EVAP System

What to Know Regarding your EVAP System

What you need to know about your vehicle’s evaporative emissions control system; or EVAP for short. Your vehicle’s fuel system is a sealed system designed to trap fuel vapors before they can escape into the atmosphere. The EVAP system draws in fresh air, gathers up unburned vaporized hydrocarbons and delivers them to the intake system to be re-burned in the engine. 

If there’s a leak or a blockage in the EVAP system, a trouble code will be generated, setting off the check engine light. There are many EVAP system components that could have problems – things as simple as a worn or loose gas cap or a rusty fuel filler pipe. Codes will indicate a large, medium or small leak.

EVAP System Components

Other EVAP system components include:

  • Fuel tank
  • Purge valve
  • Canister vent valve
  • Charcoal canister
  • Canister filter
  • Fuel tank pressure sensor
  • Fuel level sensor
  • Electronic control module
  • Vapor lines
  • Vapor switching valve.

As you can imagine, with a list like that, it takes some skill – and some specialized equipment – to properly diagnose an EVAP system problem.

Our master technicians will attach scan tool and monitor readings and perform a function test on the various valves isolating different parts of the EVAP system to isolate the leak. If necessary, a low-pressure smoke test will be performed to visually spot any leaks. Again, proper equipment is required so that the tests don’t cause further damage.

EVAP system problems don’t usually hurt performance or cause damage. However, there are very good reasons for making the repairs. First, you only have one check engine light – but there are hundreds of problems that can trigger it. When you don’t fix an EVAP problem, the check engine light will stay on, masking other problems that might occur.

Of course, if local regulations require passing an emissions test, your vehicle will fail. Finally, harmful emissions are being released into the atmosphere.

If you have an illuminated check engine light – get in and have your vehicle diagnosed. You’ll want the peace of mind.


EVAP problems are in the top five reasons for the Check Engine Light to come on. Our 7 service facilities throughout Maine and New Hampshire can properly diagnose EVAP system problems and other, more serious causes of illuminated Check Engine Lights.



shop for tires

Special Offers


Auto Care Plus, LLC, Auto Repair & Service, Merrimack, NH

Ten Locations Throughout NH and ME:

Manchester, NH

991 Candia Road | Manchester, NH 03109
(603) 232-1521

Merrimack, NH

738 D.W. Highway | Merrimack, NH 03054
(603) 429-1002

Hooksett, NH

1112 Hooksett Rd | Hooksett, NH 03106
(603) 644-7238

South Portland, ME

509 Westbrook St. | South Portland, ME 04106
(207) 773-8560

Wolfeboro, NH

635 Center St. | Wolfeboro, NH 03894
(603) 569-1068

Conway, NH

675 White Mountain Hwy | Conway, NH 03818
(603) 447-3873

Derry, NH

418 Island Pond Rd, Bldg #3 | Derry, NH 03038
(603) 845-3900

Lebanon, NH

258 Mechanic St, Lebanon, NH 03766
(603) 448-1381

Dover, NH

28 Sumner Dr, Dover, NH 03820
(603) 742-8627

Londoneryy, NH

107 Nashua Rd, Londonderry, NH 03053
(603) 404-5120

Auto Care Corner: