my 80' 300D has been sitting for about 5 yrs. i have drained out all the old fuel changed out both fuel filters and glow plugs. but still it does not want to start. engine turns and starter is good. what may be the problem behind this.

Make sure your glow plug circuit is really working by reading the voltage at the plugs. Pump your primer a lot of times until you hear fuel going past the relief valve on pump. Then crank engine to see if fuel is coming out injector line by loosening the line nut at injector. Should run if those conditions are met and you have adaquate compression. If you are certain both of those conditions have been met you might want to consider a tow but read about it beforehand in the archives.

how do i check the voltage of my glow plugs?

Since your car is a 1980 I think it has the older large series plugs. So get a friend to turn the key on and you take a voltmeter. Your friend can tell you when the light goes out as well. You want to establish first that their is about 11.0 volts or so on the glow plug closest to the firewall. If that is true take your meter down to the second plug from the front of the engine and you should get a lower reading of about 2.5-4volts. All measurements are from the glow plugs to ground. Another clue is the squiggly wires between the glow plugs should warm up a little with a couple of cycles of the dash light if things are in order as they are resistors and indicate the current is flowing. Also since the car has been sitting for 5 years you perhaps want to clean up any connections before going further with troubleshooting if the first two tests do not produce the expected results. There is a small chance the engine was converted to the newer style non series plugs. In that case the squiggly wires between the glow plugs will not be there and you will be looking for about 11.0 volts on any plug you touch. Also the series plugs act like a string of old fashion christmas lights. If one is bad none will work. Also follow the wire from the glow plug closest to the firewall and it will lead you to a fusable link. I would also remove, inspect, clean the terminals up as well especially if the 11.0 volts is missing on the plug closest to the firewall. Do not hesitate to drop another note if there is something that needs clarification or with any indication that things are not as they should be.

im kind of new to this so please dont get mad. where should i touch the meter in order to do the reading? thanks