2015-2018 Thomas Built Minotour School Buses FL903 Solenoid Connector to CNG Fuel Tank May Corrode

September 23, 2021 NHTSA CAMPAIGN NUMBER: 21V741000

Solenoid Connector to CNG Fuel Tank May Corrode

A short at the connector may cause a flame or overheating, increasing the risk of a fire.

 

NHTSA Campaign Number: 21V741

Manufacturer Daimler TruckseBay logo North America, LLC

Components FUEL SYSTEM, OTHER, ELECTRICAL SYSTEM

Potential Number of Units Affected 87

 

Summary

Daimler TruckseBay logo North America, LLC. (DTNA) is recalling certain 2015-2018 Thomas Built Minotour school buses. The under-body shut-off solenoid connector that connects to the CNG fuel tank may corrode, which could result in an electrical short.

 

Remedy

Dealers will replace the CNG fuel shut-off solenoid, free of charge. Owner notification letters are were mailed February 03, 2022. Owners may contact DTNA’s customer service at 1-800-547-0712. DTNA’s number for this recall is FL-903.

 

Notes

Owners may also contact the National Highway Traffic Safety Administration Vehicle Safety Hotline at 1-888-327-4236 (TTY 1-800-424-9153), or go to www.nhtsa.gov.

 

Check for Daimler Trucks North America Recalls

 


Thomas Built Buses
Thomas Built Buses

 


Subject: TBB Minotour CNG Solenoid

Models Affected: Specific model years 2015-2018 Thomas Built Buses Minotour school buses built on a General MotorseBay logo (GM) chassis and manufactured December 14, 2013, through June 29, 2017, and equipped with an IMPCO Automotive Compressed Natural Gas (CNG) conversion.

 

General Information

Daimler Truck North America LLC (DTNA), on behalf of its wholly owned subsidiary, Thomas Built Buses (TBB), has decided that a defect that relates to motor vehicle safety exists on the vehicles mentioned above.

On certain vehicles, the underbody shutoff solenoid connector to a CNG fuel tank may corrode and could form a high-resistance short in the connector, potentially causing overheating or, in rare circumstances, a self-extinguishing flame. If there is a fuel leak or other combustible material in the vicinity, there is a risk of fire.

The CNG fuel shutoff solenoid will be replaced.

There are approximately 90 vehicles involved.

 

Additional Repairs

Dealers must complete all outstanding Recall and Field Service campaigns prior to the sale or delivery of a vehicle. A Dealer will be liable for any progressive damage that results from its failure to complete campaigns before sale or delivery of a vehicle.

Owners may be liable for any progressive damage that results from failure to complete campaigns within a reasonable time after receiving notification.

Please contact Warranty Campaigns for consideration of additional charges prior to performing the repair.

 

Work Instructions

Please refer to the attached work instructions.

Replacement Parts

Installation kits for the CNG fuel shutoff solenoid have been sent directly to the specific dealers who will install them on the affected buses. If you have not been contacted by TBB, then your location will not be performing this recall.

 

Removed Parts

U.S. and Canadian Dealers, please follow Warranty Failed Parts Tracking shipping instructions for the disposition of all removed parts. Export distributors, please destroy removed parts unless otherwise advised.

 

CNG Fuel Shutoff Solenoid Replacement

1. Park the vehicle on a level surface, turn engine OFF, place in park, chock tires, and turn the body circuit breaker to the OFF position.

2. Disconnect negative battery cables at the batteries.

 

Fuse replacement

3. Remove the under hood electrical center cover (fuse center). See Fig. 1.

4. Locate the 30-AMP fuel pump fuse and remove it from the under hood electrical center.

5. Discard the 30-AMP fuse.

 

6. Replace the fuse with the appropriate fuse as follows:

  • If vehicle has three CNG tanks, then replace with a 5 AMP fuse.
  • If vehicle has four CNG tanks, then replace with a 7.5 AMP fuse.

7. Reinstall the under hood electrical center cover. Remove the Midship and the Aft Axle Tank Shield

8. Lift the vehicle and support it.

9. Using a 17 mm socket, 16 mm socket and a #3 Phillips bit. Remove the eight bolts holding the driverโ€™s side, and sixteen screws holding the passenger side midship tank shields in place; then remove shields. See Fig. 3.

10. Using a 16 mm socket, remove the twelve bolts securing the AFT axle tank shield; then remove shield. See Fig. 2.

 

Midship Tank Repair Work.

11. Close the main shutoff valve for the midship tanks. See Fig. 4.

12. Disconnect the high-pressure lockoff (HPL) solenoid electrical connector, and cut the zip tie holding it to the HPL solenoid.

 

NOTICE

Due to HPL solenoid supply issues, some of these new parts have blue and brown wires, and others have red and black wires.

 

13. Cut the harness and replace the connector making sure to splice the matching wire colors (blue-to-blue, and brown-to-brown) shown in Fig. 5, or red-to-blue, and black-to-brown referenced in Fig. 6. To minimize water intrusion, use a moisture resistant type of splice that is equal to IP67 protection.

14. Put a mark on the valve to indicate the orientation of solenoid to ensure proper installation of the new solenoid.

15. Remove the 7/8โ€ HPL solenoid coil retaining nut.

16. Remove the HPL solenoid coil and discard it.

17. Remove the old HPL seal, and install a new one, then apply lubrication to the new seal.

18. Remove the old seal of the HPL solenoid-retaining nut. Apply lubrication to the new seal, then install.

19. Using the reference mark from step 14, install the new HPL solenoid coil.

20. Install the HPL solenoid coil-retaining nut. Tighten the retaining nut to 6.5 NM (57.5 lbfยทin).

21. Apply dielectric grease on the electrical connector and reinstall it.

22. Zip tie the harness back up making sure there is no strain on the harness. See Fig. 7.

 

AFT Axle Tank Repair Work

23. Close the manual shutoff valve.

24. Disconnect the HPL solenoid electrical harness and cut the zip tie holding it to the solenoid.

25. Replace the HPL electrical harness with the harness provided.

26. Mark the correct orientation of the solenoid on the valve using this mark to ensure the correct installation of the new solenoid.

27. Remove the HPL solenoid coil-retaining nut.

28. Remove the HPL solenoid coil and discard.

 

29. With solenoid removed, inspect the stem for any dirt or debris. See Fig. 8.

30. Remove and replace the HPL solenoid coil seal and apply lubrication.

31. Remove and replace the HPL solenoid coil retaining nut seal and apply lubrication. See Fig. 9.

32. Install the new HPL solenoid coil and retaining nut. Tighten to 6.5 NM (57.5 lbfยทin).

33. Apply dielectric grease on the electrical connector and reinstall it.

34. Install a new zip tie making sure the harness wiring has strain relief at the connector.

 

CNG Fuel System Check

35. Lower the vehicle.

36. Connect the negative battery cable, and turn the body circuit breaker ON.

37.Start the engine.

38. Raise and support the vehicle.

39. Verify operation of the solenoid by performing a magnetic function test on the CNG HPL solenoid.

40. With the engine running, place a paper clip or equivalent on the HPL retaining nut.

41. Determine if the HPL solenoid-retaining nut is magnetic. If it is magnetic, it is working properly.

42. Lower the vehicle.

 

43. Turn engine off.

44. Raise vehicle and support.

45. Install the midship tank shield and bolts.

46. Install the AFT axle tank shield and bolts.

47. Lower vehicle, and return to service.

 


Chronology :

IMPCO Automotive designed and installed CNG conversions for gasoline powered General MotorseBay logo vehicles and other vehicle makes including chassis used in the Minotour bus. IMPCO Automotive no longer operates as a company. In February 2021 Thomas Built Buses received a report on a Minotour bus with an IMPCO Automotive CNG fuel system installed. The bus was preparing to leave the yard when the engine shutdown. The driver went to get a technician from the shop and when they returned, there was smoke coming from under the bus. In mid March of 2021, an investigation by the customer and Thomas Built Buses of the bus identified the CNG fuel shut-off solenoid as the source of the event. At this time, Thomas Built Buses identified an IMPCO Automotive/General MotorseBay logo recall, 13V-225, that affected vehicles built prior to the bus involved in this incident and may have related to the reported Minotour issue. DTNA began an investigation to better determine if the event was related to the previous IMPCO Automotive recall. In or about that time, DTNA reviewed the fuel shut-off solenoid from the bus involved in the incident. The solenoid did not have any identifying part numbers printed on it so it could not be determined if it was the solenoid that was previously recalled. In the course of this investigation DTNA discovered that that some of IMPCO Automotiveโ€™s assets were purchased by another company. DTNA reached out to this company to see if they had any production records or knowledge related to the Thomas Built Buses that IMPCO Automotive had converted to CNG. The new company was unable to provide any records to help determine if the bus contained the same defect that IMPCO had previously recalled. In September 2021, out of an abundance of caution, DTNA decided to issue a voluntary safety recall on certain Thomas Built Buses Minotour school buses with an IMPCO Automotive CNG fuel system in order to replace that supplierโ€™s defective parts.

 


4 Affected Products

Vehicle

MAKEMODELYEAR
THOMAS BUILT BUSESMINOTOUR2015-2018

 


10 Associated Documents

ISSUED Owner Notification Letter(Part 577)

RCONL-21V741-9832.pdf 98.442KB

 


ISSUED Interim Owner Notification Letter(Part 577)

RIONL-21V741-5380.pdf 139.422KB

 


Recall 573 Report- Amendment 1

RCLRPT-21V741-4719.PDF 214.088KB

 


Defect Notice 573 Report

RCLRPT-21V741-1220.PDF 214.082KB

 


Recall Acknowledgement

RCAK-21V741-5886.pdf 645.857KB

 


Miscellaneous Document- Defect Information Report

RMISC-21V741-9453.pdf 814.634KB

 


Miscellaneous Document- Defect Information Report

RMISC-21V741-9365.pdf 814.584KB

 


Manufacturer Notices(to Dealers,etc)

RCMN-21V741-5887.pdf 752.291KB

 


Recall Quarterly Report #1, 2022-1

RCLQRT-21V741-7006.PDF 211.154KB

 


Recall Quarterly Report #2, 2022-2

RCLQRT-21V741-3166.PDF 211.251KB

 


Latest Recalls Documents

https://www-odi.nhtsa.dot.gov/acms/cs/documentList.xhtml?docId=21V741&docType=RCL

 


 

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