What is the reason why the hand oil pump does not become hard when pressed?

[Susan]

The hand oil pump does not become hard when pressed. This situation is most likely due to air leakage in the hand oil pump. In addition, air leakage in the hand oil pump pipeline can also cause the hand oil pump to not become hard when pressed. The main reason for this situation is that when the hand oil pump leaks air, the pressure decreases, making it difficult for the fuel pump to effectively pressurize the fuel, leading to issues with the vehicle's fuel supply. Relevant information about engine oil is as follows: 1. Introduction: Engine oil, also known as engine lubricant (English name: Engine-oil), has a density of approximately 0.91×10³ (kg/m³). It serves to lubricate and reduce friction, assist in cooling, seal against leaks, prevent rust and corrosion, and provide shock absorption for the engine. It is often referred to as the 'blood' of a car. 2. Composition: Engine oil consists of two main components: base oil and additives. The base oil is the primary component of lubricating oil, determining its basic properties. Additives are used to compensate for and improve any deficiencies in the base oil's performance, providing new characteristics, and are an essential part of lubricating oil.

[LaHaven]

This issue is quite common. When manually pressing the fuel pump, it often feels spongy. The most frequent cause is air entering the fuel system. Air bubbles can block the fuel line, preventing pressure buildup—similar to how air bubbles in a water pump's intake pipe affect performance. Another major reason is the aging or cracking of the pump's sealing ring. Over time, rubber rings can deform or develop cracks, leading to internal fuel leakage, which naturally results in no response when pressed. If the fuel filter is severely clogged, fuel can't pass through, making the pump pressure ineffective. Sometimes, loose or leaking fuel line connections can also draw in air. Temperature plays a significant role too—cold weather thickens the fuel, slowing its flow and making the problem more noticeable. My recommendation is to start with a bleeding procedure: press the pump several times until it feels firm. If that doesn’t work, check the cleanliness of the filter and the fuel lines. In severe cases, replacing the pump assembly may be necessary. Don’t underestimate this issue—delaying repairs could lead to engine starting difficulties or even stalling. Address it early to avoid complications.

[VonDiana]

My old pickup had this exact issue - the manual fuel pump felt mushy when pressed. After inspection, I found air had entered the system, especially when fuel line connections loosened, letting air sneak in. The pumping action felt like pushing against cotton. Worn-out seals were another culprit - deteriorated rubber components couldn't contain fuel properly, causing severe internal leakage. A clogged fuel filter also creates weak pumping sensation by restricting fuel flow. I've even encountered thickened diesel in winter slowing down circulation. Quick diagnosis: First bleed the system by pumping repeatedly. If that fails, remove and clean the filter. Next step is checking pump seals. Bleeding means repeatedly operating the pump to gradually remove air bubbles. Though seemingly minor, this can cause hard starting or even engine failure. I often DIY to save money and gain experience, but complex cases warrant professional shop attention for safety.

[VonFinley]

Manual fuel pump not building pressure? Classic symptom of air entering the system, blocking fuel passage and preventing pressure buildup. From my repair experience: damaged seals are a common culprit - rubber components degrade over time causing leaks; clogged filters also restrict fuel flow. Bleeding the system solves it - repeatedly press the pump to purge air bubbles. If the pump is functional, it should firm up after pressing. Cold weather thickening fuel also causes issues. Neglecting this affects normal starting - recommend timely bleeding or part replacement. Always prioritize safety to avoid burns during repairs.

[StRowan]

When I first started learning about cars, I also encountered the issue of the hand fuel pump not building pressure properly. The experienced mechanic explained that it might be due to air leaks or bubbles in the fuel line, preventing the system from building pressure. If the seals are worn out or the filter is clogged, fuel can't pass through, making the pump feel weak. The simplest way to bleed the system is to press the pump a few times to see if the air can be expelled. I once solved the problem by cleaning the filter. Poor fuel quality can also cause this issue, so using proper fuel reduces such faults. Safety comes first—don’t ignore these signs to avoid starting difficulties. Beginners should take time to learn these details and gradually build experience.