Md. Code Regs. 11.14.04.07
Current through Register Vol. 51, No. 12, June 14, 2024
Section 11.14.04.07 - Emission Control System on School VehiclesA. This regulation represents the current recommendations of the Vehicle Emissions Inspection Panel of the Motor Vehicle Manufacturers Association, Inc., regarding engine maintenance inspection required to minimize vehicle emissions. This section is advisory and is primarily related to 1968 and later models.B. The inspection of emission control systems applies only to spark ignition engines, not to diesels.C. This regulation is applicable to school vehicles only.D. Crankcase Ventilation. The ventilation system of the crankcase is common to engines using either an "air injection" system of control or an "engine modification" system. The engine should be warm and running at idle before inspection of vent system. | Procedures | Reject Vehicle If: |
| (1) Crankcase Ventilation Valve: Inspect valve to make sure it is an approved device. | (1) Valve is not designed for the vehicle if originally equipped. |
| (2) Plumbing Connections: Inspect plumbing connections for tightness and proper routing of blow-by fumes and fresh air. | (2) Plumbing is loose, restricted, broken, leaking, or improperly routed. |
| (3) Operation: Disconnect crankcase ventilation valve from engine. A definite "hissing" noise is heard if valve is OK, caused by air being "sucked" into the valve and hose. Place finger or thumb over end of valve and feel for suction. | (3) There is no hissing sound or suction. |
E. Air Injection Type-Idle Speed and Timing. An air injection-type exhaust emission control system can be identified by an air pump and a distribution system to the exhaust ports. The air pump is normally driven by a belt off the crankshaft or water pump pulleys. Only the plumbing, idle speed and ignition timing need be inspected. Reference is made to the Idle Setting Limits Table I. | Procedures | Reject Vehicle If: |
| (1) Installation: With engine stopped, inspect hose connections and belts for tightness and breakage. Inspect ignition wiring for damage or deterioration. With engine running, inspect for air or vacuum leaks. | (1) (a) Belt is loose. (b) Connections are loose, broken, or leaking. (c) Ignition wires are damaged or deteriorated. |
| (2) Idle Speed: With engine at operating temperature and at idle speed: (a) Automatic Transmission: Check idle speed as recommended by vehicle manufacturer; (b) Manual Transmission: Place transmission in neutral and check idle speed. | (2) Idle speed is beyond limits in Table I. |
| (3) Basic Ignition Timing: Disconnect vacuum spark advance line(s) and insert plug(s). Connect timing light and check basic ignition timing (when finished replace line(s)). | (3) Basic timing is beyond limits in Table I. |
F. Engine Modification Type-Idle Speed and Timing. An "engine modification" control system may be most easily identified as one without an air pump. The emissions are primarily controlled by engine design. The items to be inspected are vacuum, idle speed, ignition timing, and idle air-fuel mixture by measuring the carbon monoxide (CO) content of the exhaust. Refer to Table II, Idle Setting Limits. | Procedures | Reject Vehicle If: |
| (1) Installation. With engine stopped, inspect vacuum hose connections for tightness, or breakage. Inspect ignition wiring for damage or deterioration. With engine running inspect for air or vacuum leaks. | (1) Connections are loose, broken, or leaking. (2) Ignition wires are damaged or deteriorated. (3) Idle speed is beyond limits in Table II. (4) Basic timing is beyond limits in Table II. |
| (2) Idle Speed: With engine at operating temperature and at idle speed. (a) Automatic Transmission: Check idle speed as recommended by vehicle manufacturer; (b) Manual Transmission: Place transmission in neutral and check idle speed. | |
| (3) Basic Ignition Timing: Disconnect vacuum spark advance line(s) and insert plug(s). Connect timing light and check basic ignition timing. (When finished remove plug(s) and replace line(s).) | |
G. Engine Modification-Type Fuel Mixture (Carbon Monoxide). The carbon monoxide (CO) concentration in the exhaust of most vehicles may not be more than 3 percent. Be sure that the testing is done by an experienced operator and that the exhaust analyzer is properly calibrated. | Procedures | Reject Vehicle If: |
| (1) Idle Fuel Mixture: With engine at normal operating temperature and idle speed, insert sampling probe into tail pipe and note carbon monoxide (CO) concentrations. (Major leaks in the exhaust system could cause erroneous readings.) | (1) Carbon monoxide concentrations are greater than limits in Table II. |
Table IIDLE SETTING LIMITS TABLE (Exhaust Air Injection Systems)
| Manufacturer | RPMManufacturer'sSpecifications | Basic Ignition Timing in Degrees |
| American Motors Corp. | +100 | -25 | ±3 |
| Ford Motor Co. | +100 | -50 | ±3 |
| General Motors Corp. | +100 | -50 | ±3 |
| International Harvester Co. | +100 | -25 | ±3 |
| Jeep Corp. | +100 | -25 | ±3 |
| Other | As specified by the particular manufacturer | |
Table IIIDLE SETTING LIMITS TABLE (Engine Modification Systems)
| Manufacturer | RPMManufacturer'sSpecifications | Basic Ignition Timing in Degrees | Mixture |
| American Motors Corp. | +100 | -25 | ±3 | 3% CO Maximum |
| Ford Motor Co. | +100 | -50 | ±3 | 3% CO Maximum* |
| General Motors Corp. | +100 | -50 | ±3 | 3% CO Maximum |
| International Harvester Co. | +100 | -25 | ±3 | Set with tachometer method |
| Jeep Corp. | +100 | -25 | ±3 | 3% CO Maximum |
| Other | | As specified by the particular manufacturer | |
* or 13.3/1 Air-Fuel Ratio-Minimum.
Md. Code Regs. 11.14.04.07