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7 Symptoms of a Failing CP4 on 6.7 Powerstroke

A bad injection pump can cause all sorts of engine problems that can hinder your vehicle’s performance.

If you have a 6.7 Powerstroke with a damaged, worn, or ineffective CP4 fuel pump and you don’t repair it, you’ll end up with all sorts of expensive repairs down the road.

Symptoms of a failing CP4 on a 6.7 Powerstroke include metal shavings in the fuel filter, sputtering while accelerating, poor ignition attempts, and slow acceleration. Other symptoms include reduced fuel economy and engine overheating. You can use a digital diagnostics tool to pinpoint these issues.

Throughout this article, I’ll dive into the seven main symptoms of a failing CP4 on a 6.7 Powerstroke, why they happen, and what you should do about them.

I’ll also provide you with a few suggestions to prevent your CP4 fuel pump from wearing out earlier than expected.

1. Metal Shavings in the Fuel Filter

Perhaps one of the most common symptoms of failure in a CP4 on a 6.7 Powerstroke is finding metal bits and pieces in the fuel filter. As your fuel pump suffers wear and tear due to high operating pressures, you may find metal particles appearing in the fuel filter.

If you’re worried about your fuel pump failing, turn off the ignition, let it cool down, and check the filter. The filter shouldn’t have too much debris, nor should it have any metal in it.

TXD Service recommends replacing your fuel filter every 10,000 to 15,000 miles (16,000 to 24,000 kilometers). This replacement frequency ensures your fuel filter doesn’t get clogged.

Filter clogs can overheat the injection pump, causing it to fail. Furthermore, it increases the likelihood of letting contaminants into the engine.

Usually, replacing your fuel filter will help, but the new one will still get metal shavings if the fuel pump is on its way out.

Once this happens, your CP4 fuel injector will go through a snowball effect of expensive issues. You’ll find all of these issues in the following sections.

If you’re interested in learning more about fuel shavings in your fuel pump’s filter (specifically for a CP4), review this helpful YouTube video:

2. Sputtering and Stalling While Accelerating

A failing CP4 on a 6.7 Powerstroke engine will sputter and stall when you’re trying to accelerate quickly. This happens because the fuel pump can’t supply enough fuel to the engine, which means it’s providing power in intervals rather than continuous acceleration.

A broken fuel pump can make your engine useless. If it can’t get enough fuel at the right time, there’s no way you can expect to power the vehicle.

Once the problem worsens, there’s an increased risk of stalling. Unfortunately, your vehicle might stall without any warning.

You’ll be driving along, trying to accelerate, and suddenly the engine will stop burning fuel. This can be quite hazardous, especially if you’re driving on a busy highway.

Sputtering and stalling from a failing CP4 typically happen at higher speeds. This is because the engine is using more fuel while you’re accelerating.

The sputtering stops once you level your speed, which often leads drivers to believe nothing is wrong with their engine or fuel pump.

One way to prevent this issue is to keep your fuel tank at least 10% fuel at all times. When the fuel tank gets too low, it can’t provide enough weight and coverage to supply the fuel pump.

Many experts recommend keeping a CP4 around 10% to 20% full for the best fuel efficiency and fuel pump longevity. It’ll also save you money by reducing your trips to the gas station.

3. Spotty Ignitions

If you’re having trouble turning your vehicle over with the key, the CP4 could be failing. However, there are numerous reasons your vehicle might have spotty ignitions, including:

  • Faulty battery
  • Malfunctioning alternator
  • Worn alternator bearings
  • Key compatibility issues
  • Kinked fuel hoses
  • Failing CP4 fuel pump

Using a multimeter to check the battery, make sure that it has between 12V to 14V. If everything else is in good condition, it could be the fuel pump.

Failed ignitions are typically associated with a shot CP4. If you can’t start the vehicle due to a faulty fuel injector, the only solution is to replace it.

