1.Make sure the vehicle has some
fuel in the tank. If in doubt, add a few gallons and again try
starting the vehicle before proceeding.
2.Check the vehicle's on-board
diagnostic system for any fault codes. These should be corrected
before diagnosing the fuel system.
3.Using a wiring diagram and
voltmeter, check specific voltage at pump relay, fuse, inertia
switch. oil-pressure switch and engine-control module.
4.If the
pump is receiving the correct voltage, turn key on. Pump should
start and run from two to four seconds.
5.If the vehicle runs, but
is hard to start, install a pressure gauge by teeing into the fuel
line (TBI) or using the service fitting on the fuel rail (EFI).
Turn the key on and check the gauge to make sure that the pressure
does not drop more than 10% of its maximum reading. If adequate
pressure is not maintained, the check-valve is stuck. Replace the
fuel-pump assembly.
6.Start the vehicle and check fuel-system pressure
with the gauge still hooked up. If system pressure is too high,
it may indicate a defective pressure regulator, a kinked or broken
vacuum line, or a blocked return line.
7.If the fuel-system pressure
is too low, it may indicate a leaking pressure regulator, a clogged
fuel-pickup strainer, or a blocked fuel-line filter.
Removing the Fuel Tank
When the in-tank fuel pump is identified as the problem
component, the fuel tank must be removed or lowered enough for
access to the pump hanger assembly. (Refer to vehicle repair manual.)
Before
servicing, please review the safety precautions 1 and prepare the
work area for the cleanliness requirements.
1.First, release tank
pressure by removing the filler cap. Then relieve fuel system pressure
by removing the pump fuse and running the engine until it quits
from fuel starvation. Crank engine briefly to confirm pressure
relief. NOTE: Some systems have two fuel pumps: low-pressure in-tank,
and high-pressure in-line. Be sure to disable both fuel pumps when
this applies.
2.WARNING: Gasoline vapors are explosive! To reduce
the possibility of sparking, disable the electrical system by disconnecting
the negative (-) battery cable.
3.Drain fuel to lighten the tank
and avoid spilling when removing the pump hanger assembly. Use
only an approved container, preferably one that filters the fuel
for reuse in the vehicle.
4.Remove the fasteners for the fuel filler
neck, noting their different sizes and locations, then raise vehicle
on the hoist. (If working without a hoist, use an approved floor
jack to raise the vehicle and approved jack stands to support it.)
5.Support
the tank with a transmission stand or floor jack. Note location
of fuel outlet, fuel return and vapor return lines. Remove the
lines, using a clean shop towel to absorb draining fuel, and inspect
them for cracking or chafing. When replacing high-pressure lines,
use only SAE R-7 hoses or higher. Disconnect pump wiring harness.
6.Remove
tank straps, and filler neck tube if necessary. Lower tank enough
to access fuel pump hanger assembly, or completely remove tank.If tank is rusted inside, or seriously damaged,
it must be repaired or replaced before proceeding. Also replace
hangers that show excessive rust, wear or damage. Do not return
sour or contaminated fuel to the vehicle. Dispose of properly.
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