Q: I have a 1996 Plymouth Breeze, and ever since I had the fuel pump replaced with a used one, it doesn't start normally.
When I start the car it just cranks over, like it's going to start, but I have to do it a few times before it actually does start up. I know it will mess up my starter. It's as if the fuel pump isn't keeping the fuel in the lines, because when I start the car and turn it off, then start it again immediately, it will work on the first try.
What do you think the problem is?
A: Sounds like the check valve in the pump isn't maintaining pressure in the line, and the pump has to refill the lines while you're spinning the motor with the starter.
You can check the pressure in the fuel rail with a simple mechanical gauge attached to the Schrader valve on the rail.
One suggestion: Turn the key on, but not to the start position, and wait five seconds or so. This will let the pump run until the engine computer realizes that the engine isn't spinning and shuts off the pump. If you listen, you'll be able to hear the pump run and then quit. Repeat this procedure a couple of times to pressurize the fuel lines, and it will make your starter and battery last much longer.
Q: I have a Jeep Wagoneer Limited 242 fuel-injection engine. Something very strange happened during a recent repair.
The mechanic was trying to test the electric fuel pump by applying 12 volts directly from a battery to the terminals of the pump, which was lying outside the fuel tank with connections and hardware installed. Another mechanic was cranking the engine and a third mechanic was checking the fuel pressure with the nanometer connected at the pressure port next to the fuel regulator.
Apparently gasoline passed through directly to the cylinders, causing the engine to become stuck, because the void space between the head of the pistons and the cylinders was full of gas.
What caused this to happen? Could this problem have caused any internal damage to the engine?
A: I am not sure how they did it, but the mechanics managed to hydrostatically lock up the engine by filling at least one combustion chamber with a volume of liquid gasoline greater than the residual volume in the cylinder at top dead center.
Applying 12 volts to the fuel pump to test its pressure output should not, in and of itself, have caused any problem. Somehow they had to keep the fuel injection spraying fuel into the intake ports for awhile. Maybe there's a leaky injector that dribbled fuel into the engine.
Filling the combustion chamber with fuel shouldn't be a problem. All you need to do is to wait an hour or so, and the fuel should run down into the crankcase, where it will mix with the oil. Simply change the oil and the filter, and your engine should be fine.
One remote possibility: If you tried to start the engine, and if one cylinder fired and spun the crankshaft merrily along until the partially filled cylinder crashed to a catastrophic halt, there might be the potential for a bent connecting rod, a cracked piston, or a bent crankshaft. Don't ask how I know this, but this sort of thing makes a really, big, ugly noise that's hard to miss.
But, almost certainly, your engine is fine. Change the oil and filter, and sort out your fuel-injection issues.
Q: Mobil says that it is safe to extend oil-change intervals to 15,000 miles with Mobil 1 Extended Life motor oil. Do you think that it is OK to use for my 2007 Honda CRV?
A: No. And neither does Honda.
Q: Have you heard about the prototype of a fully self-contained, magnetic power module called Genie? I've been following this little company for awhile.
A: It's perpetual motion. It's something for nothing, and it doesn't work.
Mike Allen is a senior editor for Popular Mechanics magazine. Questions should be sent via e-mail to driveit@nytimes.com.
