The latest Cummins webinar featured advice and tips on how to best maintain and service diesel and CNG school bus engines.
Technical Support Managers Ziggy Meluskey and Ryan Vaughn began the Aug. 13 webinar by reviewing the school bus engines Cummins has offered since 1983, when the B-series was introduced. Each iteration brought new or improved features with the latest model, the B6.7 being released in 2017.
“Maintenance can change based on your duty cycle, your application and your average mile per hour,” Meluskey said. Because of this, the OEM manual should be consulted for maintenance intervals.
He advised basing oil drain intervals on hours and not miles. Since school buses travel at slower speeds, it takes them longer to reach what may be the standard recommended mileage threshold for a change. But in reality, he added, they do need to be changed sooner.
Lubricating oil must meet or exceed Cummins Engine Standard Classifications (CES) 20078 or 20081. Since ash content in the oil affects DPFs, using non-low ash lubricating oil meeting CES 20078 reduces after-treatment service intervals.
“Cleanliness is godliness when it comes to the fuel system,” Vaughn declared. Meluskey, meanwhile, stressed that it is important to follow procedures for fuel filters because a lack of care can lead to contaminated or unfiltered fuel.
“The precision of the fuel systems today that is required to meet emissions [standards] is greater than what it was in the past,” Vaughn explained. While it may not result in an immediate vehicle failure, he said that debris takes away from the “precision that’s required for optimal performance.”
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Technicians are also advised to wash their hands with nonabrasive cleaners, clean the engine and fuel system before beginning work, and be aware of contaminants like paint chips or rust on nearby engine parts.
The webinar also touched on the water, base, and additives that make up a quality coolant. The types of coolants include Conventional, Hybrid, Noat and Oat. Each has its pros and cons. Low coolant levels result in progressive damage and are the leading cause of premature EGR cooler failures, they reported.
Tips were provided for maintaining the overhead and closed crankcase, especially in cold weather. “When we do increase these tolerances and we have the overhead out of spec, it affects our regen strategy,” noted Vaughn.
Meluskey talked about the recommended intervals for DPF cleaning, which also should be based on hours of engine operation and not simply mileage. He said that some school bus routes do not allow the bus to drive above 40 mph. Since some information in the Cummins manual is based on transit market applications, Vaughn urged listeners to take them as recommendations. “You know your fleet better than anyone,” he added.
Cummins provides a white paper and a checklist with tips, plus a hands-on guide on best practices for DPF and after-treatment. These detail how features like idle shutdown timers and overrides can be tracked, preset and reviewed with the electronic diagnostic tools PowerSpec and/or INSITE. Also available is the ReCon DPF program, which the company said is an efficient and cost-effective way to handle DPF maintenance and service requirements.
Vaughn and Meluskey reviewed more differences between CNG and diesel school bus engines and provided best practices for the natural gas engines that are made by the Cummins Westport division. Notably, CNG engines use a different type of oil and after-treatment system than do diesel engines.
They also have spark plugs and ignition coils instead of injectors. Both presenters noted that it is important to observe correct procedures for ignition coil inspection, spark plug replacements, valve adjustments and low-pressure fuel filter draining.
A short Q & A session followed. Vaughn concluded by reminding listeners that the best source of information on Cummins parts and services is QuickServe Online, which is free for up to five engine serial numbers.