Today: Harvey's Harebrained Idea

Dear Car Talk

Dear Car Talk | Aug 13, 2013

Dear Tom and Ray:

OK, I know this is a pretty ridiculous question, but I've done a little research and can't find anything written on the subject. I was wondering if it's possible to implement a sort of pull-start system (like a lawnmower has) on my truck.

The reason I would want this is for a situation such as a dead battery with no one to give me a jump-start. I just figured that it would be nice to have a system like this for occasional use. Now, I know I can just buy a portable jump-starter and keep that in my truck, but is a modification such as this possible? I appreciate your time and help.

-- Harvey

RAY: Sure. On almost every car, there's a big, fat nut on the crankshaft pulley that bolts to the front of the crankshaft. That's the pulley with the serpentine belt running around it. If you were to turn that nut, you'd be turning the crankshaft and thereby "cranking the car."

TOM: In fact, on old cars like the Model T Fords, that's exactly what people did. They went to the front of the car, fit a wrench on that nut and "cranked it" until the engine started.

RAY: But it's not so easy with modern cars. First of all, you don't have easy access to it. Most modern engines are mounted transversely (aka installed sideways). So you'd have to smash a hole in one of your front fenders to get at the crankshaft pulley with a crank handle.

TOM: And even on a truck with a longitudinally mounted engine, like yours, you'd still have to blast a hole through the radiator.

RAY: But more importantly, it's not easy to crank a modern engine. By comparison, Model T engines were tiny. You simply wouldn't be strong enough to turn over a modern, high-compression engine by hand -- even with the mechanical advantage of a pull starter or a wrench.

TOM: Think about it: Even a tiny lawnmower engine takes some effort to pull-start, and lawnmowers typically have 0.15-liter engines, as compared with the 2.0- to 3.0-liter engines found in typical cars. Or 4.0-, 5.0- and 6.0-liter engines in trucks!

RAY: So, a pull start is out of the question. But if you still want to pursue this idea, I guess you could employ some sort of separate electric motor to help you turn the crankshaft. Actually, we have those, Harvey. They're called starter motors! Your car already has one.

TOM: I suppose you could buy yourself a powerful electric drill instead -- something that delivers, say, 5 horsepower (the starter motor, for comparison, delivers 8-10 hp). But that drill will cost you about $4,000. And don't forget the cost to replace the radiator you had to pop a hole in.

RAY: So as you suggested, Harvey, this is a harebrained idea. You're much better off with one of those portable "jump packs" that you can use to jump your battery. The most powerful one you can get (which is what you should look for, in terms of the amps it produces) will cost you less than $200. That's the way to go.

Get the Car Talk Newsletter