Saturday, March 26, 2016

Diagnosis of air in the fuel system

Bicki Howell, Nellie D. 37VT63

If you have ever had your engine start revving and increasing in RMP it is the dreaded signal that air is being sucked into the engine.  It can mean the fuel in the tank(s) is lower than your fuel pickup line or it can be something much harder to diagnose.  A cracked hose, broken fitting or loose connection in the fuel system can be frustrating and difficult to find.  

We made a simple tool to visibly show where air is getting into the fuel system.  It is a clear hose, retrofitted with brass fittings, that can be easily placed in various parts of the fuel tank manifold.  The clear hose enables us to see if air bubbles are present as the fuel passes through.  With this tool we located a cracked elbow in our manifold system.  





















Recently, the engine was revving again, Yikes!   We started hunting down the culprit.  We verified first that there was plenty of fuel and the manifold test tool showed no problems from the tanks or manifold.  Next in the line was the Racor filter, which was visually filled with air.  We replaced the Recor hose with a piece of clear line and quickly found the problem.  The old hose was cracked and we were pulling huge amounts of air into the engine.  It was an easy fix, but without the clear hose it would have been a devil to find.  


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