[T3] Fuel Primer Switch.....

[Jim Adney]

On 25 Sep 2018 at 5:33, J. Jonik wrote:

> Why doesn't turning on the key multiple times, not to point of ignition, prime
> the fuel system?

Turning the key multiple times clearly works, but it adds wear to the 
ignition switch. That's not as much of a problem on your '73 as it 
would be on a '71, where a replacement switch is almost impossible to 
find, but even replacing a '73 switch is much more work and more 
expensive than a primer switch.

I think it's also likely that having a switch that allows you to run 
the pump continuously, as opposed to a series of 1 second pulses, is 
more effective in clearing the air out of the fuel system.

> Then, what's wrong that it NEEDS special priming tricks, or primer
> switches?Is there an old, worn out, or dirty Primer Switch somewhere that ought
> be replaced, or cleaned?

That's the $64k question. I don't know. I've worried about that for 
decades and tried replacing everything in the system without 
discovering the key.

The ONLY remaining suspect I have is the fact that when these systems 
were new, all the fuel lines in the engine compartment had grey vinyl 
covers over the gas lines. It's possible that this gave just enough 
extra heat shielding that the heating/boiling problem didn't occur.  

Over time, as we replaced those hoses, those sheaths were discarded, 
because they were too hard to get over the new lines. Plus, most of 
the time the new lines were larger than the OE so it would have been 
impossible to slide the sheaths on.

It's also possible that this problem always occurred in our hotter 
climates, and that it has gotten worse with global warming (yes, it's 
real) and possible changes in the vapor pressure of modern gasolines.

I designed the primer switch kits to solve this very common problem 
simply and cheaply. They're effective and cheap. They work.

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