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The fuel pump, also known as the fuel injector pump, plays a crucial role in your vehicle’s operation. It delivers fuel from the tank to the engine’s combustion chamber, allowing the engine to start and run smoothly. However, over time, excessive wear and tear can make it difficult—or even unsafe—to start your car. Fuel pumps often deteriorate gradually before eventually failing, which is a common issue in older cars, trucks, and heavy-duty vehicles.
If you suspect your fuel pump is failing and you’re having trouble starting the engine, there are a few temporary steps you can take to get the car running—provided it’s safe to do so and no other transportation options are available. Once the engine starts, drive immediately to your local mechanic to have the issue properly diagnosed and repaired. It’s always best to plan ahead and learn how to start a car with a bad fuel pump in case of emergency.
The fuel pump is an essential component in your vehicle’s ignition and acceleration systems—it’s often considered the heart of the engine, setting the rhythm according to the engine’s revolutions per minute (RPM). Typically located beneath the driver’s seat, between the fuel tank and the fuel injectors, the pump’s job is to pull fuel from the tank, pressurize it, and deliver it to the fuel injectors, which then supply the combustion chambers.
Fuel pumps are essential in both diesel and gasoline engines, but they operate in distinct ways. While both systems rely on a precise mixture of pressurized fuel and air to enable combustion, gas engines use spark plugs to ignite this mixture, whereas diesel engines depend on glow plugs to heat the compressed air until the injected fuel ignites spontaneously. In gasoline engines, the electric spark guarantees ignition, but in diesel engines, insufficient fuel pressure can make ignition difficult or inconsistent.
In diesel engines, the fuel injectors open directly into the combustion chamber, typically at pressures around 30,000 PSI—enough force, for comparison, to allow water to cut through glass. Because of these extreme pressures, diesel fuel pumps are built to be stronger and more durable than their gasoline counterparts. By contrast, gasoline is more volatile and requires lower pressure, while diesel fuel, being more viscous, is harder to push through fuel rails, demanding more robust components.
Despite their critical function, fuel pumps are relatively straightforward in design. The plunger within the pump compresses and delivers metered amounts of fuel according to the engine’s needs. Older systems—often referred to as jerk pumps—were mechanically controlled by a cam connected to the engine, regulating both fuel pressure and volume. Modern diesel engines, however, use electronically timed fuel pumps, which improve accuracy and efficiency. These systems rely on a fuel pressure regulator and remote sensors to precisely control the timing, pressure, and flow of fuel delivered to the injectors.
Some fuel pumps fail simply due to old age, while others stop working because of poor maintenance or dirty fuel. Diesel vehicles are known to last for hundreds of thousands, even up to a million miles, so if you bought a used one, there’s a good chance you’ve inherited a clogged or worn-out fuel pump. Most fuel pumps last at least 100,000 miles, but that number varies depending on how well you care for your engine and how often you tow heavy loads. Below are the most common reasons a fuel pump might fail:
Your fuel pump will only perform as well as the fuel you put into it. Low-quality or contaminated fuel can leave deposits inside the pump, causing clogs. It can also carry debris from the fuel tank. Storing fuel in unsealed or dirty containers may lead to contamination, while keeping it for long periods can cause water separation, especially in cold weather, increasing the risk of oxidation. Bell Performance recommends storing fuel for no more than 12 to 18 months.
Driving with too little fuel in the tank can also damage the pump. When the tank is nearly empty, the pump may push air through the system instead of fuel, which causes overheating. Keeping your tank filled helps maintain a steady operating temperature and extends pump life.
The bearings inside the fuel pump can become damaged or rusted, making it difficult for the pump to regulate pressure and volume. Look out for rust, leaks, or burnt fuel residue around the O-rings and ball seals, which can be signs of internal wear.
You never want to get stuck with a broken fuel pump. If you drive an older engine or frequently haul heavy equipment, it’s a good idea to keep a spare fuel pump on hand in preparation for eventual failure. Always shop for a diesel fuel pump that matches your vehicle’s make and model to get your truck back on the road as soon as possible.
