Fuel System - Hard Start/White Smoke/Poor Idle
84ford11Article No. 84-16-32
HARD START/PERFORMANCE POOR (6.9L) - DIAGNOSTIC PROCEDURE FOR DETERMINING AIR LEAKS
LIGHT TRUCKS 1983-84 F & E-SERIES
Hard starting, white smoke in the normal engine operating range, poor idle quality, or lack of power under load can be caused by several conditions. One of these conditions is air leaks in the fuel supply system.
This procedure is provided to assist in the diagnosis of 6.9L diesel engine fuel system air leaks.
NOTE: Prior to starting the diagnostic procedure, (A) Verify that the fuel tank(s) contain at least a half tank of fuel - the fuel level compensates for the range of vehicle attitudes that may uncover the fuel sender pickup hose in the fuel tank when the fuel level is low, and (B) Visually inspect the fuel system for obvious problems such as kinked hoses, loose clamps, or damaged lines/ hoses.
NOTE: Care should be taken when removing or installing hose to the plastic fitting at the fuel injection nozzle return lines. Lubricate hose with diesel fuel to ease installation.
FIGURE 24:
1. Remove the rubber fuel return by-pass hose which connects the fuel filter outlet fitting by-pass orifice to the return lines at the fuel injection nozzles (Figure 24).
2. Install a 12 inch length of 3/16" I.D. color polyvinyl chloride, TYGON hose (to view fuel flow) in place of the above rubber fuel hose, and tighten hose clamps, 8-13 in.lbs.
TYGON is a registered trademark of Norton Industries Plastics.
3. Run engine at approximately 3,000 RPM for 2 to 3 minutes to clear air from the system, which was induced by the previous operation.
After stabilizing the fuel flow, observe fuel hose for air bubbles at 3,000 engine RPM.
^ Any continuous stream of bubbles (larger than "champagne-size") indicates air ingestion somewhere in the fuel system.
"Champagne-size" is defined as 1/16" dia. or smaller bubbles. A moving concentration of bubbles of any size, or foam is unacceptable.
^ Proceed to Step 4.
^ If no bubbles (larger than "champagne-size") are noted, and the concern continues, refer to the Engine Performance Diagnostic Procedure for other causes.
NOTE: After completing each of the following required steps to resolve the concern, run the engine at 3,000 RPM for 2 to 3 minutes to insure that the fuel flowing through the TYGON hose at the fuel filter is clear of bubbles larger than "champagne-size".
4. Observe the direction that the bubbles are traveling in the hose. The bubbles should be moving from the fuel filter outlet fitting down towards the fuel injection nozzle return system.
^ If the bubbles are flowing backwards (from the return system up towards the fuel filter outlet fitting), this indicates that the fuel supply system is restricted.
Refer to the following Diagnostic Manual sections to resolve this restriction.
Model Year Section Test Numbers
1983 25-61 As required;
EPC.3A thru 3E Only.
1984 32-50 As required;
and EPC.3 and EPC.6A thru
32-52 E Only.
^ If the bubbles are flowing properly (towards the return system) proceed as follows:
DUAL TANK UNITS:
^ If the bubbles are present when the selector valve is switched to both fuel tanks, proceed to Step 5.
^ If the bubbles are present when the selector valve is switched to only one of the two tanks, check selector valve hose clamps to verify tightness.
- If clamps are not tight, re-tighten clamps and repeat Step 3.
FIGURE 25:
- If clamps are tight, bypass the selector valve ports (corresponding to the tank switch position) with a 2 ft. section of 3/8" I.D. TYGON hose (Figure 25). Run engine at approximately 3,000 RPM for 2 to 3 minutes to clear air induced by this operation, and then run the engine at 3,000 RPM for an additional 1 to 3 minutes.
^ If bubbles (larger than "champagne-size") are not present in the by-pass hose, replace the selector valve. Concern resolved.
^ If bubbles (larger than "champagne-size") are present in the by-pass hose, the air leak is towards the fuel tank. Check for damag- ed fuel hose, or loose hose clamps, and service as required. Concern resolved.
