Anthing inside of the Fuel Injection Hard Lines between the Fuel Injection Pump and the Injectors has to be able to overcome the Spring tension inside of the Injectors.

When Air gets into the Fuel Injection Hard Lines it compresses and moves only a tiny bit towards the Injectors. Trying to do that can easily kill a Batter and overheat a Starter.

In order to allow the Air an easy way to escape as jsain86 said you loosen the Fuel Injection Hard Lines at the Injectors and allow the Air a place to escape to. When you are geting Fuel out of those lines you can tighten the Nuts and attempt to start.

If you are just doing a Filter change it is best to fill the Filter with as much clean Diesel Fuel as you can so that less Air will get inside the Fuel Injection Pump Housing.

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84 300D, 82 Volvo 244Gl Diesel