Air Pump & Relief Valve
NOTE:
A faulty air injection pump is usually indicated by excessive air pump noise.
- Check air pump drive belt adjustment. Belt is adjusted properly if it can be deflected 3/4-1" midway on its longest run.
- Disconnect air pump output hose and connect a pressure gauge to hose. Start and idle engine at 850 RPM and check pressure gauge reading.
- Air pump pressure should be at least 1.0-1.5 psi (.07-.11 kg/cm2 ). If not, pump is defective and must be replaced.
- Next, increase engine speed and note the pressure at which pressure relief valve relieves excess pump pressure. Valve should relieve pressure at high engine speeds on Spitfire, and at specifications shown in table for other models.Air Pump Relief Valve Pressure
Application Psi(kg/cm2 ) MGB 4.5-6.5 (.32-.45) TR7 8.2-10.5 (.57-74) TR8 4.0 (.28)