Exam 38: Natural Gas, Propane, and Biodiesel Fuels

Technician A says that post-2010 NG fueled commercial engines must be equipped with a DPF in the exhaust gas aftertreatment circuit. Technician B says that post-2010 NG fueled commercial engines are normally equipped with passive reduction and oxidation catalysts in the exhaust system. Who is correct??

Technician A says that some OEMs have abandoned manufacturing NG fueled engines because of the difficulty in meeting EPA 2010 NOx emissions standards. Technician B says that a problem in using NG as a fuel, is that carbon dioxide emissions tend to greatly increase. Who is correct?

Technician A says that LNG is stored in liquid form on vehicles using the fuel. Technician B says that CNG is stored in gaseous form in vehicles using the fuel. Who is correct?

Which of the following would properly describe the type of SI system used on a current CNG fuel system on commercial vehicle applications? ?

What pressure must liquified natural gas (LNG) be stored at in vehicle fuel tanks

What must be done to a vehicle LNG fuel before it is delivered to the fuel injection apparatus?

Technician A says that hydrogen can be reformed from natural gas(NG).. Technician B says that hydrogen does not appear naturally in its elemental form on Earth. Who is correct??

Which of the following fuels meets the ASTM 975 standard for highway diesel fuels?

Technician A says that a disadvantage of propane as a fuel is that its pricing fluctuates along with petroleum fuel pricing. Technician B says that an advantage of propane compared with NG is that it auto-ignites at diesel engine compression temperatures and pressures. Who is correct?

Which of the following are indications that oil is present within the fuel system of an NG fueled commercial engine??

Technician A says that the Westport LNG high pressure direct injector (HPDI) uses piezo actuators. Technican B says that the Westport HPDI is a dual fuel, electronically-controlled, common rail injector. Who is correct?

Technician A says that it is likely that biodiesel will replace petroleum base diesel fuel within the next decade because of its lower emissions. Technician B says that all ASTM 6751 biodiesel has a yellow tint. Who is correct?

Technician A says the best way to avoid rapid fuel degradation problems in biodiesel cuts is to routinely treat it using biocides. Technician B says that when biodiesel is suspected to be under bacterial attack, shocking the fuel with biocides may eliminate the problem. Who is correct?

What is the likely performance outcome of a defective coil pack in a CPS SI system used in a current CNG engine??

Technician A says that when B20 fuel in a highway truck fuel tank appears greenish in color, it should be discarded. Technician B says that the B15 fuel in a highway truck fuel tank has a strong septic tank odor and that treating it with kerosene may recover it. Who is correct?

Technician A says that biodiesel has greater resistance to water absorption than petroleum base diesel fuel. Technician B says that biodiesel has greater resistance to biological attack than petroleum base diesel fuel giving it a longer shelf life. Who is correct?

Technician A says that the fuel specification B5 describes a fuel that is 95% petroleum based cut with 5% biodiesel. Technician B says that most engine OEMs do not approve of the use of biodiesel cuts in their engines. Who is correct?

What is the usual method of igniting the fuel charge when a Westport CNG-DI Mono injector is used to deliver the gas charge?

What is used to ignite a NG fuel charge in the engine cylinder

Technician A says that West Coast drayage trucks tend to run on NG fuel. Technician B says that the City of Los Angeles currently uses no diesel power in its entire transit fleet. Who is correct?