Is "priming" a vehicle beneficial?

[lawman1909]

Is it beneficial especially on cold mornings to "prime" the engine, fuel pump, etc. by turning the key to the accessory position for a few seconds and then cranking the engine? I have heard recently that doing this reduces wear to the engine and fuel pump. Any credible input is welcome

 

[Jimzz]

It helps a little but not much. Most newer cars prime much faster than older ones that bleed down more as the car sat.

Same as letting the car warm up is a waste now. Newer cars warm up faster by being driven. Start car and by the time you have your seat belt on you can drive away.

 

[Quest]

electric fuel pump is submerged in the fuel (and gets it's lubrication from there---the fuel), so no need to prime it.

Engine bearings, etc. get it's lubrication as soon as it fires up, where the oil pump with pressurise and suspends the bearings, etc.

So, why you think priming the engine is beneficial?

Q.

 

[spasm3]

I see no advantage. The fuel system has fuel in it, pressure comes back up pretty quick. I don't see that much that would save starter wear.

 

[ueberooo]

it helps heat up the O2 sensor; it s a very small benefit. So, I don't make a point to wait to prime it on startup, but I will turn it off on a traffic light sometimes when engine is cold to reduce obnoxious cold running rich burn fumes; then turn key to on, to warm the O2 sensor while waiting for light. This reduces the driving time until the car runs in clean mode and when the o2 sensor works correctly without expending time or effort.

 

[dishdude]

I'm not even sure newer cars power up the fuel pump until the key is turned to start. This isn't even an option on cars that have push button start!

 

[Bluestream]

No, just turn the key and start it up

 

[splinter]

My modern cars will start as quickly as the key can be turned.

I still momentarily KOEO to get my bearings...and then focus in on the OP gauge.

 

[oilpsi2high]

When it's single digits, if I get in and immediately turn the key the engine sometime sputters and dies. If I turn it to ON and then wait for the pump to prime and then START there is never any issues, even down below zero.

Chalked it up to being a somewhat low compression engine running bigger than stock fuel injectors.

 

[JHZR2]

They start fine without it, and if you check pressure in the fuel injection line, youll find it with the car off (most likely...).

That said, all my cars including my DI vehicle, all make a bit of fuel pump noise in the on position, so it does at least spin up a second. Its one of those cant hurt things...

A related note... I had heard more than once that one should turn on their headlights before starting the car, so that the battery could start moving some current. That is counter intuitive to me, since then the battery will have a lower voltage under load. But I will say that the key sitting in on for a second has the same sort of effect, likely in a more beneficial way (e.g. heating the O2 sensor), so isnt a bad move...

 

[HerrStig]

Newer EFI systems are series regulated, no return line to the tank. Not much there to prime since fuel, like water, doesn't compress well. As far aa "warming up the battery", I'd rather do that with the starter. With a weak battery you might just drain it enough playing with the headlights to not be able to start.

 

[lawman1909]

Both mornings I have not primed my CR-V I get a grinding sound. No clue where it is from but was told in a few CR-V forums and from a mechanic that priming the engine reduces this to near zero occurrences.

 

[Finz]

My '05 Accord... All 7th generation 4 cyl accords... have a marginally sized battery which can be unnerving on cold mornings

Some time ago, I started turning the key to on position and waited about 2 seconds before starting.

Makes a heck of a difference... warm weather or cold... And car starts a bit faster

 

[bvance554]

I've never heard of such a thing as 'priming' a fuel injected engine. Never had a starting issue either so I don't plan on starting this 'priming' regimen.

 

[klt1986]

Originally Posted By: lawman1909
Both mornings I have not primed my CR-V I get a grinding sound. No clue where it is from but was told in a few CR-V forums and from a mechanic that priming the engine reduces this to near zero occurrences.


When you hear the noise is it right when you bump the key over to start?

 

[SteveSRT8]

Originally Posted By: dishdude
I'm not even sure newer cars power up the fuel pump until the key is turned to start. This isn't even an option on cars that have push button start!


Not true on all of them. My new Ram can easily be turned to ACC by simply not pushing the brake pedal but still pushing the start button...

 

[Hokiefyd]

Originally Posted By: lawman1909
Both mornings I have not primed my CR-V I get a grinding sound. No clue where it is from but was told in a few CR-V forums and from a mechanic that priming the engine reduces this to near zero occurrences.


It could be a mechanical noise from a super cold starter rather than something related to fuel system prime.

The only time I've had to "prime" a fuel injected car is when I had a bad fuel pressure regulator on my 1997 Cadillac Seville, and fuel pressure would bleed down after an hour or so. Hot starts were fine, but cold starts would take a few seconds or cranking/stuttering unless you did the key-on dance to let the fuel pump re-pressurize the system. Once I replaced the fuel pressure regulator, all was well.

On most fuel-injected cars, if you perceive a significant difference in time-to-start because of priming or not, check the fuel pressure regulator...you may be bleeding fuel back to the tank overnight.

 

[hattaresguy]

No.

Unless your car has a Rolls Royce Merlin under the hood...

 

[itguy08]

Can't think of how it would help. As soon as the pump starts spinning it's going to build pressure. And if the car is so poorly designed that it needs you to manually prime it then it is a POS.

The only vehicles that I know of that prime are the Ford Ecoboost 3.5's (and possibly all DI engines). When you unlock the doors or open the drivers door the low pressure pump turns on to build pressure for the High Pressure Fuel Pump. It's all automatic and requires no intervention by the driver.

 

[paulo57509]

I don't particularly think it's beneficial to "prime" the fuel pump prior to engaging the starter. I don't think the fuel pump circuit is hot with the key in the ACC position.

All of my vehicles will run the fuel pump for a few seconds to build pressure when you turn the key from OFF to the ON position.

I should say "most" of my vehicles. I don't know if the LS400 does this because I really can't hear the pump or a relay switching on or off.

I've gotten into the habit (for no particular reason) of letting the fuel pump run through the pressure building process or (in the case of the Lexus) wait until the instruments and warning lights cycle before starting up the engine.