The DME relay is actually two relays in a single package. BOSCH refers to them as the main relay and the fuel pump relay. But why two relays? Relays are used to lower the current that actually travels through the ignition key. With a relay, only the relay turn-on current is routed through the ignition key. This is the job of the Main relay. The fuel pump relay is at the control of the DME. In the event of a fender bender, the DME will turn off the fuel pump. This prevents the pumping of raw fuel into a raging fire when the engine is off but the ignition key is still turned on. If the engine rpm drops bellow 200rpm, the DME will turn off the fuel pump relay and the fuel pump.
The DME relay is very "cheap" and the cause of many problems with the 944's fuel injection. This includes the no start problem. It is cheap in that it is inexpensive ($25) and it is cheap in that it is poorly built. If only a better source for the relay existed, this source of engine problems could be eliminated.
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Jumper to test fuel pump |
Jumper to run the car without a DME Relay. This will put more current through the ignition switch but will work in an emergency. Possibly too much so get it fixed ASAP. |
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Be safe. Carry a new DME Relay in your glove box!
