How to Troubleshoot the Fuel Injection System on a 1986 Mazda RX 7

The fuel injector on a 1986 Mazda RX 7 is a mechanical or electro-mechanical device that meters fuel into the car's engine. The RX 7's fuel injection system has three sub-systems: electronic control, fuel delivery and air induction. The electronic control sub-system determines how much fuel should reach the engine. The fuel delivery sub-system pulls gas from the gas tank and sends it to the engine. The air induction sub-system controls the amount of fuel traveling through the car's fuel system. Signs of a malfunctioning fuel injection system tend to trace back to backfiring, loss of power or lower emission quality.

Tools Used: Fuel pressure gauge, Manufacturer fuel pressure specifications

How do I Troubleshoot the Fuel Injection System

Conduct a static fuel pressure test. Connect a fuel pressure gauge to the RX 7's pressure test fitting and examine whether the pressure is too low in the Mazda's fuel system. The fitting is located next to the alternator. It is covered with a small black cap and has a gold or silver colored metal base that resembles a lug nut. The 1986 RX 7 should have between 64 and 85.3 psi. Low fuel pressure indicates a weak fuel pump, blockage in the fuel lines, faulty fuel pressure regulator or blocked fuel filter. If there is not enough fuel pressure, the RX 7's engine will probably not start.

Perform a residual fuel pressure test. A fuel pressure system will hold residual pressure after the engine is shut off. Turn the car on and let it run for a few minutes. Check the fuel pressure with a fuel pressure gauge while the car is running. Turn the car off and read the gauge. If the gauge suddenly drops in pressure within several minutes of turning the car off, the Mazda may have a leaky fuel line.

Check the fuel pressure while the car's engine is idling. Compare the fuel pressure gauge reading to the fuel pressure specifications for the RX 7. The car should have between 64 and 85.3 psi. If the gauge shows a low fuel pressure, the vehicle may have a weak or disabled fuel pump, clogged fuel filter, bad pressure regulator, nearly empty fuel tank or clogged inlet or line sock.

Inspect the fuel pump, which is located inside the gas tank. You need to remove the fuel pump from the RX 7's body by removing the straps that hold it together. Disconnect all of the fuel lines connected to the top of the fuel tank. Loosen and remove the metal locking ring holding the fuel pump to the top of the tank. Pull out the fuel pump and inspect it for broken wires, missing pieces or warped components.

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