[xj] Flat bedded home

Update:
Embarrassingly enough. Problem turned out to be lack of
gas. However, in my defense, seems that gas is only being
drawn from the left tank. Right tank is full and when
selected car will not run. Selector switch seems to be
working properly as it will switch back to the left tank
and car will run properly. I listened for gas return to
the left tank and believe I heard it coming back. There
was no sound coming from the right tank. Unfortunately I
can’t seem to wrap my head around this whole system and at
this point need to know if the problem is in the right
tank changeover valve or in the valve in the trunk.
Appreciate the help.
Ron
1986 VDP series III–
reron25@gmai
Bayside/NY, United States
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The valve in the trunk is the selector valve that determines which tank
the pump draws fuel from. The ones in the wheel wells are the return
valves that determine which tank the fuel is returned to. One return
valve is normally open, the other normally closed and applying power
reverses their state.

If you are not able to draw fuel from the right tank, then it is the 3
way valve in the trunk. I’d remove it and clean it out, there may be
debris in it that prevents it from switching, as the valve is between
the tank and filter, so unfiltered fuel goes through it. Be prepared to
plug off the hose when you pull it off the valve, as fuel will drain out
of the full right tank without the valve in place.

Craig

reron25@gmai wrote:> Unfortunately I

can’t seem to wrap my head around this whole system and at
this point need to know if the problem is in the right
tank changeover valve or in the valve in the trunk.
Appreciate the help.

===================================================
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reron25@gmai wrote:

Update:
Embarrassingly enough. Problem turned out to be lack of
gas. However, in my defense, seems that gas is only being
drawn from the left tank. Right tank is full and when
selected car will not run. Selector switch seems to be
working properly as it will switch back to the left tank
and car will run properly. I listened for gas return to
the left tank and believe I heard it coming back. There
was no sound coming from the right tank. Unfortunately I
can’t seem to wrap my head around this whole system and at
this point need to know if the problem is in the right
tank changeover valve or in the valve in the trunk.

The return test is unambiguous, Ron - fuel should only return to the
selected tank…

…however; fuel return also requires that the pump is delivering fuel
to the rail, which makes an ambiguity in your case, of course. The
engine may not run for two reasons; it gets no fuel - or the ‘right’
return has failed closed, causing excessive fuel pressure, as the ‘left’
return is also closed.

The simplest verification is to run on the working ‘left’ tank and
switch over while observing exhaust; excessive fueling will cause heavy
exhaust smoking before the engine quits…

The pump is fed by gravity via the changeover valve in the boot, and
pending the above verification, I tend to agree with Craig that the
valve has failed or is sticking. Remove as he outlines and clean/test…

You can also disconnect the changeover valve lead and test if it has
power (test lamp) with ‘right’ selected. If so, repeately poking the
powered wire to the contact should elicit valve action as it then alters
between unpowered ‘default’ and powered switching. The point here is
that while the changeover switch, at the dash, operates all valves in
unison - three different wires are involved…:slight_smile:

Hypothetically, the fuel line from the ‘right’ tank to the valve may
also be blocked - but the usual problem lies with the changeover valve
itself…

Frank
xj6 85 Sov Europe (UK/NZ)===================================================
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In reply to a message from Craig Talbot sent Fri 13 Apr 2012:

And if the valve is suffering debris, it’s coming from a
26yr old fuel tank that’s famous for these issues. Put in a
generic filter on each tank supply line before the
(selector) changeover valve to hopefully avoid debris right
back into your freshly cleaned valve. Of course, a quick
tank check by draining a bit of fuel from the bottom drains
would be in order first if there is junk in the valve or it
doesn’t work properly (completely open/completely close when
tested electrically).
Bill–
The original message included these comments:

If you are not able to draw fuel from the right tank, then it is the 3
way valve in the trunk. I’d remove it and clean it out, there may be
debris in it that prevents it from switching, as the valve is between
the tank and filter, so unfiltered fuel goes through it. Be prepared to
plug off the hose when you pull it off the valve, as fuel will drain out


'75XJ6C about to be unlumped, '86 XJ6, '67 FHC, '75TR6
moultrie, ga, United States
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