Inertia Switch Stops Engine in Accidents


Question: My daughter and grandmother were on the freeway recently when a piece of plywood flew out of a truck and hit their 1987 Taurus station wagon. It shattered the window, but some tint film kept the broken pieces in place. The problem was that the car went dead. The tow truck operator couldn’t get the car started and towed it to a Ford dealership. After some effort, the mechanic there found a shut-off switch. Shouldn’t the public be informed about this unusual thing? --R.L.

Answer: The public should be informed, but it isn’t always as easy as you think to inform the public. The switch is called an inertia switch and is designed to shut off the fuel pump supplying gasoline to the fuel injection system in an accident. The purpose is to prevent the electric fuel pump from continuing to pump explosive gasoline after an accident that may have resulted in a fuel-system leak.

The switch activates when a tiny ball runs up a ramp, which is triggered during the sharp deceleration during an accident. The ball makes an electrical contact at the top of the ramp, and the electrical current to the fuel pump is discontinued. It is a safety item found on every modern fuel-injected vehicle.


The owner’s manual to your car makes mention of the switch and where it is located, which on Fords is usually in the trunk area. Probably your grandmother or daughter never read the owner’s manual, especially if they don’t own the car. But many car owners don’t read their manuals, even after spending $10,000 or $20,000. They should, because the manuals contain a lot of important information that will help keep the car running properly or sometimes running at all.

Q: I recently took my 1988 Buick Le Sabre to the service department of the dealership, and the mechanic there noticed a quick-oil-change sticker on the door. They said those places can not lubricate the front-wheel-drive cars properly, because the car must be lifted to get weight off the ball joints. What is your opinion? --L.M.

A: That advice was unadulterated sales talk from somebody who wants to sell you a service at an inflated price. According to General Motors’ own technical experts, the ball joints can be properly lubricated with the car sitting on the ground. Moreover, most of the quick lubrication shops do a reasonably good job of lubricating suspension systems.

Although car manufacturers have reduced the number of nipples on newer cars, there are still quite a few moving parts that need a shot of grease. The small and medium-size GM cars typically contain six nipples, all in the front. The larger cars can have as many as six in the front and six in the back.

Q: You recently wrote a column about a motorist who described a problem with coolant loss on a 1986 Ford Taurus that mechanics could not fix. I had the same problem on my Ford that was baffling mechanics. Eventually, I noticed that the overflow tank did not seem to change in level regardless of the engine temperature. After much searching, I found a small hole in the tube running from the radiator to the overflow tank. I replaced the tube and now I don’t have any more problems. --P.L.H.

A: That’s good detective work. You ought to go to Dearborn and straighten things out for Ford. The company has no service bulletins describing the problem you found.