Cranking engine with coil disconnected

Not worth the effort. I have never seen this recommended in any manufacturer's service literature. If you drain and change the oil and filter with the engine warm as you should, everything in there that needs oil still has a coating of oil sufficient to protect it well beyond the 5 or

6 seconds needed to restore the flow of oil after the engine starts. Removing the coil wire and cranking the engine with an open coil tower is a good way to start a carbon track which later results in failure. If you still choose to do this, disconnect the primary power to the coil - not the secondary. On an EFI engine, this may generate a fault code for you to track down.

It is a good idea to prime or prelube a freshly built engine or one which has been inactive for a very long time. This should be done with the distributor removed and the oil pump driven by a healthy drill and an adapter for the purpose.

Lugnut

Overkill. What I do is fill the oil filter (if possible) when reinstalling it. Minimizes the time spent at 0psi without needing to disconnect and monkey with the ignition.

If you're going to do it, I'd try disconnecting the distributor input wires instead - no juice in = no stress on the coil and no chance of arcing high voltage inside the cap. Or ground the coil wire. It's not practical on most newer cars - my TA has 8 coils and no distributor... I'd have to ground 8 coils.

My thought is most people don't bother doing ANYTHING when they bother changing the oil and your average engine still makes 100,000+ miles... so I'm sure it's overkill.

Ray

And, oil wets metal. Some ads for these pre-oilers claim oil drains completely away from bearing surfaces when car is not running. Actually, it is hard to get bearing surfaces completely clean of oil. Oil stays there a LONG time. Now, this is just a film, and will not support heavy pressure of high speed running, but as long as you do not start car at full throttle, pre-oiling is not really necessary.

If the engine has sat a year or so without running, that is something else.

They intentionaly use oils that stick to metal. :)

In the early days of the industrial revolution machines were lubricated with rapeseed oil because it would cling to metal. (Canola oil is a variety of rapeseed oil developed by selective breeding to reduce some unhealthy fats and make it the second healthiest eating oil after olive.)

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funny story...we were priming my Camaro engine on the stand and forgot to plug the oil pressure gauge fitting. Dunno the PSI, but fortunately my garage has flourescent lights that didn't seem to mind being sprayed with a 6' high oil fountain.

Ray

Thanks for all the advice. I probably won't bother to do it when I change the oil. I'd fill the oil filter with oil if I could, but in many cases the filter is horizontal, which makes doing that basically impossible.

I do have a car that hasn't been driven in 9 to 12 months. It has been sitting less than a year, and I may have started the engine and ran it for a few minutes once, but I don't remember how long ago that was. It has definitely been sitting for at least six months, though. So I'd rather not suddenly shock the engine by getting in and starting it up in the normal way.

Would it be okay to crank the engine for about thirty seconds with the coil completely disconnected? By "completely," I mean that I will pull off the heavy-duty wire that goes to the distributor *and* I will disconnect the wires that supply the 12V to the coil's primary side.

Phil

You can remove the spark plugs and squirt some motor oil directly into the cylinders before trying to start the engine. When my car has been sitting for a few days I crank the engine over a few times without pressing down on the gas pedal. The engine doesn't fire. I wait a second or two imaging oil is running down the cylinder walls and other helpful places and doing the engine good, then start the engine. I don't know if it does any good, but it does no harm.

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If you disconnect the 12V wires going to the coil, you shouldn't have to do anything else. At least when coils were coils. :)

A fuel pump fuse would be easier.

Hi Sam,

Thanks for the suggestion. I like that idea. I think that should work on fuel-injected vehicles, but I don't know if it would always work on those that have a carb. Depending on how long the engine has been sitting, there might be enough fuel left in the carb for the engine to start briefly before conking out. If the engine has been sitting for a year, though, I would think that it ought to work fine.

Phil

You are most likely correct. But since disconnecting the wire carrying the high voltage from the coil to the distributor is so easy, I figured I'd go ahead and do that too. Besides, the guys at the Department of Redundancy Dept. think it's a great idea. :-)

Phil

wrote

Some carberaters have an electronic fuel cutoff valve. I've found that cranking with the fuel supply on tend to destroy a spark plug. But, my Honda service manual simply ask that I ground the high voltage line (secondary) anyway.