Strange starting issue, or rather lack of starting

If it was a normal car, it would be simple case of sticking hammer into engine bay to prompt the solenoid when the engine wouldn't start... but I don't think there is a hammer designed that you fit over the alternator and reach the starter in a 911!

I have a feeling this will turn into one of my very long and boreing posts so if you want the answer just skip to the end ..

If you have an earth lead fault or indeed an engine earth lead fault when you try and start it , the huge consumer of power (the starter motor ) will in effect take all the power .. your dash lights would go off , interior lights go off .. basically the starter trys to take all the power through a high resistance lead ... this will lower or cut out the voltage to everything else .. kinda like a flat battery .

Engine earth lead fault and things start to smoke as the car uses any earth it can find .

Its not enough to turn it but it will take away the voltage from everything else on start position only ..

You have said you have dash lights but no crank .. so i would tend to rule that out .

CPS fault .. car will spin over but not fire up .. so thats out .

Ignition lock .. it causes various electrical faults but ive never seen one cause a non start .. so thats out .

The starter needs a 12 volts supply to the solinoid .. this then basically shorts x2 pins inside to send power to the starter .. if a poor connection or a poor solinoid connection (knackered starter basically ) then it will not spin over .

So you have replaced the starter .. unless it was an absoulute fortune then its a refurb unit ..

A refurb is a 15 year old plus starter than someone has taken appart .. replaced what they think is broken with it , bench tested , painted it silver then sold as a refurb ..

No guarentee they have actually fixed the fault with it though .. so a refurb is not always a fix .. it can still be faulty .. in your case .. i think not .

You have a main power lead from the battery to the starter .. its not a one piece lead , there are connection points which can get corroded .. on the gearbox .. think 997 starter lead fault .. its possible .. but i think not .

Immobiliser .. there will be fault codes , it is possible but there needs to be a reason .. if a cab then water ingress .. so check under the passenger seat .. is it wet there .. any water bottles stuck there that might leak ?

From memory the car will spin but not fire up with an immobiliser fault .. but thats from memory so i may be wrong .

Sooo .. what are we left with . the car intermitantly doesnt spin over .. the dash lights stay on .. we will assume the 12 v supply is ok to the solinoid but that is a guess .. i cant see the car after all ..

How about the starter relay ?

Its worth chucking a new one in if only to prove its not this ..

Relay board 2 is behind the rear seats , remove the carpet panel , it pulls upwards in the center .. bend it basically . .. you pull it out then undo the 10 mm nuts and lift up the ally panel.

Relay is position 7 and called start lock on the diagram .

Just my guess anyways .


EDIT ..

Ill just add that any system that has a relay then you use that as the diagnostic point .. 4 pin relay so 30 - 87 will be the switched feed .. if you brigde these wires it will activate the item to be tested .. 85 - 86 are the switched inputs to activate the realy .

30 - 87 .. one is 12 volts and the other the item that needs the power .

85- 86 ..

One will be 12 volts the other an earth when activated .. in this case ignition key in start position . .

If you bridge a starter relay and the car is in gear you WILL be heading off down the road with you in the back of the car .. dont do it .. be safe


Second EDIT ..

Starter relay .

Thanks everyone for your input, Demort you are a mikon-esque Porsche genius so I'm going to give the relay a try as a first port of call.

It is a new starter but it is a Dansk one not Bosch, maybe that is the problem. Seems I may need to get at it again now my cracked rib has healed (broke it wrestling the old unit off that had welded itself to the bell housing)

I like a tinker and find nothing more therapeutic than taking something apart, cleaning/fixing/improving it and feeling the warm cosy glow of satisfaction it brings. Tools out time I feel, no stop it, you are awful!

I might as well change any earthing straps at the same time as the car is knocking on a bit so probably beyond their prime but when I last looked I struggled to find a lot of info about the locations of these. Any guidance on that front would be greatly appreciated!

DANSK stuff does have a habit of dropping to bits :grin:

I knew I cursed it when someone asked me to recommend a new starter and I said mine had given me no problems....damn you Dansk

Still could be the relay, just checked design911 and they want, get this...£82 plus vat! Is it made of angels tears and unicorn horns in a factory on Pluto or what. I'm a Yorkshireman, that just isn't happening. The search continues...

No doubt OPC will be a similar price.

Hans Gruber said:

I might as well change any earthing straps at the same time as the car is knocking on a bit so probably beyond their prime but when I last looked I struggled to find a lot of info about the locations of these. Any guidance on that front would be greatly appreciated!

Click to expand...

There's an earth strap on the offside of the engine - cylinder head I think - accessed from the wheel arch. It's worth cleaning that connection.
But there's also a positive supply which connects the battery to the alternator and the starter. This is renowned for the connections corroding and breaking down further with heat. From memory it's visible and accessible with the air box and alternator removed. It emerges from the bulkhead somewhere and joins two more sections in a junction box (black plastic). One section runs to the back of the alternator - you can trace it from here - one to the starter. It's worth checking and cleaning all these connections.
I hope the above is some help. It's a few years since I did mine preventatively as I'd read it's a problem area. Never given any trouble.

Relay i found is £20 so not as cheap as Alex,s one ..

https://www.ebay.co.uk/itm/152869989353

Pict below of the engine earth strap .. a 997 but they are in the same location .

That relay is a usefull place to diagnose your fault .. rig up a meter or a bulb on term 87 so when it doesnt start you can see if theres power going to the starter or not.


I have no idea what " mikon-esque Porsche " means but it sounds nice :thumb:

Thanks for the pic deMort that is exactly what I am after!

The mikon-esque Porsche mind refers to the huge brain you must have to contain all the vital info that you so kindly and readily share with this forum. In short sir you are a diamond :thumbs:

Bless you young man .. but i think we all contribute .. i just say what i think ..

I have to admit though .. this forum is by far the best i have ever seen .. the knowledge of the people here often makes me think i have no need to repy to a question .. people have already answered it .

There are far too many people i would like to list here but sufice to say im sure they know .

Wont be long before im out of a job me thinks !

Hats off to you all .. im supposed to know this stuff , it is after all my job .. you lot have learnt it and help everyone else out .. im not worthy .. :worship: