5.9 Cummins Problems

The Cummins Diesel engine is one of the most reliable engines on the market and is known to the most efficient as well. Unlike other 8 valve engines on the market, the Cummins has 6 in-line cylinders each with 4 valves making them 24.

Though it is known for reliability, the Cummins is also known to have problems at times. In this article, we are going to be looking at some of these problems in detail. So, what are these problems common to the Cummins engine?

In short, the Cummins 5.9 engine is known to have the following problems: Engine Block Crack (This is a rare problem), Fuel Injector Leaks, APPS (Accelerator Pedal Position Sensor) Failure  Leaking Exhaust Manifold, Fuel Lift Pump Failure.

Cummins 5.9 Engine Problems

Let’s look at the Cummins problems individually.

1. Engine Block Crack

This problem is a very rare occurrence but we will mention it anyway so that you recognise it in the rare event it happens to you. This happens in Brazilian-made engine blocks that were used from 1998 to 2004.

2. Fuel Injector Leaks

The fuel injectors will fail around the 125,000 to 150,000 mark. They may get blocked from dirt in the diesel fuel especially when the fuel filters are not working properly. This will lead to the injectors clogging up resulting in not enough fuel being injected into the pistons or leaking into the engine.

The result will be a misfiring engine or lack of sufficient power being supplied to the engine. To fix this, you can replace the faulty injector if the engine is still new.

If the engine is older though (above the 125,000 mile mark, you should replace all the injectors as the others are bound to fail eventually. Replacing all the injectors is a costly exercise that can cost you up to $2,000 for all injectors.

3. APPS (Accelerator Pedal Position Sensor) Failure

The APPS Is responsible for sensing how far the accelerator is depressed and signals how much fuel should be released into the engine. When this is faulty, your system won’t know how much fuel to inject into the engine.

The result can be the engine stalling. You could also experience the engine jerking. This happens when the sensor switches on and off randomly.

When you experience this, the best thing to do is to get it fixed as soon as possible. Though a replacement APPS is expensive, you can do the installation yourself as it’s simple to do.

4. Leaking Exhaust Manifold

Another common problem in the Cummins engine is a leaking exhaust manifold. The engine block and exhaust manifold are both made of cast iron and attached to each other.

When the engine heats and cools repeatedly, the resulting expansion and contraction will result in the manifold cracking. The resultant crack will mean that pressure will not be able to build up leading to reduced power from the engine.

5. Fuel Lift Pump Failure

The lift pump is responsible for pumping fuel from the tank to the engine. In older Cummins engines the fuel lift was located in the engine block and was subject to immense pressure. It also needed to work a lot harder to draw the fuel from the tank.

In later Cummins engines, it was moved to inside the tank making it more efficient. After-market solutions are also available that place it closer to the tank and further from the engine. These are the most common Cummins engine problems. Cummins Engine Lifespan

How long can you expect your Cummins engine to last?

A Cummins engine can easily go up to 200,000 miles or more especially if you maintain it well. It’s one of the most reliable engine out there.

Conclusion on 5.9 Cummings Problems

When it comes to reliability, the Cummins can hold its own against the best of the best. It is a stable diesel powered engine that has 6 cylinders each with 4 valves. That’s why the engine is sometimes referred to as a 24v.

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