puma

either that or the fuse to pull when you remove the car from storage, etc.

I always read that it was better to pull fuse C4, which is the fuel pump fuse so that you don't get fuel pressure when trying to build the oil pressure (car won't fire up).

But, the way i see it is that by cutting the fuel pump, the injectors will still fire as well as the coils. While the injectors fire, it will put some fuel in the chamber (not much) and remove all fuel pressure from the system, which would then need to be primed before starting the car.

I checked and saw fuse C2, which is injectors, coils and O2 sensor heater. Wouldn't it be better to pull that one instead? You don't get any fuel in the chamber, you don't get any unnecessary spark from the plugs and you still have fuel pressure ready for when you put the fuse back in.

Plus, if you do a compression test, you don't have to worry about the first couple of cycle still spitting fuel at you while you crank the engine with no plugs.

That's without considering the danger of the coil sparking at you if you let them plugged hanging down. (ask how i know...)

But since these cars are still fairly new to me, i thought i would ask, i always like some techincal discussion.

thanks

Macster

Unless I'm totally clueless if the engine has been run recently and you just changed the oil there's no reason to remove any fuse to crank the engine over to build oil pressure.

The factory manual doesn't have this step in its oil change section and no tech I know of does this.

After draining the crankcase, the oil tank, the turbo oil containers, the manual says to add 7.8l of oil to the oil tank filler tube and wait a while for some oil to flow from the tank to the crankcase. There is no time given. If you want wait 15 minutes. 30 minutes. Whatever you feel ok with.

Then start the engine and let it idle until an oil level check can be done and add more oil to bring the level up so all 7 of the lower segments/bars are lit and the oil level is at the max line. Done.

BTW, my Boxster is in for a camshaft actuator solenoid and camshaft actuator and I saw the camshaft cover off. I asked if after reassembly if the tech would dry crank the engine to get oil back to the engine's upper end and he said there's no need. The Boxster's oil pressure sensor is located in a camshaft cover and oil pressure appears almost instantly. I asked about my Turbo and the tech pointed out the Turbo's oil pressure sensor is up around the filter housing and is quite a ways from the oil pump and the fuel pressure rises almost instantly when the engine is cranked.

But if you want to remove the fuel fuse you should be ok. A bit of of gas could get injected sure even with no fuel pump but if the engine's been sitting long fuel pressure might have bleed away.

If you think the engine's really dry squirt a bit of clean engine oil in each spark plug hole then turn the engine over a few complete revs by hand before you then use the starter to spin the engine some. Don't run the starter long. Just a few seconds then let it cool down a few minutes or so before you hit it again. Depends upon how much oiling you think the engine needs.

Manually putting a bit of oil in each cylinder helps provides a bit of early/extra lube to the upper ends of the cylinders and pistons.

The bit of oil will smoke some upon engine start but unless you go overboard with the oil, and you shouldn't, the smoking will be over with before you know it.

Sincerely,

Macster.

Danyol

I pull c4 before an oil change, crank over to relieve fuel pressure, then change oil. Squirt some oil into the filter port before installing filter. After refilling crank, till I see pressure on the gauge and reinstall fuse.

This is advice i've read from our resident guru, Kevin. On my last pcar I didn't do this, my heart would miss a beat watching the time it took for the oil pressure to rise after firing up the engine!

Kevin

Alex, before you start to do your oil change, pull the fuse>fuel pump and crank the engine. You will purge any fuel in the injector. Keep the fuse out and do your oil change. When you crank the engine over when you get ready to prime for "oil pressure" the engine will not fire..

Alex can you tell Maxster that there are owners that want to pre-prime there engines.. And yes, I am a tech that does pull all my customer fuses to pre-prime the oil system on every turbocharger install AND oil change.

Kevin

Danyol, we posted a minute apart.. BTW can you tell us how long that "heart beat" was while you watch ZERO oil pressure on the gauge while the engine was running...

Danyol

More than one beat.. 2 or 3 seconds

puma

ok i understand that but what i want to do is mostly a compression test and the car has not been running for while (winter).

Wouldn't it be "easier" or more appropriate to just pull C2? Maybe there is something that i don't know that makes it a bad idea but if not, i feel it would be a better fuse to pull, maybe just nobody ever thought about it?

just want to see if my reasoning is good or not.

Kevin

I would caution pulling the injector and coil fuse. The ECU gets power and you have the injector and coil drivers in the ECU. Shorting to ground will cause a FAILED ECU>> $1600 ECU vs unpluging the coil packs and removing the fuel pump fuse is the safe method.

Macster

So, is Alex your owl?

Tell me yourself.

A turbo charger change I agree a bit of cranking with the fuel pump disabled probably a good thing. However, I hope there is a way to pre-oil the turbo chargers to ensure the bearings are not totally dry cause I would think by believing the engine needs a bit of cranking beforehand that the turbo's are completely dry and begin turning as the engine cranks away.

But after every oil change? When I presume the engine was run maybe just minutes prior to the oil change? And I presume not left on the lift with the drain plugs out for a long long time?

Ok. It is your decision or that of the owner and I can't argue with a business that gives customers what they want.

But if these engines so delicate as to need dry cranking after an otherwise normal and regular/periodic oil change I'm wondering if I want to continue to own a Turbo?

And if this delicate an engine who in God's name would ever consider hopping one up? It is is a wonder they hold together any length of time unmodified.

Sincerely,

Macster.

ltc

What speed will a turbocharger be spinning at with fuse C4 pulled and the engine cranking under starter only (no combustion)?

I don't see your concern regarding turbocharger pre oiling...

Kevin

Macster> is the OP. Puma=Alex..

When you change turbochargers on the 930,965,993TT,996TT & 997TT you will have oil siphoning out of the oil feed/supply line. Air will migrate all the way into the cam housing or crankcase. You need to bleed and pre-prime the oil system or you will have a dry startup with the turbochargers. At idle the K16s and K24's are turning 18,000RPM's a second without oil equal bearing transfer on the turbine shaft. Turbo failure is certain.

Staring at your oil pressure gauge on start up after you do a oil change which reads "0" for more than 4 to 5 seconds is something that does not need to occur.

Pre-priming your engine oil system is "my" advice to everyone that owns these cars. It is good common sense and preventative maintenance.

If someone like yourself doesn't want to be bothered with it.. So be it.. However, on this thread the OP > Puma > Alex was asking for other methods to crank the engine.

Kevin

Lewis, you don't see the benefit of prelubing the turbochargers on a new install?

No HTwo O

Kevin do you still need to do this if we have your Oil Line Check Valves installed?

Kevin

New turbo install >yes.. Oil change YES.. What am I missing?

Danyol

As an enthusiast I tend to do more preventative stuff on my cars, it's your choice.

Like Oil changes <5k miles, priming reduces start-up wear = Cheap Insurance. I forgot to mention the metallic sounds I heard on my previous 911 while watching the oil pressure at zero for a few seconds at start-up after oil changes. I've never had to experience that on the turbo with the C4 trick.