Hello everyone
I have a 1985 XJS HE that attempts to start (I have good , blue
spark at the plugs).I have a problem with the wiring to the inertia
switch- no voltage at either wire with the ignition on - so I
jumped the relay in order to activate the fuel pump…still no
start.I then began checking the fuel supply to the rail.I have good
flow to the intake fuel pressure regulator , so I disconnected the
fitting between the regulator and the fuel rail and there is no
fuel present with the fuel pump running in bypass mode.Do I have to
actually turn over the motor to enact this regulator , or should
there be fuel passing through without attempting to start the motor?
Also , can this intake regulator be bypassed at least long enough
to check if that is the cause of my no-start condition?Last , but
not least , if I don’t have voltage at either wire of the inertia
switch , where do I trace it back to? Thanks.–
David Rae
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In reply to a message from David Rae sent Tue 11 Dec 2007:
David,
The enertia switch is supplied from the ignition circuit, at least
on my '85 it is. I got rid of this switch years ago. Check your
ignition switch, as per Kirby’s book, you may find your power
problem?.
The inlet (RH) fuel regulator can be removed permenantly, and the
fuel fed straight into the rail. The LH reg is the actual pressure
control regulator.
The RH reg should pass fuel with the pump only running. If not it
is probably jammed?, or you have a very weak fuel pump.
The best thing is to get a fuel pressure test gauge, and see what
fuel pressure you actually have.
Grant Francis–
The original message included these comments:
Also , can this intake regulator be bypassed at least long enough
to check if that is the cause of my no-start condition?Last , but
not least , if I don’t have voltage at either wire of the inertia
switch , where do I trace it back to? Thanks.
In reply to a message from Grant Francis sent Tue 11 Dec 2007:
David,
Do you realize the inertia switch is a vital safety item? Its
purpose is to remove power from the fuel pump relay and shut down
the fuel pump in the event of a crash. That prevents pressurized
fuel from spraying all over the place should any of the pressurized
fuel lines or fuel rail be ruptured in the crash. But then, your
decision, your fire, and potentially your life!–
lockheed
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In reply to a message from Grant Francis sent Tue 11 Dec 2007:
Hi Grant,
Thank you for your response. If someone had in mind to permantly
remove the intake FPR what fittings would you use and what would
become of the vacuum line to that FPR?–
The original message included these comments:
The inlet (RH) fuel regulator can be removed permenantly, and the
fuel fed straight into the rail. The LH reg is the actual pressure
control regulator.
In reply to a message from David Rae sent Wed 12 Dec 2007:
Dave,
The A bank FPR is considered to be more of a pressure dampner
between the tank and the fuel rail. It has NO control over fuel
pressure in the rail…which is performed by the B bank FPR.
A FPR is not that expensive…maybe $30-$40. And 10-20 minutes to
remove and replace.
Never heard of one to get stuck…but anything is possible…and
from your description…sounds like yours is.
I would suggest replace it. Forget about eliminating it. The
fittings are odd-ball and not that easy to locate. Then get the
inertia switch/wiring operational.