Fuel Pump Wires Color Codes With Diagram (2024)

Updated on March 16, 2023

Whenever it comes to any kind of automotive wiring and color codes, there is hardly ever a universal standard. Instead, the wire colors differ between brands, model years, and even models.

However, there are some alternative ways you can recognize the wires without knowing the exact color, and you can also probe them with a multimeter to see which wire does what. But before we go into more detail, here is everything you should know for now.

The fuel pump wires’ color codes are as follows. The power supply to the fuel pump is most often light grey or other light colors such as yellow or bright pink. The fuel pump ground wire, in most cases, is solid black, and the same goes for the fuel level sender ground. The fuel level reference (positive) wire can be purple, yellow, orange, and a slew of other colors.

Fuel Pump Positive Wire

The fuel pump’s positive wire comes from the fuel pump relay, goes through the inertia switch, and ends up on the fuel pump, powering it only when you turn the ignition on. The first thing you should note here is that the fuel pump positive wire is rarely black, and it’s a thicker gauge than the fuel level sender unit wires. That way, you can immediately tell it apart.

If the wire isn’t black and is thicker than two of the remaining three wires, it’s the fuel pump positive. The wire color, in most cases, is light grey – that’s the color of virtually all GM and Ford vehicles. In other cases, it can be pink (most often found on Fords), orange, and other light colors with or without a stripe.

Fuel Pump Positive Wire Colors

• Light Grey (Solid)
• Bright Pink (Solid)
• Bright Orange (Black Stripe)

Fuel Pump Ground Wire

The fuel pump ground wire is just that, a ground strap from the fuel pump to the chassis. In most cases, the ground is solid black or black with a white stripe. But whatever the case, the ground wire will almost always be darker than the positive wire, and it’s the same gauge as the positive. Meaning the positive and ground fuel pump wires are thicker than the fuel level sender wires.

To simplify, figure out which wires are thicker, and those will be the fuel pump wires. Then, note which of the two thicker wires is darker, and that’s the fuel pump ground, and the lighter wire is the fuel pump positive. Although the fuel level sender ground wire is black, it will often have a white or orange stripe, so you don’t have to differentiate them by wire gauge.

Fuel Pump Ground Wire Colors

• Black (Solid)

Fuel Level Sender Ground Wire

The fuel level sender is what controls the fuel gauge in the instrument cluster as well as the low fuel warning light. While the fuel level sender doesn’t have anything to do with the fuel pump, its wires are a part of the same connector. Both the ground and the positive fuel level sender wires are thinner or smaller gauges than the fuel pump wires, something we already mentioned.

Furthermore, the ground wire will also be darker than the positive wire making it easier to differentiate even without knowing the exact colors. The most common colors are solid black, black with an orange stripe, and green with a blue stripe. The solid back is most common on GM vehicles, while the black/orange and green/blue are most common on Fords.

Fuel Level Sender Ground Wire Colors

• Black (Solid)
• Black (Orange Stripe)
• Green (Blue Stripe)
• Orange (Black Stripe)

Fuel Level Sender Positive Wire

The fuel level sender positive or signal wire is what supplies a constant voltage to the fuel level unit potentiometer. The thickness of this wire is the same as the ground wire, meaning it’s thinner than both fuel pump wires.

Also, the voltage of this wire is around 5 volts, whereas the fuel pump positive is around 12 volts. The voltage is the easiest and most bulletproof way of differentiating the two wires, but more on that later.

The fuel level positive wire colors are typically lighter than the ground wire. Those colors can be yellow with a white stripe, yellow with a purple stripe, or solid purple. The yellow/white and yellow/purple are what you will find on Ford vehicles, while the solid purple is most common on GM vehicles. But again, all these wire colors can be different between vehicles, so it’s best to test them with a multimeter.

Fuel Level Sender Positive Wire Colors

• Yellow (Purple Stripe)
• Yellow (White Stripe)
• Purple (Solid)

Fuel Pump Wiring Diagram

• Black Wire – Fuel Pump Ground
• Grey Wire – Fuel Pump Positive
• Purple Wire – Fuel Level Sender Ground
• Orange Wire – Fuel Level Sender Positive

Differences in Wire Gauge

This is something we have mentioned multiple times so far, but in case you missed it, you can know which fuel pump wire does what by its thickness. The fuel pump connector has four wires, two of which are for the fuel pump and the other two for the fuel level sender (fuel level gauge).

Of those four wires, two will be thicker, and those two are positive and negative for the fuel pump. The other, thinner two wires are positive and negative fuel level sender wires. Once you note the thickness, you can check the wire color codes above, or you can go by color shade. Specifically, the positive wires will be of lighter color while the ground wires are darker, most often black.

