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Any benefit in priming fuel pump? #4458402
07/13/17 03:43 PM
07/13/17 03:43 PM
Joined: Apr 2013
Posts: 6,077
FL, USA
gregk24 Offline OP
gregk24  Offline OP

Joined: Apr 2013
Posts: 6,077
FL, USA
Title says it all. I've always turned the ignition to "run" for about two seconds before starting my cars to prime the fuel pump. Does this actually have any merit?


2012 Honda Accord EX-L K24z3
56,xxx miles
PPPP 0w20 / Fram Ultra

2014 VW Jetta SE 1.8T ea888
44,xxx miles
Castrol Edge 0w40 / OEM filter
Re: Any benefit in priming fuel pump? [Re: gregk24] #4458405
07/13/17 03:46 PM
07/13/17 03:46 PM
Joined: Apr 2017
Posts: 1,520
Ontario, Canada
mightymousetech Offline
mightymousetech  Offline

Joined: Apr 2017
Posts: 1,520
Ontario, Canada
Originally Posted By: gregk24
Title says it all. I've always turned the ignition to "run" for about two seconds before starting my cars to prime the fuel pump. Does this actually have any merit?


Well, BMW changed the programming on the N55 engines so the low pressure fuel pump primes as soon as you unlock the doors. They did this to try and prevent damage to the HPFP.

I have always said, it is best to turn the key to the "on" position, wait for the fuel pump to prime the system, when the check engine light goes off, start the car.

Last edited by mightymousetech; 07/13/17 03:48 PM.

Mighty Mouse Tech
BMW Tech, Former Acura Tech
2010 Civic Si Castrol 0W40, Redline MTL
2013 BMW 135i M Sport Edition Castrol 0W40, Redline MTL
Re: Any benefit in priming fuel pump? [Re: gregk24] #4458427
07/13/17 04:10 PM
07/13/17 04:10 PM
Joined: May 2014
Posts: 3,942
Columbus,Nebraska
Yah-Tah-Hey Offline
Yah-Tah-Hey  Offline

Joined: May 2014
Posts: 3,942
Columbus,Nebraska
My 04 Camry V6 starts after about two seconds of cranking so there must be fuel at the injectors. Don't think it makes any difference at all.

Re: Any benefit in priming fuel pump? [Re: gregk24] #4458448
07/13/17 04:25 PM
07/13/17 04:25 PM
Joined: Nov 2008
Posts: 9,592
Phoenix
dishdude Offline
dishdude  Offline

Joined: Nov 2008
Posts: 9,592
Phoenix
No.


2018 Challenger SRT 392 PUP 0w-40 Wix 57899XP
2018 GTI
Re: Any benefit in priming fuel pump? [Re: gregk24] #4458458
07/13/17 04:30 PM
07/13/17 04:30 PM
Joined: Dec 2016
Posts: 7,991
Waco, TX
Linctex Offline
Linctex  Offline

Joined: Dec 2016
Posts: 7,991
Waco, TX
I don't mind at all when my engine makes several revolutions before it fires off.

I'd rather it have a second or two to prime the oil pump first.

On my drag car, I wouldn't turn on the Ign/fuel pump until I saw oil pressure come up (3-4 seconds cranking)


"The evidence demands a verdict".
(Re:VOA)"it's nearly impossible to actually know the particular additives that are in there at what concentrations."
Re: Any benefit in priming fuel pump? [Re: gregk24] #4458461
07/13/17 04:32 PM
07/13/17 04:32 PM
Joined: Apr 2016
Posts: 813
Specific Ocean
Kibitoshin Online content
Kibitoshin  Online Content

Joined: Apr 2016
Posts: 813
Specific Ocean
Most cars don't turn on the fuel pump unless the engine is started.


Shin Gekiretsu Shin'ou'hou
01 Toyota Tundra 2WD V8 4.7L
02 Chevy Silverado C1500 V8 5.3L
Re: Any benefit in priming fuel pump? [Re: gregk24] #4458486
07/13/17 04:43 PM
07/13/17 04:43 PM
Joined: Sep 2016
Posts: 1,418
Minnesota
bioburner Offline
bioburner  Offline

Joined: Sep 2016
Posts: 1,418
Minnesota
my old 97 Jeep Wrangler one could hear it run as soon as you turned the key to on and if you attempted to start before it stopped you were just wasting your time and battery

Last edited by bioburner; 07/13/17 04:43 PM.


97 Ford E350 D,99 F350 dually D
13 Scion Xb
12 Ford Transit Connect
06 Nissan Xterra
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13 Madass
Re: Any benefit in priming fuel pump? [Re: gregk24] #4458497
07/13/17 04:53 PM
07/13/17 04:53 PM
Joined: Jun 2005
Posts: 11,942
Santa Barbara, CA
bdcardinal Offline
bdcardinal  Offline

Joined: Jun 2005
Posts: 11,942
Santa Barbara, CA
I do it on my Mustang. You can hear the fuel pump priming. I will turn the key to "on" and wait until fuel gauge moves up, then I hit the key.


2014 Ford Mustang GT Track Pack
1995 Ford Mustang GT

Ford/Mazda Parts Counter
NRA Benefactor Member
Opinions expressed are my own.
Re: Any benefit in priming fuel pump? [Re: Kibitoshin] #4458518
07/13/17 05:11 PM
07/13/17 05:11 PM
Joined: Mar 2004
Posts: 21,810
Upstate NY
Donald Offline
Donald  Offline

Joined: Mar 2004
Posts: 21,810
Upstate NY
Originally Posted By: Kibitoshin
Most cars don't turn on the fuel pump unless the engine is started.


