Mark R.

On the first start of the morning, my 88 always starts immediately at the bump of the key.
On all the subsequent warm restarts, it will labor to start unless I give it some throttle.
When I hold the pedal at half throttle, then hit the starter, it rips to life and starts up quick and normal.
I’m pretty sure that it’s cranking too rich, because I get a single puff of smoke out the tailpipe.
Also, it idles a little bit rough for the first few seconds until it clears.

After doing a search (found TONS of info available as usual), I focused on the TempII sensor.
So I checked the resistance at both pins of the sensor, the LH input pin #13, and the EZK input pin #19.
I got the exact same readings at all four locations, which were:
1 - Before starting the car after an overnight soak in the garage at approximately 50-F, it reads 2.77 k-ohms.
2 - Immediately after the car is shut down once it has gotten fully warmed up, it reads 258 ohms.
I believe those readings are acceptably within the proper ranges... Correct..?

I also confirmed that the fuel system checks and holds pressure quite well after the engine is shut down.
That would seem to exonerate the fuel injectors, the regulator/dampeners, and the fuel pump check valve.

So my question is:
What other devices and/or inputs control the commanded pulse width to the fuel injectors during cranking?

Thanks in advance...
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Mark in Atlanta

87 S4 Grandprixweiss Auto w/LSD (Daily Driver Since 2004).
88 S4 Silbermetallic 5 speed w/LSD (Weekend Driver Since 2003).
84 S Schwarz Auto w/LSD (Sold in 2007 - Daily Driver 1997-2004).
Lots of other non-Porsche vehicles...
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Mark R.

Well, lots of views, but no responses yet...

OK, some additional data:
I checked the resistance across MAF pins #3 and #5.
At garage temperature (~55-F) it reads 4.4 ohms.
I realize that's only a crude check, but I think that's proper.
Does the MAF signal even get used during cranking?

Any ideas about the rich fueling during crank..?

___________________________________________

Mark in Atlanta

87 S4 Grandprixweiss Auto w/LSD (Daily Driver Since 2004).
88 S4 Silbermetallic 5 speed w/LSD (Weekend Driver Since 2003).
84 S Schwarz Auto w/LSD (Sold in 2007 - Daily Driver 1997-2004).
Lots of other non-Porsche vehicles...
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jcorenman

No.

You are correct that it is rich, and opening the throttle allows additional air to go along with the too-much fuel.

But I do not think it is too much cranking fuel. If this only happens on warm restarts then something is leaking fuel into the intake while it sits with pressure in the fuel lines.

Candidates are one or more injectors that leak when sitting under pressure, or possibly the fuel regulator or damper is leaking fuel into the vacuum lines, again when it sits under pressure.

Overnight, the extra fuel fuel evaporates and dissipates, and the engine starts normally.

Try a tankload of Techron or similar, that may clean up the injectors. Or send them off for cleaning and checking.

Regulator/dampers can be checked for leakage by disconnecting the vacuum lines and sniffing for gasoline. Or, jumper the fuel pump and then check for fuel leakage out of the vacuum lines. (Note: regulator/damper leaks will usually mess up the idle also).