911 SC not starting clicking noise

[mydangemail]

Once a week or so, when I turn the key, I will get a clicking noise that seems to be coming from the dash passenger area. Usually, when the car starts, I believe it's like a loud buzzing noise and then it starts right up. If I hear the clicking noise instead, I know the car won't start.

Any idea what that could be? Thanks for your help!

Porsche 1980 911 sc

[JSV798]

Sounds like a failed starter motor solenoid. My 1978SC is on its third solenoid in my 30 years' ownership.

Roy

[smadsen]

Battery? Just waiting for a cold snap. See if a jump cures your "clicking."

[PeteKz]

The clicking or buzzing noise you describe coming from the passenger dash area has me wondering if that's a seat belt warning buzzer. If it clicks instead of buzzes, that could be because the ignition switch isn't making good contact.

Check battery health first. Then see if you are getting full voltage to the yellow wire on the starter solenoid. If not, that indicates a poor connection in the ignition switch or starting circuit.

[Schulisco]

Relay from lambda control unit? Sits under the passengers seat. Be aware: This relay is a special version with two 85 - correction - 87 outputs. Normally black and square housing, has an own socket. Feel in case manually by hand if this is the source of the noise.

Added the circuit diagrams:





Otherwise a video would help a lot.

Thomas

[targa80]

Originally Posted by Schulisco

Relay from lambda control unit? Sits under the passengers seat. Be aware: This relay is a special version with two 85 outputs. Normally black and square housing, has an own socket. Feel in case manually by hand if this is the source of the noise.
Otherwise a video would help a lot.

Thomas

I looked at the 81 schematic and the oxy relay coil contact 66 (rd/wt) connects to fuel pump relay terminal 30. Terminal 30 is switched from normally open contact to closed on with terminal 87 when the fuel pump relay coil is energized by ignition switch power applied to terminal 87a. With terminals 87 to 30 closed and ignition switch in the start position power is supplied to starter solenoid and to the oxy sensor circuit. I doubt this is your problem but just disconnect the oxy relay and see if starter cranks over.

More than likely you have arching on the starter solenoid contacts causing the issue of no start. Granted, this is just my opinion based on my experience with my 80 sc.

[JSV798]

Originally Posted by targa80

More than likely you have arching on the starter solenoid contacts causing the issue of no start. Granted, this is just my opinion based on my experience with my 80 sc.

You can check for this by shorting out the two big nuts on the solenoid. Use a screwdriver with an insulated handle and be prepared for some sparks. Remember that the the thick black cable to the starter is always live (with the battery connected). If the starter turns then it's most likely the solenoid. But the engine won't be turned because the solenoid has not levered the pinion into mesh.

Roy