diesel truck

Diesel Testing

Why is Maine Testing Trucks?
Maine's testing program is part of a regional testing program which includes other New England states, New York and New Jersey. The program was established in 1997. Only vehicles with a GVWR of over 18,000 pounds are subject to the program.
What is the test?
The test, known as a "snap-acceleration test", is conducted while the truck is stopped roadside. It involves rapidly depressing the accelerator until the engine reaches maximum governed speed, at which time the smoke is measured at the end of the exhaust pipe. Several "snaps" or tests are conducted; however, not all trucks are selected for testing -- only those that appear to have excessive smoke.
What are the standards?
1990 and older: 55% opacity
1991 and newer: 40% opacity
Opacity means the degree of light obscuring capability of emissions of visible air contaminants expressed as 100% opacity.
What happens if the vehicle fails the opacity standards?
Vehicles failing the opacity standards have 30 days from the date of the initial test to make appropriate repairs and send documentation to the DEP. Owners that fail to repair and send documentation will be fined 250 dollars. Vehicles found in violation for a second and subsequent time will be fined 500 dollars.
What's to be gained?
Regionally, on-road diesels contribute nearly 40% of mobile source particulate emissions. On-highway diesel trucks also emit about 15% of oxides of Nitrogen (NOx) in the Northeast Region. Well maintained vehicles help reduce particulates which have been linked to respiratory problems and cancer.

High smoke levels can be caused by a number of problems including:

Restricted air filter Air manifold leaks
Clogged, worn or mismatched fuel injectors Malfunctioning turbocharger
Faulty fuel injection pump Malfunctioning after cooler
Defective or maladjusted puff limiter Maladjusted fuel rack
Low air box pressure Defective air fuel controller
Improperly adjusted valve lash or governor Poor fuel quality

Proper maintenance at manufacturers recommended intervals should easily detect, repair and prevent these problems, while assuring that your truck is in the best operating condition.

Engine Tampering
Common misunderstanding about smoke and power are often the cause of tampering with engine emission controls. More smoke comes at a cost. Turning up the fuel flow, changing timing or disabling air/fuel controls can cause more wear and tear on your engine, increase fuel use, and increase emissions.

Tampering with any component of an emissions control system is a violation of state and federal law.

  • Raising fuel pump rates
  • Disabling puff limiter
  • Disabling exhaust gas circulation systems
  • Installing wrong injectors
  • Changing injector timing

For more information Contact

Scott Wilson (207) 287-2437