Bleeding the Fuel Injection System of a Diesel Engine


Bleeding a diesel engine properly requires following specific general guidelines. Diesel fuel injection systems are plentiful, but they’re all based on the same basic idea. The primary idea is to de-air the fuel system. Take a look at the example given below.

Your diesel engine begins to knock, you lose power, and white smoke begins to billow from your exhaust as you continue down the road. After a few turns of the crank, it gives out for good, and you decide to investigate. The gas gauge shows that you’re almost out of gas. You’ve driven a hundred miles since the last time you checked the fuel gauge, which still indicates half a tank. A faulty fuel gauge sender (found in the tank) is a typical issue that can lead to engine shutdown and further discomfort.

Now that you know the issue, you may fix it by filling up the diesel tank and bleeding the fuel system. Diesel engines often require a highly pressurized atomized spray that forms an explosive mixture when paired with high compression. Diesel engines get renowned for their powerful thrust thanks to the combustion chamber’s high-temperature air.

How to Bleed a Diesel Engine Step One

Clean diesel fuel should be poured into the primary fuel filter (nearest to the fuel tank), and the tank should be filled to the top. The fuel transfer pump creates a vacuum or suction that primes this filter and moves the fuel through to the next filter. A camshaft, a mechanical pump, or an electric motor can power diesel fuel transfer pumps. A hand-priming pump would be the icing on the cake.

Second, we will purge the diesel fuel injection system of any air.

No matter how you cut it, you must get the air out of the fuel injection system. It is standard practice to loosen fuel lines in older diesel vehicles. Before the injection pump, unscrew the connectors on the fuel lines and prime the system by hand until you observe no more bubbles. This will guarantee that the injection pump has fuel.

Third, bleed the Bosch mechanical diesel fuel injection system to remove air bubbles.

A bleeder plug on the front right side of the Bosch fuel injection pump used in Cummins diesel engines must be unfastened before the hand primer on the driver side of the block can be pumped. These engines use a mechanical fuel injection system, leaving the fuel lines exposed for convenience. The needles in the head should be loosened. If you rev the engine, the air can be sucked out faster. The machine will try to start and sputter as soon as the fuel system begins to pick up fuel. Keep turning the engine over and ensuring the gasoline lines are snug; you’ll have firepower in no time.

Diesel fuel injection system bleeding

Electric fuel transfer pumps are standard on modern diesel engines. When the ignition is turned on, the fuel pump begins priming the system. For instance, when priming a Cummins ISC diesel engine, the primary filter should be filled with clean diesel fuel before the secondary fuel filter is installed. When the key is turned on, the fuel transfer pump sends filtered energy from the primary fuel filter to the secondary filter to prime it.

You won’t fully appreciate the significance of bleeding air from a diesel engine until you’ve done it a few times. The high pressures generated by diesel fuel injection systems are necessary to start and maintain engine operation, but air compression prevents diesel fuel from moving.

To learn more about bleeding a diesel engine equipped with a Bosch inline fuel injection pump, check out John Whelan’s Mechanic Tips Blog. You’ll also get great advice on fixing and diagnosing issues like the vehicle’s engine, transmission, air brakes, 12 Volt electrical system, and hydraulics. His 34 years of mechanical experience will shed light on the inner workings of these apparatuses.

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