Turning ignition to ON before starting the engine

Not open for further replies.
Jan 7, 2011
Florida, USA
I always turn the ignition to "ON" to prime the fuel pump, power sensors, etc before starting the engine. Is there any reason not to do this, or does it really not make a difference either way? This has to be one of the more mundane ever questions asked on BITOG...
I do the same. A habit I picked up with diesels. There are 100's of millions of people that don't and will never have a problem.
Get that motor running as fast as you can before building oil pressure. Why is it some of these mechanics recommend disabling ignition or fuel and cranking the engine to build oil pressure when it has drained off? Don't want to put any extra drain on the battery? Jesse-ASE Master Auto Tech
I do it during the winter as it helps the engine start easier with less cranks. During the summer, I don't see much of a difference so I don't do it.
This is very platform dependent. For some of our vehicles it makes no difference at all, others it seems to help it a bit to wait a sec. But many of you are in the frozen north so it's very different conditions AND fuels.
That's a habit I picked up when I first started driving and always do it to this day. I've never really thought about the reasons behind it though.
I've been doing it ever since I owned a FI engine. Once I hear the fuel pump stop priming I turn the key and fire the engine up.
Towncivilian, the way you do it is exactly how it's described in most owners manuals, for the reasons you mentioned. I teach all those close to me to do this. If you tune your ear to listen for the fuel pump each time, you'll know when it (or the fuel pump relay) goes bad.
I think most computerized cars already do this to some extent. On my current GM products, it doesn't matter if I just bump the key or hold it for 30 seconds. Turning the key to "start" initiates a startup sequence that engages the starter and disconnects it when it detects the engine is running.
Don't forget the ON position also primes the engine with a spritz from the injector to each cylinder. If for some reason you need a better prime, you can turn to ON twice.
I've never done that on any vehicle I own. Put the key in, start it up and go. I've never counted the number of "cranks" the engine makes, but all my engines start almost immediately after turning the key from "Off" to "Start", without pausing the ignition switch at "On".
I pause but only half a second, I don't wait for the fuel pump to shut off again.
I do it. My 11 BMW primes the fuel pump at unlock because it is pushbutton start.
Not open for further replies.