Before you try to start the car, it’s important to confirm whether the fuel pump is actually broken. A professional mechanic is the best person to diagnose the issue, but you can do a bit of basic troubleshooting yourself before risking damage to the engine. If the pump malfunctions, the check engine light will usually turn on — though keep in mind, a faulty sensor may prevent it from illuminating. Follow the steps below to check whether your fuel pump has failed:
Use a fuel pressure gauge to determine whether the pump is delivering fuel at the correct PSI. You’ll need a pressure gauge, ratchets, sockets, and a screwdriver for this test. Park your car, turn off the engine, and engage the parking brake. Once the engine is cool, locate the fuel pressure test port under the hood and attach the gauge according to the manufacturer’s instructions. Be prepared for some fuel spillage — place a rag underneath to catch any overflow.
Start the engine and record the PSI shown on the gauge. Then, consult your vehicle owner’s manual to find the proper pressure required for startup. Most manufacturers recommend comparing readings at different RPM levels. If the pressure is consistently low, the issue likely lies with the fuel pump or the injectors.
An OBD-II scanner is a portable diagnostic tool used to identify engine problems quickly. To use it, park your car and turn the engine off. Connect the scanner’s plug to the OBD-II port located underneath the steering wheel. Turn the ignition to the “on” position without starting the engine — this should automatically activate the scan. The display will then show a diagnostic trouble code (DTC) along with a short description of the issue.
Driving any vehicle with a bad fuel pump is not recommended. If you attempt to start the engine when there isn’t enough fuel in the combustion chamber — or when the fuel isn’t pressurized properly — compressed air will fill the gap, causing the engine to overheat. In severe cases, this can even lead to an engine fire or explosion.
To safely start your car, you’ll likely need to replace the fuel pump and any dirty or clogged components in the fuel system. However, if you’re in a tight spot, your current pump might last just long enough to get you to the nearest mechanic. Once the pump starts to sputter or lose pressure, avoid cranking the engine repeatedly — frequent misfiring will only cause the engine to overheat faster.
If possible, let the engine rest for about eight hours before trying again. Once it has cooled completely, the pump may be able to push whatever fuel remains in the rails to the injectors, allowing the car to start temporarily. Drive cautiously — accelerate slowly, keep your speed under 30 mph, and turn on your hazard lights so other drivers know to pass safely.
Take good care of your fuel pump to prevent it from working harder than necessary. Regular preventative maintenance and close monitoring of fuel consumption will help you spot issues early and keep your vehicle running smoothly. Make these habits part of your driving routine:
Avoid driving with less than a quarter of a tank. If the fuel gauge dips too close to “E,” you risk running out before reaching the next gas station. Remember that your engine consumes more fuel than usual to cover the same distance when running low, so always allow extra margin when estimating your fuel needs.
Always fill the tank with fresh, high-quality diesel or gasoline, and avoid using fuel that hasn’t been stored properly. Keeping fuel for more than a year requires special equipment. Regularly replace any emergency fuel reserves and store them away from extreme temperatures to prevent gelling, water separation, and oxidation.
Even with good-quality fuel, your fuel filter will eventually become clogged with debris. Replace your fuel filter every 10,000 to 25,000 miles, depending on your vehicle type and usage. Older engines and hard-working haulers often need more frequent filter changes. Keeping an eye on how quickly the filters fill with dirt can help you gauge the overall cleanliness of your fuel system.
You can’t get far with a bad fuel pump — but in some situations, you may have no choice but to try starting your car. If your engine struggles to start, let it cool down first. Whenever possible, call for a tow or arrange alternative transport rather than driving with a faulty fuel pump or clogged system. Waiting for a professional to replace the pump, injectors, and filters is far cheaper — and much safer — than risking serious engine damage. Don’t compromise your safety; trust a professional mechanic to get you back on the road safely.
Shindary Automotive Parts Co., Ltd.
