[T3] engine miss, solved?!

Jim Adney jadney at vwtype3.org
Thu May 20 09:58:07 PDT 2021

On 19 May 2021 at 22:15, Keith Park wrote:

> Recently the retard side of the advance can had a vacuum leak and wasn't
> working properly, It did move but it DID leak.  The hose was a bit loose on
> the nipple too.

I hate those dual advance/retard vacuum cans. They are fragile and the 
retard sides are always failing, but this usually makes it impossible to do a 
correct tuneup. Those cans are also frightfully expensive, IF you can find the 
right one at all. Part of that tuneup requires that you test the retard by pulling 
off the retard hose and verifying that the timing advances by some significant 
amount. If it doesn't you can't set the timing properly.

Small leaks in the diaphram won't hurt anything; they get washed out by the 
suction from the intake, but I'd be worried that a small leak was about to 
become a large one. I've never caught a retard diaphram leak when it was 
small; by the time I see them they are HUGE.

> I think it was Jim that mentioned that one screw for the can needs to be the
> shorter one otherwise its awfully close to the points spring, which is hot.

Yes, that was me. I'm always careful about the screws in our distributors. 
Bosch used about 4 different length screws, and they are different for good 
reasons. [BTW, if the screws that hold the FI trigger points in place are too 
long, they can short out the trigger points the same way. You can only see 
this if you install the trigger points before you install the points plate, so you 
can look down there to verify that the screw isn't sticking in beyond the 
inside of the distributor body.]

> I cant say for sure it was touching, or intermittently touching but that
> does change with RPM, advance etc.  Ah HA!  Put the correct screw in, set
> the timing, now I have a higher idle so I was able to adjust it down, it was
> now running too RICH.  no more missing  

Sounds good!

> Cant say for sure it was that little too long screw, or routing of the plug
> wires, or a connection I wiggled, but that screw was definitely asking for
> trouble and a good example of why to just send your dizzy to Jim to have it
> rebuilt, its those little tiny details that he remembers and that matter so
> much.

Thanks for the compliment. I've rebuilt a LOT of distributors over the past 50 
years, so eventually the important points start to sink in.  ;-)  

I know I'm as likely to jump into the deep end looking for the cause of a 
problem, but I also know that the simple solutions are usually the best and 
always the quickest and cheapest.

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

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