1991 SL 500 Starts cold but not when Hot!
 

Checked fuel pressure, OK.
Ignition control module tseted OK.
HFM Control Unit tested OK.
MAS unit tested OK.
OVP Relay Tested OK.
Crank Sensor Tested OK.
I have the following codes;
Crank Sensor
O2 Sensor


Driving me crazy, any help will be appreciated, :annoyed:

Thanks to all in advance. :)


Regards,


Victor

not sure if you have a fuel accumulator, which is next to fuel pump, but this i was the problem with my 380SE. After it wrmed up it would take a lot of cranking and sputtering before it would start. Fuel accumulator keeps fuel from vaporizing in the injector lines and thus prevents hard start when hot.

My 91 SL had the Fuel Accumlator problem. Sounds exactly the same as described.

Crank sensor
 

Check the crankshaft sensor.That is what went out in my 190e started good cold, but wore out a starter trying to start!At highway temp>

Your code told you what it was. There are sources for the hall sensors (crank trigger) other than mercedes. They do fail and as you have described.