I have a 2005 Honda Accord EX 4-cyl with a very peculiar problem. The car will start and run fine as long as I don’t have to shut it off and restart it. However, once I shut it off, it will not start back up unless I give it some gas. Once started, the car will not idle unless the gas is pressed to maintain revs. This happens when the car is shutoff for a just one second, and only when warm. Once the car cools down, it starts and idles fine.
I’ve tried changing the FI Main Relay and it didn’t help. I’ve also flushed the coolant and changed the radiator cap which seemed to help a little bit. I recently cleaned the Idle Air Control Valve which didn’t make any difference. The Fuel Filter has been replaced as well. There are no CELs on and the car has 267,000 miles.
Have someone check the fuel pressure. And what they want to check is the residual fuel pressure.
The residual fuel pressure is the amount of time it takes for the fuel pressure to bleed down once the fuel pump shuts off. If takes 15-20 minutes before the residual fuel pressure bleeds down to zero PSI, then you won’t have vapor lock. If the residual fuel pressure drops to zero PSI as soon as the fuel pump shuts off then you can have vapor lock.
Vapor lock is caused when the gas in the fuel rail begins to boil from the heat off the hot engine when it’s shut off and the fuel pump stops running. If the residual pressure drops to zero PSI when the fuel pump stops running and the engine is hot, the gas boils, the engine is hard to start, and it runs like crap until the vapor lock clears out. The cause for the residual fuel pressure bleeding off too fast is a defective anti- drainback valve in the fuel pump assembly.
If you want to find out if this is the problem, carry a bottle of water in the vehicle. The next time the engine won’t start when hot, open the hood and pour the bottle water over the fuel rail and then try starting the engne. If the engine starts right up, that’s vapor lock.