The engine cranks and has spark but won’t start. Does it need a new fuel pump?
A.
Maybe. A dead fuel pump will obviously prevent an engine from starting.
But a number of other conditions can also cause a no start problem.
These other possibilities should be investigated and ruled out before
replacing the fuel pump.
Many fuel pumps are replaced unnecessarily.
If a newly installed fuel pump fails to solve a starting or
driveability problem, many customers blame the pump and bring it back.
They may be swapping parts in an attempt to diagnose a problem, or they
may think the pump is no good. Either way, it wastes time, money and
goodwill. Returns also mean extra paperwork for the parts store,
warehouse distributor and pump manufacturer, not to mention shipping
costs and the potential of losing a repeat customer.
According to
the Fuel Pump Manufacturer’s Council, nearly 10 percent of all the fuel
pumps that are sold by auto parts stores are returned because the pump
did not seem to work properly after it was installed. Yet 80 percent or
more of the fuel pumps that are brought back for being “defective” work
just fine when they are tested.
Some common causes of no starts due to no fuel include:
•
A bad fuel pump relay. If the relay fails or has a bad electrical
connection, it can’t energize the fuel pump and the engine won’t start.
But it depends on the application. On many vehicles, the fuel pump
power circuit is also wired through the oil pressure sender unit. When
the engine is cranking and builds up oil pressure, power is routed
directly to the fuel pump through this switch. So the engine should
start even if the relay is bad.
• A blown fuse in the fuel pump
circuit can prevent the pump from running. If a replacement fuse blows,
there’s a short in the circuit that needs to be found and fixed.
•
Corroded wiring connections and bad grounds at the fuel tank are also
faults that can prevent a fuel pump from running or spinning fast
enough to generate normal pressure.
• Low fuel pressure can also
cause hard starting or a no start. Fuel injectors are designed to
operate within a specific pressure range.
• Low fuel pressure can
also be caused by a leaky fuel pressure regulator. The pump may be
working fine, but if the regulator is leaking and can’t hold enough
pressure in the fuel rail that supplies the injectors, the engine may
be slow to start or may not start at all.
• Bad gas (too much alcohol or water in the tank) can also cause a no start that is not the pump’s fault.
•
No gas in the tank. The fuel gauge may show fuel in the tank, but if
the gauge is not reading accurately, the tank may in fact be empty. The
fix here is to replace the sending unit or the gauge.
Q. What else should be replaced when changing a fuel pump?
A.
Most electric fuel pumps are mounted inside the gas tank. Replacing the
pump requires draining and dropping the tank. On top of the tank are
rubber fuel hoses (inlet and outlet, except on returnless systems that
only have an outlet hose), and evaporative emission control (EVAP)
vapor hoses. All of these hoses should be closely inspected and
replaced if hard, cracked, loose or leaking. The same goes for any
other rubber hose connections in the fuel system.
A new fuel inlet
filter sock inside the tank, and a new inline fuel filter are always
recommended — especially if the old pump failed due to rust or dirt in
the system. This may also require steam cleaning or replacing the old
fuel tank with a new one.