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Re: [T3] FI rich mix cyl. 2 & 3 only, poor mpg (11 mpg)

On 28 Mar 2006 at 3:04, Will McCreight wrote:

> Still working on a sick 1970 squareback...new points/plugs/plug wires,
> checked all injectors, replaced fuel rail, checked sensors, fuel line
> pressure, timing, dwell, generator voltage, new voltage regulator. 

> Today, pulled plugs to check compression only to find plugs 2 & 3 to
> be entirely black, 3 dry/fluffy, 2 slightly wet/oily but just a  much
> carbon as 3, 1 & 4 look just right...and this after only about one or
> two tankfuls of gas since new plugs. 

Just to make sure the cylinders are numbered like this, when seen 
from the rear:

3		1
4		2


Okay, here are some things to check.

1) The female connector pins in the injector plugs seem to loosen up 
after all these years. You can take them apart and VERY gently 
squeeze them slightly tighter, so they make better contact on the 
injector pins.  

To do this, you need a small tool, like a steel toothpick, to stick 
in the front of the connector and depress the locking tab on the pin, 
so the pin and wire can slide out the back of the connector body. Do 
this carefully and you won't damage anything.

I don't know if this could cause your problem, but I see quite a bit 
of this and it often helps a lot.

2) Get a clean hose and connect it to the vacuum connection on your 
pressure sensor. Suck on the hose. The pressure sensor should hold 
vacuum. If it leaks, you have a torn diaphram which is making 
everything run rich.

3) It's possible that the trigger points are not working right. I 
don't know if this would create the blackened plugs, but it can 
certainly make the engine run badly. I'm afraid the only way I know 
of to test them is to either find someone with the Bosch D-Jet 
tester, or to send your points to me to test. 

Testing in the car with the Bosch tester is the best test.

BTW, the injector end caps can be replaced. I probably have a couple 
of them here. Don't throw your old one away if that's its only 
problem, but for it to last, you should store it in kerosene. I'll 
take it if you don't want to bother.

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

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