Re: [DML] Re: Warm Start Issue (David McKeen)
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Re: [DML] Re: Warm Start Issue (David McKeen)

I brought the tech manual with me to work today and over lunch I
looked some of this fuel pressure stuff up. I hope the following
information will be useful.

"The accumulator keeps the system under pressure when the pump is not
running." --Tech manual, page 43

"An electric fuel pump runs constantly during cranking and when the
engine is running. It supplies fuel to the lower chambers of the fuel
distributor. Any fuel that is not used returns to the fuel tank by
passing through the primary pressure regulator.

"The primary pressure regulator controls main line fuel pressure. If
the main line pressure increases above a pre-set value, the pressure
forces the regulator open. This allows fuel to return to the tank,
maintaining a constant main line pressure.

"If the primary pressure decreases, the pressure regulator will close
by opposing spring tension and restrict the amount of fuel returning
to the tank. The movement of this regulator valve will maintain
constant main line pressure and distributor lower chamber pressure
regardless of engine fuel requirements or voltage fluxuations at the
fuel pump. Main line pressure is regulated at approximately 5.2Bar
(75.4 PSI). The pump continuously circulates approximately 29 gallons
of fuel per hour through the system.

"The fuel accumulator will charge during the first few seconds of
operation. This charging process will dampen initial fuel pump surge.
When the engine is shut down, several check valves close throughout
the system and prevent fuel from returning to the tank. The
accumulator maintains pressure in the fuel system to prevent fuel
vaporization while the vehicle is not in use." --Tech manual, pages

"When the fuel pump is not operating, it is necessary to retain fuel
under pressure in all lines. This "rest" pressure will prevent vapor
from forming in the lines and insure instant restarting. When the fuel
pump stops, a check valve and two seals close, sealing off the fuel
return lines to the tank. The accumulator will then maintain pressure
in the system to prevent vaporization.

"In addition to the check valves and seals, it is important that the
control plunger returns to the closed position, all injectors close
tightly, cold start valve closes tightly, and all fuel connections are
tight and leak-free." --Tech manual, page 54.

"Positive pressure buildup in the tank is normal for this system."
--Tech manual, page 59.

"When checking fuel pressures, it is necessary to operate the fuel
pump without the engine running. To by-pass the RPM relay, remove
relay and connect a jumper wire between terminals #87 and #30 in the
connector. The RPM relay is located in the relay compartment behind
the passenger seat."


Farrar Hudkins

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