Audi 80 Quiz
KE-III-Jetronic Injection System

Checking the fuel injectors

In this manual: KE-III-Jetronic Injection System
Technical Description — 39Engines — 41Exhaust System — 13Cooling System — 28Fuel tank and fuel pump — 12Air Filter and Intake Ducts — 13Mono-Motronic Injection System — 18Digifant Injection System — 19KE-III-Jetronic Injection System — 35MPI and MPFI Injection Systems — 32Clutch — 11Transmission and Driveline — 21Suspension and Steering — 33Brake System — 41Anti-lock brake system — 8Wheels and Tires — 13Body Electrical System — 35Ignition System — 24Lighting — 14Signaling Devices — 7Instruments and Auxiliary Equipment — 54Heating and Ventilation — 7Body Components — 18Troubleshooting — 6Specifications — 13
~2min read

PROCEDURE

Disable the ignition system as described in the Ignition System chapter.

To check whether fuel is reaching the injection system, loosen the bolts on the fuel supply line.

Do not forget the rag, because in most cases fuel will spray out of the fuel line. Otherwise, ask an assistant to crank the engine with the starter.

If fuel is flowing, the supply is in order; the next step is to check the injectors themselves.

Remove the injector, see the description later in this chapter. To do this, the upper part of the intake manifold must first be removed.

Keep a container or rag ready to catch the fuel.

Remove the large air hose between the mixture control unit and the throttle valve housing to gain access to the shut-off valve.

In the central relay box, remove the fuel pump relay at connector cell 10 (see the chapter Fuel Tank and Fuel Pump).

At cell 10, connect connector terminals 48 (or 30) and 52 (or 87) with a short piece of wire. The fuel pump should start running.

Lift the metering distributor shut-off valve slightly by hand. The injector should now spray fuel in a cone shape. If not:
Lift the shut-off valve once to its stop. Repeat the check.

The difference in injected fuel quantity between individual cylinders can be checked in the same way. However, this method is only a substitute for a better one.

Direct all five injectors into five measuring containers, without kinking the fuel line hoses.

Lift the shut-off valve slightly (approximately 2 cm).

An assistant must hold the said jumper until 20 cm³ (ml) of fuel has collected in the first container.

Compare the injected fuel quantities. The difference must not exceed 2.5 cm³.

In case of large deviations, swap the injectors with the highest and lowest values. Repeat the measurement.

If the deviations move with the injectors, replace the injectors with the corresponding deviations.

If you obtain the previous measurement results with deviations for the cylinders, it is possible that the fuel line to the injector is restricted or the metering distributor is faulty.

Injector leak test: if the fuel pump is switched off after two minutes of operation with the shut-off valve lifted (jumper removed), no fuel should emerge from the injectors.

Test yourself

A quick Audi 80 quiz: every answer comes with an explanation and a link to the manual page.