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AIRTEX Technical Service Bulletin Fuel System Troubleshooting and Electrical Checks The Problem Fuel system repairs are often performed without proper diagnosis leading to unneeded parts and the inconvenience of doing a complex repair tha t does not x the vehicle problem The Solution Basic fuel system troubleshooting and diagnosis can be accomplished with a digital voltmeter and some knowledge of vehicle electrical systems This bulletin provides some guidelines for system electrical tests System Components to Check First If the vehicle will not start check the following Fuel level in tank P ower at the fuel pump fuse relay Vehicle System Voltage Test 1 Connect digital voltmeter positive lead to positive battery terminal 2 Connect digital voltmeter negative lead to negative battery terminal 3 System voltage should read 12 4v DC or higher with no electrical loads on the system If voltage reads less starting and charging system should be investigated before performing fuel system electrical testing Fuel Pump Voltage Test 1 Connect digital voltmeter to fuel pump wiring at fuel pump connector 2 Turn key on pump will only have voltage for a few seconds 3 Measure voltage at pump Reading should be within 0 5v DC of system voltage Fuel Pump Voltage Test System Voltage Test TM 6810 TSB 0307 ENG indd 1 6810 TSB 0307 ENG indd 1 2 3 11 2 33 19 PM 2 3 11 2 33 19 PM AIRTEX Technical Service Bulletin Fuel System Troubleshooting and Electrical Checks Voltage Drop Test Negative Circuit Voltage Drop Test Positive Circuit Fuel System Voltage Drop Test 1 Address the negative side of the circuit rst then the positive side 2 Connect one digital voltmeter test lead to the negative battery terminal and the other to the negative terminal at the fuel pump 3 The fuel pump circuit must be energized to properly test Energize the fuel pump relay and power the fuel pump circuit see NOTE below 4 If the negative circuit is in good condition the voltage drop measured should be 0 5v DC or less Larger voltage drop readings indicate a problem Damaged or corroded vehicle wiring or harness connectors are likely sources of the problem 5 Repeat the voltage drop test on the positive side of the circuit Connect one digital voltmeter probe to the positive terminal on the battery and the other to the positive fuel pump terminal 6 Energize the fuel pump relay and power the fuel pump circuit see NOTE below 7 As with the ground circuit voltage drop readings larger than 0 5v DC indicate system wiring or connector issues NOTE The majority of fuel pumps run for only a few seconds once the relay is energized only long enough to prime the system until an RPM signal is generated Some vehicles may require a scan tool to trigger the fuel pump Refer to the service information for your speci c vehicle TSB 0307 01_ATX 407 West Main Street Fair eld IL 62837 Tech Line 1 800 424 7839 2010 Airtex Products LP airtexproducts com TM 6810 TSB 0307 ENG indd 2 6810 TSB 0307 ENG indd 2 2 3 11 2 33 21 PM 2 3 11 2 33 21 PM
