Porsche 944 where is dme

The car will not want to start again immediately but will most likely restart as normal after being given some time to cool off. In the event of a complete failure of the DME relay, the car may not start at all regardless of temperature or condition.

Since the DME relay is critical to the cars operation it should be the first component checked in the event of any no start condition. The easiest way to check for a faulty DME relay is to simply replace it with a known good unit. Here you can see a diagram showing the pins on the bottom of the DME relay and relay socket. Different DME relays may have one of two different numbering systems. Both are provided here for your convenience.

Bypassing the DME relay completely should be done only for testing purposes. Go Go. Home Page. New Products. My Account. Contact Us. In the and the ECU has a permanent volt feed that maintains it in standby mode essentially to preserve its internal memory, fault codes and so on. Then when the the starter motor is cranked, the ECU activates the second relay in the DME relay and power is supplied to the fuel pump for as long as the engine is running.

In the other cars power comes from the ignition switch direct to the DME relay. This then powers up the ECU which itself then controls the second part of the relay that relates to the fuel pump. Both systems offer a clue to the primary function of the DME relay. If the vehicle is involved in an accident and the engine stops the ECU will sense this via the flywheel sensors from which the ECU constantly works out the ignition and fuelling requirements and immediately cut the power to the fuel pump by turning off the DME relay.

This significantly reduces the risk of an explosion from leaking high-pressure fuel lines. The DME relay in your Porsche has a pretty tough life. And over a period of time this heat has a marked effect on the soldered joints on the printed-circuit board inside the casing on which both the relays and a number of other small electronic components are attached.

Caused primarily by the effects of heating and cooling, expansion and contraction, dry joints occur where the tiny blob of solder by which the wire projecting from each individual component is fused to the metal track on the board begins to fracture.

Put it this way: if light aircraft had DME relays and the Carrera 3. That said, some DME relays are remarkably awkward to get at. If you have a spare and, considering the notoriety of the things, you should always keep one in the glovebox fit that and see if it solves the problem. In fact, you can bypass the relay with a couple of pieces of wire. In a real emergency you can get away with a couple of paperclips, but ideally you need a pair of jumper leads incorporating an eight-amp, in-line fuse.

In the case of a flat-pin relay you need to place them across holes 3, 7 and 5 of the socket corresponding to terminals 30, 87, and 87b of the relay itself , or from 86 to 87 and 87b if you have a round-pin relay.

If the relay was faulty the engine should now start. You should also remove the link after you have finished your journey, otherwise the battery will be flattened if you leave the car idle for any length of time. Another short-term fix is to allow the relay to cool. Often it will fail when hot and because of the way electricity works the more those solder joints deteriorate the warmer the relay will become.

You can take the relay out of its socket and blow on it to accelerate cooling. On average DME relays seem to have a life of about 80, miles or eight years. And what of modern Porsches such as s, s Boxsters, Caymans and Cayennes? Well, Porsche realised that DME relays were potentially troublesome, and so these cars have much simpler relays controlling the power to the fuel pumps.

These items contain none of the soldered joints typical of DME relays, and so are inherently more durable. If you are so inclined, however, then there are some useful tests you can make once you have removed the unit from the car.

First, and using an accurate multimeter, measure the resistance between terminals 30 and 87b and between terminals 30 and In both cases the reading should be open circuit no connection, in other words. This should activate the relay and close the connection between terminals 30 and 87b. Check that there is no resistance between them or certainly no more than 0. Now connect your power supply to terminals 85 negative and 86 positive and check that there is no resistance or again no more than 0.

If you see a higher resistance between the terminals when you make these two powered tests then you can assume that the relay is faulty. The problem will either be poor contacts or a failing soldered joint. Look for a gap between the blob of solder and the wire that may be poking through it, and for flux a brown, waxy substance around the joint.

Still, you could keep the repaired one as a spare. Does your Porsche have a DME relay?