Since three new carburators haven't solved anything, the problem may not be with carburetor.

Dear Car Talk

Dear Car Talk | Feb 01, 1992

Dear Tom and Ray:

At the age of 80, the transportation love of my life is a '79 Cadillac that runs like a jewel after it gets two miles from home. The car starts perfectly, and runs fine until you stop or make a turn. Then it dies a quick death. It won't restart until it's allowed to cool off. Once it's completely warmed up, the problem ceases. The mechanics have checked everything--the gas tank, fuel lines, fuel pump, the works! We are now awaiting our fourth carburetor. We've had two rebuilts and one new one--all with the same results. For safety reasons, at the age of 80, I don't want to start fumbling around with a new car. Do you have any insights?

RAY: Well, I'm going to go way out on a limb here, Wally, and suggest that since three new carburetors haven't solved anything, the problem may not be the carburetor.

TOM: Whoa! He IS a risk taker, isn't he?

RAY: In fact, I'd be willing to stake my brother's reputation on it. The truth is, Wally, it sounds like a flooding to me, so the choke or carburetor would have been MY first guess, too. But even at our shop, after you sell a guy three carburetors, it's time to come up with another theory.

TOM: And the next thing I would suspect would be weak spark. Flooding occurs when the gasoline in the cylinder literally washes out the spark. That tends to happen when you have either A) Too much gas (because of a choke or carburetor problem), or 2) not enough spark to begin with.

RAY: The best way to test for weak spark is to put the engine on an oscilloscope and measure the spark voltage.

TOM: The spark could be weak for any number of reasons. You could have the wrong spark plug gap, bad wires, a weak ignition coil, a faulty pick up coil, a cracked distributor, or some other some other problem in the ignition system. All of these things can be tested one at a time--and they're all less expensive than that fourth carburetor you don't need.

RAY: I'd suggest you leave the car with your mechanic for a couple of days. If he can experience the problem, he'll have a better chance of finding out what's causing it. Just tell him to drop you off at the shuffleboard court, and pick you up in a couple of weeks when he's figured it out. Good luck, Wally.

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