In reply to a message from SD Faircloth sent Fri 5 Apr 2013:
SD,
Here’s what I understand so far:
On earlier XJ40s the pump is in the fuel line outside of the
tank, and a check valve is in the fuel line at the outlet of
the pump. I have not researched to see if there is another
check valve in the system on the inlet side of the pump.
On later XJ40s the pump is mounted vertically inside a
plastic canister in the fuel tank. The canister has two
check valves, one at the eductor, or ‘‘jet’’ pump, and one at
the outlet on the top of the canister. The eductor uses the
venturi effect to allow the small pump motor to circulate a
larger volume of fuel than it otherwise could.
The canister has an inlet on the bottom end fitted with a
rectangular filter packet, but via an inlet on its top end
it also receives fuel returned from the fuel rail as
released by the fuel pressure regulator. Theoretically,
these two fuel inlets should keep the canister full at all
times. But if the fuel in the line vaporizes as Bryan has
described, and/or the fuel level in the tank is so low that
the bottom inlet sometimes sucks air instead of fuel (e.g.
while cornering), it seems possible that under some
conditions the canister might contain some vapor or bubbles
which could be ingested by the pump.–
The original message included these comments:
I am not familiar with where the fuel pump is located on an XJ40?
However, I suspect it is in the fuel tank. If so, then the pump is
fully submerged in fuel and should therefore always be full of fuel.
If that is true, then there should be no need for a check valve on
the suction/upstream side of the pump in order to keep the pump
full of fuel. So then, only requiring a check valve on the
outlet/discharge side, to keep everything downstream full of
fuel…the fuel line to the engine, the filter and the rail.
–
Don B : '93 VDP Flamenco Red 189K : (ex-'88 Sovereign)
Franklin, TN, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !