It's technically known as a judder....

[LL 1975]

Hi

 

Have an issue with my 2015 42 HP Canaline engine.

 

Started about 6 months ago when it would once in aprox every 10 hours of idling the engine it would, without warning, make a shudder very similar to when when it has run out of fuel in the past. However, instead of making a loud and vibratory shudder (when it ran out of fuel) then stopping it stutters a little then almost finds it's feet then comes back to life and carries on running as normal.

 

More recently its happened more frequently and sometimes not when idling (particularly when put into reverse for some reason), it does the same but then cuts out. Upon reignition it behaves normally again (so definitely not run out of fuel which is about 15% but well above the take off line).

 

I have requested a slot for an engineer but would like to start narrowing down the likely causes and going through a process of elimination.

 

For what it's worth my unqualified guesswirks is it is most likely linked to issue with either the fuel or the air not reaching the engine at the moment that it is struggling. But given it is no out of fuel and the air filter isnt blocked (have checked) i am at a loss as to what to do whilst i wait for an engineer to get through his pre xmas waiting list and onto me.

 

Thanks

[Mike Tee]

fuel filter?

[nicknorman]

Or a slight air leak into the fuel system. I suggest filling up with fuel and see if that makes any difference. That may increase the pressure slightly in the fuel lines, so it is slightly above ambient instead of slightly below, so less inclination to suck in air.

[LL 1975]

1 minute ago, Mike Tee said:

fuel filter?

quite possibly Mike, just needs changing? What would be the reason behind it? filter is being blocked? with what? 

Also which filter - there's 2.

[LL 1975]

17 minutes ago, nicknorman said:

Or a slight air leak into the fuel system. I suggest filling up with fuel and see if that makes any difference. That may increase the pressure slightly in the fuel lines, so it is slightly above ambient instead of slightly below, so less inclination to suck in air.

Thanks Nick, needs filling soon anyway so could be the first step to identifying the issue.

[nicknorman]

As a general point, it is not a good idea to run out fuel. Diesel tanks tend to collect water and gunge which sits happily at the bottom of the tank, below the takeoff point. But when the level gets very low, this tends to slosh around and thus mix more and most likely some makes its way into the fuel takeoff pipe.

[LL 1975]

Just now, nicknorman said:

As a general point, it is not a good idea to run out fuel. Diesel tanks tend to collect water and gunge which sits happily at the bottom of the tank, below the takeoff point. But when the level gets very low, this tends to slosh around and thus mix more and most likely some makes its way into the fuel takeoff pipe.

well received Nick

[Tony Brooks]

Be aware that a good installation, but by no means all, will have two filters. the obvious one on the engine and another somewhere along the pipe between fuel tank and engine lift pump. I have known the one on the fuel line to not have been serviced for years until it blocks. This one could be all sorts of things and one type may not contain anything but an inverted cone at the top..

[dor]

Water in the fuel tank?  15%. Is getting quite low, and if the tank hasn’t been checked it could have a few litres sloshing about.

[nicknorman]

8 minutes ago, LL 1975 said:

well received Nick

No probs! If it turns out that the filters are full of gunge, it may be worth trying to suck out the bottom of the tank with some sort of pump, separate out the diesel from the dirty water and dispose of the latter. Depends on how old the boat is, and where the tank is. Boats with tanks above the waterline are exposed to rapid variations in temperature which can cause condensation to form on the inside of the tank, which then runs down to the bottom. The lower the fuel level, the more moist air there is inside the tank to form condensation. Over the years this can build up to be quite a lot.

[Tracy D'arth]

Suck the tank dregs out with a wet and dry vac, a length of copper pipe in the sucking end  will get you into the lower corner of most boat tanks.

 

Check you prop too, I've known poly bags cause some odd effects especially when going into reverse.

[LL 1975]

9 minutes ago, dor said:

Water in the fuel tank?  15%. Is getting quite low, and if the tank hasn’t been checked it could have a few litres sloshing about.

testing is drop a pipe down right to the bottom, thumb over the end, pull out then release contents (which should be a vertical section of the tank) into an empty ,cleaned out plastic bottle, let it settle and analyse (as in look at ? the contents?

