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Random no start problem


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On occasion my 1988 3.2 911 won't start with (immobiliser off) but then it will start vigorously and idle and run perfectly over the next few weeks.  Today I have the battery fully charged and showing 13.9V, (2) grounds all good, lights work fine and the starter just starts to turn and then the ignition lights and gauges on the dash just die.

I can check the solenoid connections tomorrow but could this be the DME relay or even a faulty IGN switch?

 

Many thanks

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The lights going dim points towards low voltage.

Does the voltage across the battery terminals drop significantly when you spin the starter ?.  If the battery voltage drops dramatically, then that points to  a duff battery or a starter gone bad and drawing excess current.  However, it could also be caused by a dirty connection on the battery terminals or any of the earth and power connections.  In this case I would not expect a dramatic drop in battery voltage, measured directly on the terminal posts.

Earths - battery to body, gearbox to body, engine to body, earth points under the dash in the front (both corners), under the dash above the heater (least likely this one), behind the fuel filer in the engine ebay, etc

Power - battery to power cable, power cable to solenoid, solenoid to alternator, alternator to multipoint connector in rear left corner of engine bay, connector to fuse panel, connector to CDI, etc, etc

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Whilst it's a 'no start' put some jump leads on it and see if that works.  If it does, then your battery is b*ggered.

My current battery is in a state of limbo due to cold weather and a lack of use.  Sometimes it appears fine the next its dead.

Annoyingly its not that old, its predecessor of same make and brand (Bosch Silver) got used and abused for years.  This one is more fragile.

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1 hour ago, Merv said:

On occasion my 1988 3.2 911 won't start with (immobiliser off) but then it will start vigorously and idle and run perfectly over the next few weeks.  Today I have the battery fully charged and showing 13.9V, (2) grounds all good, lights work fine and the starter just starts to turn and then the ignition lights and gauges on the dash just die.

I can check the solenoid connections tomorrow but could this be the DME relay or even a faulty IGN switch?

 

Many thanks

Had exactly the same problem. It was a faulty gearbox earth strap, it was split and falling apart, bought a new strap and cleaned the connections. Problem solved !

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Many thanks.  The Starter cranks about once or twice only, unless on some occasions it spins up normally and starts. The headlights don't seem to dim at all. I had replaced the woven earth straps with 2 cable types a year ago at different chassis points. I will check the voltage across the battery while cranking in the morning and the solenoid connection and report back.

 

If I do need a new battery what cranking amps are recommended (I have a CTEK 5.0A charger/maintainer)??

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Pretty sure its a fecked battery..............................try topping it up with Swepco:P

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6 hours ago, Merv said:

Many thanks.  The Starter cranks about once or twice only, unless on some occasions it spins up normally and starts. The headlights don't seem to dim at all. I had replaced the woven earth straps with 2 cable types a year ago at different chassis points. I will check the voltage across the battery while cranking in the morning and the solenoid connection and report back.

 

If I do need a new battery what cranking amps are recommended (I have a CTEK 5.0A charger/maintainer)??

I had this on a motorcycle many years ago and it was a flat spot on one of the starter gears which explained the intermittent scenario. Next time it does it, start the car in gear and obviously be ready to dip the clutch after the initial judder. Put in neutral and attempt to start normally. It could be starter gear related.

Just advice - I'm no guru.

Flappa2

 

 

 

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Cleaned all the earth connections and tested for resistance. All good.  Also cleaned the connections on the starter and solenoid. Tested voltage at the yellow cable from the ignition to the solenoid when cranking and it just dies. So I suspect either a faulty electrical module on the back of the ignition switch or more likely, a battery that won't crank any longer.  Battery voltage is fine and it is less than 5 years old, however if it won't crank ... maybe time for a new one to test that aspect.

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Edit - fitted a new battery and its starts perfectly! I was led to believe the battery was 3.5 years old (hence initially ruling that out)  when the code I found on it says 6years.  Thanks for the help! I might also replace the DME before long but it seems that there is no solid state version for the 87-89 cars?

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