[T3] Old Type IIIs (Exhaust Tester)

[J. Jonik]

Back in Feb. I got the advice below about testing Air -Fuel balance with an Exhaust Tester.  Mix should be  14.7  : 1 ...meaning 14.7 parts air to 1 part fuel, I assume.

But, it seems that garages don't automatically have Exhaust Testers nowadays...they use computer equipment that doesn't test for fuel-air ratio.  

So, If I find a garage that has Exhaust Tester, and if there's a little too much fuel, can this be easily corrected by lowering the Fuel Pressure adjustment?  My fuel pressure is a constant 29.  Should I adjust to 28...which is what's needed anyway?  Can that one fuel pressure point make a noticeable difference?

 Car's still running (and idling and starting and accelerating) alarmingly perfectly.   I'm not used to that.

From: Jim Adney <jadney at vwtype3.org>
To: type3 at vwtype3.org
Subject: Re: [T3] Old Type IIIs
Message-ID: <4D667E21.5591.4ABD438A at jadney.vwtype3.org>
Content-Type: text/plain; charset=ISO-8859-1

On 24 Feb 2011 at 13:31, J. Jonik wrote:

> Never used an Exhaust Tester. Will visit my friend's shop.? What does an
> exhaust tester tell you? Is it generally known what a Perfect Balance
> between rich and lean is?

It should tell you the air/fuel ratio, which should be 14.7:1.

> ? And, couldn't a rich reading mean something besides fuel pressure
> adjustment is needed?   (My fuel pressure is consistent 29) 

There are any number of things that will change the richness. Fuel pressure is 
the only one you can actually adjust up and down easily.

> For the record...my 72 FI, with "new" Control Box AND disconnected temp
> sensor (at Air Regulator) is working just great...driving, accelerating,
> idling, everything. Mystery is why disconnecting that temp sensor helped the
> idling oddities so much.? VW must have wanted it there for some reason. 

By disconnecting that sensor, you've set the sensor resistance at infinity. I 
think that corresponds to telling the brain that the engine is cold. I would 
expect the brain to respond by making the mixture richer.

BTW, a '72 should have 2 temp sensors: one on the left head, just beneath the 
#4 spark plug, and the other in the intake air distributor. Sounds like you may 
still have a few things to sort out.


      
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