Fuel Pump Secrets

So ok..what had my friend gotten herself into this time? She had called and told me she was stranded at her Mother's house...and that her car would not start. Knowing better than to quiz her about anything to do with cars beyond how to put fuel into it, and actually drive it, I made a run over there to see if I could help her out.

The first thing I noticed when I arrived was the rather guilty look on her face. She pointed at the dent in the rear bumper where she had tapped her Father's truck as she parked in the drive way. She explained the car had shut off at that point and having arrived, she just went on in to visit with her parents. And when she tried to leave, the car simply would not start. She went on like this for some time as I raised the rear hatch and felt around in behind the cosmetic effect wheel well liner where I knew the centrifigal fuel pump shut off switch was usually located. As she ranted on what a useless car this had been I gave the reset lanyard a sharp pull and felt the switch reset.

I asked her for the keys and as she was winding up for a fourth redition of how this car was the lowest form of mechanical assemblage on the face of the known universe, I started the engine and stepped out to allow her entry into the vehicle. She was astonished at such a rapid repair and asked me what I had done. I had her place her hand on the lanyard and told her what it was..and why it was there.

This car has an electric fuel pump. In the past, fuel pumps had been mechanical and had been powered by a running engine. In the event of a collision, the engine usually was damaged beyond the point of running, and so the delivery of fuel would stop, thereby reducing the chance of fire. Not so in a vehicle equipped with an electric fuel pump. This kind of pump runs until turned off by the ignition switch. In the event of collison and even with the engine stopped, there was the pump happily supplying fuel...and if a fuel line had been broken in the engine compartment, the chance of a disastrous fire was very real.

Hence, the centrifigal fuel pump shut off switch. Very simple really, a spring loaded switch is installed that will shut off the power to the fuel pump in the event of a collision...think of a mouse trap arrangement. Enough of a jolt, and it will snap into action and in the case of our pump, shutting it off cleanly and with no sparks. My friend bouncing her car off of her Father's truck bumper had been sufficient to pop the switch, and her car would not start with no fuel being supplied.

She was overjoyed at my quick fix and took the opportunity to have me look at another problem she had been experiencing. Her car kept trying to overheat at traffic lights and slow moving traffic. I glanced in at the temperature gauge and sure enough in the few minutes we had been talking the gauge was beginning to edge up into hot territory. I popped the hood and after shutting off the engine I checked her coolant level and condition of her radiator cap and looked for any indications of a leak and asked her if she had added any coolant to the engine. Coolant? Her look asked..whats that?

I had an idea of what may have been the problem and locating the coolant temperature sensor I unplugged it and finding a couple of pieces stray wire in my truck bed I formed a quick and dirty connection between the connector plug in my hand, and the sensor still mounted on the engine. I had her turn the key to the on position and after using my wires to form a better ground connection, much to my satisfaction, the electric fan began pulling air through the radiator as it was designed to do. So it was a bad sensor and I told her so. I even offered to replace it for her if she would pay for the sensor.

She drove off happy again knowing her car would start again barring any more bumper thumps and that I would fix her car's overheating problem. I stood there mindful of how funny people can be sometimes. Something I have always marveled at and I was as guilty of this as anyone depending on what the topic was. So many of us use todays gadgets with no idea what so ever of what makes it go...how and why it is designed the way it is...and for some, never even wondering as to what makes it go. Never even crosses their minds. My friends rear hatch was still open as she sped off around the curve. It was obvious she was one of those types of people..and not very observant either.