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TTW
Newbie


Joined: 28 Jun 2014
Posts: 47
Location: Midlands

2004 Porsche 997 Carrera 2S

PostPosted: Tue Dec 05, 2017 1:42 pm    Post subject: Yet Another 'Poor Starting' Post Reply with quote

Hi Everyone,

I know there are several posts on here in respect of starting problems, and I think I have previously posted one myself, when the symptoms were slightly different, but having replaced many suspect parts, and the problem still persisting; im hoping im not too far away from working out the root cause.

The Problem: Simply Inconsistent POOR Starting! - whether Cold, warm or hot? - Press the clutch, turn the Key, engine Cranks, but wont fire? - typically takes 2-3 attempts when encountering the problem (otherwise starts immediately when not encountering the problem?)

- There are NO Error Codes being logged
- It has had New Fuel Pump & Sender Unit
- It has a New Battery
- It has a New Starter Motor
- It has a New Starter/Alternator/Battery Lead
- It has a New Crank Position Sensor
- It has just had a FULL Service (New Plugs, etc)

Following the Service, the issue went away for about 2 weeks, but has now returned?

Other possibilities I have sourced from different threads but not managed to eliminate yet include...

...Battery -> Board Earth Strap
...Relay #8 (Under Dashboard)
...Relay #11 (Under Dashboard)
...Ignition Switch Assembly?

I dont know whether the fact the vehicle cranks but does not fire would eliminate any the above 4 items?

History wise, the vehicle appears to have only had this issue following the replacement of the Fuel Pump & Sender Unit by OPC last year (although the fuel pressure has been checked by porsche OPC & confirmed fine). - Not sure if this relevant or coincidental?

Once the vehicle is running, it is PERFECT! - Starting is either Immediate when issue not present, or can be 2-3 attempts to start when is present.

Any help or ideas greatly appreciated?

Confused

Last edited by TTW on Tue Dec 05, 2017 4:54 pm; edited 1 time in total
 
  
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116618LN
Newbie


Joined: 30 Apr 2017
Posts: 34
Location: London/Dubai


PostPosted: Tue Dec 05, 2017 1:45 pm    Post subject: Reply with quote

Leaky injector maybe..
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TTW
Newbie


Joined: 28 Jun 2014
Posts: 47
Location: Midlands

2004 Porsche 997 Carrera 2S

PostPosted: Tue Dec 05, 2017 2:08 pm    Post subject: Reply with quote

Thanks for quick reply... Leaky Injector isn't even on my list of potentials? :O ...Hadnt even considered injectors? ...how would this lead to these symptoms?
 
  
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116618LN
Newbie


Joined: 30 Apr 2017
Posts: 34
Location: London/Dubai


PostPosted: Tue Dec 05, 2017 2:18 pm    Post subject: Reply with quote

Can cause cylinder flooding/dampness, needing a few cranks to clear it before it fires up.
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pzero
General
General


Joined: 18 Jul 2010
Posts: 4207
Location: London


PostPosted: Tue Dec 05, 2017 2:22 pm    Post subject: Reply with quote

Have you seen this thread?

http://911uk.com/viewtopic.php?t=77471
 
  
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TTW
Newbie


Joined: 28 Jun 2014
Posts: 47
Location: Midlands

2004 Porsche 997 Carrera 2S

PostPosted: Tue Dec 05, 2017 2:29 pm    Post subject: Reply with quote

pzero wrote:
Have you seen this thread?

http://911uk.com/viewtopic.php?t=77471


Thanks.. I have eliminated the Clutch switch, as this appears to function normally, in that I get the message if the clutch isnt pressed, and when it is the engine ALWAYS cranks/turns, just doesn't fire/start (whereas I suspect if the switch if faulty, then the engine wouldn't turn at all)
 
  
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Demort
Estoril


Joined: 21 Mar 2015
Posts: 3502
Location: Sussex


PostPosted: Tue Dec 05, 2017 3:44 pm    Post subject: Reply with quote

Ok so we have a car that spins over but wont start , i assume you mean you can keep cranking it but it wont even try ? no coughs or splutters to indicate some cylinders are trying ?

