preglow light stays on. No start
 

Hi: I have a strange problem that appeared after the battery went dead I was doing some electrical testing and was turning the the ignition on without engine start. To reduce the drain on the battery I disconnected the plug that goes to the preglow plugs (6 pin). Meanwhile, the battery went dead anyway. Noticed the preglow light was blinking when the battery discharged, but thought it is due to low voltage. The light than started to stay on all the time. After all the testing put a charged battery, connected all plugs back to tried to start the engine. The preglow light does not go off at all. It comes on, stays on until the safety shut off happens. Can not start the engine. Any ideas beside "new relay is needed"? Thanks Car is 1987 300TD

OK. It looks like preglow plugs work. After a lot of struggle, the engine finally started. I think there was air in the system. Anyway, the glow light went off when the engine was running, but still does not go off after I turn the key to "ignition on" position. Timing part went bad? Anyone had this problem?