mobile mechanic fort wayne. muller auto llc. how to test a fuel pump

Starter fluid was sprayed into the intake and then the engine was cranked. The goal is to add fuel to the air mixture entering the engine and see if that causes the engine to fire. if it does theres a good chance your issue is fuel. if it does not work, it is not a sure sign that the issue isnt fuel. either way keep testing.

inser photos of rails and ways to disconnect inside the engine bay

it is important to test in two places. the easiest place is usually in the engine bay on the fuel rail. typically theres a shrader valve you can connact to. on some vehicles its easier to just disconnect a line. be careful once you open the fuel system. flames and fuel dont mix. if there is no or low pressure at the engine bay, open the system before the fuel filter if possible. youll be able to test directly at the fuel pump but if you can save the time of potentially dropping the tank it is ideal. its very rare but make sure the fuel filter isnt clogged. if it is check the direction on it. theyre usally directional.

voltage at the pump is important but its not the full story. a wire that is frayed but leaves a single strand will pass continuity and resistance tests and carry 12v, however it will not be able to carry the load of the fuel pump. one one is extreme but the example gets thebpoint across. the load test is a more accurate way of verifying the integrity of the wire. in this video i have the wire that is supposed to carry power to the fuel pump going to one side of the light bulb. the other side is connected to ground. when the fuel pump is commanded on with the key or a scan tool the light will illuminate. if it doesnt illuminate or is dim, the wiring may be the culprit. this test was done with the light bulb by the battery but in some cases it may be quicker or easier to complete the load tests at the connacgor going into the fuel pump.

assuming you have power you have more testing to do. test ground. in this video i have one ground for my motor circuit and one ground for my fuel level sensor circuit. both lit up bright. this test can be more dangerous than some other ones. if done wrong sparks can be made. this test was done at the connector going into the fuel pump. in the test power was connacted to one side of the bulb and then ground was touched to the other. power can come from the connector or the battery itself. if the power comes from the connector the fuel pump must be powered on by a scan tool ot the ignition for the light to illuminate. if power is good and ground is good theres one test left to diagnose the fuel pump. try running power and ground to the fuel pump manually. no not create sparks. if your fuel pump does not spray, replace and retest.