You then stop and try again and have to do this several times before it will finally start ? you are in effect turning the ignition key on and off several times to get it to start and this is cold / warm or hot ?


No fault codes means the car thinks everything is ok .. no sensors out of limits .. it cant check fuel pressure though.

Clutch switch stops the car from spinning over , it disables the starter so not that.

I was thinking fuel pressure to be honest right up untill you said the pump had been replaced .. BUT you also said it seemed to have started at that point ..

I would like the pipes on the pump to actually be checked , are they correctly fitted etc .

My second thought is its not fuel its an electrical fault .. you are after all turning the key on and off several times .. perhaps a faulty ignition lock as that would dissapear after the car has started .

If it was me working on the car .. hmm ..

Id swop out the ignition lock with a spare to check that .. i would rig up something to tell me if there was spark and injector switch and see what was missing when it wouldn,t start and then go from there .
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TTW
Newbie


Joined: 28 Jun 2014
Posts: 47
Location: Midlands

2004 Porsche 997 Carrera 2S

PostPosted: Tue Dec 05, 2017 4:52 pm    Post subject: Reply with quote

Cheers for the responses...

Would it be possible to eliminate any of the following, based on the symptoms?

...Battery -> Board Earth Strap
...Relay #8 (Under Dashboard)
...Relay #11 (Under Dashboard)

+ Leaky Injector(s)?

Or could these still be likely suspects?

In addition, in respect of troubleshooting the ignition switch, if I turn the engine off after a journey, then immediately back on; the engine will consistently start immediately, time after time?. (guess I need to try this when the engine cold too!) - could this support the leaky injector theory?
 
  
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Demort
Estoril


Joined: 21 Mar 2015
Posts: 3502
Location: Sussex


PostPosted: Tue Dec 05, 2017 5:32 pm    Post subject: Reply with quote

Earth strap .. high resistance so would cause electrical faults .. the starter motor being the biggest current user would either not spin or spin slowly .

Relay 8 ..fuel pump relay .. yes its possible , you would need a pressure gauge on the fuel rail and the car cranking but not starting to see if there is no fuel pressure but then it could be any part of the fuel system back to the pump .

Relay 11 .. MFI .. yes its possible .. put a noid light in an injector harness and crank but car not starting .. no light would indicate this relay along with the rest of the injector / coil wiring .

Leaky injectors .. they would tend to always leak .. the car would try and start unless multiple injectors faulty .. you would have high fuel consumption , eml faults for lambdas black smoke etc etc

Ignition switch is unlikely but possible .. im just trying to think why turning the car on and off would allow it to start .


EDIT ..

If you think its relays then swop them with others to prove the fault.
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TTW
Newbie


Joined: 28 Jun 2014
Posts: 47
Location: Midlands

2004 Porsche 997 Carrera 2S

PostPosted: Tue Dec 05, 2017 5:56 pm    Post subject: Reply with quote

FUTHER Troubleshooting the Ignition switch....

Car stood in carpark for 8 Hours, so cold. (outdoor temp 8c).

- Key in & Turn (Attempt 1) ..... Engine cranks, no start.
- Key out, key in & Turn (Attempt 2) ...Engine cranks, sounds like tries to start but fails.
- Key Out, key in & Turn (Attempt 3) ..Engine starts immediately on key turn.

- Engine running fine.
- Turn off Engine..

- Key Out, key in & Turn (Attempt 4) ..Engine starts immediately on key turn.
- Key Out, key in & Turn (Attempt 5) ..Engine starts immediately on key turn.
- Key Out, key in & Turn (Attempt 6) ..Engine starts immediately on key turn.

