[neyshule]

I find one interesting phenomenon:
My car tends to shake less during start if I press the start button without stepping on brake and wait for 1 minute. then fire it.
I was wondering if any engine oil is pumped up with this"ignition on" state?

[robthewrench]

No oil is pumped, but fuel is pumped when the ignition is turned on.

This was a common phenomenon on my old subaru. If I didn't pause for a second between turning on the ignition and starting the engine, it would be a rough start or a long crank. It was usually attributed to not giving the fuel pump enough time to raise the fuel pressure up enough.

Originally Posted by robthewrench

This was a common phenomenon on my old subaru. If I didn't pause for a second between turning on the ignition and starting the engine, it would be a rough start or a long crank. It was usually attributed to not giving the fuel pump enough time to raise the fuel pressure up enough.

Huh?

The LPFP usually primes (if needed) when you open the door, trunk, etc. Not sure why yours would "come on" any later than that.

[maxgohan]

Originally Posted by FCobra94

Huh?

The LPFP usually primes (if needed) when you open the door, trunk, etc. Not sure why yours would "come on" any later than that.

yup, I hear a faint whine when I unlock the doors, the fuel pump priming....

[neyshule]

what about parts in the engine like check value, does it start to work?

[robthewrench]

Originally Posted by FCobra94

Huh?

The LPFP usually primes (if needed) when you open the door, trunk, etc. Not sure why yours would "come on" any later than that.

I don't think the OPs comes on later, but I do think that a shudder or rough start up condition is most likely linked to lack of fuel pressure. It may that his fuel pump is not able to easily reach the required pressure due to a pump or electrical issue.

[Aashenfox]

I wonder how much role the LPFP is playing, since the main symptom of HPFP failure is long cranking. I suppose then that its the HPFP that does the priming.

Originally Posted by Aashenfox

I wonder how much role the LPFP is playing, since the main symptom of HPFP failure is long cranking. I suppose then that its the HPFP that does the priming.

^^ This.

[HCGxKaLiBeR]

Now I know why my car starts like crap this winter in CT.

I did a experiment:

1. Unlocked the door and jumped in started the car, engine started after a slightly long crank, RPM jumped back and forth, etc. (In another word, started like sh*t)

2. Unlocked the door, inserted the key and waited a few seconds, engine started normal.

In conclusion, engine oil and perhaps gas are being pumped after ignition.

[Douche]

Originally Posted by HCGxKaLiBeR

Now I know why my car starts like crap this winter in CT.

I did a experiment:

1. Unlocked the door and jumped in started the car, engine started after a slightly long crank, RPM jumped back and forth, etc. (In another word, started like sh*t)

2. Unlocked the door, inserted the key and waited a few seconds, engine started normal.

In conclusion, engine oil and perhaps gas are being pumped after ignition.

Brilliant.

[weq92f]

In an early software update to the E9X, BMW had the fuel pump prime up as soon as a door was opened. This was an attempt to prevent long cranks and probably good 'tonic' in their eyes regarding the fuel pump failures.

Same is true for my GM V8 6mt RWD beater, put the key in and turn it to the accessory position. Then listen and let the tank mounted fuel pump go through its prime cycle ( about 4 seconds ) before cranking over the engine to get the best possible result.

Hth,

-klb

Originally Posted by valter

Brilliant.

lol dat electric oil pump doe

[Douche]

Originally Posted by FCobra94

lol dat electric oil pump doe

Fah sho

[ferocity02]

Originally Posted by HCGxKaLiBeR

Now I know why my car starts like crap this winter in CT.

I did a experiment:

1. Unlocked the door and jumped in started the car, engine started after a slightly long crank, RPM jumped back and forth, etc. (In another word, started like sh*t)

2. Unlocked the door, inserted the key and waited a few seconds, engine started normal.

In conclusion, engine oil and perhaps gas are being pumped after ignition.

Fuel pump primes when you unlock the car (whereas most cars prime the fuel pump when you turn the ignition on). If the fuel pump isn't done priming before you try to start it then I suppose this could cause a longer crank, but usually fuel pressure comes up to full within a second.

Pretty sure these cars have mechanical oil pumps, so no oil is pumping until the engine is running.

[Tiago@VRSF]

If you have the latest software, the fuel pump will prime when you unlock or open your door.

[neyshule]

I don't think engine oil will be pumped without a running engine, but besides fuel pump, are there any other parts also starting work????? like VANOS??

[Meeni]

The oil pump turns with the crankshaft. It cannot prime when the engine is not turning.

[NGEE]

Originally Posted by Tiago@VRSF

If you have the latest software...

Key point.

[Aashenfox]

Just to throw my data in here, it doesn't matter how quick I jump in my car and hit the button, I cannot cause a long crank condition, my car fires up instantly, and I'm pretty spry, I'm not taking my time. JM2C