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Possible Vapor Lock Problem

I have taken my car to three different Firestone’s (they have checked the starter, battery, two of them did the engine diagnostics, but found nothing (one charged me almost $500 replacing spark plugs, filters and other things), the third could not find anything. Of course the problem will not duplicate itself at the repair shop) but I am still having the same issue. The car will not start back up when making frequent stops (do not know how to get around them). If I wait a while it will start up again. I know nothing about cars and do not like being stranded. I had to return home this morning because I forgot something, the car would not start when I went back out–good thing my husband was here to take me to work. Got a ride back home–the car starts right up (although roughly). It has been over 90 degrees for over month here where we live–heavy use of air condition(not sure if that has anything to do with it). Someone at work mentioned that it could possibly be a vapor lock issue, as it has some of the same symptons as what I have read when I googled “vapor lock”. But supposedly since my car is a 2000 Mazda 626 (just shy of 140,000 miles without a lot of problems until now), vapor lock should not be an issue, but reading the symptoms on this and other websites, it surely sounds like what is going on with my car. I am taking it to the dealership in the morning, but just like most people, I don’t have the money to keep shelling out for car repairs. Can someone please give me suggestions on how to cure my car problem or what else to look for. I hope I was not too long. Thanks for any help.

If the gas you use contains ethanol, it can cause vapor lock on a fuel injected engine.

The ethanol in the gas makes the gas more volotile. Which means it boils easier. When you shut a hot fuel injected engine off the fuel pump stops running and the pressure bleeds off. The gas sitting in the fuel rails starts boiling from the engine heat and you have vapor lock.

Here’s a quick way to determine if it’s vapor lock. Have someone show you where the fuel rails are. Carry a bottle of water in the vehicle. The next time you think vapor lock is occuring, take the bottle of water and pour it over the fuel rails. If the engine starts, that’s vapor lock.


Another source of apparent vapor lock is a weak fuel pump that fails to keep the fuel system at designed pressure, allowing the gas to vaporize. Please find a good independent mechanic (google ‘mechx’ for the cartalk mechanic finder), have them check the fuel pressure.

Thanks for the suggestion. I will let you know what I find out

Since you mention the starter and battery being replaced you might define exactly what is meant by no-start because the starter/battery would denote something completely different than spark plugs and filters.
Those plugs and filters will not cause a no-start condition except under the most extreme circumstances and once running, would likely barely run at all.

Do you mean the starter motor does not physically crank the engine over or do you mean that it cranks the engine over fine but the engine will simply not start?
If the engine does not crank over at all do you hear any click sounds when you turn the key?

When it does start and runs roughly as you say, does this roughness clear up after a minute?

Have you tried depressing the accelerator pedal when there is a no-start condition? (assuming the starter is cranking the engine over)