Is This a Case of a Bad Battery, or Evaporating Gas?

Dear Car Talk

Dear Car Talk | Apr 06, 2017

Dear Car Talk:

I have a 1986 Toyota two-wheel-drive pickup with a four-speed manual transmission, no power steering and a carburetor. To start, the old beast requires cranking for at least two minutes before it will fire up. Usually, I need to jump the battery, as the old battery doesn't last long enough. After starting, it runs fine, so a tune-up is not needed. If I stop the engine and restart it, it'll start right up. Is the gas in my carburetor evaporating? There's never any gas smell or gas on the ground. Any idea what else could be causing the need to crank the engine so much? -- Dave


This sounds like a real beauty, Dave. I'm surprised the Pebble Beach Concourse d'Elegance folks haven't been hounding you for it.

You could be right about the gasoline evaporating. But before you go down that road, make sure it's not just a weak battery.

If the battery is weak, or your starter motor is drawing too much current, then maybe the engine just isn't cranking fast enough to start. That could explain why it'll crank for two minutes without starting, and then start up after you give it a jump from a healthy battery. So don't crank it first with your existing battery.

Try jump-starting the engine right away next time, and see what happens.

If you still can't get the truck to start, then the gasoline probably is evaporating. It's likely leaking out of the float chamber into the intake manifold, and evaporating overnight while you're dreaming of 2017 Tundras.

Then, when you try to start it the next day, there's no fuel left in the reservoir. So the mechanical fuel pump has to draw fuel all the way from the gas tank at the back of the truck. That takes a while. Especially with the starter motor turning the engine at 100 rpm (versus 1,000 rpm when the engine is idling).

Here's how you test this theory: You are fortunate to have a carburetor so old that it has a glass observation window in it, so you may be able to see if there's gasoline in there in the morning. When the truck is cold, remove the air cleaner, locate the glass window in the carburetor, and push down a little bit on the fender. If there's gasoline in there, you often can see it sloshing around. My guess is you won't see any.

Then crank it for a couple of minutes until the truck starts, shut it off and check again. Once you know there's gasoline in the float chamber (because the truck has just been running), shake the fender and look again. If you see gasoline sloshing around, you have your answer.

Then you'll have two options: You can either visit some local assisted-living centers and see if you can find someone who remembers how to rebuild an '86 Toyota carburetor, or you can buy yourself a new one. It'll probably cost you a few hundred bucks, but thanks to the miracle of the worldwide web these days, you can order it in your pajamas, Dave.

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