Fuel pump of my car works only when i give voltage to the fuel pump from a battery direct to the pins. I replaced relay but still does not work when i start the motor. I think that the wires must cause the problem, what can i do to detect it ?

The fuel pump receives signal to pump from the ECU, but firstly, you need to find out whether the pump is working, does it cycle when you turn the key on with a whiring noise or sound. This is the initial priming, where the pump turns or cycles to create pressure in the common rail or injectors prior to the actual startup when you turn the key to start engine position. If fuses are all ok, go by process of elimination. unplug the feed to the pump, usually under back seat of a sedan or at back of a truck and use a tester or test lamp to see if there is voltage to the pump. if there is, next power the pump with 12volts directly from battery at the points where the power shows on the supply plug of the pump but keep the feed plug off preferably so feed the male pins on the pump side of the plug or male plug with female casing fixed to the pump but on pins that correspond to the pins on other plug that supple the pos and neg power from battery. If pump does not run when you feed power to the pins from a battery directly, then the pump is toast. Hope that helps and makes some sense.

Did you have it checked for code's ? The PCM / ECM supply's Battery voltage to control ( energize ) the fuel pump relay . Using a voltmeter you can check for B+ voltage at pin 85 or 86 ,which ever one comes from the engine computer ,the other goes to ground . This is provided the anti-theft system light isn't lit . Watch this video on testing at the fuel pump relay GM vehicle's
GM Fuel Pump Relay Testing

Your sure that B+ voltage is present at pin 30 ? If so an you measure no + battery voltage back at the fuel pump , you have an open circuit in that wire . Try supplying B + right to the fuel pump .

Did you check for voltage at the relay socket before replacing the relay ? Most relays have four or five pins , two should have battery voltage , one goes to the fuel pump an the last one is a ground supply from the PCM - powertrain control module - engine computer if you know what that is . If you look on the bottom of the relay it should have some numbers 85,86 , 30,87 ! 30 an 87 are the fuel pump side . 30 is battery voltage for the pump ! 85 is battery voltage an 86 is ground from PCM . VEHICLE RELAYS Operation Diagnosis Before replacing wiring harness test ! Check out these videos... Fuel Pump Electrical Circuits Description and Operation

Well you need to get out the DVOM - digital volt ohm meter an check for battery voltage at the fuel pump relay ! if you replaced it you saw the holes it plugs into in the relay / fuse box ? Put you volt meter on the 20 volt scale , hook the black lead to the battery negative or a good engine ground an take the red lead an touch - don't stick it in an spread the terminals . Two of the holes should have battery voltage ,if not check the EEC power relay ! If you find voltage at two holes change the meter to ohms , leave the black connector on a good ground an touch the red to the two holes left , one should be open or OL on the meter , this is the control side from the engine computer . the last hole should show a few ohms resistance , this is down through the wiring to an through the fuel pump to ground . You have two different wiring circuits , control an load side , load side being power to the fuel pump an control side is power an the engine computer supplying a ground energizing the relay closing the contacts in the relay sending battery voltage to the fuel pump. Test don't guess !

Hi Jeanette , what kind of damage did the vehicle receive ? I'm looking at a wiring diagram for your vehicle an there is no reset on this vehicle ! There is a fuel pump relay located in the passenger compartment relay box , under the dash somewhere ! The fuel pump relay is energized by the engine computer . The fuel pump receives battery voltage from a fusible link - blue , in the under hood relay / fuse box ! The thing to do is find the fuel pump relay an test from there . do you have a volt ohm meter , do you know how to use one . The relay has four pins on the bottom if you pull it out an look at it . Two of the pins should have battery voltage one of the others should show ground through the fuel pump an the last will be open , this is from the PCM - engine computer , control circuit . When you crank over the engine the computer gives a ground to this circuit turning on the fuel pump ! Check power an grounds ,don't just replace parts !!!!!!!!

What make , model an year vehicle ? Did you check for Battery + voltage at the fuse an relay FIRST ? You test before replacing parts . Take a volt meter an measure for voltage at the fuse then at the relay ! There are four pins on the relay an four holes the relay plugs in two , Two of these holes should have Battery voltage , One is the control from the engine computer that energizes the relay coil . The last hole is the wire that goes to the fuel pump. You could jump pins 30 to 87 , if you look on the side there is a diagram . Also on the bottom sometimes the pins are marked 85 an 86 an 30 an 87 ! The last two 30 an 87 are the load side , the fuel pump side . You could jumper 30 to 87 ,direct power to the fuel pump ! You have to test the electric circuit ! GM Fuel Pump Relay Testing How do you know you have no fuel pressure ?

Check the pcm ground pins to make sure they are grounded. 6, 28, 34, and 55.

There is a red and white wire feeding the fuel pump relay from a 30 amp fuse. Both the shutdown relay and the fuel pump relay are grounded by the PCM, so if the fuel pump relay is grounded it should be "on" and providing a direct link from the pump to that fuse.
You should have battery voltage on that 30 amp wire before the relay and then on the dark green and black wire going to the pump.
If you don't have battery voltage coming from the 30 amp fuse, the problem could be before the fuse.
That 30 amp fuse is hot all the time, so it is powered by a fuseable link coming off the battery.

Hi there, i have a guide that will help you troubleshoot this device. its a step by step situation that will help you find the issue with your fuel pump functions.

tep1 Go to the back of your car and take off the fuel filler cap. Ask an assistant to turn the ignition on but do not start the engine. Listen closely for a brief, vibratory sound coming from the tank. If you cannot hear the sound, go to the next step. Step2 Check the fuel pump circuit fuse. It should be in the fuse panel under the dashboard or in the engine compartment Verify that it is in good condition and the contacts are free from corrosion. If necessary, replace it and test the pump again. Step3 Inspect fuel lines, hoses and connectors. Make sure hoses are not torn, bent or obstructed. Verify there are no gas leaks. Step4 Locate the fuel pump relay. You might find it in the engine compartment, at the driver or passenger side and close to the windshield or at the front of the engine as part of a cluster of relays. Another common place is under the dashboard. Step5 Remove the fuel pump relay. Ask an assistant to turn the ignition on but do not start the engine. Using a test light, check for incoming voltage at the relay connector. If there is no voltage, check for an open or short at the wire between the relay and the fuse panel. Step6 Jump the relay connector to apply battery voltage to the fuel pump. After the jumper wire is connected, ask an assistant to turn on the ignition while you listen for fuel pump operation as described in step 1. If the fuel pump works now, replace the relay and test again. Another alternative is to test the fuel pump relay for proper operation. Step7 Locate the fuel pump connector at the back of the car and check for incoming voltage with a test light. While you check for voltage, ask an assistant to turn on the ignition but do not start the engine. If there is no voltage, check for an open or short at the wire between the relay and the fuel pump. Step8 Check the power and ground connections at the pump and make sure they are good and free of corrosion. Step9 Test the fuel pump. Apply direct voltage to the fuel pump. If you cannot easily remove the fuel pump through the trunk of your vehicle, you might want to take a fully charge car battery to the back of the car. Raise the vehicle and secure it firmly on jack stands. Unplug the fuel connector and use a couple of jumper wires to connect the battery to the fuel pump. If the pump does not work, replace it.


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