6.7 Cummins Lift Pump Failure Symptoms and How To Fix

6.7 Cummins lift pump failure symptoms are signs that you should consider to keep your Cummins truck running properly, as these can cause engine failure. From loss of power to overheating, there are different symptoms of a faulty pump in a 6.7 Cummins.

Lift Pump Failure Symptoms ~ Ran When Parked

In most cases, you would have to replace the suction pump entirely when it fails, but it’s also possible to repair it in different ways. In this guide, we take a closer look at the symptoms of a damaged 6.7 Cummins lift pump and ways to fix it.

What Are the 6.7 Cummins Lift Pump Failure Symptoms?

The 6.7 Cummins lift pump failure symptoms include a delay in the engine starting, low engine compression, low fuel pressure, low cranking speed, fuel injection failure, lower fuel supply, and engine performance problems. There might also be engine sounds and sputtering, fuel leaks and overheating.

Delay in Engine Start

If the suction pump of your 6.7 Cummins truck is not working, it would make it harder for the engine to start. It would cause a delay in the diesel engine starting whenever you start the car. The engine would stall because the fuel would not reach the injectors in time for it to combust.

If the injection pump becomes faulty, the engine will stall and have a hard start. This is because the fuel won’t reach the injectors in time for the combustion.

Low Engine Compression

Another sign of a defective Dodge Ram Cummins suction pump is low engine compression.

Low Engine Compression ~ Ran When Parked

A faulty suction pump would not be able to generate enough pressure for the fuel, leading to low engine compression and other engine problems.

Fuel Injector Fails and Other Fuel Problems

Failing pumps would eventually cause the fuel injector of your car to fail. The fuel won’t be able to reach the injectors in time for the combustion, and this would eventually damage the fuel injector. Aside from that, there would be other fuel-related issues.

These include the low fuel pressure, as the damaged suction pump would be unable to generate suction to draw fuel from the tank. It would eventually reduce your engine performance.

There would also be a lower fuel supply along with the reduced pressure, which is another symptom you need to consider. Although, check the fuel filter to be safe.

If your high-pressure fuel injection pump is not working, you will consume more fuel than usual when driving. If you notice you’re refilling your fuel tank too often, you should check the suction pump or fuel injector.

Another fuel-related problem might be a fuel leak, which is due to the faulty pump. It can contaminate the environment or cause a fire hazard.

Low Cranking Speed

If the 6.7 Cummins suction pump gets damaged, it can reduce the cranking speed drastically. The low cranking speed would be because the fuel is not reaching the injectors in time.

Poor Engine Performance

A faulty suction pump would also lead to poor engine performance. If the injection pump is not working, it can lead to different problems with the Cummins engine performance.

Poor Engine Performance ~ Ran When Parked

These include a stalling engine or misfiring when you’re driving. The engine might also lose power, which would be dangerous when you’re driving.

Spluttering and Strange Sounds

If the engine splutters when you accelerate, that could be a sign that there has been damage done to the pump. This is a sign that the suction pump needs to be replaced. Aside from spluttering, the engine might make strange sounds while you’re driving, so you should inspect the suction pump.

Engine Overheating

Another problem is the high temperature of your engine, which would cause it to overheat. A faulty suction pump would make the engine run at a higher temperature than normal. If your engine is overheating often, this can cause it to get damaged faster.

Blue or Black Smoke

A faulty pump would also cause black or blue smoke to come out of your engine or exhaust system. If you notice pitch-black or dark blue smoke coming out of your Cummins diesel truck while driving, you should pull over and check the injection pump.

What Are the Solutions to A Faulty 6.7 Cummins Lift Pump?

The solutions to a faulty 6.7 Cummins lift pump include repairing the suction pump if there is a problem with the electrical system, replacing the vent valve, checking the fuel lines, replacing the pump or rebuilding the entire engine. Replacing the Cummins suction pump is the best solution.

Solutions to Faulty Lift Pump ~ Ran When Parked

If you think there is damage to your 6.7 Cummins suction pump, you should contact a professional mechanic to inspect it. The mechanic will be able to figure out the problem and will let you know if you should replace or repair it. If you repair it, it might get damaged again, which is why it’s a good idea to replace it outright.

Repair the Suction Pump

One course of action you can consider is repairing the pump. If the damage is not severe and the problem is with the electrical system, it would be possible to repair the pump rather than spend money on a replacement.

Replace the Lift Pump

The best way to stop your 6.7 suction pump from getting damaged again is to replace it with a new one. You can ask your mechanic to handle the replacement or do it yourself if you’re handy with tools.

