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Dec. 14, 2021

If your engine doesn’t get any fuel, it’s not going to start. But there are many other reasons why this might happen other than the customer simply overlooked filling the tank. Read on to see how one SureTrack community member was able to figure out why their customer’s 1992 Mazda Protégé DX 1.8 engine would not start.

Diagnosis

The technician started by performing an inspection of the engine compartment which showed no issues. Next he connected a spark tester to spark plug wire #1 and cranked the engine, finding that a spark was present. Then, he connected a fuel pressure gauge to the fuel filter outlet, tested the fuel pressure with KOEO and found the measured fuel pressure was below the specified range.

The tech followed that by using a multi-meter to check for the presence of voltage at the fuel pump and found no voltage. However, the engine did start when he used fused jumper wire to apply voltage to the fuel pump. With this, he decided to use the multi-meter to check for voltage at the input terminal of the fuel pump relay, a fused jumper wire to bypass the relay and presence of voltage and ground at the control circuit of the fuel pump relay.

He found there was voltage and the fuel pump was responsive as well as the ground not being present. Luckily, he wiggled the mass airflow sensor wiring harness while monitoring the multi-meter and found the relay ground was affected by the movement, indicating a circuit was faulty.

Fix

Visually, he inspected the harness only to find that it was indeed damaged, preventing the fuel pump relay from activating. He repaired the wiring harness the problem was solved.

Real Fixes from Mitchell 1’s SureTrack® expert information resource are documented issues from actual shop repair orders and community discussions. Read the Real Fix in the Mitchell 1 ShopConnection Blog.

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