Porsche 944 Turbo DME Relay Troubleshooting (1986 - 1989)

If your Porsche 944 will not start or suddenly dies on you, one of the first places you should check is the DME relay.
On the older 944s the relay is known as the fuel pump relay and is located on the fuse panel under the dash on the driver side. On later 944s and 951s, the relay is located in the fuse /relay panel in the rear left side of the engine compartment close to the windshield and A-pillar. These relays are prone to failure; a lot of failures. They usually fail from broken joints in the circuits but they can also fail from the diode and or have issues with heat sink.
This article will show you how to check your relay for proper function and show two emergency stop gaps to get you home, but these stop gaps should only be used in the most extreme of emergency situations. If you are going to drive a 944 or 951, invest in a couple of extra DME relays and always carry a spare, there is even room in the fuse box for the spare. With a proper functioning relay buy a spare and swap it out with the good relay, if the car starts and runs with no problems then you know the new relay is good, switch them back and place the spare in the fuse box. While all of these tests will help track down a problem it is still easier just to install a known good relay
The relay on the later 994s actually has two relays within it; one that powers the DME and KLR on the 951 and a separate relay that powers the fuel pump and heater for the O2 sensor.
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[@mikalaconway7568]

For fig8 does the arrangement of the power supply matter? Does a specific terminal have to be high with the other low?

[@pelicanparts]

If you mean battery positive and negative, yes. There is a correct orientation.