Hot start problem 88 5kt automatic

[Joshua van Tol]

Has your friend checked for spark while this is happening? That would  
be the very first thing to do before swapping a bunch of parts. None  
of the things your friend has replaced are likely to fix a hot start  
problem.

On Feb 2, 2006, at 6:52 PM, Doyt W. Echelberger wrote:

> Friend's 1988 5000 turbo (fwd automatic) has developed a tendency  
> to not restart after being shut down hot. In desperation he asked  
> for suggestions yesterday.
>
> He drives for 30 minutes, parks in driveway, turns off engine, trys  
> restart and all it does is crank. Won't catch.
>
> MUST cool down before it will restart when this happens.....20-30  
> minutes. And it doesn't happen all the time. No apparent pattern.
>
> Runs_ great _when started cold and stays that way as long as it is  
> driven without being turned off.....sometimes. He already replaced  
> the oxygen sensor, the plugs, the wires, the cap and rotor.
>
> Good-running spare parts type 44 of same year is sitting there  
> waiting to swap anything and everything to see what will make the  
> problem go away.
>
> Here is what I found in the archives:
>
> This problem is rampant among UrQ's and 5000 models. Apparently is  
> a vapor-lock thing. It is the reason Audi put the jury-rig blower  
> in there to cool down the injectors and reduce under-hood temps.   
> Also one of the reasons for coming out with the next generation of  
> inline 5's.
>
> This vapor-lock explanation makes sense to me because we have been  
> having unusually warm winter weather (50 degrees F) here in Ohio,  
> and the gas station fuel mix is still being supplied to our area is  
> set for normal winters.
>
> Also could be aging of a relay that controls the fuel pump or the  
> one that causes hot-start pulsing of the cold-start valve. Or maybe  
> a poor ground for any of those relays. Or maybe a temperature  
> sensor is telling the ECU that the engine is cold. and needs the  
> cold-start valve open, and the mixture is so rich it won't run. Or  
> maybe the RPM sensor resistance is out of its range and needs  
> replacing.
>
> Anyhow, before I get back to my friend, are there any other ideas?
>
> Doyt Echelberger
> 87 5ktq that runs just fine (!) (today)
>
>
>
>
>
>
>
> _______________________________________________
> quattro mailing list
> quattro at audifans.com
> http://www.audifans.com/mailman/listinfo/quattro