What could be causing this Buick's slow morning starts?

Dear Car Talk

Dear Car Talk | Dec 01, 2001

Dear Tom and Ray:

I have a 1992 Buick Century with more than 60,000 miles that is very difficult to start, but just in the morning. It must be cranked several times before the car will finally start. Once it has been started, no problems are encountered for the rest of the day. I have replaced sensors, spark plugs, batteries, a starter and a fuel filter, but with no success. A Buick dealer hooked the car up to his computer and found no problems. Thinking I might be at fault, I've had other people start my car in the morning, with the same result. What could possibly be causing this car so much trouble waking up in the morning? -- Margaret

RAY: Good question, Margaret. Maybe it's the same thing that gives my brother so much trouble getting up in the morning: work.

TOM: I'm going to suggest a few possibilities, Margaret. One is a weak fuel pump. If the fuel pump is weak, it would take awhile for enough fuel to get from the gas tank to the engine, especially when the car's been sitting for a while.

RAY: The car could still start fine for the rest of the day because once the car is started, the fuel pump maintains "rest pressure" in the fuel line. That keeps enough gasoline in the line for quick subsequent starts.

TOM: So you can ask your mechanic to test your fuel-pump pressure and your rest pressure. And if either are lower than they're supposed to be, go ahead and replace the pump.

RAY: Another possibility is a faulty fuel-pump relay that is acting "lazy" when the car is cold. That would keep the fuel pump from being activated until the relay kicked in.

TOM: So that's something else your mechanic can investigate.

RAY: And one other possibility is the oft-overlooked coolant-temperature sensor, assuming you haven't replaced that yet. The "coolant temp sensor" reads the temperature of the coolant to determine whether the engine is hot or cold.

TOM: And if the sensor is malfunctioning, it could be telling the computer that the engine is hot when it's really ice-cold. And that would lead the computer to set the fuel mixture incorrectly for a cold start, also leading to slow starting.

RAY: If none of those suggestions help you solve the problem, Margaret, you can always try the approach I use on my brother to get him going in the morning: a swift kick. Good luck.

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