Re: [T3] Trigger points question

[Jim Adney <jadney@vwtype3.org>]

On 24 Mar 2003 at 9:16, jim wrote:

> This weekend was warm so I did basic tune-up on my SQBK (72 FI engine, MT).  I
> drove very little over the winter, but the car lacked some power and had poor
> mileage (12 mpg?) and cylinder 1 missed intermittently while the other three ran
> fine.  

Gas mileage this low makes me wonder if your voltage regulator is worn out. 
Check your system voltage: It should be above 13.5V at med rpm with the engine 
warm after a drive.

> As part of the tune-up, I replaced the spark plugs.  Plugs 2 & 3 were fine while
> 1 & 4 were black and evidently running VERY rich.  I believe the trigger points
> fire the cylinders in pairs (2&3/1&4), correct?  I used an ohmeter to check both
> trigger point leads from the dizzy and it swung from 0 --> inf. for both sides
> using the middle prong as ground.  I also cleaned the trigger points with an
> index card but they were not dirty.

It may not be a FI problem. It could also be an ignition problem, due to #1 & 4 
not firing for some reason. Check your dist cap for tracks that might cause 
this. Low system voltage could also cause this, and it might just be that #1 & 
4 were the first to be overwhelmed by the over rich mixture. 

You are correct about #1 & 4 being injected together.

> Am I looking in the wrong direction for the problem?  My valves are okay, the
> car points and timing in spec (the car has a 68 FI dizzy, so the timing is
> slightly different than a stock 72), and the fuel pressure is 31.

If this is a 72 engine with a 68 dist you should be timing it to the mark that 
is the second from the left. (The 68 and 72 timing marks are different.)

> Any ideas are welcome and appreciated.  Thanks for the help.  Also, I drove the
> car a bit and changing the spark plugs made a huge difference, but I know if I
> don't fix the problem, 1 & 4 will run into the same problems over time.  I'd
> like to catch this right away.

It is also possible that the plugs WERE the problem, so if everything else is 
good the problem may not come back.

-- 
Jim Adney
jadney@vwtype3.org
Madison, WI 53711-3054
USA

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