The general causes that make a fuel pump relay stick usually involve interference with normal electricity flow to the fuel pump. Major reasons include contact wear inside the relay. These are internal contacts that open and close the electrical circuit and may wear out or corrode after some time, due to the constant switching between open and closed positions. Especially for high-mileage vehicles, this may equate to several thousand power cycling of the relay. In most instances, contact degradation results in the sticking of the relay in an “on” or “off” position, hence disrupting fuel delivery and leading to symptoms like hard starting or engine stalling.
Another cause is electrical arcing. Small sparks or arcs that happen as the relay switches between contacts form carbon deposits overtime. These can make the contacts stick and limit the capability of the relay to move freely among positions. Vehicles which are frequently running at high load tend to have higher rates of arcing within the relay due to the more current demanded from the fuel pump. Replacing the relay every 50,000 miles, especially under high-load conditions, can help avoid these problems and ensure smooth operation of the fuel pump.
Another probable cause of a stuck relay may be excessive heat caused by thermal expansion of the plastic housing or internal components of the relay. Under-hood temperatures could be as high as 200°F (93°C) in most vehicles and even higher on most high-performance or turbocharged vehicles. Over time, this heat causes parts in the relay to warp or soften with the result that the relay jams. Most mechanics will recommend that the position of the relay in the fuse box be regularly checked; relays placed near hot components are going to have to be changed more often or better shielded against overheating.
Sometimes, stuck relays can also be caused by defects in manufacturing or poor-quality parts. Low-quality relays may not be designed to handle the almost constant high-current switching found in today’s fuel systems, especially those with high-pressure fuel pumps running between 30 and 80 psi. Thus, by having a proper and reliable Fuel Pump relay, one reduces the chances of its sticking and prolongs its life span.
As Lee Iacocca, one of the pioneers in the automobile industry, once said, “Quality is job one.” Quality assurance plays a major role in ensuring that the relay works smoothly. For Fuel Pump Relays that are guaranteed to work every time, check out Fuel Pump for more details.