Finding a Fuel or Air leak
A modified fuel cap can be used to easily pressurize a fuel tank and fuel supply system, looking for an air leak or fuel leak.
Member Bob Lyons sent this photo to me a while back that illustrates how to modify an old diesel fuel cap with an air fitting, allowing an easy way to test the fuel tank and fuel supply system for either a fuel leak or an air leak.
It's important to not use more than 5 to 10 psi pressure. More pressure could pose a risk to the fuel tank, in that it may rupture when subjected to excessive pressure.
If the tank, fuel lines or fuel filter assembly has a leak, you'll see an oozing fuel leak at the leak site when the tank is under pressure. Take your time, allow a few minutes to pass without evedence of a leak before declaring the fuel system leak-free, if a leak cannot be located.
A test cap like this would be essential for a diesel shop or anyone who is perplexed by a stalling/hard to start problem.
Jim
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