Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
High Altitude Compensation System: Operation
The altitude compensator mixes air into the gasoline when it enters the idle/low speed circuit and main metering circuit passages in the carburetor. The metering of the air bled into the carburetor is accomplished by the use of an aneroid valve bellows, which simultaneously moves 3 spring-loaded needle valves.
As altitude increases, atmospheric pressure will exert less force on the bellows, causing the bellows to expand and mechanically open the needle valves. Fresh filtered air is supplied to the needle valves from the inboard side of the air cleaner element.
The 1987 1/2 models have one-way check valves located in series in the primary and secondary main metering air lines. These check valves will prevent any liquid fuel from entering the altitude compensator housing. The altitude compensator is attached to the front of the heater air intake duct. The fresh air inlet to the compensator is connected at the bottom of the air cleaner housing. The one-way check valves (if equipped) are located in the air lines near the carburetor.
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
Rather have a pro handle this?
A certified mobile mechanic comes to your home or office. They bring the tools, you stay comfortable. No tow truck, no waiting room, no surprises.
No obligation. See pricing before you book.