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1995 Merc 200 suddenly dies

G

gcumbie

New member
"My 1995 Merc 200 EFI suddenly

"My 1995 Merc 200 EFI suddenly dies. Very abruptly and the tach stays where it was prior to dieing. When I "exercise" the key switch, I get NO effect. Sometimes it will start back up in a couple minutes, sometimes it may take as long 30 minutes. The motor also seems to "miss" while otherwise running normally. I suspect an electrical problem due to the sudden stopping but I don't know where or how to start checking. I was overdue for a water pump impeller replacement and thought it may be getting too hot and shut down as a result. A local mechanic said that the engine did not monitor the temp for that purpose. I replaced the water pump anyway but haven't taken it back out again since to check it out. Any help would be greatly appreciated- I have a family camping trip coming up."
 
"Greg, unfortunately there is

"Greg, unfortunately there is no simple answer to your issue.

A complete "shut-down" could be ignition or fuel related.

A bad alternator would definately kill the spark to all cylinders. But a massive clog in the fuel system would do the same thing.

This is an alternator driven, computer controlled ignition where each cylinder has it's own coil/trigger/capacitor circuit - so the alternator and the ECM are the only two "common" ignition components. So you have to consider the ECM (engine computer) could be on it's way out.

You could also have a faulty kill switch, keyswitch or circuit or bad mercury switch (if equipped) - or even a harness problem feeding the electrical to the injectors.

You can fiddle around yourself or take it into Merc, have them plug it in and give you a read-out. If nothing else it will rule out many possible causes.

Your motor is complicated like a modern vehicle and you don't simply go at it with an ohm meter and a screwdriver to troubleshoot. It also utilizes a number of sensors (throttle, crank position etc) any of which could be contributing to the problem. All of which need a DDT (Digital Diagnostic Tester - Merc computer) to confirm they are working.

And the "mechanic" is correct - an overheat will not "kill" the engine like that - you would get an alarm and a 50% reduction in rpm if the temp sensor detected an overheat..."
 
"Thanks Graham. I will take i

"Thanks Graham. I will take it in to have it diagnosed on the DDT. I didn't think to mention that this was going on last year and I completely drained the gas tank, removed the fuel sending unit and swabbed the tank completely clean. I ran the motor for a whole day of skiing with no problems. Then--WHAM!!! Stuck again. The first thing I checked was the kill switch, then fiddled around with the wires on the ignition switch. But the motor had its own idea of when to start back up. Anyway, thanks for the help. I'll post the solution once we get it."
 
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