Ok, Finn, that was my guess as
well.
That then brings up a question - my understanding
of "vapor lock" is that it is caused by a low pressure area/combined with hot
fuel on the EFI pump intake which cause the gasoline to flash to vapor -
naturally the EFI pumps can not pump vapor - therefore as fuel is injected
from the high pressure side of the pump (reducing pressure on that side),
vapor can form there as well. In any case, insufficient fuel is injected
into the engine.
Since the injectors are still clicking open, it would
seem that any vapor on that side of the pump already has a chance to vacate
the line (through the injector) - so my assessment is that it is not the
relief of vapor/gas from the high pressure side that remedies the problem,
it's removing the gas from the low pressure side (pump inlet) and thereby
permitting liquid fuel to be pumped that "cures" a vapor lock situation.
So I am puzzled why a gas vent on the high pressure side
would have much (if any) effect on vapor lock. IF there is pressure on
the injector side - I question whether it would be as high as pump pressure -
and even if it were, the injector opening would provide a path for it to be
release - not to mention the pressure regulator. So as I said -I'm a bit
puzzled as to the mechanism that a vent in the high pressure side prevents
vapor lock.
In my opinion, there are two ways to reduce/eliminate
the vapor in the low pressure side - either cool the fuel sufficiently
(somewhat difficult to do) or to increase the pressure in the low pressure
line forcing the vapor back into the liquid - ergo - use a boost
pump.
FWIW
Ed
Sent: Saturday, August 13, 2011 2:53 AM
Subject: [FlyRotary] Re: vapor lock
Hi Ed,
I believe it's simply a return to the tank from
the high-pressure side via a very small orifice. How small I do not
know.
Finn
On 8/10/2011 9:28 AM, Ed Anderson wrote:
The one I potential preventive measure/fix I have not
looked into is the vapor by-pass/dump that I know a few folks are
using. I search the archive but could not find a description of this
method - anyone care to provide
one?