There are additives to boost octane, and/or aviation gasoline (expensive for smooth burns and no pinging). The exception to this is some muscle car applications (pre-computer controls) where higher compression ratios (9:1 or more) may cause detonation. Octane: Today’s octane levels are adequate for providing good combustion burns, no pinging (with correct tune-up specs), best mileage, good drivability (no stumbles or bogs), and lower emissions. This lowered liquid fuel temperatures under the hood and inside fuel lines. Liquid and vapor gasoline was continually re-circulated back to the fuel tank to minimize vapor lock problems. In the later carburetion years (1975- 85), fuel vapor return lines were installed from the fuel pump or near the carburetor. Vapor lock is not an issue, even with one supply line to the fuel rail and no return line to the tank. Modern fuel injection systems operate at 30-75 psi pressure. Today’s gasoline provides easier startups and lower emissions during engine warm-up for our modern vehicles. The higher Reid Vapor pressures mean, in today’s gasoline, hydrocarbons start boiling at lower temperatures, like 90-100☏. One gas does not fit all areas or climates. Today Reid Vapor Pressures vary from 9-13 psi depending on climate, elevation, geography and season. This means the gasoline did not start boiling at low temperatures, like in today’s gasolines. Gasoline Vapor Pressure: In the old days(1925) gasoline “Reid Vapor Pressures” were around 4-5 psi as measured using the SAE tests procedures. The “heavier ends” finish boiling at up to 400☏. Generally, gasoline “lighter end” hydrocarbons start to boil as low as 90° F. Standardized tests are conducted for octane, vapor pressure (a “biggie” in fuel foaming), and fuel additives to control fuel injection, carburetion and combustion chamber carbon buildup.ĭistillation:All gasolines have a “distillation” curve. All gasoline manufacturers follow these tests to measure and control the quality, performance and production of gasoline. Please Note: Any restrictions or sharp bends in the fuel supply system promote vapor lock (fuel foaming) formation.įuel Testing: Gasoline testing,technical research and development is well documented by the SAE (Society of Automotive Engineers).
#SMALL ENGINE VAPOR LOCK CRACKED#
Vapor lock (fuel foaming) is caused by overheating engines, insufficient fuel supply, fuel pump failures, 90° bends in fittings, cracked fuel lines, collapsed fuel lines, excessive under hood temperatures, engine block overheating, old radiators, and rotted-out block distribution tubes. Then, add around 50 degrees to estimate the coolant temperature. Using an infrared temperature gun, measure the outer surface on coolant passages.
The carburetor handles liquid gasoline until the air-fuel mixture enters the main jet discharge nozzle. The same process happens in the carburetor bowl bottom surface at fuel temperatures from 90° to 100° F. Take a look at a pan of water on the stove just before the water temperature reaches 212° F. Vapor lock: In this article vapor lock is “fuel foaming” in technical terms.įuel foaming occurs when “lighter end” gasoline hydrocarbons start “boiling” and forming vapor This article will show you some servicing techniques for identifying causes for vapor lock and controlling boil over on your collectible vehicle.īut first, just what is vapor lock and boilin’ over? Is The gasoline with 10% ethanol causing the vapor lock? Maybe! Or is your cooling system boilin’ over? elevation in the Sierras, or going over 50 mph? How about idling in a parade? IS VAPOR LOCK your big problem on warm days over 80° or 100°, at sea level or at a 10,000 ft.
Here Are Some Ways to Diagnose and Fix the Situation. Febru| By Milt Webb These Problems Are Experienced by Many Older Cars & Trucks.
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