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Marty
Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 53904
Experience:  Bosch Certified Master Tech. Over 35 years experience.
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Mercedes-Benz SL500: 1995 l500 will not stay running breaks

This answer was rated:

1995 l500 will not stay running breaks up

eurotec :

Hi, the distributor caps and rotors are notorious for causing misfires on this model. If you have not replaced the caps and rotors yet I would remove and inspect them. Most likely you will find traces of spark arcing inside the caps.

eurotec :

Please let me know if you have any questions.

Customer:

caps and rotors are new

eurotec :

Ok, can you describe the symptoms?

Customer:

first had mis fire once in a while noticed injector harnes was bad and replaced it

Customer:

no difference ..... changed plugs and wires

Customer:

noticed throttle body wiring was bad replaced throttle body

Customer:

car will start idle fine for about 3 min

Customer:

and sometimes die if you raise the idle it will break up very bad then die

Customer:

tgen hard to restart

eurotec :

It sounds like an ignition fault but have you checked the fuel pressure?

Customer:

yes about 45 if i remember

eurotec :

Ok, have you substituted new coils?

Customer:

no ihave not

eurotec :

If it's breaking up under load I'd have to try a new coil. You could swap one and if it doesn't help reinstall that one and swap the other. If you can identify the misfiring cylinders you may be able to trace the miss back to one coil. If all of the missing cylinders are in the same cap I'd replace that coil.

eurotec :

I assume that the entire engine harness has been checked or replaced.

eurotec :

95 was a bad year for the harnesses.

Customer:

only the upper

eurotec :

Ok, but you bought the complete harness, correct?

Customer:

comlete upper for injectors from the computer

eurotec :

Ok, if the harness is good I'd have to try a new coil or two and then I'd suspect the ignition module.

eurotec :

You should also make sure that you have good voltage going to the coils.

Customer:

let me check the coils tomorrow voltage should be 12v

eurotec :

Yes, approximately battery voltage.

Customer:

great

Customer:

are nodules

Customer:

are modules and coils common

eurotec :

Coils are fairly common. The module can fail on only 1/2 and give you spark from only one coil.

Customer:

ok

eurotec :

Let me know if you need anything. I'll be around in the afternoon tomorrow.

Customer:

thanks

eurotec :

You're quite welcome.

eurotec :

If you would please remember to rate my service tonight I would appreciate it. You can still reply back if you need further assistance after you rate my service.

Marty and other Mercedes Specialists are ready to help you
Customer: replied 4 years ago.

replaced colils and no difference

Hi Joe, sorry for the wait I am away on vacation and not able to get online very often. When this problem occurs does the car idle rough? Are you able to determine which cylinders are misfiring by pulling the plug wires one at a time using a spark plug wire pliers?
Customer: replied 4 years ago.

will run smootthe at idle raise the idle it starts to break up then cuts right off this all happens within a minute