CAUTION: The Bosch LH Jetronic fuel injection system maintains constant fuel pressure in the fuel lines and component parts at all times. Be sure to relieve pressure before attempting to open system at any point for testing. DO NOT allow fuel to flow onto engine or electrical parts or allow an open flame in area while testing fuel system components.

Connect a fuel pressure gauge between fuel line and injection manifold. Switch on ignition to activate fuel pump. Fuel pressure should be 35.5 psi (2.5 kg/cm² ).
CAUTION: DO NOT let pressure exceed 85.2 psi (6.0 kg/cm² ).
If pressure is too low, pinch off fuel return line by hand and check if pressure rises. If pressure quickly rises pump and lines are functioning correctly. Replace pressure regulator and measure pressure.
If pressure rises slowly, fuel filter, tank pump filter or lines are blocked. If pressure does not rise, pump is defective.
If fuel pressure is high, disconnect fuel return line from pressure regulator and blow in line. If line is open pressure regulator is defective and should be replaced.
Pressure may also be checked with engine off and fuel gauge connected. Attach a hand vacuum pump to pressure regulator. Line pressure should decrease as regulator is evacuated.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Fuel Line Pressure

Use the Manual With the Right Hardware

When to See a Mechanic