‘86 All the sudden no start. Ideas?

[lucifer572]

‘86 911, drives regularly. Been about a week or so since it’s been out. Today, turn the key to on, everything is normal, turn key to start ignition and just a strange motor-type noise. I do notice that I don’t hear the typical buzz of the fuel pump after the first step of turning the key before ignition.

Sound is in the video below. Any ideas?

https://youtube.com/shorts/JkVy7XXaBBs?si=D9M69saukxqnnNnA

[76FJ55]

based on the noise, I would guess it is the fuel pump priming the system, but the factory system does not have a prime sequence built in. it will however supply power to the fuel pump in the start position. As I have no way of knowing how long and in what position the key is in during the noise, it make is a bit challenging to give a fully informed response. also if you replaced the original DME relay with a solid state relay, they are offered with a prime function, so that could be in action here as well.

What DME Relay are you using?
Is the noise only in the START position?

Disconnect the 14 pin harness on the left side of the engine bay and using an incandescent test light connected to pin #1 on the chassis side of the c0onnector, see if you have power on that pin (#1) with the key in the cranking position. conversely, you could supply +12V to the #1 pin on the engine side and see if the engnie cranks (make sure it is in Neutral first).

My first guess is that the starter is failing to turn the engine over and that everything else is probably functioning correctly. Is it in a position where you could try to push start it?

[GH85Carrera]

The first step is replace the DME relay under the seat. Pull it out, and see if it has a date on it. The DME relay is what supplies power to the fuel pump, and the DME as well.

The DME relay has a shelf life. You should carry a spare in the car at all times.

[76FJ55]

Originally Posted by GH85Carrera

The first step is replace the DME relay under the seat. Pull it out, and see if it has a date on it. The DME relay is what supplies power to the fuel pump, and the DME as well.

The DME relay has a shelf life. You should carry a spare in the car at all times.

The car doesn't appear to be cranking. at this point the DME relay is not involved. if it starts cranking and still won't start, then he can potentially look at the DME Relay.

I only mentioned the DME Relay in my previous post to get a better understanding as to whether or not Bus 50 is receiving power in the start position. if he has a solid state DME Relay with fuel pump prime, then we don't know anything definitive about Bus 50, but if no prime feature, then we can assume Bus 50 in the ignition is getting power to turn on the fuel pump during cranking even though the starter itself isn't turning.

[A930Rocket]

We should have a sticky at the top of the forum, on why my car doesn’t start. I did that on the 911 turbo/supercharging for ages ago.

[lucifer572]

I really appreciate all the responses. Best forum ever. I do have a spare DME relay and plugged it in to try it and no joy. For a more informed analysis the video below shows the ignition procedure. Only when attempting to ‘start’ does the “wirring” noise happen and no sound from the starter. I’ll have to familiarize myself with all of the pin checking. I haven’t worked on the car in years. It always just runs. I drive it quite a bit. All fuses appear intact.

https://youtube.com/shorts/CZGUAc7oGOY?si=j-SHhaOauAdvmq0S

I live in the north east corner of CT if any Pelican geniuses happen to live near me. I’m not much of a mechanic and my ‘superwrench’, René, recently passed away. I no longer have a go-to expert on all things classic Porsche.

[ant7]

First check battery voltage, especially when trying to crank it.

Sounds like there isn't any power going to the solenoid of the starter, or its too low to engage the solenoid, check the wiring on the starter for corrosion, also could be the ignition switch, [make sure the plug on the back of the ignition switch is pushed on properly] you will need to check the voltage you have at the starter solenoid while someone turns the key to see what voltage you have at the solenoid low current wire [the thin one, yellow]
While your under the car, check the thick ground wire going to the chassis from the gearbox, remove it and clean its contacts, refit using some copper grease!
Ant.

[RDM]

I had a similar problem recently with my SC. Sounded the same. Battery voltage dropped on cranking to the point the cigarette voltmeter went dark. The solenoid engaged but the starter motor did not turn. I put in my backup and am now looking for a rebuilder....

[lucifer572]

Problem fixed!! So in short, it was the battery.

The battery is only 2 years old and I haven’t used the car in about 2 weeks. I normally have it on a tender, but it’s been 2 weeks since it’s been plugged in, but I plugged it in a few days ago since creating this post.

I tested the battery and it read 4.5V, so it apparently it ran down low enough that the tender couldn’t keep it up. I know I have a parasitic draw I need to deal with somewhere.

An automotive box store tested and charged the battery, giving it a clean bill of health.

It’s a strange circumstance I haven’t run into before. When turning the key the first step powering the locks, lights, and radio, everything turns on as if the battery is ‘strong’. But when going to crank it made that noise as heard in the videos above. I havnt experienced that before with a ‘low’ battery.

Thanks everyone for all of the input.

[ant7]

Good to hear,
Always check the simple things first, as for the battery drain, if nothing obvious shows up [frunk light staying on, faulty alarm, etc] then you might need to get the alternator checked, when the diodes fail, they can drain the battery quite quickly over a matter of a day or so, depending of course on the severity of the fault. For now I would advise disconnecting the battery when the car is not in use, you can keep the battery conditioner connected to the battery to keep it charged.
Ant...

Originally Posted by lucifer572

Problem fixed!! So in short, it was the battery.

The battery is only 2 years old and I haven’t used the car in about 2 weeks. I normally have it on a tender, but it’s been 2 weeks since it’s been plugged in, but I plugged it in a few days ago since creating this post.

I tested the battery and it read 4.5V, so it apparently it ran down low enough that the tender couldn’t keep it up. I know I have a parasitic draw I need to deal with somewhere.

An automotive box store tested and charged the battery, giving it a clean bill of health.

It’s a strange circumstance I haven’t run into before. When turning the key the first step powering the locks, lights, and radio, everything turns on as if the battery is ‘strong’. But when going to crank it made that noise as heard in the videos above. I havnt experienced that before with a ‘low’ battery.

Thanks everyone for all of the input.

[darrin]

lucifer572 -- I'd start your parasitic drain investigation by seeing whether, with the ignition key in the off position (or taken out of the ignition lock), you can still operate your power windows when your driver's door is open. I know this sounds like an odd ask, but I had exactly the same situation with my '86 targa. Specifically, I traced my parasitic drain to a failed driver's side door's pin switch (which activates the dome lights when the driver's door's opened). Turns out that our cars (at least '86 model year 911s) have a feature that allows us to operate (roll up) our power windows after turning off the engine. The feature's SUPPOSED to be disabled once a door's been open. If the door pin switch fails, the relay that activates this feature remains energized even after the door's been open and the power draw from this energized relay will drain your battery in about a week.

[lucifer572]

Thanks for the suggestions. I’ll begin investigating.