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RobertN · Joined: 19 Apr 2015 Posts: 142 Location: Lisburn Co Antrim

Hi, fitted new plugs air filter and HT leads. Still same issue when cold, it takes a few cranks fires and stops a couple of times and then with a little extra help on the throttle initially to get her fired up she starts but idles lumpy until warm after 1 minute or so! After a run she runs brill and starts on the button. Can anyone help with the cold start please?
Thanks.
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Robert.
Porsche 924 N/A 1984.
Electrical Engineering Sales to Control panel builders.

Ozzie · Posted: Sun May 17, 2015 9:03 am Post subject:

hot idle should be about 900rpm
Sounds like the AAV could be faulty
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Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

leadfoot · Posted: Sun May 17, 2015 1:40 pm Post subject:

+1
check your aav and csv are getting 12v,
if you want to pull the hose from the aav you can check the air hole is open at cold temps... it closes when warm...
It's possible its gummed up too... or the hoses around it...
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1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

RobertN · Joined: 19 Apr 2015 Posts: 142 Location: Lisburn Co Antrim

Idle is around 850/900. Wil check cold start valve for voltage.
Aav?
_________________
Robert.
Porsche 924 N/A 1984.
Electrical Engineering Sales to Control panel builders.

jason c · Joined: 13 Jan 2014 Posts: 1018 Location: Nwi

leadfoot · Posted: Sun May 17, 2015 7:04 pm Post subject:

there's a funny Porsche name for everything, it's what supplies extra air for the engine at cold starts, has a rotating disc that starts with an opening and closes after a minute or so... powered by the same circuit as the csv
_________________
1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

RobertN · Joined: 19 Apr 2015 Posts: 142 Location: Lisburn Co Antrim

Thanks guys. I understand the process now. Thermo TS for csv operation and csv and AAV work like a " choke " system so to speak?
I'll check all my hoses etc,
Is there a way to check all 3 with voltmeter/ ohmmeter?
_________________
Robert.
Porsche 924 N/A 1984.
Electrical Engineering Sales to Control panel builders.

leadfoot · Posted: Sun May 17, 2015 11:17 pm Post subject:

unplug the aav and apply a multimeter to the coonector looking for 12v at ignition on,
A better test for the csv is to unbolt it from the manifold with it still connected to fuel and electrics spray it into a glass drink bottle whilst cranking over the engine, it only runs for about 8 secs approx, this will tell you if the tts is working and let you monitor the spray pattern for the csv
_________________
1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

RobertN · Joined: 19 Apr 2015 Posts: 142 Location: Lisburn Co Antrim

Hey guys. 12.6v at AAV connector on crank, but only 10.5 at csv blue connector on crank?? Haven't disconnected csv to test, but shouldn't there be at least 12v? I did notice when checking hoses etc a rubber bung at the bottom of the air flow sensor unit which had split, so I removed it and taped it up and re-installed it!!
Starts better after a few cranks and spluttering she fired up! but still a but lumpy for around a minute. After 1 minute running I switched off and back on again and she fired up immediately, should I just leave it or should she start better than this from cold?
_________________
Robert.
Porsche 924 N/A 1984.
Electrical Engineering Sales to Control panel builders.

Ozzie · Posted: Mon May 18, 2015 6:54 am Post subject:

starting straight up usually means the CSV is OK.
lumpy at cold could be the AAV keeping the revs too low or the WUR not working properly.
I suspect the AAV needs a removal and clean.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

RobertN · Joined: 19 Apr 2015 Posts: 142 Location: Lisburn Co Antrim

Yes Ozzie, revs are low at cold idle around 650-750 ish, then climbs to around 900 after a while. I'll pull the AAV and test. I read you put it in fridge for an hour in a bag and then check the opening and then apply 12v for about 5 mins and watch the regulator to see if it closes?
You mention the WUR is that the same as the csv?
_________________
Robert.
Porsche 924 N/A 1984.
Electrical Engineering Sales to Control panel builders.

Ozzie · Posted: Mon May 18, 2015 5:37 pm Post subject:

Warm Up Regulator is also Control Pressure Regulator and alters the control pressure as it warms up to lean the mixture.
Cold start valve squirts a pile of fuel in only when cranking.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

chris79 · Joined: 29 Jan 2014 Posts: 551 Location: milan

I have same problem of cold start, but because I replaced wur with pressure regulator set 3.4 bar (my wur is restoring).
I have to try for about 1 minute before start engine.
I have always to set control pressure about 1 bar to start engine ?
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Porsche 924 2.0 na 125hp (1979) euro
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Alfa Romeo Spider "Duetto" 1.6 104hp (1986) euro

Fasteddie313 · Joined: 29 Sep 2013 Posts: 2595 Location: MI

I'd recommend a CIS pressure test to make sure the WUR is dropping the control pressure when its cold like it should and then slowly raising it while its warming up...

Mine seems to start best when its either really cold (10-45F) or warmed up, Starts like a champ, It's in the 70's-80's here now and it seems to start and idle a bit low at these temps for a few seconds but it starts almost instantly in any condition...

I'm very impressed at how well the CIS is able to deal with cold start conditions especially real COLD starts..
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80 Turbo - Slightly Modified

Fasteddie313 · Joined: 29 Sep 2013 Posts: 2595 Location: MI