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MY 996 carrera cranks but wont start?

mileet

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16 Jan 2018
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Hi There,

I'm new to the site so not to sure if I'm posting in the right place?

can anyone help please my 2003 996 wont start it turns but wont fire up?

over the past year or so ive had about seven episodes where she starts to misfire until cut out usually when coming to a stand still, normaly i wait thirty seconds or so and she fires strait back up. the last two times this happend low oil pressure displayed.

the last straw was when i left her ticking over for about half an hour i was in my house and i could hear the misfiring, by the time i got out she had cut out and would not fire up again.

i put some fuel in and no joy towed it in to my local garage he plugged his hand held machine, no faults, changed the crank position sensor still no joy.

i had her serviced before she cut out about a hundred miles ago.

somebody suggested the dmv relay but when I've looked it only brings pages on the 993, do does the 996 suffer with this problem?

can anyone please help

thanks
Mileet
 
If there are no faults showing my guess would be a fuel pump issue.

Welcome to the forum.

MC
 
:welcome: to 911uk

As your post is 996 specific I've moved it to the 996 sub-forum.

Good luck with your query.

ps. When you've got chance to say a hello post again in the newbie forum. Pics of your car and some details about your car owning history always go down well. :thumb:
 
You left your car running outside for half an hour :?:

When you say 'low oil pressure'define low?

There's numerous things that could be causing your issue but without more information, it's hard to diagnose.
 
Hi there, and welcome....


I'm with MC, id say fuel pump failing but this is only a guess obviously.

I just recently changed my fuel pump, not because there was anything wrong with my old one, it's just i was told they go weak as they get older and struggle to supply fuel higher up the revs so thought it best to change.

I have my old pump here which you are more than welcome to have for free, just cover the postage. Then that should hopefully either fix the issue or knock one thing off the list to try.

Hope you get sorted.

Just to add, mines a 1999 C2 3.4. i'm asuming the pumps are the same.... probably best to check first.

Craig
 
Your garage should be able to do a fuel pressure check .. pretty easy on these to get to the fuel rail and test.

The lack of a fault code means its going to be items that are not monitored by the engine management system and as has already been mentioned the fuel pump is the main one .

The symptoms are also what i would expect from a failing fuel pump .
 
Initially it does sound like crank sensor and if this is faulty it doesn't let the fuel pump run so the engine won't start, this then leads to it being a fuel delivery problem and possibly the pump, I bought a tester for fuel pressure for my 944 quite cheaply. Could also be fuel pressure regulator.

I had an issue where mine started stalling and eventually wouldn't start at all over the period of about a week it got worse, I scanned it and it came up with crank sensor fault. OPC changed this but it still wouldn't start, they eventually traced it out to the engine wiring loom, being the wire from the crank sensor to the electrical plugs in the engine bay, worth doing a continuity check to see if there is a connection issue.
 
DME relay isn't really an issue on the 996 - it doesn't govern as much as it did on older porsches such as the 944/968... car wont run if its faulty but you dont get a load of associated starting issues from a slow deteriorating relay...
(seem to recall that with the 996, that if it cranks, its not the DME relay)

996 does have a fuel pump relay (pink script on the back of it - lives second row up, just left of the middle of the centre of the relay board in the driver footwell, past the fuse board)
- fuel pump relay is 2 stage, stage 1 pressurises/primes the system so that you can start, stage 2 keeps it open so that the pump is running while the car is running

I start my car in the garage, whilst reaching in/stood alongside it
i.e. this allows me to clearly hear the stage 1 relay action run the pump

to test the pump you can bridge the pump relay (breifly) with a wire
- see the fuel pump replacement article on Pelican Parts

could be the pump... could be the relay.... to be honest I'd be more suspicious of the condition of the socket in the relay board or the wiring just behind it
- my relay seems to need to be "just so" for the car to be happy (haven't to round to investigating/resolving further - its still too bloody cold!)


could equally be something else, but the pump and pump relay are fairly easy to test and eliminate

Note: the 996 also has a EVAP system with a number of valves/vents in it that can cause starting issues (although these are mostly "hot" starting issues)
- there is one in the fuel filler neck, which can be replaced (typical symptom associated with this vent is a "howling" noise from that area whilst driving and/or issues difficulty fueling the car) and another in the top of the fuel tank (can be replaced, not serviceable - more expensive!)
- any EVAP issues disrupting running will be felt at idle (e.g. hunting/racing, etc) - there is a (stutter) vent inline to the throttle body which can foul up, leaks can occur from the AOS vent line to the TB, etc

...sounds most like faulty coil packs, lack of consistent fuel delivery (could be pump, rail or injectors), or crank position sensor fault (or similar)
- fully eliminate the "spark" and "fuel" causes before you dive too deep into "general electrical" though (can be very lonely/misleading/expensive if you haven't first truly eliminated all else)
 

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