[T3] TWO Successful Repairs!!!

[Jim Adney]

On 18 Sep 2023 at 9:58, John Riley wrote:

> I'm curious, if you were experiencing running rich and it were due to the
> pressure regulator not having "a good vent to atmosphere", wold the
> regulator be running at a higher psi than you set it at?  I think that's
> what you're saying in the first paragraph above.

Yes, that's correct. The fuel pressure regulator, like most pressure 
regulators, has a diaphram with fuel on one side and spring pressure plus 
atmospheric pressure on the other side. This supplies an output pressure 
that is always a fixed amount above atmospheric. But this depends on the 
atmospheric side to actually be reliably at atmospheric pressure.

If the air side becomes sealed off, and experiences an increase in internal 
pressure for any reason, this will be reflected in an equal increase in output 
pressure. This is what I believe has happened, both for Keith, decades ago, 
and me, just this year.

Consequently, I'm recommending that everyone with d-jetronic FI drill a vent 
hole in their regulator. If you're not confident in your ability to drill a tiny hole 
there, I'll drill it for you for $5 plus return shipping. Unfortunately, removing 
and replacing the regulator is the hard part.  

FYI, I drill a 0.050" hole, on the underside, so dirt won't tend to filter in there. 
I think it's best to keep it small, so insects don't enter and affect the 
operation.

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