Jameskeith here with some interesting things about the "car won't start issue or car stops running and won't start again until engine cools down"
What Is a DME Relay?An AC coil relay, similar to the DME relay-photo courtesy of Wm Seán Glen at Wikipedia.org. The Digital Motor Electronics (DME) relay unit is used on many Porsche and some BMW models. This is actually a double-relay-in-one component. The main relay is used to fire the DME control unit (computer), while the secondary relay gives power to the fuel pump and heater element inside the oxygen sensor. Failure in the injection system is usually related to the DME relay, but some technicians seem to have found a solution for it.
You can find the DME relay used on Porsche 944, 924 and 968 models. BMW uses this relay for its 1992-1995 BMW 318I E36, 1991-1992 BMW 318IC E30, 1994-1995 BMW 318IC E36, 1991-1995 BMW 318IS E36, 1995-1995 BMW 318TI E36 and 1991-1992 BMW 318I E30 models.
The primary circuit within the relay control unit carries a very small amount of voltage and amperage, which runs through a small coil. This primary current is used to control a much larger current on the secondary path with another coil installed. This secondary current is then used to switch on the fuel pump.
The DME relay is a small cube of about 1 inch that may be located under the hood in the engine compartment, inside the fuse and relay box under the driver's seat or inside a fuse box, hidden under the dashboard. The relay itself may be marked with the legend DME-relais on top.
Problems starting your car, the engine dying while driving down the road (but able to start after it has cooled down) are common problems associated with the DME relay, which may be reaching the end of its life. This may be due to breaking solder joints inside the unit--the most common cause--or an internal diode failure.
Auto technicians recommend basically two ways to deal with a DME relay. First, you can carry a spare relay in your glove compartment, ready to be installed whenever the unit fails to avoid being stranded on the way home; second, reinforce the solder joints on a good or failed unit. Steve Grosekemper, shop foreman for Dieter's Motor Sports, recommends adding solder to the joints in the relay's circuit board to keep the heat from breaking the connections. Keep in mind that a diode in the primary circuit may also be the cause of a failed relay. This diode can be removed and replaced with a new one found at most electronic auto parts stores.
Read more: What Is a DME Relay? | eHow.com What Is a DME Relay? | eHow.com