Thinking that the engine (1985 500 SEL) continuing to run after turning the ignition key switch to "off" was caused by a bad ignition switch, I replaced it with a new switch. However it did not resolve the problem. The only way I can stop the engine is to pull the coil wire. Once I have stopped the engine this way, there is no power to the #15 terminal of the coil. Otherwise the car starts and run fine. The key / ignition switch seems to operate correctly. Everything was working fine until once I turned it off, removed the key, locked the doors, started to walk away and noticed that the engine was still running. What could be going on?? Help!

It might not be too late for "cash for clunkers".

I don't have your wiring diagram, but it sounds like that's where you need to look (as opposed to detonation based run-on). There's probably a relay that energizes when you start the car that isn't dropping out like it should once you turn off the ignition switch.

__________________
Prost!

The #15 coil terminal is not hot with the ignition key switch in the run position, but becomes hot in the start position. It remains hot, engine continues to run with the key in either the ACC or Off position. Other fuses are hot in the run position so current is going thru the ignition switch, just not to the coil. It seems from the wiring diagram that the #coil terminal should be hot when ever the key is in the run position but it is not, maybe a safety issue? It looks like it becomes hot through the fuel pump relay. I can't see any other place that could be providing power when the switch is off?? The car is in overall excellent condition, very original and un-mess-around-with. So the problem of not being able to shut it off is very annoying. Any ideas would be appreciated. Has anyone seen this caused by a bad fuel pump relay?

I vote for fuel pump relay. Makes sense since your fuel pump also has to be energized to keep running, and see:
'87 560sel - Engine Running With Ignition Off!

__________________
Prost!

I'll hate to pay the $200+ (local MB dealer) for a fuel relay, not being sure that it is the problem, but I don't see what else it could be, so I'll get a fuel relay and let you know. Thanks for the response. JTS

I'd stop for a second and make sure before you spend the $$.

It could also be the EZL, as it takes a signal from the ignition switch, which if I am reading this schematic correctly is the pin 15 that you were testing before.

I can't really tell, but it looks as if you interrupt the voltage on pin 15, the car should stop. Somebody with more experience with these cars should verify that.

It's just that I'd hate to see you spend money on a fuel pump relay when you don't need one. I doubt that the only way the car shuts off is by killing the fuel pump, that seems awfully inelegant for a MB.

It seems like something upstream is signaling the ignition unit and the pump relay to stay on.

I would do more testing.... What's the first 8 characters of your VIN so I can look up your motor?

__________________
-tp


1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition

The vin # is WDBCA37D0FA168***, Should be May 1985 manufacture, engine is M117.963. I didn't mean that the engine is shut off by shutting down the fuel pump, but that there may be an interlock in the fuel pump relay, as part of the K-Jetronic system to shut the fuel pump off in the event of an accident, ie. engine not firing or not turning. The ignition switch should interrupt power to the relay and cause it to drop out and cut power to the #15 circuit, or the coil. Which is what I suspect my not be happening. As I know the ignition switch is OK, I guess it must be the relay?? Sound reasonable?? Any ideas appreciated. JTS