Benz quits running!

I have a 1989 190E 2.6 Mercedes. The other day, I turned the ignition switch and the car did nothing. The dash lights came on, and did not dim. The battery was ok, the cables were on tight and had no corrosion. After a few turns, it finally engaged and cranked, until the next day when it did the same thing. I took it to my mechanic. It did the same to him. When it does crank, it will run for about 30 minutes, and then quit running and won’t start until it cools down.

The mechanic has checked everything. The starter, the key, etc. He thinks that the anti theft system is going bad, and simply shuts the car down after it runs a while, and prevents it from starting at times when you turn the switch and it won’t start. Can the anti theft system be bypassed to check if it is going bad and is shutting the car down? If so, how do you do that? Can it be disabled altogether? Even when we by-pass the ignition switch, and go directly to the starter, it will crank, and then it will shut the car down.

In the past 6 months I have noticed that the alarm system has been going down hill. If the alarm is activated, the alarm will not sound, but the lights will blink. Sometimes the lights will begin to blink on their own, and the doors will lock, but the alarm will not sound.


I’m not real sure the problem is related to the security system and it’s possible that you could have more than one problem based on the symptoms.

The failure to start (no starter motor operation?) could point to a security system fault, faulty ignition switch, faulty neutral switch, cable end, etc. IF you do not hear a starter solenoid “click” sound when the key is turned.

The dying and failing to restart until it has a chance to cool off could be anything from a failing ignition switch to a failing ignition module to the usual suspect; a failing fuel pump. Those Bosch pumps are high pressure units that really take a beating (especially on CIS type cars) and the commutators on the pumps can really develop some excessive wear. When that happens the pump can be a “works at times” type of thing.

Sorry I can’t be more precise but it’s extremely difficult when it’s not known if the problem is lack of spark or lack of fuel; and the two are often intertwined to some degree.
Making a strictly wild guess (and considering a 20 year old car with high miles?) I’d say a fuel pump if that has never been replaced.
In the meantime, about all I can suggest is that the car be run until it dies and then a determination made as to whether there is no fuel pressure or spark. That would narrow it down quite a bit.

You may be money ahead if you have an automotive alarm and security specialist disable the alarm system. Find one in the Yellow Pages.

I suggest finding a Mercedes Benz specialist, someone with intimate knowledge of the car and its security system and access to factory diagnostic and test procedures for this particular model.

This will probably cost some money, as chasing electrical gremlins is a time-consuming process.