Hi all.I really need some help before I go mad. My 1990 SL one day will run beautifully no probs, then the next time I go to use it it will not start,spins over ok but thats all.I have taken a plug out to see if it has flooded but they seem quite dry which makes me think it must be a solenoid but where!!! Any ideas please so that I might know were to start. Regards Ian

 

can only be two things. fuel or electrical. get a spark indicator at one of your auto parts stores or get one at autohausaz.com. if no spark, the overload relay in the module compartment by the passenger side hood hinge is good place to start. it will have a red top with a fuse. the coil maybe or coil wire? maybe crank or cam position sensor, fuel pump relay or unlikely, but the ecm could be bad.

 

Hi Bob.Thanks for your reply. I have checked the spark and that is good. I next going to check the fuel pump to see if power is getting to it. Many thanks for your ideas. Ian

 

does it not start when hot or cold. I had a ecm temperature sensor go bad. The four wire one on the thermostat housing. When hot, one in ten starts or so the car wouldn't start without cranking for about 30 or more seconds. Then would fire up with no problems. It never was a problem when cold. test for continuity on opposing pins 1 & 3 and 2 & 4 there is a lot of resistance, so it won't show much movement in your meter. if no resistance it's bad.

 

Hi Bob.On checking the power supply at the fuel pump it is only 0.15 on the metre.I believe that the pumps are controlled from the main engine management ecu so I think that the ecu is at fault. Having spoken to MB they say that they had trouble with it.The only thing is I don't seem to be able to get it out of its holder and I don't want to damage it.Regards Ian

 

It's designated MAS. I forgot, the MAS module does have the fuel pump relay built in to it. so it could be a possibility. once you turn the **** at the top of the module to the O position it will pull out. it may hang up a little but should come out with a little effort. if you get a flashlight you can see the tabs that are not part of the module that are keeping it from coming out. you can see the clips the module slips into that's mounted to the compartment. the metal catches at the bottom of the module at each end will bend in enough for it to come out. The module should be 011 545 83 32 and is replaced by the 012 545 83 32 rebuilt for $232 at autohausaz.com.

 

Hi Bob .Thanks very much that has really helped. Regards Ian

 

Hi Bob. Thought you like an update. On further investigation I found the offending unit and it has turned out that it is the wrong one, infact it was the unit for a E190,E300 or E300sel, God only know's how it fitted and or worked for any length of time, I am amazed that they are interchangeable. I am now waiting for a replacement to be delivered. Thanks once again for your help and advice.Regards Ian