Car won’t start after fender-bender

Dear Mike: I was involved in a minor fender-bender with my Lincoln Town Car. I could have driven the car away from the scene, but the engine stalled and wouldn’t restart.

The tow-truck driver told me that he could start the car very easily without towing it to the garage, but I was afraid of being ripped off because he wanted $50 in his hand first. The garage charged me $100 for the tow and another $110 for the repair, which took less than two minutes. I guess getting ripped off is relative.

Please tell me how I can keep from getting ripped off in the future.

— A.M., New York, N.Y.

A: What the tow-truck driver was going to do, and what the mechanic probably did, was to reset the fuel-pump shutoff switch.

Most Ford products have this device mounted in the trunk, in the glovebox or under the dashboard. It’s an inertial switch that interrupts the electrical supply to the fuel pump so that it won’t continue to pump gas after an accident. This will kill the engine immediately and, if the fuel lines are damaged in the crash, it can prevent a fire.

A minor accident, or even leaping a curb or hitting a big pothole, can trip this switch. It’s a simple matter to reset it by pushing the button. Then you can start the car normally and drive away.

The instructions for finding and resetting the switch are in your owner’s manual.

Dear Mike: Based on your experience, what is the life expectancy of a water pump, alternator and starter motor? How often should I replace them?

— J.B., via e-mail

A: The electrical components could easily last for the life of the vehicle — 150,000 miles or longer. I generally don’t replace them unless they show symptoms of impending failure. On most vehicles the labor to replace them is pretty reasonable, generally less than an hour, but they can cost as much as several hundred dollars on some premium makes.

Water pumps are a different kettle of fish. The basic pump on most vehicles costs less than 50 bucks, but the labor can be extensive because many other parts need to be removed in order to get at it. Also the cooling system has to be drained, refilled and properly bled. All of this can wind up taking three to four hours, depending on the vehicle.

So, whenever I am working on a high-mileage car, I replace the pump as a preventive measure. The cam-belt replacement interval on modern cars, around 60,000 to 90,000 miles, is a good opportunity to do this. The front of the engine has to be pretty well stripped to replace the belt.

If you do it at the normal flush-and-fill interval for the cooling system, the pump replacement will be virtually free of extra labor charges. Your mileage may vary.

Dear Mike: I was reading a report about the 2005 Corvette, and it says that the engine uses a dry-sump oil system.

What is a dry sump, and why is it better?

— F.K., via e-mail

A: Most engines use a wet-sump oil pan: Oil drains off the crankshaft and down from the cylinder head, then pools into an oil pan under the engine. An oil pickup sticks into this “sump” and feeds the oil pump, which in turn pumps the oil into galleries that carry the pressurized oil around the engine. Simple and low-tech.

Dry-sump engines use one or more engine-driven pumps to scavenge the oil from a similar but smaller sump and deliver it to an external tank near the engine. This tank holds far more oil than the wet sump could, and it allows any air in the oil to bubble to the top before the main oil-pressure pump sends it back into the engine.

A major advantage of a dry sump is that the entire engine can be lower in the car when there’s no large oil pan.

Another advantage is better control over the oil in hard cornering and braking. The system keeps it from sloshing around and uncovering the pickup, or splashing into the crankshaft and getting aerated. This saves horsepower by letting the crank rotate freely instead of pushing oil around.