Fuel System - Fuel Starvation and Hard Start
Article No. 85-15-19FUEL STARVATION/HARD START (7.5L) - FUEL SYSTEM SERVICE PROCEDURE
LIGHT TRUCK 1980-85 E & F SERIES
Service procedures for concerns of fuel starvation are summarized as follows. These procedures apply to motor home and other conversion units with after market pumps and tanks, as well as vehicles with Ford fuel systems.
1. Vehicles equipped with electric fuel pumps and those converted from mechanical to electric fuel pumps per TSB's 83-11-12, 83-11-12-S (84-20) and 84-22-14:
Refer to TSB 84-24-14 for a description of the fuel system.
1. Perform service of Fuel System Plumbing Concerns as described on Page 31 of TSB 84-24-14.
NOTE: On motor home vehicles, the fuel tank straps may be ovenightened causing the tank to collapse, thus blocking the fuel pick-up filter.
2. Check for Fuel System Electrical Concerns as described on Page 37 of the above TSB, 84-24-14.
3. Check for electrical continuity to the fuel pump as described on Page 24-35-8 of the 1985 Light Truck Shop Manual, Volume B. Then check electric fuel pump operation through Step (d) as described on the same page of that manual.
Figure 22 - Fuel System:
4. Remove and discard the fuel line to the carburetor from the vapor separator, carburetor bronze fuel filter and gasket. Then rework the fuel system (Figure 22) using the parts listed below.
CAUTION: Back-up wrench must be used on fuel filter during assembly.
Hardware required for fuel system rework:
E3TZ-9155-C Fuel Filter
E5TZ-9C399-A Fuel Line Assembly
D177-9229-A Gasket (Fuel Filter to Carb)
Figure 22 - Fuel System:
Figure 23 - Pressure Test Location:
5. Pressure test the fuel system as described on Page 24-30-2 of the above Shop Manual. Even though the test is in the mechanical fuel pump section, the test procedure is the same for electric fuel pump systems. The pressure should be 3.5 to 4.5 psi. If the pressure is incorrect and a pressure test before the vapor separator as described below is 5.5 psi. or higher, then replace the vapor separator as shown in Figure
22. However, if the pressure before the vapor separator is low, check the fuel supply line for kinks and/or blockage. If it is free of kinks and/or blockage, replace the pump/sender assembly. To test pressure before the vapor separator, install a fuel pressure gauge in fuel line before vapor separator. This can be done at rubber hose connections downstream from the fuel tank selector switch, or at the rubber hose connector from the frame to the front of the engine (Figure 23). DO NOT DISCONNECT FUEL RETURN LINE. Record pressure reading with engine idling. Line pressure should range from 5.5 to 6.5 psi. between the vapor separator and fuel tank.
If previously tested pressure at the carburetor was below 3.5 psi., install one of the following vapor separators to increase the fuel pressure.
E3TZ-9N176-A gives 1.0 psi. increase at the carburetor (RED DOT).
E3TZ-9N176-B gives 2.0 psi. increase at the carburetor (BLUE DOT).
If the fuel pressure at the carburetor was too high or the concern still exists, replace the vapor separator with vapor separator E0TZ-9N176-B. If the pressure is still incorrect, check the fuel return line for blockage. If the return line is clear, it will be necessary to replace the pump/sender assembly. After service is completed, recheck pressure at the carburetor to confirm correction of the concern.
NOTE: Be sure fuel pressure is correct. High fuel pressure may cause carburetor flooding.
II. Vehicles equipped with mechanical fuel pumps:
1. Perform the diagnosis described in the 1985 Light Truck Shop Manual, Volume B, Page 24-30-1.
2. Perform the capacity test and the pressure test described on Page 24-30-2 of the above Shop Manual.
3. If the fuel starvation condition persists, modify the vehicle as described in TSB's 83-11-12-S (84-20) and 84-22-14. This applies to vehicles with Ford fuel tanks only. On F Series trucks with mechanical fuel pump systems, use the 351/400 listing in TSB 83-11-12-S (84-20), but substitute Kit "G" for Kit "F".
PART NUMBER PART NAME CLASS
E3TZ-9155-C Fuel Filter R
E5TZ-9C399-A Fuel Line Assembly C
D1ZZ-9229-A Gasket C
E3TZ-9N176-A Vapor Separator R
E3TZ-9N176-B Vapor Separator R
E0TZ-9N176-B Vapor Separator A
OTHER APPLICABLE ARTICLES: None
WARRANTY STATUS: Reimbursable within the provisions of the Warranty and Policy Manual.
OPERATION/TIME: "Actual Time" as defined in the Warranty and Policy Manual. DLR. CODING: Basic Part No. DRIVE - Code: N7, L3, M2, M3, M6