CNG Fuel System - Rough Idle/No Start Condition
Article No.03-18-3
09/15/03
DRIVEABILITY - DEDICATED COMPRESSED
NATURAL GAS (CNG) - ROUGH IDLE OR NO START
WHEN COLD - VEHICLES EQUIPPED WITH
DEDICATED 4.6L OR 5.4L CNG ENGINE ONLY
FORD:
1996-2003 CROWN VICTORIA
1997-2003 E SERIES, F-150
Article 01-22-1 is being republished in its entirety to update the vehicle model years and service procedures.
ISSUE
Some dedicated Compressed Natural Gas (CNG) vehicles may exhibit a temporary Rough Idle, Hard Start, or No Start when the engine is cold. The condition may be most noticeable on the first start of the day, and during the first cold days of Fall or Winter.
ACTION
Perform normal diagnostic procedures per the appropriate PC/ED manual section 2 Diagnostic Methods. If it is identified that the injectors are partially or completely clogged then perform the following service procedure to clean the CNG injectors. Clean the CNG fuel injectors using Motorcraft PM-5 Power Flush Injector Fluid.
SERVICE PROCEDURE
NOTE
THIS PROCEDURE SHOULD ONLY BE PERFORMED BY A CERTIFIED CNG TECHNICIAN.
NOTE
FOLLOW ALL FUEL SYSTEM SAFETY PROCEDURES LISTED IN THE WORKSHOP MANUAL SECTION 303-04 FUEL SYSTEM PRECAUTIONS.
INJECTOR CLEANING PROCEDURE
NOTE
IF THE VEHICLE WILL NOT START, GO DIRECTLY TO THE "VEHICLE NO START PROCEDURE"
1. Start vehicle and idle for 5 minutes, then turn engine off. The cleaning fluid is more effective with a warm engine.
2. Remove CNG Coalescent Filter Bowl after properly venting the fuel line. Refer to Workshop Manual Section 303-04 General Procedures.
3. Drain any oil from the coalescent bowl, remove the 0-ring and wipe clean the bowl interior 0-ring groove and external threads. Reinstall the original 0-ring.
4. Fill the Coalescent filter bowl 3/4 inch from the top with Motorcraft PM-5 Power Flush Injector Fluid.
5. Reinstall the filter bowl, torque bowl to. 40 +/- N.m (30 +/- 5 lb-ft). Re-pressurize the fuel system and leak test.
6. Start engine and run at idle for 30 seconds, turn engine off, wait 5 minutes allowing the cleaning fluid to remain in the injectors.
7. Repeat Step 6 one time.
8. Test Drive Vehicle to verify that the Rough Idle condition is corrected. VEHICLE SHOULD BE DRIVEN IMMEDIATELY FOR AT LEAST 10 MINUTES TO ENSURE CLEANING FLUID IS FLUSHED OUT OF FUEL SYSTEM.
NOTE
IN SOME CASES, IF ROUGH IDLE REMAINS DUE TO TOUGH CLOGGING OF INJECTORS, REPEAT THE INJECTOR CLEANING PROCEDURE STEPS 1-8. IF ROUGH IDLE STILL REMAINS, FOLLOW THE "VEHICLE NO START PROCEDURE".
9. After all injector cleaning and other service is completed, drain the CNG Coalescent Filter Bowl, replace coalescent filter element, drain plug and bowl 0-ring using Part Number F5TZ-9365-AA. Re-pressurize fuel system and leak test.
VEHICLE NO START PROCEDURE
1. If vehicle will not start due to Clogged Injectors, the injectors may be completely stuck closed. Attempt to free the injectors by applying 12 Volts directly to the injector coil.
NOTE
DO NOT APPLY VOLTAGE TO THE INJECTOR FOR MORE THAN "TEN SECONDS" OR INJECTOR DAMAGE MAY RESULT.
2. Apply battery voltage to the red wire (circuit 361) side of the injector connector. Ground the other side of the injector connector momentarily and listen for an AUDIBLE CLICK to confirm that the injector has opened. Continue with Step 1 of the "INJECTOR CLEANING PROCEDURE".
NOTE
IF AN INJECTOR REMAINS STUCK (NO AUDIBLE CLICK), WAIT 10 SECONDS AND REPEAT STEP 2 OF THE "VEHICLE NO START PROCEDURE". IF AN INJECTOR DOES NOT PRODUCE AN AUDIBLE CLICK AFTER THREE ATTEMPTS REPLACE THE INJECTOR PER "INJECTOR REPLACEMENT PROCEDURE".
INJECTOR REPLACEMENT PROCEDURE
1. Vent fuel system per Section 310-00B of appropriate Workshop Manual.
2. Replace injector(s) per Section 303-04 (Crown Victoria), 303-04D (F-150), 303-04G (E-Series).
3. Leak Check all connections removed for fuel injector replacement. Use a quality leak reactant or equivalent over fuel system pressure fittings and lines.
NOTE
TO LEAK TEST A MILD SOAP AND WATER SOLUTION MAY BE USED AS AN ALTERNATIVE LEAK REACTANT. LEAKS FROM THE SYSTEM WILL EXHIBIT SOAPY BUBBLES.
4. Test drive vehicle to confirm correction of rough idle. If rough idle condition is still present, continue with Step 1 of the INJECTOR CLEANING PROCEDURE.
Labor Operation Claiming Chart
Parts Block
OTHER APPLICABLE ARTICLES: NONE
SUPERSEDES: 01-22-01
WARRANTY STATUS: Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage And Emissions Warranty Coverage
DEALER CODING
CONDITION
BASIC PART NO. CODE
9F593 49
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