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ch3tman
Montreal


Joined: 08 Dec 2012
Posts: 588
Location: RBWM & W.London

1995 Porsche 993 Carrera 4

PostPosted: Wed Jul 04, 2018 5:41 pm    Post subject: Hot start / vapour lock? Reply with quote

Anyone experienced so called 'vapour lock' on a 993?

After a long run >45min, in hot weather conditions ~30degreesC, turning the engine off and then attempting to restart within a few minutes results in a failed start: starter turns per normal but engine doesn't fire. Waiting ~30 sec, going through the immobiliser cycle, and trying a second time results in success with no hesitation. This has only happened 4 times in 4 years - all this summer! Incidentally, a cold start is always fine.

Searches for hot start issues tend to point to the starter motor being on its way out, but it seems to turn over just fine. Trusted indy has suggested vapour lock, so will have this tested for during the next visit.

Would be good to know if others have experienced anything similar?
 
  
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Sutton
Spa-Francorchamps


Joined: 04 Mar 2009
Posts: 269
Location: Surrey


PostPosted: Wed Jul 04, 2018 6:03 pm    Post subject: Reply with quote

I have a spare DME you can try to rule out this as a possible issue.
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1994 993 C4
 
  
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ColinC
Österreich


Joined: 16 May 2013
Posts: 955
Location: Sunny Central Scotland


PostPosted: Wed Jul 04, 2018 6:13 pm    Post subject: Reply with quote

I would change the earth strap - the route of all evil and cheap to fix ......
_________________
94 993 C2 - Black with Marble Grey Leather
 
  
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madalaa
Fuji


Joined: 13 Mar 2008
Posts: 9253
Location: West London

2009 Porsche Boxster (987)

PostPosted: Wed Jul 04, 2018 6:39 pm    Post subject: Reply with quote

Happened to me in Spain about eight years ago when it was extremely hot and I had filled the tank to the brim ....... nothing .....couldn't start the car ....... then a memory from the dim and distant past came to mind of when I was running a VW Beetle and had much the same problem and I loosened off the filler cap and the car started first turn of the key ....... did the same on the 993 and likewise the car started immediately ...... perhaps that might of some help for others down the line ...... Smile
 
  
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Endoman
Suzuka


Joined: 11 Apr 2011
Posts: 1056
Location: Bolton U.K.


PostPosted: Wed Jul 04, 2018 7:46 pm    Post subject: Reply with quote

I've had exactly the same recently especially if the car has been out in the sun and I've no rear blower so the engine compartment gets pretty hot.
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Porsche 944 S2 Coupe Guards Red
Porsche 993 Coupe 9m RS Replica
 
  
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ch3tman
Montreal


Joined: 08 Dec 2012
Posts: 588
Location: RBWM & W.London

1995 Porsche 993 Carrera 4

PostPosted: Wed Jul 04, 2018 10:35 pm    Post subject: Reply with quote

Sutton wrote:
I have a spare DME you can try to rule out this as a possible issue.

I appreciate kind your offer thumbsup I also have a spare DME but never really know when this issue is going to occur (its not consistent or frequent but crucially starts just fine on the second attempt). If I could reproduce it I could easily test between DMEs.

ColinC wrote:
I would change the earth strap - the route of all evil and cheap to fix ......

Thanks! Will do this for piece of mind.

Endoman wrote:
I've had exactly the same recently especially if the car has been out in the sun and I've no rear blower so the engine compartment gets pretty hot.

Yes, it's only happened in this heatwave the UK is currently experiencing - or the one I experienced on a recent Euro roadtrip. In normal, milder conditions, it's never been an issue. Given you're rather clued up mechanically Wink, are you generally accepting of this phenomenon or doing anything to investigate/address it? if so, what..? Smile If it's considered normal, I'll be content to live with it.
 
  
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Kat1
Monza


Joined: 04 Nov 2010
Posts: 154
Location: Ely, Cambs


PostPosted: Thu Jul 05, 2018 7:31 am    Post subject: Reply with quote

I had the same problem during a tour of Scotland during a spell of particularly clement weather a few years ago.

A DME relay change soon sorted that starting issue.
 
  
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HPNer
Hockenheim


Joined: 25 Jun 2014
Posts: 712
Location: Jolly Boyos Country


PostPosted: Tue Jul 10, 2018 8:24 am    Post subject: Reply with quote

All very strange, I blasted up to Tetbury on Friday, parked for a meal . . . two and half hours later, started the car no problem and drove to my son's house about six miles away, parked for twenty minutes and then . . .

No start!

Swapped the DME relay and all was well.

What I need to do now is swap the DME relay back to confirm it was the DME relay not any other 'vapour lock' or whatnot. (Except I hear that dodgy relays can repair themselves, hot or cold solder in the innards or something)

Funnily enough my last words to my son before turning the key were "these engines are bulletproof. . ."


Bandit
_________________
Today, I shall mostly be driving my 993 . . .
-------
You've bought the ticket, so take the ride . . .
Faster, faster, faster, until the thrill of speed overcomes the fear of death...
 
  
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ch3tman
Montreal


Joined: 08 Dec 2012
Posts: 588
Location: RBWM & W.London

1995 Porsche 993 Carrera 4

PostPosted: Tue Jul 10, 2018 10:20 pm    Post subject: Reply with quote

HPNer wrote:
What I need to do now is swap the DME relay back to confirm it was the DME relay not any other 'vapour lock' or whatnot. (Except I hear that dodgy relays can repair themselves, hot or cold solder in the innards or something)

It's got to be related to this recent hot weather! Though since creating the thread I've tried to reproduce the issue several times (with the same/original DME), unsuccessfully. Starts every time, without hesitation... Laughing.
 
  
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