Motor turned off with throttle in drive

[hgrection]

Wife (seriously) turned off motor of 96 Volvo 5.7L GL with throttle forward of idle. The engine started knocking, she then turned key off and the motor kept knocking for a few seconds then stalled. I tried to re-start the motor, and it wouldn't turn over. Starter would engage fine, but just would not crank. Swapped batteries a few times, no luck. Now up a creek (literally) with a paddle and.... a friend with a new boat.<br /><br />Friend was towing me back and after about 30 minutes tried to start again, and it began cranking. Finally started up, idled roughly for a few seconds then was fine. Works like a champ now. Any ideas what happened? I know what I'm going to do to keep it from happening again, but am curious what the problem was. Thanks!

 

[Don S]

Re: Motor turned off with throttle in drive

I know exactly what happened. When the engine was shut off, it dieseled the engine and ran backwards. This in turn sucked water back into the cylineder. Had you just pulled the plugs and cranked the engine you would have pumped the water out of the cylinders and it would have restarted. What you did was hydrolock the engine. Water in the cylinders will not compress and will lock the engine as if an extra piston was laying in the cylinder.<br />Hopefully you didn't bend a rod, and no it's not an easy thing to check without disassembling the engine.<br />I would suggest you change oil and filter. The water that was in the cylinder may have seeped by the rings and into the pan.

 

[Scaaty]

Re: Motor turned off with throttle in drive

Good call, Don! It the little things like this that must be remembered. You have to leave your auto sense at the dock and go marine to survive the wrath of the mechanic! I shudder every time my old 350 doesn't stop right NOW, and have a plug wrench all set to go...paranoia pays off.

 

[deputydawg]

Re: Motor turned off with throttle in drive

If it hydrolocked the engine, then it started later, that water went somewhere. The only place it could go is into the oil pan. Check this out before running again. Also a good idea to do a compression check, this might tell if you bent a rod.<br />Don, is it possible that the water coming in would be cold enough to damage or pit the cylinder wall?

 

[Don S]

Re: Motor turned off with throttle in drive

dawg<br />Yes, the water coming in will pit, and rust the cylinder walls and rings. It will only take a few hours if it happened in salt water.<br />A bent rod will not show up on a compression check. It would still be going up and down the same distance, and the amount of bend would be very small from starter pressure.