4 minutes ago, Tracy D'arth said:

Suck the tank dregs out with a wet and dry vac, a length of copper pipe in the sucking end  will get you into the lower corner of most boat tanks.

 

Check you prop too, I've known poly bags cause some odd effects especially when going into reverse.

thanks - prop has been cleaned since this started happening so would prob rule that out as the sole cause.

[dmr]

Whilst working on my "air leak" I read an article about this on the www. It can be a leak or it can be dissolved air getting "sucked" out of the fuel. This collects at the top of the second filter and from time to time a slug of this air goes through to the injection pump. Try changing the first filter to reduce the negative pressure on the suction side (before the lift pump).

 

....................Dave

[Bee]

It does sound like fuel and the filter(s) are the first thing to look at. Water in fuel is a sod and will make the engine shudder and knock, its not good as it does not compress in the cylinder. If the filters and fuel are clean then you could have a tiny air leak. I would not add new fuel to the tank until you are sure what's in the tank is OK or you might have to drain that out as well and the whole lot will end up mixed up and ruined.

[LL 1975]

Just now, Bee said:

It does sound like fuel and the filter(s) are the first thing to look at. Water in fuel is a sod and will make the engine shudder and knock, its not good as it does not compress in the cylinder. If the filters and fuel are clean then you could have a tiny air leak. I would not add new fuel to the tank until you are sure what's in the tank is OK or you might have to drain that out as well and the whole lot will end up mixed up and ruined.

ok gotcha, make sure fuel is good via fuel filter check and fuel test before filling with more fuel....

[Tony Brooks]

1 hour ago, dmr said:

Whilst working on my "air leak" I read an article about this on the www. It can be a leak or it can be dissolved air getting "sucked" out of the fuel. This collects at the top of the second filter and from time to time a slug of this air goes through to the injection pump. Try changing the first filter to reduce the negative pressure on the suction side (before the lift pump).

 

....................Dave

On modern engines (at least as far back as the BMCs) the fuel return should vent  the top of the filter an often the injector pump as well. I am not too hot one Canaline but I would expect a leak back system on it so maybe worth making sure the leak back system is not blocked.

[Man 'o Kent]

As you admit to running dry and thus sucking up contaminated fuel I would also throw suspicion on the delivery valve(s), time maybe for a pump service?

[dmr]

44 minutes ago, Tony Brooks said:

On modern engines (at least as far back as the BMCs) the fuel return should vent  the top of the filter an often the injector pump as well. I am not too hot one Canaline but I would expect a leak back system on it so maybe worth making sure the leak back system is not blocked.

I'm not an expert on different engine types. I think a lot of modern rotary pumps have a return from the pump itself to self bleed, but I don't think many have the return from the filter top. Anyway following one of your posts I have made a BMC style return from the top of the second filter for my JD3 and so far it appears to have fixed the problem. I did this by replacing the filter air bleed screw with a banjo fitting connecting to a sort of return line union/manifold that I made out of a lump of brass. Getting the orifice right was tricky. I tried to make one but drilling 0.5mm holes is difficult. I then found a lovely set of brass jets on Amazon intended for 3D printers, a range of orifice sizes for just a few quid.

0.5mm was too small and did not shift all the air. 0.8mm turned out to be about right. I did some tests into a plastic bottle and was surprised at how much fuel squirts out of a 0.5mm orifice.

 

Have not done much proper boating of late due to Covid and stoppages so too early to say for certain if this has fixed the very occasional missed beat/puff of black smoke.

 

.............Dave

[Detling]

check the diesel cut off valve, I had very similar would run for a bit then shudder and then pick up for a bit. I had knocked the shutoff valve and it was part closed, silly me took over an hour to spot it.

[Richard T]

Another thought - Is the air vent into the fuel tank become blocked? The use of fuel can then create a vacuum in the tank which will restrict fuel flow.