Note: Spotty ignitions related to CP4 failure are much more common in cold weather because it combines with typically cold-weather starting problems (which are often caused by the battery being too cold).

4. Bad Fuel-to-Oxygen Ratio

A 6.7 Powerstroke needs to have enough oxygen and fuel for proper combustion. If your CP4 fuel injector fails and can’t supply enough fuel, there will be too much oxygen. The results may vary, but they often include the following:

  • White or black smoke coming from the exhaust pipe
  • Excessive buildup in the exhaust pipe
  • Misfires while accelerating
  • Foul odors coming from the engine
  • Failed SMOG checks and other emission checks

Too much oxygen can also cause most of the other symptoms listed in this article, including poor acceleration, reduced fuel economy, and sputtering or stalling.

While these issues seem increasingly problematic, they’re also quite helpful because they show up much more gradually than the other factors you’ll come across.

One way to prevent fuel injector issues is by using high-quality fuel as much as possible. Better fuel has a reduced chance of clumping, but it also keeps the fuel injector working smoothly.

The engine and fuel pump need to be cooled and lubricated. If they have top-notch fuel flowing through them, you won’t have to repair or replace them as often.

Additionally, consider removing and replacing kinked fuel lines. When a fuel line is partially closed or pinched, it has trouble supplying enough fuel through the CP4 fuel pump. Checking your hoses and fuel lines regularly will ensure that your fuel injector can work freely.

You can also drive your vehicle at least once every couple of weeks to prevent the fuel from coagulating. If you don’t drive often enough, most gasoline and diesel will start to jellify.

Not only does this prevent your fuel pump from working properly, but it also leads to overheating, pressure issues, kinked hoses, and more.

5. Inability To Accelerate

Another symptom of a failing CP4 fuel pump is not being able to accelerate. This is the extreme version of the previously mentioned stalling and sputtering issue.

You might be able to move the vehicle by taking your foot off of the brake pedal, but you won’t be able to accelerate with the gas pedal.

You might also notice that the engine roars when you press the accelerator. It’s trying to pull fuel without getting anything.

Much like the fuel-to-oxygen ratio, this process can make your vehicle much harder to drive without the engine grinding or bumping.

If this happens, it could be due to a pressure buildup from the filter being clogged with metal shavings. Drive your vehicle to the side of the road, then call for a tow truck.

The last thing you need is to blow through the fuel filter because the CP4 is trying to supply enough fuel to the engine to no avail.

6. Overheating Engine

Fuel pump issues often cause the engine to overheat, especially when you’re dealing with a CP4 fuel injector. These pumps overheat the engine due to these two reasons:

  • The engine can’t get enough fuel, which means the ratio is off, and there’s not enough cooling liquid. Your vehicle’s fuel powers the engine, but it also cools the engine as it moves. If your CP4 can’t supply the right amount of fuel, your engine will always run a little too hot.
  • When the CP4 is failing in your 6.7 Powerstroke, it overworks itself. It’ll run dry, then it’ll cause the engine to smoke. Many drivers misdiagnose this issue as a result of not enough coolant or a damaged radiator.

Fuel pumps get increasingly more expensive to repair and replace the longer you wait. I suggest looking through these symptoms, then determining whether or not it’s time to repair the CP4 fuel injector.

7. Poor Fuel Economy

If your CP4 is failing, you’ll notice a sudden decrease in your vehicle’s fuel economy. In other words, you won’t have the same miles per gallon as you used to. This ends up costing you a lot more money in the long run.

This common symptom happens when your fuel pump can’t use as much fuel as it used to.

Every combustion uses a fraction of the fuel it’s supposed to, so it has to go through multiple cycles to reach the proper amount of fuel going to the engine. Again, this is why your vehicle misfires, stalls, and sputters.

Keep in mind that there are many other things that affect your vehicle’s fuel economy. However, it’s likely caused by the CP4 pump if some or all of the symptoms listed above are present. Your vehicle’s fuel economy will get exponentially worse if this is the issue.