911 starting issue

[brown911]

Hi all

I am currently having an issue with starting my 1974 911(with 3.0l SC engine). When I turn the ignition to the ON position, the starter motor starts without me moving the ignition switch to the starting position.

Now I have just replaced the electrical part of the ignition switch with a new item (supplied from our sponsor), but this has not solved the issue.

Any ideas?

Thanks in advance.

[twistoffat]

I´m no expert when is comes to electrics but is the lock body properly alligned with the ignition switch?

[ossiblue]

Originally Posted by brown911

Hi all

I am currently having an issue with starting my 1974 911(with 3.0l SC engine). When I turn the ignition to the ON position, the starter motor starts without me moving the ignition switch to the starting position.

Now I have just replaced the electrical part of the ignition switch with a new item (supplied from our sponsor), but this has not solved the issue.

Any ideas?

Thanks in advance.

First question, was there a fuel pump relay added to your car? The 74 did not have a fuel pump relay as did the later cars so if one was added to allow for the air flow sensor of the 3.0, it may have been wired incorrectly and you are getting electrical "feed back" to the starter circuit.

You did not mention if this was a new problem or if it just began with the installation of the 3.0. Also, we don't know what wiring was changed to adapt to the new engine. If no relay was added and this is a new problem, it shouldn't be too hard to find as the circuit from the ignition to the solenoid is direct on a 74 (yellow wire.) You might try unplugging the 5-pin connector from the ignition switch and plugging in the new electrical part, then turn it with a screw driver to see if it works correctly. Report back any additional information.

[brown911]

Originally Posted by ossiblue

First question, was there a fuel pump relay added to your car? The 74 did not have a fuel pump relay as did the later cars so if one was added to allow for the air flow sensor of the 3.0, it may have been wired incorrectly and you are getting electrical "feed back" to the starter circuit.

You did not mention if this was a new problem or if it just began with the installation of the 3.0. Also, we don't know what wiring was changed to adapt to the new engine. If no relay was added and this is a new problem, it shouldn't be too hard to find as the circuit from the ignition to the solenoid is direct on a 74 (yellow wire.) You might try unplugging the 5-pin connector from the ignition switch and plugging in the new electrical part, then turn it with a screw driver to see if it works correctly. Report back any additional information.

Thanks for the advice, this is a new problem, I have had many years of trouble free running with the 3.0 litre, and yes a fuel pump relay was added when the 3.0 litre was installed. Looks like I will need to trace the wiring.

Thanks again.

[brown911]

I disconnected the fuel pump relay and the car turned over as normal, so definantly fuel pump relay related.

[brown911]

Problem solved, replaced fuel pump relay and all is well.