Top 4 Symptoms Of A Faulty Diesel Primer Pump

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Some of the most common symptoms of a faulty diesel primer pump include hard starting, engine misfire, etc.

As a car gets older, some of its components start wearing off. This is a natural phenomenon, and when it starts happening, the best thing anyone can do is to change the failing component – replace it with a new one.

Now, one of those components that need to be changed after a long time is the diesel primer pump.

The diesel primer pump is a bulb that is typically found close to the fuel pump itself. Its function is to transfer fuel from the tank (reservoir) to the carburetor or any other connected component (depending on the vehicle).

In other words, one can say that the primer bulb is what stands in between the fuel pump and the engine.

Functions Of a Diesel Primer Pump

Well, just like every other component in a car, the primer pump is likely to fail. When it fails, you’d definitely notice quite different symptoms.

However, before moving on to the signs and symptoms of a faulty diesel primer pump, let’s highlight how the primer pump works when it’s good.

As said earlier, you will find the primer pump bulb somewhere close to the fuel pump; it takes fuel into the carburetor where the fuel is mixed with air to trigger combustion. This process is needed for a car engine to kick up and continue running.

In some cars, the engine won’t start if the carburetor doesn’t pump. More so, it is expected that the primer pump bulb stays hard after it has pumped when you started the car.

If yours doesn’t stay hard for a long time, something is wrong. Now, let’s talk about the symptoms of a bad diesel primer pump.

Symptoms of a Faulty Diesel Primer Pump

Symptoms Of A Faulty Diesel Primer Pump

Below are some of the most common signs of a failed diesel primer pump:

1. Engine Misfire

One of the first things you may notice when fuel is unable to get to the engine as sufficiently as required is misfiring. Engine misfire is a quick hesitation you may notice when driving. It occurs when the engine is not getting enough fuel.

A faulty diesel primer pump will not pump enough fuel into the carburetor, which can also limit the performance of your car’s engine generally.

When you start to notice misfiring, it’s time to check your fuel pump system, particularly the injectors, carburetor, and primer pump bulb.

2. Loss of Power

Since a faulty diesel pump primer can actually affect the fuel pump itself, it is possible to assume that a bad pump primer bulb is the reason behind the irregular loss of power you experience while driving.

It’d be best to troubleshoot the car first and verify the actual cause of the signs you’re experiencing.

3. Hard Starting

Another possible sign of a faulty diesel primer pump is hard starting. When your car engine won’t start normally, it could be a result of an issue from the fuel pump, which the primer bulb is one of the suspects here.

Regardless, there are other things that may cause a car to hard start.

4. Check Engine

In some cars, the check engine light may illuminate on the dashboard. Apparently, the check engine light is to alert you of a potential issue with your engine.


What are the symptoms of a faulty diesel primer pump? Apparently, you will experience similar symptoms as with a failing fuel pump or a faulty injector.

The best way to fix this situation is to engage a mechanic. Fuel pump-related issues are quite mechanical and should be handled with care.

Furthermore, it is advisable to stick to a regular maintenance plan so as to detect minor issues on time and have them fixed as soon as possible.

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