1977-79 Models
- Install Tester (000 589 49 21 00) between main fuel filter and fuel injection pump. Bleed tester and fuel system. See BLEEDING FUEL SYSTEM in this article.
- Check for proper fuel delivery pressure, and opening pressure of by-pass valve. Using tester's glass tube, check for air bubbles in fuel at same time pressure is read. Check pressure at tester with engine running at idle speed. Pressure should be 8.5-11.4 psi (0.6-0.8 kg/cm2
).NOTE: When making pressure tests, observe glass tube for air bubbles. If bubbles appear, check system thoroughly for leaks. Check hose porosity, hairline cracks in fuel lines or hoses, deteriorated or scuffed hoses, or slack hose clips.
- Raise engine speed to 3000 RPM. Pressure should read 11.4 psi (0.8 kg/cm2 ). If pressure is much higher or lower, check that by-pass valve is opening properly. If excessively high, check for crushed or restricted fuel lines.
- Next, check final delivery pressure. Using fingers, squeeze hose between tester and injection pump. If pump is working properly, pressure should be at least 15.6 psi (1.1 kg/cm2 ) at idle and at least 18.5 psi (1.3 kg/cm2 ) at 3000 RPM.
- If pressure is lower than specified, either the valve requires replacing, or pump requires repair or replacement. If pressure is higher than specified, and opening pressure of by-pass valve is greater than 11.4 psi (0.8 kg/cm2 ), remove, clean and check by-pass valve for leaks. Replace valve if necessary.