Pausing After Key On Before Cranking
- Thread starter George7941
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RThere could be stuff going on, if the car gets time, like valves that go through their motions.
+2
The computer reads the sensors however many times a second.... I'm sure that's much faster than any of us can turn the key.
If I wait a second ,I hear fuel pump run then when I crank it starts immediately.
The ECM definitely doesn’t need any wake-up time, otherwise that would have been programmed into the starting sequence.
Having said that, I do wait about a second to give the fuel pump time to build up pressure. It’s probably inconsequential anyways, but it’s more of a habit than anything else at this point.
Having said that, I do wait about a second to give the fuel pump time to build up pressure. It’s probably inconsequential anyways, but it’s more of a habit than anything else at this point.
Yeah, it was an extended cab long bed automatic 2wd 2500 and pretty bare bones. I was surprised when the guy told me it was available with the 4.3 when i said it had the smallest engine. I thought the 4.3 was for the 1500 and the 2500 at least got the 305 as standard.
4.3 is reliable but i briefly owned a single cab short bed 2wd auto Silverado with it but it was inefficient. Traded it in for the sierra i have now with the 5.3 and it gets better millage with the same light driving.
I put the key in and crank it. My cars have all started up just fine.
My motorcycles are a different story. I can hear the fuel pump priming when I turn the key to ON. I typically wait until the fuel pump turns off before cranking. Just a habit, not a necessity, I guess.
My motorcycles are a different story. I can hear the fuel pump priming when I turn the key to ON. I typically wait until the fuel pump turns off before cranking. Just a habit, not a necessity, I guess.
Your cars do the same, you just don’t hear the fuel pump, unlike on a motorcycle. In my old Mazda 3 I could hear the faint fuel pump wine when it was priming. All FI systems do it.
The fuel pump on my truck takes only milliseconds to prime the fuel system. How do I know this? I have a fuel pump kill switch I installed under the driver's seat. Occasionally I will forget to cancel the kill switch and crank and not have the engine fire up, realise my mistake, reach under the seat and cancel the kill switch while the engine is still being cranked and the engine fires up instantly. There is no discernible lag between cancelling the kill switch and the engine firing up.
I don't care about the ECM "processing data". But I do it on my truck and Toyota. I can hear the fuel pump pressurizing the system as soon as the key goes to "ON". So I stop until the pump stops, then hit it. (I'm guessing it's perhaps a second or 2).
My truck will fire quicker that way, especially if it's been sitting for several days. Once it's been run and warmed up then I just go.
My truck will fire quicker that way, especially if it's been sitting for several days. Once it's been run and warmed up then I just go.
A picosecond
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That would be my guess. Its a monumentally small amount of data compared to say - processing some bloated code Microsoft wrote.
Ford, with the 4.6 in the early 90s, started requiring four complete revolutions during cranking before allowing fuel. Believe this was a cam/ crank sensor sync thing but they also wanted oil pressure to come up. Am pretty sure most are like this now, except the start-stop cars when warm in traffic.
Some 1980s injected cars caught with fewer cranks-- the 460 in my 1990 motorhome is great, particularly when warm. And of course a carbureted car can start nearly instantly when the stars are aligned.
PCMs are fast enough, with enough sensor resolution, to detect which cylinder is misfiring based on a temporary reduction in rotation speed. I think that's faster than the fastest key turning operator.
Some 1980s injected cars caught with fewer cranks-- the 460 in my 1990 motorhome is great, particularly when warm. And of course a carbureted car can start nearly instantly when the stars are aligned.
PCMs are fast enough, with enough sensor resolution, to detect which cylinder is misfiring based on a temporary reduction in rotation speed. I think that's faster than the fastest key turning operator.
Both your '03 & '05 primes the fuel system, In fact most ALL injected gasoline GM product do. I was playing with the Tune on my dads '17 LT1 6.2L powered '72 Cutlass & you can change the prime from 2 seconds to whatever you want.
I'm not so sure about these ECU's processing, "millions of things per second". If my 2015 Jeep Grand Cherokee sits for several days to a week without being run, it sometimes will start without the screen booting up. Others on the various Jeep forums have had this issue as well.
This can be remedied by pressing the "START" button twice with my foot off the brake pedal. This allows for all of this electronic crap, (including the screen), to boot up without starting the engine. (The same as turning the key to "ON", waiting, then cranking the engine).
(It also allows the fuel pump to prime the engine). Then, after a few seconds I depress the brake, press it again, and everything starts and boots up normally without issues.
This can be remedied by pressing the "START" button twice with my foot off the brake pedal. This allows for all of this electronic crap, (including the screen), to boot up without starting the engine. (The same as turning the key to "ON", waiting, then cranking the engine).
(It also allows the fuel pump to prime the engine). Then, after a few seconds I depress the brake, press it again, and everything starts and boots up normally without issues.
Why would you doubt ECU's aren't able to process millions of things per second? You do realize they have some horsepower in modern embedded processors.
Some go to a deep sleep mode now when not started for a while to save the battery, but that sounds like crappy software. Maybe that is why your screen doesn't come up?
