What to do when the engine won't start...

[MagicalArmchair]

I've been following this post with interest: http://www.ybw.com/forums/showthread.php?433485-Diesel-engine-numpty-question(s)

I must say, in the same situation, I would not think to close the raw water inlet and I would keep cranking away like crazy too (I have a 2GM20), is the advice that, in a similar event, close the raw water inlet after two failed attempts of starting and only reopen once the beast is running again and you have identified the fault that is preventing the engine starting?

 

[pvb]

I've been following this post with interest: http://www.ybw.com/forums/showthread.php?433485-Diesel-engine-numpty-question(s)

I must say, in the same situation, I would not think to close the raw water inlet and I would keep cranking away like crazy too (I have a 2GM20), is the advice that, in a similar event, close the raw water inlet after two failed attempts of starting and only reopen once the beast is running again and you have identified the fault that is preventing the engine starting?

Yes, every time you try to start the engine, you're pumping seawater in to the exhaust. Without the engine running, there's no high-velocity exhaust gas to blow the water out, so it just builds up and will ultimately flow into the cylinders through the exhaust valves. You'll find that most engine operator manuals will warn against this danger.

 

[prv]

is the advice that, in a similar event, close the raw water inlet after two failed attempts of starting and only reopen once the beast is running again and you have identified the fault that is preventing the engine starting?

In a word, yes . Although I might try more than twice before going into "something's really wrong" mode and closing the seacock.

When I was designing a new engraved engine panel for Kindred Spirit, I ended up with a blank space below the starter button. I filled it with a little warning:

Close seacock during
prolonged starting attempts
or when turning over
without running.

Pete

 

[RichardS]

Agree with all above.

One of the reasons I fitted Speedseal Life raw water pump covers is that the impeller can run dry for a 5 or 10 minutes without any damage. I feel very relaxed about trying to start the engines with the sea cock closed as there's no rush to open it when/if it starts.

Worth thinking about along with the other Speedseal benefits.

Richard

 

[TQA]

Agree with all above.

One of the reasons I fitted Speedseal Life raw water pump covers is that the impeller can run dry for a 5 or 10 minutes without any damage. I feel very relaxed about trying to start the engines with the sea cock closed as there's no rush to open it when/if it starts.

Worth thinking about along with the other Speedseal benefits.

Richard

Remember that you do have to get the water flowing fairly rapidly in the exhaust as dry diesel exhaust is hot enough to damage both flexible rubber hose and fibreglass water traps.

I have seen a hole burnt in the rubber hose and of course when the water was eventually turned on it leaked into the bilges. Gave the skipper a nasty fright.

Worst case scenario the exhaust system can catch fire.

 

[pvb]

One of the reasons I fitted Speedseal Life raw water pump covers is that the impeller can run dry for a 5 or 10 minutes without any damage. I feel very relaxed about trying to start the engines with the sea cock closed as there's no rush to open it when/if it starts.

Taking Speedseal's assertion that impellers wear on the face when run dry, I can understand how the Speedseal Life dramatically reduces that wear - but only on one face of the impeller. How come the face on the engine side doesn't wear and cause impeller disintegration?

 

[RichardS]

Taking Speedseal's assertion that impellers wear on the face when run dry, I can understand how the Speedseal Life dramatically reduces that wear - but only on one face of the impeller. How come the face on the engine side doesn't wear and cause impeller disintegration?

Good point. Perhaps the spinning force of impellers or the profiling of the cam tends to drift the impeller outwards so the pressure tends to be on the cover. This would make sense as an engineering solution as the cover plate can be much more easily reversed or refurbished when necessary than the pump body?

Just a thought.

Richard

 

[pvb]

Good point. Perhaps the spinning force of impellers or the profiling of the cam tends to drift the impeller outwards so the pressure tends to be on the cover. This would make sense as an engineering solution as the cover plate can be much more easily reversed or refurbished when necessary than the pump body?

The impellers are uniform, so spinning them won't induce a sideways movement. Similarly, the cam is uniform.

 

[RichardS]

The impellers are uniform, so spinning them won't induce a sideways movement. Similarly, the cam is uniform.

What about if the input and output points are not exactly centralised across the impeller but are offset slightly to provide a stabilising moment to stop the impeller hunting laterally? Getting desperate now but according to Speedseal the claims have been tested against the standard fitting. I think there's even a video somewhere.

I should add that dry running is not the primary reason I purchased the Speedseal but, assuming it's true, it's an added benefit.

Richard

 

[ghostlymoron]

A speedseal won't stop you flooding your engine after prolonged cranking. They're still worth having though.

 

[pvb]

What about if the input and output points are not exactly centralised across the impeller but are offset slightly to provide a stabilising moment to stop the impeller hunting laterally? Getting desperate now but according to Speedseal the claims have been tested against the standard fitting. I think there's even a video somewhere.

Yes, you're getting desperate!

 

[Avocet]

Is it because the Speedseal uses a thicker gasket (or maybe even an O ring?) so the cover isn't actually clamping down as hard on the sides of the vanes? I must say, I'm surprised about the 5-10 minute claim. Avocet doesn't have a speedseal, but I once forgot about the inlet seacock and after (what i think was) less than a minute, the pump cover was too hot to touch!

 

[MagicalArmchair]

Thanks all for the advice, I'll remember that if my delightful and problem free 2GM20 ever decides to throw a paddy

 

[charles_reed]

A speedseal won't stop you flooding your engine after prolonged cranking. They're still worth having though.

I'd rather invest the money, thrown away on a Speedseal, on a spare raw-water pump.
As it so happens the Johnson pump on my 3YM does have an O-ring and, unlike the 2GM the plate faces away from the engine.

 

[ghostlymoron]

The O ring compresses down to nothing. That's why the speedseal has a recess machined in the cover to compensate for the lack of a paper gasket and maintain the compression.
Having said that, my homemade version doesn't have a recess and seems to work fine.

Is it because the Speedseal uses a thicker gasket (or maybe even an O ring?) so the cover isn't actually clamping down as hard on the sides of the vanes? I must say, I'm surprised about the 5-10 minute claim. Avocet doesn't have a speedseal, but I once forgot about the inlet seacock and after (what i think was) less than a minute, the pump cover was too hot to touch!