Check the Fuel Lines

Another option is to check the fuel line or fuel injector. As noted earlier in this guide, most of the signs of a damaged pump are related to the fuel injector system. So, leaking or damaged fuel lines, or a blocked fuel filter can cause your pump to get damaged. You can inspect the fuel lines for damage and repair them if need be.

Check the Vent Valve

Another thing you should do to fix your Dodge Cummins suction pump is check the vent valve. A faulty vent valve can also cause the suction pump to get damaged, as it would not allow air to enter the fuel system.

Checking the Vent Valve ~ Ran When Parked

It can also cause damage to other parts of your engine and fuel lines. It’s best to repair it if it’s damaged.

Rebuild the Engine

If you’ve had pump damage for a long time, it would cause damage to other parts of the engine. This would require you to rebuild your engine while replacing the parts that are damaged. You should ask a mechanic to do this, and this solution can only be used as a last resort.

How Can You Test a 6.7 Cummins Lift Pump?

You can test a 6.7 Cummins lift pump by using a multimeter to check the fuel pump’s two-wire connector. After turning your car on and ensuring that the suction pump is on, you can use the multimeter to test it. If the suction pump fails, you can replace it.

Testing a Cummins Lift Pump ~ Ran When Parked

You should allow your engine to run even if it won’t start and leave it in the accelerator position. By the time your car has been running for about 25 seconds, that shows that the suction pump is on. Then, you would need the multimeter to run the test.

Remove the two-wire connector on the fuel pump and use a multimeter to check the pin from the wires on the supply-side fuse and suction pump. If the multimeter does not reveal any problems, that means that they are working properly. The multimeter should show 12V.

After you test the suction pump, you should start the engine cold. Keep in mind that you should remove the key and turn the engine off before you remove the fuel pump connector to prevent damage. If you’re still unsure about whether the Cummins suction pump is damaged, you can visit a professional mechanic to inspect it for you.

How Can You Replace a Faulty 6.7 Cummins Lift Pump?

You can replace a faulty 6.7 Cummins lift pump by disconnecting the battery, locating the old suction pump, removing it, and installing the new one. It’s best to install one that is compatible with your Cummins truck and test the car after the pump replacement.

Raise the Car or Truck Up

Use a jack stand to raise your car up and ensure that it is well supported. Doing this would give you access to underneath your car and the engine block, which is where you can find the 6.7 Cummins suction pump.

Disconnect The Battery

It’s best to disconnect the car battery if you want to avoid getting electrical shocks or damaging your car.

Disconnect Car Battery ~ Ran When Parked

Locate and Remove the Old pump

Find the pump, which is on the rear side of the engine, close to the fuel tank. Once you find it, you have to disconnect the fuel lines and electrical connector. After disconnecting these, you can easily remove the suction pump.

Install the New Lift Pump

Reverse the process of removing a pump to install a new one. You would connect the electrical connector and fuel lines while the suction pump is in its position. Then, bolt it into place and ensure that it is secure.

Reconnect the Battery and Test Your Car

After installing the new pump, lower your car off the jack stands and then reconnect the battery. Finally, start the engine and look out for the signs of a damaged suction pump.

Installing the New Lift Pump ~ Ran When Parked

Frequently Asked Questions

How Do I Know if My 6.7 Cummins Lift Pump Is Weak?

You know your 6.7 Cummins lift pump is weak when the engine idles roughly, there is low engine power, and the engine is cranking but refuses to start. There might also be a check engine light, so always check the fault codes.

What Causes a 6.7 Cummins Lift Pump to Get Damaged?

Using contaminated diesel or fuel additives into your car can affect the lift pump and cause it to get damaged. Worn out components in your car would also cause the suction pump to fail. You should check your car regularly for damage to the suction pump and other parts.


Now that you know the 6.7 Cummins lift pump failure symptoms, you can look out for them when driving your car and contact a mechanic. Here’s a rundown of our guide on this:

  • The symptoms of a failed 6.7 Cummins pump include delay in engine start, fuel-related problems, low engine performance and low cranking speed.
  • The solutions to a faulty suction pump include repairing or replace it, checking the vent valve or fuel line, or rebuilding the engine.
  • You can test if your suction pump is damaged with a multimeter, and ensure it is 12V.

With our detailed guide, you can take care of your suction pump and repair it when it’s damaged. It’s best to visit a mechanic if you suspect a problem with your lift pumps.


Rate this post
Ran When Parked