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Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

While sitting on jackstands for the last month and a half, Shaggy has developed a cold start issue. I did read the FAQ carefully, leading me to the following questions.

It fires right up, and dies, so the CSV is firing (right?)
Putting my foot on the gas does not keep it running, so it is not an AAV issue (right?)
WUR problem would make it run rough, but would by unlikely to make it die completely (right?)

Here is my theory. The car runs off the CSV briefly then cuts out as if there is no fuel, even with the throttle on the floor. Therefore it seems like there is insufficient vacuum to pull down the CIS metering plate. But how could this be?

The rest of the theory: I made fun of Shaggy's PO not long ago for disconnecting the vacuum limiter. I hooked it back up, and there was a noticeable decrease in exhaust side backfire. Is it possible that the vaccum limiter is stuck open, causing lack 'o fuel?

I know the easy way to check this is to look at the metering plate while cold cranking, or to disconnect the vacuum limiter, but I just wanted to know what you guys thought.

TIA

(fake) rasta (and all)
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

sequential · Joined: 18 Nov 2005 Posts: 500 Location: BANNED

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flosho · Posted: Thu Jan 11, 2007 5:59 am Post subject:

What were you doing to it while it was on jack stands? Just something simple but last time I put my intake back on I forgot to hook up a vacuum line on the back of the intake... Did the exact same thing. Would actually run, but barely.

Go back through and check vacuum lines?
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[This Space For Rent]

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

Other than flosho's vac line suggestion, I would suspect the warm-up regulator, or the CIS is just adjusted a little lean. The WUR can give the cold start-die dance.

The factory manual has a diagram of fuel pressure vs. temp. That's my guess if the vac lines check out.
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1980 931S
15psi boost, MS-II, EDIS, 951 IC, custom intake, Ford 5.0L throttle body, Forge BOV, WB o2, G31 w/LSD, 964 wheels, 968 rear sway, Bilsteins, 200# Welt. springs. A laptop, and a partridge in a pear tree.
1991 964 C4 Cabriolet

sequential · Joined: 18 Nov 2005 Posts: 500 Location: BANNED

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sequential · Joined: 18 Nov 2005 Posts: 500 Location: BANNED

deleted

Smoothie · Posted: Thu Jan 11, 2007 6:58 am Post subject: Re: Cold Start Diagnosis

Paul · Posted: Thu Jan 11, 2007 11:22 am Post subject:

Just for fun bypass the fuel pump relay or pop in your spare.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

I think The Dog (the Smooth Dog, that is) has it. The crappei-ness is slowly going away. I think a little highway blow-out is in order.

OOOOOO got my brakes/wheels installed finally! WOOT! Pics coming. . .

rasta
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

And speaking of fuel, I am eyeing a Pierburg pump on Ebay for $180. Anybody got a better price?

TIA
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

D@mn! How come my problems aren't solved this easily.

Sounds like a decent price on the Pierburg. These pumps seem to jump up in price every year. And mine's got a good howl lately...
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1980 931S
15psi boost, MS-II, EDIS, 951 IC, custom intake, Ford 5.0L throttle body, Forge BOV, WB o2, G31 w/LSD, 964 wheels, 968 rear sway, Bilsteins, 200# Welt. springs. A laptop, and a partridge in a pear tree.
1991 964 C4 Cabriolet

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

Carry a medium gauge wire with two male spade terminals on the end. I don't remember which # terminal you plug the ends into, but that's how you bypass the relay. Not a bad idea to toss the wire in your glovebox. Keep it as limp home only though.
_________________
1980 931S
15psi boost, MS-II, EDIS, 951 IC, custom intake, Ford 5.0L throttle body, Forge BOV, WB o2, G31 w/LSD, 964 wheels, 968 rear sway, Bilsteins, 200# Welt. springs. A laptop, and a partridge in a pear tree.
1991 964 C4 Cabriolet

flosho · Posted: Fri Jan 12, 2007 6:13 am Post subject:

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Wacky. Like I said above, it "felt" like the engine wasn't pulling enough vacuum to pull down the metering plate. So this morning, before driving it to the alignment shop, I popped the boot off, and had a look, and the plate and opening were pretty dirty with gooey blowby from the last 26 years. The plate seemed to move OK, but I cleaned it carefully with TB cleaner and a towel, as well as the opening. It took a bit of scrubbing!

Mind you, it was 18 degrees here this morning, but the car fired right up and idled fine. I guess the "goo factor" was preventing smooth operation of the air metering plate.

Thanks to all for the help,

rasta
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3