PRELIMINARY INSPECTION
Step 1 Check fittings and connections to insure tightness. If insufficiently tight, leaks of air and/or fuel may occur.
Step 2 Check for fuel line bends or kinks in hoses.
Step 3 With engine idling look for:
a. Leaks at pressure (outlet) side of the pump.
b. A leak on suction (inlet) side will reduce the volume of fuel on the pressure side of the pump and suck in air.
c. Also check for leaks at diaphragm, flange, and at breather holes in pump casting.
d. Check fuel pump steel cover and its fittings for leaks. Tighten or replace fittings as necessary. If fuel pump leaks (diaphragm, flange, steel cover, or pump casting breathing holes), replace pump.
FUEL FLOW TEST
Step 1 Disconnect fuel line at the filter inlet.
Step 2 Disconnect pink wire at the fuel injection pump electric shut-off (ESO) solenoid.
Place a suitable container at end of pipe and crank engine a few revolutions (Figure 4-10). If little or no fuel flows from open end of pipe, then fuel pipe is clogged or pump is inoperative.
Step 3 Before removing fuel pump, disconnect fuel line at tank and blow through it with air hose. Do not blow through fuel line without disconnecting it becasue it is possible to blow strainer off tank unit or to rupture it. Then reconnect fuel lines to pump and tank. Also, reconnect fuel lines at filter. Start engine and check for leaks.
If fuel flows in a good volume from pipe at filter 1 pint @ 30-45 seconds, fuel delivery pressure may be checked. This test is necessary because a weak pump can still produce an adequate volume of fuel when it is not under pressure. Fuel pressure should be in the 5.5 to 6.5 psi range.
VACUUM TEST, FUEL PUMP INLET (DEAD HEAD)
Low vacuum or complete loss of vacuum provides insufficient fuel to the injection pump to operate the engine throughout normal speed range. The vacuum test will determine if the pump has the ability to pump fuel and is the best indication of the quality performance of the pump (Figure 4-11).
Step 1 Disconnect hose from fuel tank to fuel pump at fuel pump. Plug or position hose to insure no fuel leakage.
Step 2 Connect one end of a short hose to fuel pump inlet and attach a vacuum gage to the other end.
Step 3 Start engine. With engine idling (using fuel in the filter assembly), check vacuum gage. If vacuum is less than 12 inches Hg (2.98 kPa) replace fuel pump.
