Why does my oil furnace keep losing prime?

Author: Urban Streich I  |  Last update: Tuesday, July 1, 2025

When the filter becomes clogged, fuel oil cannot pass through the filter medium, resulting in the oil pump losing its prime. Occasionally, the muck will pull through the line and plug the nozzle. Another possible culprit is a leak.

Why do I have to keep bleeding my oil furnace?

What Is Furnace Bleeding? Over time, air can get trapped in a furnace's fuel line, causing the furnace to sputter or even shut down completely. Furnace bleeding removes air from the fuel line, ensuring a smooth oil flow to the burner.

How do I know if my oil furnace pump is bad?

If the oil pump doesn't run, it is most likely bad and will need to be repaired or you'll need a furnace replacement. Loud humming, buzzing or other unusual sounds coming from the pump can also be a sign that it is wearing out and you need to have it replaced.

Why do I keep having to reset my oil furnace?

When your furnace runs out of fuel, whether a gas or oil furnace, the unit's reset button may be triggered; a quick check on the fuel tank will let you know whether a fuel outage is the cause. If it is, you can have the tank refilled. Dirty Air Filter.

Why does my oil boiler keep losing pressure?

What causes a boiler to lose pressure? The most common reasons for a boiler to lose pressure are: Releasing air or water from a radiator when bleeding it. A leak from the appliance or on the system most commonly from radiator valves or system components.

Oil furnace troubleshoot. Part #7. Pump pressure test

Why is my boiler losing pressure without a leak?

A boiler can indeed lose pressure without a visible leak. Common reasons include issues like a faulty expansion vessel. This vessel is essential in maintaining system pressure; if it malfunctions, pressure may drop even if there is no leak. Another reason for pressure loss is trapped air in the system.

Why does my oil pressure keep dropping?

Things like oil contamination, a jammed oil pump, or improper parts installation can all make your oil pressure drop. It's essential to repair or replace the pump immediately since it plays a decisive role in distributing oil to your engine parts.

Why is my oil furnace losing prime?

Causes of a Broken Furnace Oil Pump

When the filter becomes clogged, fuel oil cannot pass through the filter medium, resulting in the oil pump losing its prime. Occasionally, the muck will pull through the line and plug the nozzle. Another possible culprit is a leak.

How many times can you reset an oil furnace?

You should not reset the burner more than two or three times, the reason is you may be pumping some fuel into the heat exchanger that is not igniting. When it does ignite, it will poof and snort and smoke up your house. Best thing to do is have a local furnace man service your oil burner.

How to tell if primary control is bad?

If the burner will NOT run and the green flame sense light does NOT illuminate with the F terminals bridged, the primary control is defective and should be replaced.

How do I troubleshoot my oil furnace?

Here are a few things to check if your furnace doesn't fire up like it should.
  1. Check Your Circuit Breakers. Even if you use a gas or propane furnace, some of the components run on electricity. ...
  2. Check Your Thermostat. ...
  3. Check the Drain Pan. ...
  4. Check Your Air Filter. ...
  5. Check the Pilot Light. ...
  6. Check Your Natural Gas or Oil Supply.

How long does an oil boiler pump last?

As long as your central heating system is correctly installed and properly maintained, you can expect the pump to last for a long time. Typically, they keep going for well over 10 years, with some lasting 20 years or more.

How often should my oil furnace run?

On average, furnaces should kick on and turn off anywhere from three to eight times per hour.

How do you know if your furnace needs to be bled?

Signs Your Furnace Needs Bled

Even if you've never let your tank run so low that its fuel line starts drawing in air, you might notice signs of excess oxygen within the system, including: Odd sounds and vibrations.

Why does my oil furnace keep needing a reset?

If you have a gas or oil heating system, the reset switch might trip if you run out of gas. This fix is as basic as making sure there is fuel in either the gas or oil tank. If this is the case, when you ask for a refill, see to it you let them recognize that the storage tank is empty. Blocked or Closed Gas Valves.

What is the average life of an oil furnace?

Its lifespan is dependent on how often you maintain it. The life of an oil furnace can be anywhere from fifteen to twenty years, depending on its maintenance. In fact, the average oil furnace will last up to 20 years if properly maintained.

How long to leave furnace off to reset?

Leave the breaker(s) off for at least 10 minutes while the system is off and “rebooting.” After 10 minutes have elapsed, go back to the breaker box and flip the HVAC breaker(s) back on.

Can an oil pump lose its prime?

Although not a common occurrence, it is possible that the oil pump may lose its prime during the oil change. When the used engine oil is drained from the engine, the oil may also drain from the oil pump pickup tube and possibly from the oil pump itself.

Why does the flame keep going out on my oil furnace?

Dirty flame sensor rod: Every now and then, the flame sensor rod gets dirty and shuts the furnace off. Make sure you wipe it off regularly. Low fuel: Low fuel is also a common cause of burner failure. In this case, you'll need to add more fuel and then reset the burner.

What is a tiger loop for an oil furnace?

The Tigerloop® LT Oil Deaerator improves efficiency, extends the life of oil heating systems combining the benefits of a single pipe system with a two pipe system and is suitable for cold climate applications. Compatible with standard heating fuels and Biodiesel up to 5% (B5).

What are the three most common reasons for low oil pressure?

Reasons for Low Oil Pressure
  • Not Enough Oil in the Engine. ...
  • Too High or Low Viscosity. ...
  • Apparent Low Pressure. ...
  • Engine Wear. ...
  • Defective Oil Pressure Gauge. ...
  • Pump Wear. ...
  • Plugged Filter.

How to know if an oil filter is bad?

Signs of a Bad or Failing Oil Filter
  1. Reduced Engine Performance. As an oil filter gets clogged with use and mileage, it can restrict the flow of oil in the engine. ...
  2. Dirty Exhaust. ...
  3. Unusual Engine Noises. ...
  4. Oil Pressure Warning Light. ...
  5. Overheating Engine. ...
  6. Irregular Oil Texture and Color. ...
  7. Time Since Last Replacement.

How do you fix lost oil pressure?

How do you fix low oil pressure? To fix low oil pressure, start by checking your oil level and topping it up if it's low. If the oil level is fine, the next step is to inspect and possibly replace the oil filter, as a clogged filter can restrict oil flow.

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