How to Check Fuel Pump Wiring With a Multimeter

1. To check the fuel pump wires with a multimeter, you need to access the fuel pump and its connector first.
2. Now, set your multimeter to 20v DC.
3. Place the black probe on a piece of bare metal. That can be an unpainted piece of chassis, a bolt, the exhaust, etc.
4. Now, turn the ignition on but don’t start the engine.
5. With the red multimeter probe, test each of the fuel pump connector terminals. You can do that by back-probing the connector while it’s still connected to the fuel pump.
6. Now, monitor the multimeter, and when you see around 5 volts, that’s the fuel sender positive wire. And when you see around 12 volts, that’s the fuel pump positive wire.
7. The remaining two wires are ground, and you can differentiate them by thickness. The thinner wore is the fuel level sendee ground, and the thicker one is the fuel pump ground.

What Voltage Does the Fuel Pump Need?

The fuel pump runs on 12.5 to 13 volts which is the battery’s output when the engine is running. However, some fuel systems run with a ballast which lowers the voltage going to the fuel pump to about 11 to 12 volts. Also, in case you are wondering, a typical fuel pump pulls about 6 to 8 amperes.

What Causes Fuel Pump Wiring Harness Failure?

A fuel pump wiring harness rarely ever fails, but when it does, it’s because of external factors. For example, the wiring is sometimes close to a heat source, causing it to melt over time. Then, there are environmental contaminants like water and salt, as well as engine fluids like coolant and oil. Also, the if the fuel pump gets too much current because of an electrical fault, the wires will overheat and melt the insulation.

What Are the Signs of a Bad Fuel Pump?

The main signs of a bad fuel pump are the car stalling, refusing to start, and poor performance. When it comes to stalling, it can happen when idling as well as under hard acceleration. Also, you could notice the engine surging while cruising, which is caused by a lean air-fuel mixture.

How Do You Test a Fuel Pump?

You can test a fuel pump using a multimeter and test the positive wire against the ground. In the best-case scenario, it will be easy to access the fuel pump so you can test the wiring on it instead of looking for the wiring harness.

Whatever the case, turn your multimeter to 20v DC and back probe the fuel pump connector with the red probe while holding the black probe against the chassis as ground. Also, make sure the ignition is on.

After that, see if you get 12-13 volts on any of the wires and if you do, but the fuel pump isn’t working, you will know it’s bad. However, if the fuel pump isn’t getting any voltage, check the fuse, relay, and inertia switch.

How Many Years Does a Fuel Pump Last?

Fuel pumps don’t have a service schedule and are made to last the lifetime of the vehicle. However, that never happens, and the average in-tank fuel pump lasts about 10 to 15 years or 150,000 to 200,000 miles. The fuel pump is more likely to fail sooner, especially if your car has a direct injection engine with a high-pressure pump.

Do Fuel Pumps Fail Suddenly?

Yes, fuel pumps will most often fail suddenly. That means your car will suddenly stall while driving or idling, or you won’t be able to start the engine all of a sudden. However, stalling and refusing to start can happen intermittently, but it won’t be long before the fuel pump is dead for good.

Is It Expensive to Replace a Fuel Pump?

Yes, it’s fairly expensive to replace a fuel pump since the cheapest replacement cost is $150 for parts and labor, and that’s on older hatchbacks and small cars. However, on brand-new cars with high-pressure fuel pumps, the cost can be as high as $1,000, while the median cost is $250-$400.

Does a Bad Fuel Pump Throw a Code?

Yes, a bad fuel pump will throw a code, but that doesn’t happen too often. But when it does happen, you will see one of the following codes. The first is P0087 (low fuel pressure), P0171, and P0174 (lean air-fuel mixture), P0230 (fuel pump relay low voltage), P0148 (fuel starvation), P0627 (fuel pump control circuit open).

Conclusion

At the end of the day, the best thing you can do to understand fuel pump wiring on any car is to get yourself a multimeter and use our guide to learn how to probe the fuel pump wiring.

That method is the only foolproof one, and it’s extremely easy to learn. Otherwise, you can check the tables above to see the exact colors, and if you don’t find them on your car, keep in mind that ground wires are typically darker than live wires.

Here are some articles that might interest you:

How to Prime a Mechanical Fuel Pump (Easy Steps)

Will a Bad Fuel Pump Throw a Code?

How Long Does It Take to Replace Fuel Pump? (And Replacement Cost)

Fuel Pump Is Not Working (Causes and Fixes)