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Cummins 5.9 l Fuel Pump diagnosis and repair options

Cummins 5.9 l Fuel Pump diagnosis and repair options

The fuel system of a Cummins 5.9 l engine is a bit more complicated than what you would expect from a diesel engine. The engine actually needs two separate fuel pumps. The lift pump draws the fuel straight from the fuel tank. It is then syphoned to the main injection pump which feeds the engine.

With such an elaborate system, there’s more chance of something going wrong. If and when it does, you need a good mechanic to sort your problems out. San Diego County can rely on PCE for all diesel related troubles, whether it’s cars, boats or other machinery. The company also offers a wide variety of other mechanical services, in addition to Cummins 5.9L fuel pump repair.


The signs that the 5.9 Cummins lift pump broke down

Initially, you cannot tell the difference, since the injection pump continues drawing the fuel through the lift pump. However, since the lift pump doesn’t provide the necessary force, it wears down the injection pump. It cannot handle this kind of pressure loss for long. As a result, you will start to feel that the engine is underpowered and doesn’t function quite right. If the injection pump is broken as well, you essentially have two options. Rebuild or replace. Neither of these two is going to be cheap or pleasant.

The most common reasons for 5.9 Cummins injection pump repair

The most common way people find out their injection pump broke down is that the car simply dies while driving down the road. The typical reason why that happens is that the rotor seizes. This happens if the deburring process during production was faulty. The sharp edges left from the faulty deburring process tend to bend under the high pressures inside the pump. As they bend they break the drive plate, which causes the malfunction of the whole pump.

Another quite common thing to break is the computer on top of the injection pump. The reason why this component breaks is because the solder which connects it to the pump tends to become electrically semi-permeable, meaning it occasionally creates electrical connections which in turn wreak havoc on the pump.

Finally, as a result of the normal wear and tear, there are some parts that you can expect to break down over time. Old-style diaphragms crack over time, causing low pressures in the lift pump, which is manifested as a difficult cold start. Similarly to this, if the injection pump housing is worn, this will manifest as the error code 216, which indicates that the pump is getting old and tired.


The spare parts for the 5.9 Cummins injection pump are numerous and have significantly improved the original pump. If you are looking to rebuild your pump, consider buying these upgrades, since they really do make a difference. They do cost, but the expression ‘You get what you paid for’ sums it up neatly.

Cummins 5.9L fuel pump replacement

If you are set to replace your pump, make sure that the model you are buying corresponds to the model you had. Some earlier models used to have a wiring harness built in. The newer versions (including the replacements offered) do not have it. Therefore, you need to buy the harness separately and install it to the pump. Replacing your injection pump will also set you back a hefty sum of money, but you will know what you are paying for.


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