So I just bought a new entry-luxury car (woohoo!), and I’m reading through the manual…
Under “Starting the Engine”:
“In the summer, when restarting the engine within 30 minutes after it has been stopped, keep the accelerator pedal fully depressed while starting.”
What the hell? What does that do aside from flood the engine?
It doesn’t flood the engine. Depending on which entry-luxury car you have, the computer that runs the whole gas/air mixture show just opens up the air intake (since there’s fuel vapor already in the cylinder) and lets the car start.
But why do I only have to do it under the conditions above? I also don’t understand why I won’t redline myself as soon as I crank the engine (it’s an Infiniti I30).
Under those circumstances, starting the car can be harder due to vapor lock. Those steps are to avoid it.
Because you (hopefully) have the sense to let go of the pedal after it is started, and before you get to redline.
I couldn’t find the cite I was looking for, but I found this. It’s for a Porsche, but the important part…
was pretty much what I was thinking of. If you pump the gas, you’ll flood the sucker.
And when I previewed, I saw Joe_Cool’s post…yeah, what he said. Openning the throttle body breaks the vapor lock. When it’s cool, the vapor condenses back to liquid gas and it’s not a problem.
Sometimes the redline problem is circumvented by the engine computer, it won’t let you redline on startup. I wouldn’t test it though. I’d just take my foot off the gas when the car starts.
You can’t flood a modern fuel injected car; the injectors don’t open until the spark plugs are firing.
They probably want you to open the throttle because the engine doesn’t know how it is running until it begins to run. To make sense of that last statement, the engine control module (or ECM) adjusts the air/fuel ratio based on the temperature of the coolant in the engine (along with a lot of other things.) But the coolant temperature is really supposed to represent the temperature inside the cylinders.
The insides of the cylinders cool off faster than the coolant does, so the ECM probably adds a little more fuel than is necessary when when you start the engine warm. Opening the throttle allows the engine to draw in more air, evening things up. Once the engine is running, the ECM can make adjustments based on how the engine is running.
Personally, I’ve never had a problem starting an injected car with my foot off the throttle, whether the engine is hot, warm or cold.
If by “flood”, you mean “fill the carburetor with gas, so the engine can’t turn over”: then no, you can’t flood a modern fuel injected car. No carburetor to fill with gas.
If by “flood”, you mean “pump too much gas into the cylinder, so it’s hard to start”: yeah, you can do that. The fuel injectors are not open yet, but there’s a wave of gas right behind them. When the plugs fire and the injectors open, too much gas squirts through (A very little extra gas from the very little extra pressure. We’re talking gas vapor in the cylinders, just a little extra and it wouldn’t combust so well) and it’ll take a couple of “cranks” till the engine “catches” well. And a few seconds till the engine gets enverything back in working order and runs smoothly again. It’s not the classic “flood” where your carb’ sloshes around with liquid gasoline and you’re stuck till the stuff evaporates, but you’re still “flooded” in that too much gas is keeping your car from running properly. When was the last time you “dialed” a phone with an actual dial?
My assumption is: a 1996 Honda Civic DX Hatchback (Silver) qualifies as a “modern fuel injected car”. Been there, done that, bought the t-shirt.
sethdallob, the important part of the whole “keep the accelerator pedal fully depressed while starting” deally is to open up the airflow. When your car is still hot, the engine conditions don’t match the baseline the computer uses to start your car. More air in the fuel mix lets the car start easier.
Call it “vapor lock”, “flooding”, “stupid ECM”, whatever. Depressing the throttle all the way helps to start your car when it’s hot and won’t start right by giving the engine more air. It might not do anything really, it could be something for you to do while you’re trying to get your car started so you feel like your really doing something to help the process along. It could be Detroit Voodoo. Hopefully you’ll never have to find out because your car will always start the first try. Just don’t pump the gas.
Are you referring to a hydraulic lock where the cylinders fill with gas? I learned that a flooded engine is one that will not start due to a too rich condition, not one that is slow to start. You’re right, it is a matter of degree, but I have never had an injected car flood out and not start. I think my post implied that the open throttle might help the car start faster.
Why wouldn’t any pressure waves in the fuel lines pass through the bypass regulator and back into the tank?
Browsing around, I did find a reference to “the clear flood mode” (page down twice.)
This further leans out the mixture (which I think we all agree is a good thing.) Pumping the throttle while cranking the engine would limit this mode of operation.
Pumping the accelerator with the engine off of course makes no more difference than pressing ctrl-alt-del on your PC with the cord unplugged. The system is powered off, and doesn’t read the input.
I added the phrase to rule out odd stuff like Hillborn injection, where fuel flow is directly controlled by the accelerator.
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