Fuel Pump/Lines

Fuel Lines;
The rubber fuel hose from the tank to the pump is in good condition, not perished or cracked. The rubber and copper pipes from the pump to the filter are all in good condition and fitted tightly. The rubber hose from the filter to the rail is in good condition. The fuel rail is also in good condition and fitted tightly. The vacuum hose for the regulator and the fuel return line are also in good condition and do not appear perished or cracked.

Fuel pump;

fuel pump

To start testing for fuel pressures, we must first plumb a pressure gauge into the section between the fuel filter and the fuel rail.
To check fuel pressure at wide open throttle, we can simply remove the vacuum hose from the regulator and this will simulate atmospheric pressure.
Residual pressure can be checked after the engine has been turned off. Pressure at idle can be read when engine is idling, and clamping the fuel return hose we can see the max pressure of the system.

If you are to remove any fuel hoses, relieve pressure in the system by un-doing electrical connections at the fuel pump, so no power is there, and then crank engine over to relieve pressure.

The manufacturers specifications for the toyota engines were as follows;
      Wide open throttle - 38-44 PSI
       Idle -                      31-37 PSI
       Residual-                 21      PSI
       MAX                       (twice idle pressure) 61-74 PSI

Our test results were all above specified. This could be due to a faulty regulator  or a blockage in the return line.
Idle: 40PSI

fuel pressure regulator

WOT: 48PSI
Residual: 37PSI
MAX:    >87PSI

The fuel pump exceeds specifications

Manufacturers specs for fuel flow after regulator: 1 - 1.5 litres per minute.
Our test resulted in 3 litres per minute. This is quite large as a more powerful fuel pump has been fitted to this engine.

We then checked injectors on the engine.
To do this, we simply unplug each connection off each injector one at a time. On each injector, as we unplugged each one, we found that the RPMs of the engine dropped by 50 each time. Doing this test we were able to see that each injector was working correctly.
Other engine problems that could give this result could be spark plugs fowling, piston rings worn or bent valves causing loss of compression in a cylinder.
We also checked the resistance of the windings in each injector and got 13.9 ohms for each. This is within the specs of 11 - 17 ohms.