How would the car ever start? Most turn on for 10 seconds and then stay running as long as there is oil pressure.


2015 Subaru Forester 2.5 engine/CVT
2015 Ford F250 w/Powerstroke
2016 Subaru Crosstrek CVT (wife's)
Re: Any benefit in priming fuel pump? [Re: Kibitoshin] #4458548
07/13/17 05:54 PM
07/13/17 05:54 PM
Joined: Oct 2014
Posts: 13,275
Canyon County Idaho
CT8 Offline
CT8  Offline

Joined: Oct 2014
Posts: 13,275
Canyon County Idaho
Originally Posted By: Kibitoshin
Most cars don't turn on the fuel pump unless the engine is started.
O.K.


2015 Ford F150 2.7
2018 Ford F350 6.2
Re: Any benefit in priming fuel pump? [Re: gregk24] #4458658
07/13/17 07:41 PM
07/13/17 07:41 PM
Joined: Dec 2008
Posts: 2,408
CA
raytseng Offline
raytseng  Offline

Joined: Dec 2008
Posts: 2,408
CA
only needed if you have a problem with your car.

To be specific this doesnt mean extra cranks. it means like even though the car cranks the first few seconds it stumbles or sputters or dies. if it cranks for 2seconds but catches perfectly you didnt change anything.

and even so this might only happen on cold start for more than 12 hours off.

my basis is when i replaced a fuel pump but did not seat an oring correctly. so the above symptoms are the real symptoms when fuel pressure is not achieved.

Last edited by raytseng; 07/13/17 07:43 PM.
Re: Any benefit in priming fuel pump? [Re: Donald] #4458683
07/13/17 07:58 PM
07/13/17 07:58 PM
Joined: Apr 2016
Posts: 813
Specific Ocean
Kibitoshin Online content
Kibitoshin  Online Content

Joined: Apr 2016
Posts: 813
Specific Ocean
Originally Posted By: Donald
Originally Posted By: Kibitoshin
Most cars don't turn on the fuel pump unless the engine is started.


How would the car ever start? Most turn on for 10 seconds and then stay running as long as there is oil pressure.


I meant while the engine is starting. I've noticed on Toyota's that turn on the fuel pump as the engine cranks and runs. That's why you can't hear them prime when they is turned to the on position.


Shin Gekiretsu Shin'ou'hou
01 Toyota Tundra 2WD V8 4.7L
02 Chevy Silverado C1500 V8 5.3L
Re: Any benefit in priming fuel pump? [Re: gregk24] #4459126
07/14/17 09:53 AM
07/14/17 09:53 AM
Joined: Jul 2011
Posts: 1,224
Houston, TX
Coprolite Offline
Coprolite  Offline

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Posts: 1,224
Houston, TX
I don't believe this to be relevant on my 2012 F150 or 2012 BMW 335i. One is started with a button, so the computer controls the whole process and the other starts with a turn of the key that is for all intents and purposes a button. A flick of the ignition and it will start. I didn't realize this consciously until I drove my family's older Hondas. A flick of the ignition there wasn't anywhere near as productive....

I used to prime up the fuel pump on my 1967 912, but that wasn't a voluntary thing.

Re: Any benefit in priming fuel pump? [Re: Coprolite] #4459140
07/14/17 10:12 AM
07/14/17 10:12 AM
Joined: Apr 2017
Posts: 1,520
Ontario, Canada
mightymousetech Offline
mightymousetech  Offline

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Ontario, Canada
Originally Posted By: Coprolite
I don't believe this to be relevant on my 2012 F150 or 2012 BMW 335i. One is started with a button, so the computer controls the whole process and the other starts with a turn of the key that is for all intents and purposes a button. A flick of the ignition and it will start. I didn't realize this consciously until I drove my family's older Hondas. A flick of the ignition there wasn't anywhere near as productive....

I used to prime up the fuel pump on my 1967 912, but that wasn't a voluntary thing.


On the BMW, you will hear the fuel pump priming when you unlock the doors, so it is doing it without you knowing.

Last edited by mightymousetech; 07/14/17 10:21 AM.

Mighty Mouse Tech
BMW Tech, Former Acura Tech
2010 Civic Si Castrol 0W40, Redline MTL
2013 BMW 135i M Sport Edition Castrol 0W40, Redline MTL
Re: Any benefit in priming fuel pump? [Re: mightymousetech] #4459193
07/14/17 11:36 AM
07/14/17 11:36 AM
Joined: Jul 2011
Posts: 1,224
Houston, TX
Coprolite Offline
Coprolite  Offline

Joined: Jul 2011
Posts: 1,224
Houston, TX
Originally Posted By: mightymousetech
Originally Posted By: Coprolite
I don't believe this to be relevant on my 2012 F150 or 2012 BMW 335i. One is started with a button, so the computer controls the whole process and the other starts with a turn of the key that is for all intents and purposes a button. A flick of the ignition and it will start. I didn't realize this consciously until I drove my family's older Hondas. A flick of the ignition there wasn't anywhere near as productive....

I used to prime up the fuel pump on my 1967 912, but that wasn't a voluntary thing.


On the BMW, you will hear the fuel pump priming when you unlock the doors, so it is doing it without you knowing.


I would guess that it is linked to when it senses the key in the proximity of the car, not triggered by the actual act of unlocking. I would buy that it is linked to touching the door handle which will trigger both actions. It is also evident that it is doing it. The computer starts to boot up and all the systems get ready.

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