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Engine stalling at low revs


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I have a Nanny 150HE engine which has worked well for years. Today as we went down the Thames all was fine at 1800rpm but when I dropped engine speed to moor it stalled. Not just cutting out but sudden erratic shaking as if it were only firing on some cylinders then stopping. After a few minutes it would start and run fine and idling in neutral.

 

Think it might be the flue filters but dosen't quite fit as when running under load it seems fine. Problem seems to happen after engine has been under load.

 

Anyone have any ideas?

 

Martin

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Could be soft engine mounting. Engine shakes about and shakes itself to a stop. Our engine got to the shaking as going to stall level but never actually stopped. (The faulty stop timer did that before I junked it)

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Is there a possibility that it was getting overheated ?

 

 

Coolant levels ok and temp gauge reading in normal range.

 

Could be soft engine mounting. Engine shakes about and shakes itself to a stop. Our engine got to the shaking as going to stall level but never actually stopped. (The faulty stop timer did that before I junked it)

 

 

I would think that if it were engine mounts it would happen every time you go to low revs which is not the case here.

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Was it a lumpy trip on the Thames? If your boat has not been used on a waterway where you encounter waves the crud of years gets stirred up and cloggs the filters. It is a common problem for boats that rarely see the sea...

 

Have a look at your primary fuel filter and i suspect it will have gunk in it.

 

Just to add some fuel will get through as it is most likely partially blocked...

Edited by Paringa
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Was it a lumpy trip on the Thames? If your boat has not been used on a waterway where you encounter waves the crud of years gets stirred up and cloggs the filters. It is a common problem for boats that rarely see the sea...

 

Have a look at your primary fuel filter and i suspect it will have gunk in it.

 

Just to add some fuel will get through as it is most likely partially blocked...

 

 

Thats an interesting idea as the tank is only 1/4 full.

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Which bit of the Thames ?

 

I can imagine the tidal bit can cause the problems "Idleness" refers to, and we have tried to ensure lots of fuel in tank before tackling this, (particularly as we currently only have the single engine mounted filter).

 

Unless the rest of the Thames is unusually choppy, I'd have thought you would get away with a 1/4 full tank OK.

 

Guess it depends just what lies at the bottom of it.

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I have a Nanny 150HE engine which has worked well for years. Today as we went down the Thames all was fine at 1800rpm but when I dropped engine speed to moor it stalled. Not just cutting out but sudden erratic shaking as if it were only firing on some cylinders then stopping. After a few minutes it would start and run fine and idling in neutral.

 

Think it might be the flue filters but dosen't quite fit as when running under load it seems fine. Problem seems to happen after engine has been under load.

 

Anyone have any ideas?

It sounds like it could be valve timing or a sticking valve, when was it last serviced?

I would have thought if there was a fitler problem, the more you opened it up the worse it would get!

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Was the engine still in gear but at idle when the shaking occurred?

 

My Lister LPWS3 had a similar problem in that at idle in gear it would start to shake quite violently until I upped the revs a bit via the throttle lever. It started to do it for, as far as i could see, 'no reason'.

 

I noticed from the rev counter that the in-gear idle revs had dropped to too low-a-level so i adjusted the idle speed up a bit and the problem has gone away, I guess the throttle stop screw has vibrated out a bit allowing the revs to drop. Out of gear was not a problem as with no load the engine idled at higher revs.

 

Worth a try?

 

Good Luck

Ditchdabbler

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Had something similar 2 years ago. Engine went lumpy then dies. Would eventually restart, but not rev very high. Diesel bug in the water separator causing fuel starvation. First day of the holiday. Limped to Banbury and managed to get spare (and backup) filters from Tooleys. Changed all filters, dosed the tank then repeated a week later. Been ok since.

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Had something similar 2 years ago. Engine went lumpy then dies. Would eventually restart, but not rev very high. Diesel bug in the water separator causing fuel starvation. First day of the holiday. Limped to Banbury and managed to get spare (and backup) filters from Tooleys. Changed all filters, dosed the tank then repeated a week later. Been ok since.

 

The OP is saying that his engine runs OK at higher revs though.

 

Tone

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The OP is saying that his engine runs OK at higher revs though.

 

Tone

Misread it. If he can rev it the fuel deliver should be ok. Somethings knocked off the idle speed control. Options are a problem with the injection pump idle speed settings or somethings putting a load on the engine and pulling the speed below the level where it won't run e.g. tight stern gland, fouled prop, gearbox issue etc.

Could also be signs of a head gasket fault. If the engines been working hard it could have lifted the head slightly and dropped compression on a cylinder. This could affect idle which would cause the symptoms described. When it cools everything would return to normal. It is possible for a head gasket to blow and bypass oil ways and galleries - you don't get the oil and water mixing. Had this happen on an MGB and took a while to find. If it does it again get the compressions checked.

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There have been plenty of good suggestions for the OP to think about. Over the years I have had similar symptoms (well the engines have!) due to dirty fuel/overheating/idling speed set too low.

 

As a non-techy, I suggest you check ALL fuel filters including the lift pump (which might have a filter screen). If everything looks clean you might then try increasing the idle speed slightly. I always prefer to check out simple/cheap/obvious things first before looking at more expensive and time consuming options :cheers: If none of the simple checks help it is then time to ask the experts who are taking a back seat ............

 

Good luck

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Problem solved.

 

Diesel bug. Changed filters, cleaned out tanks and pipes, heavy dose of bug killing additive. Engine running like a dream. Left Harleyford Marina, Cookham yesterday lunchtime arrived Grand Union this evening. Lovely trip. Went through Teddington 3 hours before high water and motored down to Richmond Barrage, picked up a buoy and had lunch. Watched barrage raise and then on to Brentford. Measured incoming tide at about 3 mph sot trip around to Thames Lock took about 30 mins.

 

Must compliment staff at Espa Marine for sorting issue out.

 

Martin

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