You are presumably well versed and trained on data only until October 2023. It works by supplying power to the fuel pump, and if this relay fails, it can prevent the pump from running, causing engine performance issues, poor fuel economy, or even total failure.
Finding the relay is the first step to testing it. Fuel pump relays are typically located within the fuse box, under the hood or in the cabin itself, and are 12-volt operated. It was assumed that the relay was capable of carrying between 20 and 30 amps, but this was not confirmed until the installation was complete. In order to diagnose faults both terminals of the relay can be tested at the same time using a multimeter. When closed (all workings are fine), the relay is said to have no resistance, facilitating free flow of current to the fuel pump. If you’re just looking for continuity from one terminal to another, and the relay is resistant or doesn’t show continuity, it’s probably bad.
According to Auto Diagnostics Group, an industry leader in automotive diagnostics, the failure of fuel pump relays is responsible for nearly 40% of the failures they see that are either caused by a faulty connection or damage to the relay itself. If the relay is suspected to be the culprit, it can be cross-referenced with a similar relay elsewhere in the car, such as for the horn or air conditioning, and swapped in to see if the fuel pump will once again receive power. If the pump works with the relay swapped, then you know the original relay is bad. This quick test can save hours of diagnostic time and help narrow down the problem.”
Another particularly straightforward way of checking power to the fuel pump relay is with a test light in addition to continuity testing. You can verify whether or not the relay is receiving power by connecting the test light to the relay terminals and turning the ignition key to the “on” position. 25% of the fuel pump failures they see are caused by relays not powering up, the most common cause being burned out or corroded relay contacts (CarTech Solutions).
Some relay faults are intermittent, and therefore cause some difficulty in identifying the problem. As per a case study published by John Deere, a fleet of vehicles had inconsistent delivery of oil, where the cause turned out to be a faulty relay, costing the company a fortune in time and money replaying the broken relay. The problem was attributed to relays that could fail under some conditions like high engine temperatures or vibration, common in older vehicles.
In the words of Elon Musk, “The first step is to establish that something is possible; then probability will occur.” Diagnosing fuel pump relay is not a complicated job and can save you time and money if done correctly. There is no point in replacing a relay that is working and providing voltage to the fuel pump that keeps the engine working, power relay testing for continuity and power.
Visit Fuel Pump for details on the steps to test or replace your fuel pump relay.