Fuel Pressure: Testing and Inspection
ON CAR SERVICEFUEL PUMP TEST (Gasoline and Diesel)
1. Test fuel pump by connecting hose from carburetor or diesel fuel filter fuel feed Tine to a suitable unbreakable container.
a. All except V6 diesel
Start engine and let idle for 15 seconds.
b. V6 diesel, turn the ignition switch to the "run" position pump should supply 1/2 pint or more. If not, go to step 2. If OK, go to Step 4.
2. To check the fuel pump
a. All except V6 diesel; To check fuel pump, disconnect inlet hose at pump and connect a vacuum gage. Crank or run engine until maximum vacuum is reached. If less than 50.6 kpa (15 inches), replace pump. If vacuum reading is 50.6 kpa (15 inches) or more, go to Step 3.
b. V6 diesel; to check fuel pump, disconnect inlet hose at pump and connect a vacuum gage. Turn the ignition switch to the run position. Vacuum should be 135 Kpa (19.6"). If less replace the pump. If more go to step 3.
3. Check fuel lines and hoses for splits, leaks or kinks by disconnecting each section of line and connecting a vacuum gage. Operate the fuel pump (V6 diesel or crank or run the engine (ex. V6 diesel) until vacuum gage peaks. Vacuum should be at least 50.6 kpa (15") except V6 diesel and 135 kPa (19.6") V6 diesel. If less, repair or replace the malfunctioning line or hose.
4. If fuel lines and pump check OK, remove tank unit, replace strainer and clean fuel tank, if necessary.
Pump (Outlet) Pressure
Even if fuel flows in good volume from line at filter inlet or carburetor, it is advisable to make certain the pump is operating within limits.
1. Disconnect fuel line at the carburetor or filter inlet fitting. Install a rubber hose approximately 203-254mm (8" to 10') long over the line and attach a low reading pressure gage. Hold the gage up so that it is approximately 406mm (16") above the fuel pump. Pinch the fuel return line on gasoline equipped cars only.
2. On all but the V6 diesel, start the engine and run at slow idle (using the fuel in the carburetor or injection pump).
On the V6 diesel, turn the key to the run position. On all, note the reading on the pressure gage.
3a.All Gasoline and Diesel V8;
If pump is operating properly, the pressure should be 37.9 to 44.8 kPa (5-1/2 to 6-1/2 P.S.I.) constant. If pressure is too high or too low or varies materially at different engine speeds, the pump should be replaced.
3b. V6 Diesel;
If pump is operating properly the pressure should be 40 to 60 kpa (5.8 to 8.7 psi). If pressure is too high or too low or varies materially, the pump should be replaced.
NOTICE: Hold carburetor fuel inlet nut while tightening fuel line fitting to prevent carburetor damage.