"Brian" <hskr@cox.net> wrote:
> I guess I don't understand how cycling the key will produce more "volume" if
> the pressure doesn't change. The fuel pressure made by the pump is what
> pushes the fuel through the system. If the pump turns on pressurizes the
> rails, and then kicks off, cycling the key isn't going to do much more.
That's true only if the pump is able to fully pressurize the rails
during the first key-on cycle, but that is not always the case. The
fuel pump doesn't have any sort of pressure feedback system; it is time
based. When the key is turned to the "on" position, the pump kicks on
for about one second and then shuts off unless the engine is cranking
or running. With a non-pressurized line (fuel has leaked back through
the pump's check valve, through a faulty injector or through a leak in
the line), that brief period of operation may not pressurize the fuel
line sufficiently and/or move enough fuel to the injectors for an
immediate start.
As far as how cycling the key results in a faster start, a fuel
line that has completely leaked down and is starting at 0psi might go
to 15 psi on the first key-on cycle, and attempting to start may take
longer than usual as the pump takes it from 15 to 35ish during the
crank. However, in that same scenario, if the key is cycled again, it
may go from 15 to 30psi, and this time the pump only needs to go from
30psi to 35ish during the crank, resulting in a faster start.
--
-Jon-
.- Jon Steiger -- jon@dakota-truck.net or jon@jonsteiger.com -.
| '96 Kolb Firefly, '96 Suzuki Intruder, Miscellaneous Mopars |
`-------------------------------- http://www.jonsteiger.com --'
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