Pausing After Key On Before Cranking

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May 10, 2005
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Heard on a car show where the host said she waits for a few seconds after key on for the ECM to process all the data it acquires after key on, and then cranks the engine.

Tried it with my truck and really did not notice any difference, whether I paused or not.

I guess it all depends on how quickly the ECM processes data.
 
Some vehicles prime the fuel pump like my new truck. It detects the key going near it and i can hear the pump turn on before opening the door to get in. If i use remote start it primes with the first key press and by the second it cranks. And if you mean that 2006 gmc sierra then it's not applicable. Neither of mine prime the pump.

But as for the computer itself that's just silly. They process insane amounts of information in a split second.
 
I was running late to my part time job a few months ago. Had to take my '16 Cummins Ram, which I usually don't do due to the short trip. I put the key in and slammed it over to start without waiting. I got a CEL, which after later I found out was U0100 "Can Bus Communication Error" or some such thing. It went away on the next startup.

I wait a second or two now before starting.
 
This is a holdover for days gone by... Back in the PGM-FI days honda would tell you to wait for the bulb check before starting it...

Some Holley stuff does better if you let the hand held load before you crank it too...

Normal everyday new car now days - does not matter - in fact, I'm pretty sure the Escape is ready to go before you even open the door, it is just waiting to sense the key inside and someone to put their foot on the brake before pushing the button...
 
Some vehicles prime the fuel pump like my new truck. It detects the key going near it and i can hear the pump turn on before opening the door to get in. If i use remote start it primes with the first key press and by the second it cranks. And if you mean that 2006 gmc sierra then it's not applicable. Neither of mine prime the pump.

But as for the computer itself that's just silly. They process insane amounts of information in a split second.
My 2006 Sierra truck runs the fuel pump for a few seconds at key on.

The car show host was specifically referring to the ECM processing data. The reason I thought maybe there was something to the argument is that my PC will take some time to process data. For example, when I load on a file I had previously downloaded. the file does not appear instantly on the screen, it takes a bit of time.
 
I have a 1984 Chevy Cavalier with throttle body injection, and I read somewhere that the best way to start those is to crank them for a second, stop, wait a second and crank again and it'll fire right up. Seems the fuel needs time to evaporate? Not sure, but seems to work. It does fire right up on the 2nd crank.
 
My 2006 Sierra truck runs the fuel pump for a few seconds at key on.

The car show host was specifically referring to the ECM processing data. The reason I thought maybe there was something to the argument is that my PC will take some time to process data. For example, when I load on a file I had previously downloaded. the file does not appear instantly on the screen, it takes a bit of time.
That's odd. Neither my 2003 or 2005 do. The fuel pressure regulator on my 03 went out last year and I'd put it in the on position for a while and it would still crank and crank before starting. I wonder if they added that in 2005.
 
Won't hurt to pause, let the fuel pump come up (if it's not holding pressure, which is either because it's on its way out, or it's been a few months since last running), but thankfully most ECU's don't have Windows whatever running on them.

I've noticed my kids do this though. I think they have yet to learn that it's ok to just crank until full stop. I think they are afraid that they might turn one past that and it'll blow up or something. I have no idea where they got this from, I don't do this, and their mother's car for the last couple of years is push button, so...?
 
I have a 1984 Chevy Cavalier with throttle body injection, and I read somewhere that the best way to start those is to crank them for a second, stop, wait a second and crank again and it'll fire right up. Seems the fuel needs time to evaporate? Not sure, but seems to work. It does fire right up on the 2nd crank.
Oh i hated the throttle body injection. Briefly owned a 2500 with the 305 before taking it to mexico to give to a family member. The 305 itself wasn't that bad I don't know why some hate it. Now the 4.3 i understand that engine was weak.
 
Oh i hated the throttle body injection. Briefly owned a 2500 with the 305 before taking it to mexico to give to a family member. The 305 itself wasn't that bad I don't know why some hate it. Now the 4.3 i understand that engine was weak.

It seems to be better than the carburetor my 1986 Dodge Omni was equipped with. Starting that thing was an exercise in patience...and it was only 10 years old when I got it.
 
My volkswagens lift pump primes when I open the door. BCM, ECM active when I unlock with the key fob.

I don't think an ECU has needed to 'turn on and gather data' since OBD0. To be honest I don't think anyone has ever paused for an ECU. Historically we've all paused for fuel pump priming or glow plugs.
 
Oh i hated the throttle body injection. Briefly owned a 2500 with the 305 before taking it to mexico to give to a family member. The 305 itself wasn't that bad I don't know why some hate it. Now the 4.3 i understand that engine was weak.
I love the 4.3 in my 17 yr old truck. Reliable as a stone axe, only issues I have had in 17 yrs were an ignition module and a couple of thermostats. Truck will go to its grave with the engine unmolested.
I drive conservatively, so the 190 hp it produces is adequate for my needs.
 
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My volkswagens lift pump primes when I open the door. BCM, ECM active when I unlock with the key fob.

I don't think an ECU has needed to 'turn on and gather data' since OBD0. To be honest I don't think anyone has ever paused for an ECU. Historically we've all paused for fuel pump priming or glow plugs.
A ECU can be ON in the sense it is not sleeping but still not be gathering all the necessay data till its senses IGN.For instance a Hall Effect sensor is not powered up till IGN is on.
So the question narrows down to - can the ECU process the data coming in at IGN on quickly, in milliseconds? I am guessing the answer is YES.
 
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