i have an 86 f150 and i cant keep it running, the first time it did this a
machanic told me to change the spark plugs and wires, well it worked for
about six months, now it won't start again, fuel pump won't turn on but the
service manual says that it won't if the icm is faulty it won't turn on, i
changed the coil and icm and it still won't start, i don't know what to do
If you are SURE the fuel pump is not running then you need to check the
fuel pump circuit. There is the pump, a relay (located at the rear of
the engine compartment on the drivers side near the brake booster), and
AFAIK an inertia cutoff switch located somewhere else in the vehicle.
Start by checking for power to the pump at the plug that connects to
the pump on top of the fuel tank. It is a 4 wire plug 2 for power and 2
for fuel level guage circuit. The larger gauge wires are power and
should show 12 volts between them. If there's power there and the pump
doesn't run the pump is bad (most common problem). If there is no power
there then you need to check the rest of the circuit. The ecm is seldom
the cause of fuel pump failure. There is also a small inline secondary
fuel filter on some of these trucks located near the rear of the
drivers side cylinder head. It being plugged is a major cause of pump
failure, especially if you have had fuel starvation related symptoms
leading up to the failure.
Oh yeah when you check for power to the pump you need to check either
as the key is first flipped on or with someone holding the key in the
start position. The pump does not receive continuous power with the
ignition on and the engine not running or cranking.
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