[T3] Cold idle Problem

[Jim Adney]

On 20 Jul 2011 at 22:06, SCS Crewcab wrote:

> I got my '71 FI Fastback running. I plugged the holes in the gas tank 
> with epoxy paste and squirted carb cleaner in the ports of the fuel pump 
> and kept reversing polarity until it freed up. It's running pretty good 
> for being parked for 3 years. Kind of amazed it cranked at all. Anyway, 
> I've had a nagging problem ever since I got this car. When I start it 
> when the engine's cold and let it idle, it either shuts off or idles 
> like it's about to shut off. If I rev it up a few times or just hold the 
> pedal down about a quarter of the way, after about 15-20 seconds, it 
> will idle normally. I've tried all the obvious things like timing, 
> plugs, plug wires, idle setting, etc. It's no big deal, I'm just 
> wondering what's causing it.

Two possibilities come to mind.

The first is that the fuel ring gets air in it after being parked 
hot, and you're just waiting until all the bubbles are gone. The test 
for that is to park it when hot, restart it a few hours later and let 
it run for just the few seconds it takes to settle down, then leave 
it alone until the next morning. If it starts and runs nicely the 
next morning, the fix is to install a switch that will let you run 
the pump for a few seconds before starting, to fill the fuel ring. 
All my cars have this switch. I sell a kit to fix this for $10-11,  
depending on whether it's AT or MT.

The second is that it's running rich on startup and that floods a 
cylinder. The engine won't run smoothly until that cylinder is 
flushed out and starts firing again. I've had cars which did this and 
I just got around it by driving it up the street then taking my foot 
off the gas and letting the road wheels turn the engine for a few 
revolutions. This empties the cylinders and gives each of them a 
fresh start. If that's the problem, the engine will run smoothly 
after you do a little of this engine braking.

You can try both tests and decide which problem you have. You may 
also have both.

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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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