SINGLE TANK UNITS:
^ Proceed to Step 5.
5. Check the following hose connections for damage and tighten clamps (8-13 in.lbs.):
^ At the rubber fuel cross-over hose from the chassis fuel line to the mechanical lift pump.
^ At the inlet and outlet hoses to the water separator.
After tightening hose clamps, run engine for 5 minutes at 3,000 RPM and check for air bubbles at the TYGON hose.
^ If air bubbles (larger than "champagne-size") are not visible at the fuel filter outlet fitting, replace TYGON hose(s) with the original hose(s). Concern resolved.
^ If air bubbles (larger than "champagne-size") are still visible at the fuel filter outlet fitting, proceed to Step 6.
FIGURE 26:
FIGURE 27:
6. Install the following hose adaptors and transparent fuel hoses ("one at a time, to prevent hose mix-up"):
Disconnect the inlet hose from the water/fuel separator. Refer to Figure 26 for F-Series, and Figure 27 for E-Series.
FIGURE 26:
Install a hose adaptor and a transparent fuel hose, and tighten the clamps (8-13 in.lbs.). See Figure 26 to fabricate hose adaptors, or purchase similar parts locally.
Disconnect the outlet hose from the water/fuel separator, and install another adaptor and transparent hose, and tighten clamps (8-13 in.lbs.)
Operate engine at 1,500 RPM for 5 minutes to develop steady fuel flow, and then run engine at 3,000 RPM for an additional 2 minutes, and note the following:
6a. If air bubbles (larger than "champagne-size") are visible in the fuel inlet hose, of the water separator, proceed to Step 6b.
If air bubbles (larger than "champagne-size") are visible in the fuel inlet hose, proceed as follows (for dual or single tank units as appropriate):
^ Check selector valve hose connections to verify tightness.
- If clamps are not tight, re-tighten clamps and repeat Step 3.
FIGURE 25:
- If clamps are tight, bypass the selector valve ports (corresponding to the tank switch position) using a 2 ft. section of 3/8" I.D. TYGON hose (Figure 25). Run engine at approximately 3,000 RPM for 2 to 3 minutes to clear air induced by this operation and then run the engine
at 3,000 RPM for an additional 1 to 3 minutes.
^ If bubbles (larger than "champagne-size") are not present in the bypass hose, replace the selector valve. Concern resolved.
^ If bubbles (larger than "champagne-size") are present in the by-pass hose, the air leak is towards the fuel tank. Check for damaged fuel hose, or loose hose clamps, and service as required to eliminate bubbles in the by-pass hose.
Repeat this check for the other tank on dual tank units, and service as required to eliminate bubbles in the bypass hose.
- If bubbles are still visible (larger than "champagne-size") at the water separator outlet hose, continue test at Step 6b.
SINGLE TANK UNITS
^ The air leak is towards the fuel tank.
^ Check for damaged fuel hose, loose hose clamps, and service as required to eliminate bubbles in the water separator inlet hose.
- If bubbles are still visible (larger than "champagne-size") at the water separator outlet hose, continue test at Step 6b. 6b. If a continuous stream of moving air bubbles are visible only in the water separator outlet hose:
^ Stop the engine and tighten the separator air vent and drain plug, if so equipped (this is not necessary on the pull ring, or cable operated separator.)
NOTE: It is normal for a single, large non-moving bubble to be in the outlet hose of the water/fuel separator.
^ Start and operate engine at 3,000 RPM, and reinspect for a continuous stream of moving bubbles (larger than "champagne-size").
- If these bubbles continue to be visible in the separator outlet hose, replace the water/fuel separator.
- If these bubbles are no longer visible in the separator outlet hose, replace TYGON hoses with the original hoses. Concern resolved.
OTHER APPLICABLE ARTICLES: None
WARRANTY STATUS: Reimbursable within the provisions of the Warranty and Policy Manual.
OPERATION: SP9288A84
TIME: E-Series - 0.4 Hr. F-Series - 0.3 Hr. (Does not include time to perform pin point test) DLR. CODING: Basic Part No. 9A050, 9J288, 9282 as applicable Code: 48