- Drive vehicle for approx 8 miles, water & oil temp normal

- Key Out, key in & Turn (Attempt 7) ..Engine starts immediately on key turn.
- Key Out, key in & Turn (Attempt 8 ) ..Engine starts immediately on key turn.
- Key Out, key in & Turn (Attempt 9) ..Engine starts immediately on key turn.


...Personally Im thinking fuel? - either bodge job by OPC when replacing the Fuel Pump & Sender Unit, and somehow fuel is not ALWAYS readily available after a given period of time? or a leaky Injector which is intermittently slightly flooding the engine ahead of next start up? but I no expert thats for sure, just trying to apply some logic on the behaviour?

In respect of the relays, are they interchangeable then?
 
  
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Alfaian
Hockenheim


Joined: 12 Mar 2014
Posts: 641
Location: S.wales


PostPosted: Tue Dec 05, 2017 5:58 pm    Post subject: Reply with quote

It's a relay for me. Probably the fuel pump.

Relays tend to be an intermittent fault, they are only a switch really.

If it were an ignition problem, I'd have thought it would've pinged the light on or give you mis firing when running.

There again I could be totally wrong Grin

Hope you sort it and post the findings on here to help others Thumb

Good luck
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Demort
Estoril


Joined: 21 Mar 2015
Posts: 3502
Location: Sussex


PostPosted: Tue Dec 05, 2017 6:15 pm    Post subject: Reply with quote

Ok .. i agree .. thats fuel pressure .

Its almost like its takeing too long to prime .. perhaps the fuel pressure is not holding .. back to the pump and check the fuel lines , you may have an internal tank leak or incorrect fitment .

Look at the relay .. it will have 4 or 5 pins for a normal relay .. it will also have a picture on the side of how it works .. swop it with another thats the same .

Always check the picture or if possible a part number on it .. 4 pin are standard but there are x2 types of 5 pin relay and you dont want to mix them up .
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TTW
Newbie


Joined: 28 Jun 2014
Posts: 47
Location: Midlands

2004 Porsche 997 Carrera 2S

PostPosted: Tue Dec 05, 2017 6:21 pm    Post subject: Reply with quote

Demort wrote:
Ok .. i agree .. thats fuel pressure .

Its almost like its takeing too long to prime .. perhaps the fuel pressure is not holding .. back to the pump and check the fuel lines , you may have an internal tank leak or incorrect fitment .

Look at the relay .. it will have 4 or 5 pins for a normal relay .. it will also have a picture on the side of how it works .. swop it with another thats the same .

Always check the picture or if possible a part number on it .. 4 pin are standard but there are x2 types of 5 pin relay and you dont want to mix them up .


Cheers (you think it may be linked to the relay then, and not necessarily the actual pump?) I will check & report back in the next day or two.
 
  
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Demort
Estoril


Joined: 21 Mar 2015
Posts: 3502
Location: Sussex


PostPosted: Tue Dec 05, 2017 6:30 pm    Post subject: Reply with quote

Im thinking its more the pump side of it .. relay either works or not but either way swopping it to prove it is a good idea .

If it does turn out to be pump related then your Opc is not very good .. they fitted it and also checked the pressure and said it was ok .

I suggest moving down south .. say .. somewhere near Brighton Very Happy
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Harv
Suzuka


Joined: 18 Sep 2014
Posts: 1138



PostPosted: Tue Dec 05, 2017 6:40 pm    Post subject: Reply with quote

Can you also do a listening check for the fuel pump priming which should happen when the ign is switch is turned to on, you may need to make sure you are parked somewhere quiet but should hear a bzzzzzzt.

Be interesting to know if you get this when it does start and not when it doesnt.
 
  
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Mezgerite
Trainee


Joined: 02 Nov 2016
Posts: 64



PostPosted: Tue Dec 05, 2017 7:21 pm    Post subject: Reply with quote

Also can you confirm when it cranks, does it do so slowly or quickly, and is there a difference between cranking speed of when the car does start and doesn't start.

M
 
  
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