PDA

View Full Version : What's the best way to crank the engine?


yamato
09-14-2003, 02:57 PM
During a cold start. Is it necessary/better to first turn the key from the off position to the ON position, then wait a few sec, then crank the engine? There is a "zzzzziiiipppp" sound for a sec when the key goes from off to ON. Is that the sound from the fuel pump?

Does it make any difference to go from off to crank in one shot?

I haven't experiment enough times to make a good conclusion, so far it appears to me the former results in a smoother start.

Thanks.

tgravo2
09-14-2003, 03:01 PM
do you have xenons?

When I put my key in the on position I can hear my lights auto leveling, kind of makes that zip sound.

yamato
09-14-2003, 03:10 PM
do you have xenons?

When I put my key in the on position I can hear my lights auto leveling, kind of makes that zip sound.

yes, i have xenons.

I just tried it again. The sound seems to come from the rear and to be more accurate it sounds like releasing air from a tire valve. That's why I guess it could be from a fuel pump... :dunno:

tgravo2
09-14-2003, 03:30 PM
yes, i have xenons.

I just tried it again. The sound seems to come from the rear and to be more accurate it sounds like releasing air from a tire valve. That's why I guess it could be from a fuel pump... :dunno:

I'm not sure :dunno:

The Roadstergal
09-14-2003, 03:36 PM
The fuel pump makes a humm sound. I heard of that trick with 2002s and cars of that era. I dunno how useful that would be with newer cars; they have a cold start valve that delivers extra fuel when starting. But it doesn't hurt if ya want to do it; extra fuel is just recycled back by the pressure regulator.

PABS
09-15-2003, 08:10 AM
Just turn the key :rolleyes:

Kaz
09-15-2003, 11:08 AM
Yeah, just turn the key already. This isn't a 1912 Model T. All those noises are SUPPOSED to be there.

Jetfire
09-15-2003, 11:40 AM
The "zzzz" sound coming from the rear is your fuel pump priming itself. I always let the key stay in the "on" position for a second before starting it. Most newer cars won't have a problem just going straight to start. My Jeep, however, won't start quickly unless I wait for the pump to prime itself. If I don't wait those two seconds, I'll end up cranking it for longer than normal. I suspect it's a fuel filter/ignition issue.

Kaz
09-15-2003, 12:00 PM
The fuel system priming shouldn't be an issue these days with high-pressure systems and the requirement to not let them vent to the outside. I had a fuel line leak on an old car once and it wouldn't start if I had it parked at a certain angle.

yamato
09-16-2003, 11:34 AM
I haven't experiment enough times to make a good conclusion, so far it appears to me the former results in a smoother start.

Thanks.

Well, I found something interesting yesterday. The engine didn't start at all on my first attempt. I left the key to the ON position for a few seconds before cranking. This is the first time I notice this. I put the key back to OFF, then ON, then crank again, it started. Strange!! I hope this is a one time incident that will never happen again.

GregE_325
09-16-2003, 12:10 PM
Well, I found something interesting yesterday. The engine didn't start at all on my first attempt. I left the key to the ON position for a few seconds before cranking. This is the first time I notice this. I put the key back to OFF, then ON, then crank again, it started. Strange!! I hope this is a one time incident that will never happen again.



Nope, I'm afraid it won't be a one-time incident. If you don't hold the key in the start position long enough for the car to crank the first time, you have to turn it back to Off and then you can attempt to crank it again. This setup is different from most other cars, but that's the way it works.

yamato
10-14-2003, 10:54 PM
During a cold start. Is it necessary/better to first turn the key from the off position to the ON position, then wait a few sec, then crank the engine?

From the day I posted the above until now, I wait these few seconds every time. And there has been no more stalling after the engine starts, and the start has been so much smoother. The rpm ramps up to 1100 and stays there for a while. Unlike the past when I didn't wait this few seconds, the rpm might fluctuate around 800 and sometimes the engine was unable to keep itself running and stalled.

That's one good discovery for myself.

glaws
10-15-2003, 07:37 AM
Some E46 M3's had cold start problems - supposedly fixed by a software change. Mine never did - I just turn the key and crank.

