Dear Car Talk - starter column

I just read about your advice to a reader on how to replace a starter, where you advised him to disconnect the negative terminal of the battery. Why the negative?, could he have disconnected the positive terminal instead and be just as safe?refresh my memory on the proper order and why?i can see why the negative goes on last when installing a battery, but in the case of a starter replacement, disconnecting the positive terminal seems ok too. Now for my real question, why do I smell exhaust fumes when I start my truck engine. I had my catalic converters replaced on my exhaust system recently and when I took it Mack to the muffler shop they told me it was not their welding job. They said the exhaust leak could be from the exhaust manifold or some where there a easy way to check. I tried looking at the exhaust and can’t see anything wrong. I still have one of your click&clack for president stickers from years ago and think now would be a good time to run again, you would have a good chance of winning this time.

If you remove the positive cable first, the metal wrench can contact the metal frame make a hard arc spark. Damage can occur, stuff can explode, bad things happen. If you disconect the negative first, that can’t happen.

Exhaust leak… stuff a potato in each exhaust pipe while the truck idles, listen for a big hiss, there is your leak.

BTW Clack passed away a few years ago and Click isn’t here.

MM above has the straight dope on the best battery disconnection strategy. Another way of saying it, the battery negative is connected directly to the chassis. Check for yourself, you’ll see a big, thick wire from battery negative connected to the body of the car. So while there is no functional difference, as a practical matter it is safer to disconnect the negative first, b/c there’s no spark or short circuit problem if your wrench touches the negative battery post and the chassis at the same time. Once the negative is disconnected, there’s no short circuit problem to worry about when disconnecting the positive at that point either. As long as you don’t bridge the two battery posts with your wrench that is.

It’s possible that is normal. When cranking a cold engine, especially on the first start of the day, the computer injects way more gasoline that it normally would, b/c the engine needs extra help starting when it is cold. Some of that extra gas goes right through and comes out the tailpipe, creating a gasoline odor. So if you only notice this gasoline odor on starts when the engine isn’t already warmed up, absent any professional assessment to the contrary, I’d just ignore it. I notice a little gasoline odor on my Corolla on cold starts, always have since the car was new, and I’m not worrying.

BTW, replacing a starter – at least on a Corolla — isn’t quite as simple as Ray suggests. Access is really problematic when doing this w/the car on jack-stands in the driveway. I wouldn’t recommend starter replacement as a good choice for a wanna-be diyer’s first job.