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Porsche 993: Why Does My Car Crank But Won't Start?

A Porsche 993 that won't start can be very frustrating, but with a few simple checks you can rule out some relatively inexpensive problems.

By Robert Olsson - May 6, 2015
Contributors: ChrisFix, IXLR8, BobbyT

This article applies to the Porsche 993 (1993-1998).

You try to start your Porsche 993, and it's just not happening. The engine cranks over but nothing more. There could be many reasons for this scenario, but when the engine doesn't start it usually has to do with either lack of fuel pressure, or weak/no sparks from the spark plugs. Continue reading to learn how to diagnose a 993 with starting issues.

Materials Needed

  • Soldering iron (optional)
  • Solder (optional)
  • Multimeter
  • Assistant/helper

Step 1 – Check the battery

The 993 needs a good battery in order to power fuel and ignition as well as crank the engine over fast enough to start. To check the condition of the battery, it has to be measured while under load. To do that you only need a multimeter that can measure at least 15 volts.

  • Make sure that your multimeter is set to be able to measure at least 15 volts DC.
  • Attach the multimeter to your car's battery; the red cable to the positive terminal of the battery and the black cable to the negative terminal.
  • Ask a helper to turn the ignition key to the 'on' position.
  • Check the multimeter. If the multimeter is below 9 - 10 volts while cranking the car, the battery is probably bad and needs to be replaced.
  • If you get a low reading on the multimeter, just to make sure that the battery is bad, bring the battery to a garage or proper store for further testing.

(Related Article: Porsche 993: How to Replace Battery - Rennlist.com)

Figure 1. Measure car battery under load with a multimeter.

If your multimeter gets a proper reading (9 - 10 volts or higher), move on to Step 2.

Featured Video: How to Test Car Battery with a Multimeter

Step 2 – Check the fuses

Your engine needs fuel to run. If the fuel pump doesn't work, the engine will crank over but it will never start since there is no fuel to spark. Check the fuse for the fuel pump in the fusebox. While you are there, you might as well check the other fuses just to make sure that no other fuse is causing any problem.

(Related Article: Porsche 993: How to Replace Fuel Pump - Rennlist.com)

Figure 2. Fuse box.

If your fuses are okay, move on to Step 3.

Step 3 – Check the DME relay

The Digital Motor Electronics (DME) is a computer that controls the fuel pump. A faulty DME relay could therefore make it impossible to start the engine since there is no fuel pressure. The engine can still crank over, but without any fuel pressure it won't ignite any fuel and the engine won't start.

Figure 3. Fuse box with the DME relay circled in red.

It is possible to troubleshoot the DME relay. Simply remove the relay from the fuse box and remove the cover of the relay. If you take a close look at the solders on the board, they should be shiny and smooth without even small cracks. If you are good at soldering, you might want to re-solder the solders that look bad.

Since the DME relay is relatively cheap, you might want to replace the DME instead of repairing it. If you are quite unsure if the solders are good, just skip the diagnosis of the relay and simply replace the DME relay. A new DME relay costs between $35 to $55.

Figure 4. Healty DME relay with the cover removed.

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