GEN 2 Cranking with full throttle following oil change

[EricM]

SWhat is going on with all these moving parts while you are cranking it over with no oil?

Cranking without actually firing the engine puts no load on the rod bearings. The whole point of priming the system is to protect the rod bearings when it starts. Priming the oil system by cranking the engine without ignition allows the oil pump to immediately put oil pressure to the bearings when it is started, and prevents them from being hammered by the pistons for about 2 seconds while the oil filter (and the passage downstream of it that also drained when you pulled the filter) is filling.

There is significant oil pressure in the rod bearings simply from cranking the engine, before it even starts (again assuming we are talking about an engine that didn't just have it's oil changed with a non-primed system). It might take 2 seconds for it to fully go up into the heads at startup, but the rod bearings are by FAR the #1 most important thing that needs a pressurized oil film to survive, so they get oiled first and they get pressurized before the engine even fires.

You may not believe it matters, but I can clearly hear the difference in my garage when I fire them up after an oil change. If I don't prime it, the engine always makes slight ticking/tapping noise for a few seconds. It never does that when primed or during any other startup that isn't immediately after an oil change. Is that going to destroy the engine? Probably not. Is the ticking/tapping coming from metal hitting metal? Yes. I have the option to spend an extra 5-10 seconds to avoid that metal to metal contact, so I do it.

Bottom line is it's pretty stupid not to prime it when you consider the tiny amount of effort it takes to do it. All you have to do is push a gas pedal to the floor and crank the engine for 5 to 10 seconds. It's not like when are breaking out an Accusump to prime it.

 

[Jason Snokhous]

Cranking without actually firing the engine puts no load on the rod bearings. The whole point of priming the system is to protect the rod bearings when it starts. Priming the oil system by cranking the engine without ignition allows the oil pump to immediately put oil pressure to the bearings when it is started, and prevents them from being hammered by the pistons for about 2 seconds while the oil filter (and the passage downstream of it that also drained when you pulled the filter) is filling.

There is significant oil pressure in the rod bearings simply from cranking the engine, before it even starts (again assuming we are talking about an engine that didn't just have it's oil changed with a non-primed system). It might take 2 seconds for it to fully go up into the heads at startup, but the rod bearings are by FAR the #1 most important thing that needs a pressurized oil film to survive, so they get oiled first and they get pressurized before the engine even fires.

You may not believe it matters, but I can clearly hear the difference in my garage when I fire them up after an oil change. If I don't prime it, the engine always makes slight ticking/tapping noise for a few seconds. It never does that when primed or during any other startup that isn't immediately after an oil change. Is that going to destroy the engine? Probably not. Is the ticking/tapping coming from metal hitting metal? Yes. I have the option to spend an extra 5-10 seconds to avoid that metal to metal contact, so I do it.

Bottom line is it's pretty stupid not to prime it when you consider the tiny amount of effort it takes to do it. All you have to do is push a gas pedal to the floor and crank the engine for 5 to 10 seconds. It's not like when are breaking out an Accusump to prime it.

So you put the accelerator to the floor while your foot is on the brake and hit the push to start button and hold the button down? What keeps the engine from instantly firing up?

 

[EricM]

So you put the accelerator to the floor while your foot is on the brake and hit the push to start button and hold the button down? What keeps the engine from instantly firing up?

Yes. In a Ford, putting the accelerator to the floor prior to cranking the engine shuts off the injectors. No fuel, no start.

 

[Jason Snokhous]

Interesting. Thanks for sharing the info.

 

[Dustan]

I had a 2007 Aston Martin Vantage that stated in the manual to do this procedure if the car sat for more than a week. That was a dry sump engine. I’m wondering if this may have any effect on the cam phasers. My truck sits for most of the week and this procedure couldn’t hurt. All the cam phaser complaints come on start up of a cold engine.

 

[CigarPundit]

Cranking without actually firing the engine puts no load on the rod bearings. The whole point of priming the system is to protect the rod bearings when it starts. Priming the oil system by cranking the engine without ignition allows the oil pump to immediately put oil pressure to the bearings when it is started, and prevents them from being hammered by the pistons for about 2 seconds while the oil filter (and the passage downstream of it that also drained when you pulled the filter) is filling.

There is significant oil pressure in the rod bearings simply from cranking the engine, before it even starts (again assuming we are talking about an engine that didn't just have it's oil changed with a non-primed system). It might take 2 seconds for it to fully go up into the heads at startup, but the rod bearings are by FAR the #1 most important thing that needs a pressurized oil film to survive, so they get oiled first and they get pressurized before the engine even fires.

You may not believe it matters, but I can clearly hear the difference in my garage when I fire them up after an oil change. If I don't prime it, the engine always makes slight ticking/tapping noise for a few seconds. It never does that when primed or during any other startup that isn't immediately after an oil change. Is that going to destroy the engine? Probably not. Is the ticking/tapping coming from metal hitting metal? Yes. I have the option to spend an extra 5-10 seconds to avoid that metal to metal contact, so I do it.

Bottom line is it's pretty stupid not to prime it when you consider the tiny amount of effort it takes to do it. All you have to do is push a gas pedal to the floor and crank the engine for 5 to 10 seconds. It's not like when are breaking out an Accusump to prime it.

Makes sense. It would be interesting to know what the Ford shop manual says about this, and to hear from @FordTechOne

 

[goblues38]

Just because you drain the oil in the pan, and filter, does not mean there is no oil on surfaces like the pistons. They are still "lubricated" plenty to deal with a 1-2 second interruption of oil flow at start up.

When you change your oil, it is maybe 1-2 seconds on start up for the oil system to become pressurized. you can actually hear it happen. It sounds worse then it is.

 

[Ruger]

Yes. In a Ford, putting the accelerator to the floor prior to cranking the engine shuts off the injectors. No fuel, no start.

And make damn sure that the thing is in Park or Neutral.

 

[CigarPundit]

Just because you drain the oil in the pan, and filter, does not mean there is no oil on surfaces like the pistons. They are still "lubricated" plenty to deal with a 1-2 second interruption of oil flow at start up.

When you change your oil, it is maybe 1-2 seconds on start up for the oil system to become pressurized. you can actually hear it happen. It sounds worse then it is.

According to the poll, the consensus by a large majority is that this is not only unnecessary, but BS. I doubt that there is problem with not doing it, but I also don’t think there is any harm in it. If priming the system could reduce some incremental wear on rod bearings or other parts, I say, “why not?”

 

[JohnyPython]

I wonder if those with cam phaser rattle tried this procedure to see if this stopped the rattle.