Engine Hesitation Under Heavy Acceleration

Some customers may comment about an engine hesitation under heavy acceleration or after turning a corner. This condition will be more noticeable with lower levels of fuel in the fuel tank (1/4 tank or less). This condition may also accompanied by DTCs P0136 and/or P0156 on V6 (L81) equipped vehicles, or P0137 on 4 cyl. (L61) equipped vehicles.

The hesitation may be caused by a drop in fuel pressure due to malfunctioning jet valve on the fuel pump housing, or a faulty fuel pump assembly.

1. Connect a Scan tool to vehicle and check for DTCs.

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If DTCs P0136 or P0156 are present on V6 (L81) equipped vehicles, or if P0137 is present on 4 cyl. (L61) equipped vehicles, refer to the applicable DTC flow chart in the appropriate 2000 L-Series engine service manual. If the DTC flow chart followed indicates an intermittent problem, continue to step 2.





•	If no DTCs are present, continue to step 2.

Important: Use the 90 degree adapter (SA9403E), supplied with gauge bar set, when connecting to the fuel system pressure test port.

2. Install gauge bar set SA9127E to fuel system pressure test port.
3. Route and position gauge bar set so the hood can be closed and vehicle can be driven while viewing gauge readings. (Refer to illustrations on the facing page.)

L81 (V6) ENGINE




4. L61 (4 CYL) ENGINE




Important: It may be necessary to drain some fuel from fuel tank since condition is most noticeable when fuel tank is less than 1/4 full.

5. Drive vehicle under conditions that hesitation occurs and monitor fuel system pressure. Fuel system pressure should never drop below 269 kPa (39 psi).

•	If fuel system pressure remains above 269 kPa (39 psi) when hesitation occurs, problem is not related to the fuel system. Refer to "Symptom Definitions/Possible Causes" in the Engine/Emission Controls section of the appropriate 2000 L-Series engine service manual.

•	If fuel system pressure drops below 269 kPa (39 psi) when hesitation occurs, problem is related to the fuel system. Continue to step 5.

6. Remove fuel pump module. (Refer to the "Fuel Pump Module" removal procedure in the Fuel System section of the appropriate 2000 L-Series engine service manual).



7. Inspect the fuel return hose for damage. Replace fuel pump module (P/N 21018807) if damage is evident.



8. Inspect jet valve fitting (1) for proper seating and engagement on fuel pump housing. When fully seated, jet valve fitting cannot be pulled away from fuel pump housing without disengaging retaining tabs.

•	If jet valve fitting is properly seated and engaged on fuel pump housing, replace fuel pump module (P/N 21018807).

•	If jet valve fitting is not properly seated and engaged on fuel pump housing, reset and engage fitting on fuel pump housing and continue to next step.

Important: Prior to installing fuel pump module, ensure that a new fuel pump module gasket is installed.

9. Install fuel pump module. (Refer to the "Fuel Pump Module" installation procedure in the Fuel System section of the appropriate 2000 L-Series engine service manual.)
10. Test drive vehicle to verify hesitation is no longer present.

Important: Refer to the 2000 L-Series Electronic Labor Time Guide for repairs not listed above.