil to produce the spark needed to start. CPS failure is possible but rare in these cars - I've not had a CPS failure in 20+ years.

So, do you have a spark?

If not, suspect the EZL, coil and other HT components.

If yes, then check fuel delivery.

Good hunting.

RayH

 

[optimusprime]

300seman Do you have a spark ?. no spark = Crank Position Sensor ..

 

[ray_hennig]

300seman Do you have a spark ?. no spark = Crank Position Sensor ..

In my opinion, most unlikely in these cars. But yes, possible. You can measure the resistance of the CPS coil by unplugging from the EZL. Expect to see between 800 and 1200 ohms, ish. If so, the CPS should be OK.

EZL's the next suspect.

And coil?

R

 

[design guru]

Check to hear if the fuel pump is running when the key is in position 2 as often if not the fuel pump most likely the fuel pump relay fails, if the pump is running the worth looking at the HT leads as these become brittle over the years.

 

[optimusprime]

And at the other end the alarm system,, this can not be ruled out