Woody
10-15-2003, 04:01 PM
I think normal cranking time is still up to 8 seconds (holding key in start position). :yikes:

yamato
10-15-2003, 10:46 PM
I think normal cranking time is still up to 8 seconds (holding key in start position). :yikes:

wow. I normally would give up on the 5th second. I haven't tried cranking in the winter, I hope I don't need to break this 8 second barrier.

milski
10-15-2003, 10:55 PM
I would not worry about 8 seconds at all. I remember the manual of my A4 talking about giving up after 30 seconds.

Artslinger
10-16-2003, 06:39 AM
From the day I posted the above until now, I wait these few seconds every time. And there has been no more stalling after the engine starts, and the start has been so much smoother. The rpm ramps up to 1100 and stays there for a while. Unlike the past when I didn't wait this few seconds, the rpm might fluctuate around 800 and sometimes the engine was unable to keep itself running and stalled.

That's one good discovery for myself.

You should not have to do that, if it was my car I would have BMW fix that problem.

baileykb
10-16-2003, 10:59 AM
I have a '97 540 and have come to the conclusion that a straight crank from off is the best. Many say that the E39 has a large electrical-draw at start-up, so they suggest turning all possible electronics off. I used to do that but after playing around with the car I noticed that there is a delay to the to non-essential electronics. Like you say, if the ignition is turned to the on position, without starting the car, you can hear the systems or see then come on after a short delay. I believe this is to have all available power go to the starting system. But I have also noticed that if you have the radio on without the car started, the radio's power is monmetarily interrupted- so this may happen to all of the non-essential electronics. Again, I say just straight crank it.

D///Mill
10-16-2003, 01:36 PM
On my '57 Bel Air, I can pull the coil wire to crank the engine if I just want to get oil pressure and NOT start the engine. I like to do this if the car has sit more than a week. My question:
What's the easiest way to do this with late model Bimmers? Pull all the plug wires? ... OR is there simpler way?
(BTW, I have a 2000 Mcoupe.)
TIA

Pinecone
10-16-2003, 04:41 PM
A second or two to let the fuel system come up to full pressure is a good idea. Not always needed, but still a good idea. With high pressure fuel systems, there is some leak down after sitting.

With the M3 I wait until the 0 stops flashing to turn to start, and have never had it take more than a second or two to start, even after 4+ weeks of sitting.

WRT cranking for oil pressure, these are modern engines, running synthetic oils, you don't need to do that.

Anyway all modern BMWs have a coil per cylinder, so you would have to pull 6 coil packs, and this is NOT pulling the wire simple.

Just start it, but make sure your foot is off the gas to let it start to idle to allow the oil presure to build.

The Roadstergal
10-16-2003, 05:49 PM
Oh, heck with it, just park on an incline and clutch start it. :eeps: ;)

bluer1
10-16-2003, 06:16 PM
The fuel pump makes a humm sound. I heard of that trick with 2002s and cars of that era. I dunno how useful that would be with newer cars; they have a cold start valve that delivers extra fuel when starting. But it doesn't hurt if ya want to do it; extra fuel is just recycled back by the pressure regulator.

She said "regulator." Huh-huh.

:wow:http://www.olga-sosnovska.com/smilies/cupid.gif http://www.sashachase.com/slayerpride/smilies/out.gif http://www.sashachase.com/slayerpride/smilies/heart.gif

Pinecone
10-17-2003, 03:51 AM
The problem can be that after sitting the fuel rail pressure may be down. Say normal is 65 psi, after sitting it may be down to 25 psi. At that point, even the cold start valve will have trouble giving the engine enough fuel.

By waiting a couple of seconds for teh fuel rail to be fuly pressurized allows the cold start valve to work properly.

Look at it this way, you can wiat a second or two before cranking, or you can wait a second or two while cranking. :)

yamato
10-17-2003, 10:50 AM
The problem can be that after sitting the fuel rail pressure may be down. Say normal is 65 psi, after sitting it may be down to 25 psi. At that point, even the cold start valve will have trouble giving the engine enough fuel.

By waiting a couple of seconds for teh fuel rail to be fuly pressurized allows the cold start valve to work properly.


I totally agree with this hypothesis. If I don't wait these few seconds, stalling may occur during start only if the car is left off for more than ~24hours.