13 991 cold won't start
01-30-2014, 07:23 PM
#32
Instructor
Thread Starter
01-30-2014, 07:24 PM
#33
Instructor
Thread Starter
01-30-2014, 07:26 PM
#34
Instructor
Thread Starter
"Low fuel pressure... replace the fuel pump."
Sounds logical but IMHO they are throwing parts at it. Maybe the fuel pressure is low because the pump is not running. Logical, but does the car run very well all other times? Typically when a fuel pump is starting to go, you can feel the surging at high RPM. This also sounds like a strange failure...
My bet would be that the fuel pump is not getting the signal to do its job, or there is a check valve leak.
I had an older Volvo that would not start for 3 hours after it was driven. Modern fuel systems have a return line, the return line has a check valve that would prevent all of the fuel from leaking back into the tank when the car was off, to keep pressure in the system. If the car detected a warm start, it would not send large amounts of fuel to engine, assuming the pressure was good from previous operation. So it resulted in a crank off, until the engine was cold again. On cold starts, it worked perfectly. To be honest, I didn't understand exactly what was happening, but when I replaced the check valve in the return line, I never had a problem again. I typed this just to confuse people and make the OP worry! ;-)
Sounds logical but IMHO they are throwing parts at it. Maybe the fuel pressure is low because the pump is not running. Logical, but does the car run very well all other times? Typically when a fuel pump is starting to go, you can feel the surging at high RPM. This also sounds like a strange failure...
My bet would be that the fuel pump is not getting the signal to do its job, or there is a check valve leak.
I had an older Volvo that would not start for 3 hours after it was driven. Modern fuel systems have a return line, the return line has a check valve that would prevent all of the fuel from leaking back into the tank when the car was off, to keep pressure in the system. If the car detected a warm start, it would not send large amounts of fuel to engine, assuming the pressure was good from previous operation. So it resulted in a crank off, until the engine was cold again. On cold starts, it worked perfectly. To be honest, I didn't understand exactly what was happening, but when I replaced the check valve in the return line, I never had a problem again. I typed this just to confuse people and make the OP worry! ;-)
Maybe it will burst into flames and then I won't have to worry about it!
01-30-2014, 09:05 PM
#36
Rennlist Member
It doesn't make sense. An electric pump works or it doesn't. First of all congrats on the car and the warranty that go with it. The description of the failure seems to point more to ECM than mechanical. The car starts OK first thing in the cold but later in the day won't fire, that suggests electrical more than mechanical. Plse keep us apprised.
01-30-2014, 09:25 PM
#37
Instructor
Thread Starter
I think because under warranty they might not give me the old part....yet I wouldn't know what it should look like. I highly doubt I will keep this car past three years. I have had it since July 6th and could sell at any time....lol
01-30-2014, 09:32 PM
#38
Instructor
Thread Starter
It doesn't make sense. An electric pump works or it doesn't. First of all congrats on the car and the warranty that go with it. The description of the failure seems to point more to ECM than mechanical. The car starts OK first thing in the cold but later in the day won't fire, that suggests electrical more than mechanical. Plse keep us apprised.
Anyways, I will keep this updated to see what happens.
maybe the car is now for sale....
13 991 C2 PDK, sunroof, PASM, sport chrono, aqua blue on black, entry/drive, heat/cool seats 14 way etc etc....
01-30-2014, 11:20 PM
#40
Nordschleife Master
It doesn't make sense. An electric pump works or it doesn't. First of all congrats on the car and the warranty that go with it. The description of the failure seems to point more to ECM than mechanical. The car starts OK first thing in the cold but later in the day won't fire, that suggests electrical more than mechanical. Plse keep us apprised.
01-30-2014, 11:30 PM
#41
Just my $0.02!!
01-31-2014, 08:38 AM
#42
Instructor
Thread Starter
01-31-2014, 08:40 AM
#43
Instructor
Thread Starter
My guess is that as temperature drops it causes fuel volume to decrease. Car starts initially because small amount of fuel already in the lines has enough displacement to initiate combustion. As fuel in lines is replaced with gas from the fuel tank the newly introduced gas has a lesser density and causes starting problems. As the fuel in the tank heats up due to ambient temperature increases throughout the day the problem dissipates.
Just my $0.02!!
Just my $0.02!!
02-03-2014, 03:59 AM
#45
Drifting
If you do a search on the 991 forums here and on 6th gear you'll find your not the only person with this exact issue. The latest 'theory' from some seems to be a cam sensor issue. There are also issues on the 991's with the auto start/stop and a recall for fuel injectors. A few people have had injectors go full rich when idling and they get stalling/rough ride as a result. Your low fuel pressure code could have been the result of a sensor issue?
Seems generic: Car starts fine and owner goes for spirited drive and stops somewhere and after 20 minutes car won't start. Will crank and crank but no joy. Outside temps seems to be part of it as most are reporting the issue in northern climates. Then like magic the car starts hours later - although yours is funny in that it seems to have a Rolex 24 like ability to find 2:00PM to start.
Why not try Oakville next time it happens - their closer to you and a second opinion can't hurt.
Seems generic: Car starts fine and owner goes for spirited drive and stops somewhere and after 20 minutes car won't start. Will crank and crank but no joy. Outside temps seems to be part of it as most are reporting the issue in northern climates. Then like magic the car starts hours later - although yours is funny in that it seems to have a Rolex 24 like ability to find 2:00PM to start.
Why not try Oakville next time it happens - their closer to you and a second opinion can't hurt.