[T3] Chasing Engine Gremlins

Jim Adney jadney at vwtype3.org
Mon Apr 11 20:15:09 PDT 2011


On 11 Apr 2011 at 17:40, Robert Bills  wrote:

>  The existing regulator tested at 13.5 volts at the battery at
> moderate rpm.  I replaced it with a new unit and tested again.  This
> time the result was 14.7 volts regulated voltage at the battery. 

> I was able to road test my Squareback the next day on a 330-mile round
> trip to a VW event in Solvang CA.  Not only did the engine run better,
> my fuel consumption went from 20mpg to 27.5 mpg. 

Low system voltage makes the FI run rich, so your experience is 
typical, actually better than typical, because 27.5 is great gas 
mileage for these cars.

> My next quest is to determine why the idle is rough when cold, and why
> the engine still "loads up" so that I sometimes have to rev it up to
> "clear" the cylinders before it will accelerate like it should.   An
> experienced (but prohibitively expensive) local mechanic looked at my
> motor and immediately observed that the injectors weren't matched
> (something my inexperience and lack of VW knowledge prevented me from
> seeing).    If that is true, it would explain a rough idle.  I suspect
> that one injector is bad and causing that cylinder to load up with
> fuel at idle and low rpms.  Two injectors (1 & 2) have yellow caps at
> the tip.  No. 4 has a green cap.  No. 3 is the oldest and appears to
> have a black cap. 

68-9 FI Type 3s came with black injectors with Bosch numbers ending 
in 001. They were superceeded by yellow Bosch ending in 007. Green 
ones don't belong on your car. Black ones are NLA, and old black ones 
seem to have a somewhat greater chance of leaking, but I may just be 
dreaming this. Yellow 007s are the correct replacements. I have new 
ones in stock, as well as used ones that may also be good. Someday I 
will set up something to test them, so for now I recommend the new 
ones. 

> Which are the correct injectors?  (If any)    Please school me on flow
> rates and which injectors are the best for a stock motor with the goal
> of maximizing fuel economy while retaining reasonable performance.  
> Someone, in a forum somewhere else, suggested bus injectors but my
> limited experience has thus far proven that the experts are here, not
> there. 

I don't know the flow rates, all I know is that the Bosch 007s work 
right for our cars. I have also seen aftermarket yellow ones that 
don't seem to work right. They tend to have square corners in the 
molded plastic unlike the nicely rounded Bosch ones.

The most common problem with injectors is little short hose that's 
crimped on there. The hose deteiorates and leaks, but the hose and 
crimp ferrule can be carefully cut off and replaced. Other than 
replacing the hose, I've replaced VERY few Bosch injectors over the 
years: less than a handful. I've replace LOTs of hose.

I've had cars that tended to get a flooded cylinder upon starting. I 
could tell that it was just running on 3 for the first block or 2. 
The fix for this with our FI cars is just to speed up and then take 
you foot off the gas and let engine braking slow the engine down. 
Under these conditions the FI stops injecting, but the ignition 
continues, burning any excess fuel. 3-4 seconds of decel and you're 
back on 4 cylinders.

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