Will cranking an engine without oil cause damage? (fuel pump fuse pulled)

[Owen Lucas]

Would cranking for a few seconds cause any damage to an engine with out oil?

I think the bearings would be at the most risk but without a load from combustion, maybe a few revolutions would be OK?

 

[GSCJR]

No damage will be done.

 

[MRC01]

Note: spinning without oil for a few secs is what the engine does on every cold start.

 

[bullwinkle]

No oil in the pan? Not sure I would recommend it, the oil pump COULD lose its’ prime.

 

[Hall]

Note: spinning without oil for a few secs is what the engine does on every cold start.

I thought I saw a demonstration of a typical automobile engine and the oil pump has the engine fully "protected" with oil in fractions of a second. It's not instant but extremely quick.

 

[MRC01]

I thought I saw a demonstration of a typical automobile engine and the oil pump has the engine fully "protected" with oil in fractions of a second. It's not instant but extremely quick.

I've seen that too, yet just because oil appears in one spot of the engine doesn't necessarily mean it's everywhere else at the same time, nor at the pressure or volume needed. Certainly not within a single rotation.

 

[Fitter30]

So when did it have oil in it or a new rebuilt?

 

[MRC01]

No oil in the pan? Not sure I would recommend it, the oil pump COULD lose its’ prime.

This can happen with some Continental aircraft engines. If it sits long enough even with oil in the pan, the oil pump can lose its prime. If the airplane is a taildragger, you can rotate the prop horizontal for ground clearance, then lift the tail up high to flow oil from the pan toward the pump to re-prime it. I've never heard of this being an issue with car engines, but who knows?

 

[wpod]

Why would one crank the engine with no oil and the FP ruse removed?

 

[Revving2Redline]

Why would one crank the engine with no oil and the FP ruse removed?

Sometimes if you have a real lightweight oil or a kerosene in the crankcase. You want it to get stuck up in certain parts of the motor but you don't want the motor to start that is why I would do this procedure the way that it's listed. It's going to take about 30 to 50 times to get it done though.

 

[Revving2Redline]

Sometimes if you have a real lightweight oil or a kerosene in the crankcase. You want it to get stuck up in certain parts of the motor but you don't want the motor to start that is why I would do this procedure the way that it's listed. It's going to take about 30 to 50 times to get it done though.

I think piston soaks for the rings are seized or highly contaminated with crud and if people are trying to do a sophisticated oil flush

 

[tblt44]

Seconds no, but I wouldn't do it

 

[meep]

I’ve absolutely done it with no issues, especially if I was trying to drain old oil out of passages. Oil doesn’t evaporate out of the bearing surfaces once pressure falls… it stays in there a good while, especially under no-load conditions. you can take apart an engine that’s been sitting for 2 years and find oil in all the spinning places. So, for a few seconds, i don’t see any risk for a healthy engine that’s run recently. Remember, it’s not oil pressure that maintains the lubrication, it’s the presence of oil itself.

 

[KrisZ]

Note: spinning without oil for a few secs is what the engine does on every cold start.

No it is not. There is plenty of residual oil in there to provide lubrication. Also the bearings draw the oil in as soon as the crank starts turning, it is not just the oil pump that forces the oil in. So bearings get the oil first before anything else.

“Dry start” is another oil related myth that simply refuses to die.

 

[Duffyjr]

If your ADBV is working like it should you should have instant lubrication, isn't that the whole idea behind an ADBV to keep oil in the galleries and passages for the next start up.

Even if you drained the oil out of the sump as long as you left the oil filter alone it should still have a bit of lubrication, like say a few seconds.

 

[nthach]

There’s enough oil on the journals for low-speed cranking but that’s it.

Are we talking new engine(after assembly) or repair work? Supposedly, GM dry-cranks Corvette engines for a second or two before they fill them with oil, at the time before GIII base stocks, Mobil 1 was made with GIV PAO base stocks and was too “slick” to allow the rings to seat. Hence the dry crank before oil fill.

 

[y_p_w]

Sacrificial antiwear additives should help and they don't drain back.

 

[Chris142]

This can happen with some Continental aircraft engines. If it sits long enough even with oil in the pan, the oil pump can lose its prime. If the airplane is a taildragger, you can rotate the prop horizontal for ground clearance, then lift the tail up high to flow oil from the pan toward the pump to re-prime it. I've never heard of this being an issue with car engines, but who knows?

It was very common on Buick engines where the oil pump was part of the aluminum timing cover and wore enough to cause excessive clearance.

 

[dishdude]

In the 80's Slick 50 used to run Chrysler 2.2 engines with no valve cover at idle claiming the Slick 50 protected it, when in reality idle with no load on the engine wasn't causing any wear.

 

[wings&wheels]

It was very common on Buick engines where the oil pump was part of the aluminum timing cover and wore enough to cause excessive clearance.

Was just going to type that this can happen w/ certain older Land Rover and BL V8's......the Buick engine!