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Dealers and Customer Information

Owners of the 1986 low altitude vehicles taking up permanent residence in one of these high altitude counties, should be encouraged to have these adjustments performed when vehicles are brought in for service.

After performing these adjustments, dealers should advise customers that, IF THE VEHICLE IS RETURNED TO CONTINUOUS, LOW ALTITUDE OPERATION, THE ENGINE SHOULD BE RE-ADJUSTED TO LOW ALTITUDE SPECIFICATION PER THE CORRECT CHASSIS SERVICE MANUAL FOR IMPROVED PERFORMANCE. IF RE-ADJUSTED TO LOW ALTITUDE SPECIFICATIONS, THE SUPPLEMENTAL LABEL SHOULD BE REMOVED.

PROCEDURE I

To be used for the following 1986 low altitude (NA5) engines used primarily at high altitudes.


^ 4.3L Federal All except "M" Vans

1. Advance base timing to a maximum of 4~ over specification if little or no detonation occurs at high altitude.

2a. Manual Transmission

Reset idles to original specifications on the Emission Control Information Label.

2b. Automatic Transmission

Set fast idle speed to 1800 RPM in N (neutral).

^ 5.0L/5.7L Federal

1. Advance base timing to a maximum of 4~ over specifications if little or no detonation occurs at high altitude.

2a. Manual Transmission

Do not adjust the carburetor vacuum break.

2b. Automatic Transmission

Reset carburetor vacuum break to 26~.

3. Reset base, A/C solenoid (if present) and fast idles to the specifications on the Emission Control Information Label.
^ Heavy Duty Gasoline Emission Packages

1. Advance base timing to a maximum of 4~ over specification if little or no detonation occurs at high altitude.

2. Set idle speed to specifications in accordance to Emission Control Information Label.

^ LIGHT DUTY FEDERAL DIESEL ENGINE (LH6)

The high altitude modification involves the recalibration of the fuel injection pump to a different fuel rate which will compensate for the lower air density at high altitudes.

The injection pump cannot be modified on the vehicle. The following procedure should be used:

1. Remove the injection pump per Service Manual procedures. Be sure to note the relationship of the timing marks on the pump and front housing. The pump must be reinstalled to its exact previous position.

2. Send the pump to an ADS (Association of Diesel Specialists) Service Center for the altitude performance adjustment. The ADS Service Centers will be advised by Stanadyne Corporation Bulletin as to injection pump recalibration procedures.

3. Reinstall the pump per Service Manual procedure. The pump must be installed to its original timing setting. If the original timing relationship was not retained, refer to Bulletin detailing the timing procedure to follow.

PROCEDURE II

To be used for the following 1986 high altitude (NA6) engines used primarily at low altitudes.

^ 4.3L Federal All Except "M" Vans

1. Retard base timing up to 4~ from specification if detonation occurs at low altitude.

2a. Manual Transmission Reset idles to specifications on the Emission Control Information Label. 2b. Automatic Transmission
1. Set fast idle speed to 2200 RPM in N (neutral).
2. Reset all other idles to specifications on the Emission Control Information Label.
^ 5.0L/5.7L Federal

1. Reset base timing to specification on the Emission Control Information Label.

2a. Manual Transmission

Do not adjust the carburetor vacuum break.

2b. Automatic Transmission

Reset carburetor vacuum break to 24~

3. Reset base idle speed to specification on the Emission Control Information Label.

4. Reset fast idle speed to specification on the Emission Control Information Label.

^ LIGHT DUTY FEDERAL DIESEL ENGINE (LH6)

Vehicles designed for principal use at high altitude perform satisfactorily at low altitude without excessive smoke levels and need not be adjusted for extended operation at low altitude.

DEALERS AND CUSTOMER INFORMATION

Owners of the 1986 high altitude vehicles taking up permanent residence in one of the low altitude counties, should be encouraged to have these adjustments performed when vehicles are brought in for service.

After performing these adjustments, dealers should advise customers that, IF THE VEHICLE IS RETURNED TO CONTINUOUS, HIGH ALTITUDE OPERATION, THE ENGINE SHOULD BE RE-ADJUSTED TO HIGH ALTITUDE SPECIFICATION PER THE CORRECT CHASSIS SERVICE MANUAL FOR IMPROVED PERFORMANCE. IF RE-ADJUSTED TO HIGH ALTITUDE SPECIFICATIONS, THE SUPPLEMENTAL LABEL SHOULD BE REMOVED.

HIGH ALTITUDE COUNTIES

The following is a list of high altitude counties:

STATE OF COLORADO

Adams Fremont Montezuma
Alamosa Garfield Montrose
Arapahoe Gilpin Morgan
Archuleta Grand Otero
Boulder Gunnison Ouray
Chaffee Hinsdale Park
Cheyenne Huerfano Pitkin
Clear Creek Jackson Pueblo
Conejos Jefferson Rio Blanco
Costilla Kit Carson Rio Grande
Crowley Lake Routt
Custer La Plata Saguache
Delta Larimer San Juan
Denver Las Animas San Miguel
Dolores Lincoln Summit
Douglas Mesa Teller
Eagle Mineral Washington
Elbert Moffat Weld
El Paso STATE OF NEVADA

Carson City Humboldt Nye
Douglas Lander Pershing
Elko Lincoln Storey
Esmeralda Lyon Washoe
Eureka Mineral White Pine

STATE OF NEW MEXICO

Bernalillo Lincoln San Juan
Catron Los Alamos San Miguel
Colfax Luna Santa Fe
Curry McKinley Sierra
DeBaca Otero Socorro
Grant Mora Taos
Guadalupe Rio Arriba Torrance
Harding Roosevelt Union
Hidalgo Sandoval Valencia

STATE OF UTAH

Beaver Iron Sanpete
Box Elder Juab Sevier
Cache Kane Summit
Carbon Millard Tooele
Daggett Morgan Uintah
Duchesne Piute Utah
Emery Rich Wasatch
Garfield Salt Lake Wayne
Grand San Juan Weber
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