Exactly that. Just disconnect the fuel line going into the filter and attach a piece of hose, clear will show fuel being drawn up when you operate the primer. Once primed you shouldn’t see the fuel get bubbles in or the level drop back. Sometimes fuel primer pump diaphragms get perforated and allow air in but your symptoms don’t sound like that.
Not being familiar with your truck, I’m curios to know what you mean by ‘the bladder’?
Not being familiar with your truck, I’m curios to know what you mean by ‘the bladder’?