How To Test The Ford Fuel Pump Relay -No Start Troubleshooting (Green Relay)
Testing the Ford fuel pump relay on the car is not that hard to do.
With the help of this ‘How To’ tutorial, I’ll show you how to do it using only a multimeter.
You’ll be able to find out if the fuel pump relay, or the fuel pump Inertia Switch, or the fuel pump is the cause of the No Start Condition on your Ford car or pickup.
If your fuel injected Ford pickup, van, or car still has the Ford relay, this bad boy will be a green color (like the one in the image viewer). If it has already been replaced with an after-market one, this relay won’t be green, but will have a gray body.
The following tutorial may be of help: How To Test The Fuel Pump (Ford 4.9L, 5.0L, 5.8L) (at: troubleshootmyvehicle.com).
For your cross reference information:
- AutoZone part #:
- Duralast 19911
- BWD R647
- Master Pro Ignition 2DR-1039
- STANDARD MOTOR PRODUCTS Part # RY46T
- STANDARD MOTOR PRODUCTS Part # RY46
- ORIGINAL ENGINE MANAGEMENT Part # DR1039
- AIRTEX / WELLS Part # 1R1294
You can find this tutorial in Spanish here: Cómo Probar El Relé De La Bomba De Gasolina (Relé Verde) (at: autotecnico-online.com).
Table of Contents
I. What is an Automotive Relay?
II. How It Works
III. Locating the Fuel Pump Relay
IV. The Fastest Way to Test a Fuel Pump Relay or Other Automotive Relays
V. Using a Special Relay Tester
VI. Using a Digital Multimeter to Test the Fuel Pump RelayWhat Tools Do I Need To Test The Relay?
You need a few basic things and they are:
- Multimeter
- A digital or analog multimeter will work.
- If you need to buy one or are looking to upgrade, check out my recommendations here: Buying A Digital Multimeter For Automotive Diagnostic Testing.
- This tool is a time saver of the first order. To see what this tool looks like, click here: Wire Piercing Probe.
- You’ll need two of them with alligator clips on both ends (you can make these yourself).
I. What Is an Automotive Relay?
Physically, a common 12-volt relay contains a series of electrical components set inside a small cube or cylinder box made up of hard plastic or aluminum.
A common fuel pump relay has four electrical terminals or pins sticking out of its base. The terminals in an automotive relay hook up to an internal coil, possibly one or more resistors or diode, and one or more switches or contacts, depending on the particular configuration.
You'll see relays with 3 or 4 pins often, but others with 5 and 6 terminals are not unusual. These automotive relays come in different sizes and ratings. And you'll find them under the hood inside the "block" or "power distribution center" box; inside the cabin, in fuse boxes under the dashboard; behind kick panels, and even mounted by themselves.
They switch power on and off circuits around the transmission, engine and accessories like the fuel pump, the headlights, the brake lights, the wipers and horn.
A common electromechanical relay.
Fuel Pump Relay Circuit Descriptions
The Ford fuel pump relay has 4 wires that connect to it.
Each wire has a specific job to do and these are their circuit descriptions:
IMPORTANT: Your specific Ford vehicle may not have the exact same colors listed below. This is no big deal, since the circuit descriptions are the same. You will be able to use the info in this article to diagnose the fuel pump relay on your Ford vehicle even if the colors of the fuel pump relay connector’s wires are different!
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Ford Fuel Pump Circuits Pin Wire Color Description 1 Tan w/ Green stripe * Fuel Pump Relay Control 2 Red * Power (from EEC Power Relay) 3 Brown * Fuel Pump Output 4 Yellow * Ignition Fused Power (Fuel Pump Fuse) * Your specific Ford vehicle may have different colors.
II. How It Works
It helps to think of a relay as a regular switch, like the one you use at home to turn on and off the lights in a room.
A relay works in a similar way, but instead of you reaching into the relay to flip on the internal switch directly, you energize a control circuit that connects to a coil inside the relay — this happens to the fuel pump relay when you turn the ignition switch to fire up the engine, for instance.
The coil creates an electromagnetic filed that closes a pair of metal contacts inside the relay that connect to a controlled circuit that activates a load — the electric fuel pump, for example.
Why duplicate a simple switching function by having an extra switch inside a box?
Actually, this turned up to be a convenient set up in electrical circuits. You not only use a small, safer current circuit — the control circuit — to switch on and off a higher current circuit — the controlled circuit — but a relay can be placed in a strategic location to reduce the amount of — and expenses in — thicker gauge wire needed for high current circuits.
IV. The Fastest Way to Test a Fuel Pump Relay or Other Automotive Relays
By far, the easiest way to test a suspect fuel pump relay — or some other automotive relay — is to swap the suspect relay with a good one.
You may find another relay in your car with the same configuration — arrangement and number of terminals — as your fuel pump relay. Or you can borrow a relay from a relative's or friend's car. Just make sure the other relay has the same configuration.
Remove the suspect relay and install the good relay and check if your engine fires up. If it does, install a new relay. Otherwise, the problem lies somewhere else.
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V. Using a Special Relay Tester
Another way to test your fuel pump relay is with a relay tester. You can find testers to help you troubleshoot the most common vehicle relays and more sophisticated testers to troubleshoot relays with different configurations.
The fact that you don't need schematics or wiring diagram speeds up the troubleshooting process. Just follow the instructions that come with the tool.
You can use a digital multimeter to test relays.
Questions & Answers
Question: My relay is good but the car still won't start so we took the fuell pump relay out and stuck a bobby pin into the circuits so it starts up. Why is that?
Answer: If voltage is going through the relay, check if voltage is reaching the fuel pump. The problem might be at that end.
Question: When I switch the ignition on, the fuel does not kick in. What could the problem be?
Answer: If the engine cranks but it doesn't start check the fuel pump. Usually you can hear it when turn the key On and pressurize the fuel line. If not check the pump.
Question: What is a fuel pump relay supposed to read on a multimeter?
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