SERVICING THE ELECTRIC FUEL PUMP
Where is the fuel pump?
Most of today's fuel injected automobiles have a fuel tank stored pump, setting in a small cavity at the bottom of the fuel tank. This location is both good and bad for the pump. First the good part: The fuel is a coolant and lubrication for the operation of the pump and at the bottom of the tank, it is primed and ready to work when turned on.
Now the bad part of this location: The pump is submerged in all the contents of the tank. Fuel water, and a collection of foreign matter and temperature change from cold to extreme hot. All of the above is a possible cause for pump failure and the most often cause of pump failure is heat. The fuel system has a return line to the fuel tank and about 40 % of the pumped fuel is heated from the operation of a very hot engine and exhaust system. The fuel in the tank will get very hot if the fuel is allowed to get lower than 1/4 of a tank.
Why does the fuel pump fail? When the pump gets hot the brush assembly fails because of the extreme heat the springs lose tension and break with the brush leads and the pump stops or can not pump enough to run the auto. Some other reasons the pump fails is the collection of foreign particles that jam the operation of the pump.
Life of the Pump
Like all other parts of the vehicle, it will fail. However, there is some things that can be done to help the pump last longer:
A. Never let the fuel level be less than 1/4 tank. This helps to cool the pump.
B. Never fuel-up while the service station tanks are being filled. This agitates all of the water and settlements in the ground tanks and some may be pumped into your fuel tank.
C. Never run your tank empty. This is very bad for the pump; about three times of no fuel and your pump will be finished.
Test Information
Fuel Pressure for Three different Systems. TBI 9 - 13 psi , ... PFI 36 - 41 psi,... CPI 55 - 64 psi. To test the pump pressure, hook up the pressure gauge and turn the KOEO. The relay should run the pump for two seconds. The ECM or oil pressure switch will turn the pump on while cranking. Most auto's must have a flow test of 1 pint in 15 seconds. If not, check for restricted line or filter. To check the fuel regulator removing the vacuum hose, the pressure should rise to the max. reading. Note: If the relay is bad or the pressure is low, this will cause a slow or no start.
By Carlis B. Wilson