Sluggish engine

[RobP]

We have a Lister LPW4 engine which has had a problem since June,

 

The engine starts and runs fine, burns no oil, smokes a little when cold then clears up, and uses under 1l/hr

 

Recently when we first set off it will not rev over 800rpm for a few minutes,

Then it will suddenly burst into life and the engine revs start to climb and whe is back to normal.

 

It started on the Chesterfield canal, and we put it down to weeds and short cruises + long moorings with engine only charging batteries, but is has contiinued.

 

Yesterday we had a tricky manoevre getting off an angled pontoon mooring in high wind at Boston, and I had to run the engine in gear still tied up until the revs came up before even attempting to move off.

 

We then cruised for 5 hrs to Bardnay, no problems, but this morning, moving from the lock area to a pontoon, che resumed normal non-service.

 

I have cleared the water trap, replaced the fel filter, and put some injector cleaner into the tank, no real improvement.

 

Any ideas?

 

[jake_crew]

^{Was there water in the water trap ?}

 

^{Did you open up the fuel filter to see what it looked like inside ?}

[RLWP]

Is it the same in and out of gear?

 

Richard

[RobP]

Is it the same in and out of gear?

 

Richard

 

No, if we pop the clutch it revs OK, only in gear (forward and reverse)

[nicknorman]

Must surely be lack of fuel anyway. Maybe a slight air leak which accumulates air over night, and which takes a while to push through the system?

[RobP]

^{Was there water in the water trap ?}

 

^{Did you open up the fuel filter to see what it looked like inside ?}

 

No, but some slime - like frogspawn,

Not opened the old fuel filter, no.

[RLWP]

 

No, if we pop the clutch it revs OK, only in gear (forward and reverse)

 

How is the oil level in your gearbox (I'm grasping at straws a bit here while I have a think). Which gearbox too

 

Richard

[nicknorman]

No, but some slime - like frogspawn,

Not opened the old fuel filter, no.

Sounds like fuel bug.

[matty40s]

No, but some slime - like frogspawn,

 

It's toadally knackered then.

 

I was going to suggest turning all electrislcs/ inverter off when you start in the morning but your latest comment suggests fuel contamination

[RLWP]

Sounds like fuel bug.

 

Sounds like water in the water trap, which is what it is supposed to do

 

If it is diesel bug, why does it get better after a few minutes, not worse?

 

Richard

[nicknorman]

Sounds like water in the water trap, which is what it is supposed to do

 

If it is diesel bug, why does it get better after a few minutes, not worse?

 

Richard

Slime implies organic growth to me, but without seeing it its hard to know. Waters is surely just water?

 

Why it gets better? Maybe the bug settles overnight and clogs stuff up, but the pressure of fuel helps to clear a gap for the fuel to get through. It's hard to be able to suggest the answer because it depends on where and how much bug etc. but if I had slime like frogspawn in the trap, I would want to investigate the tank.

 

Anyway it seems almost certainly a lack of fuel so you can either have a blockage, with bug being a likely culprit, or air getting in. Could it be anything else (bearing in mind it all runs fine after a while)?

[RLWP]

Sticky clutches in the gearbox?

 

Your air leak on the injector feed also sounds credible. The LPWS will self bleed, clearing air from the delivery pipe allowing an errant injector to cut in again

 

I suppose it could also a be a reluctant cylinder that only starts to fire when warm, but I'd expect to see smoke

 

Richard

[nicknorman]

Sticky clutches in the gearbox?

 

If a sticky gearbox clutch was the issue, wouldn't there be some other indicators?:

Prop turns significantly when boat should be in neutral

With clutch friction absorbing all the torque that the engine can put out (even at low rpm) there would be a lot of heat generated, with accompanying smell (maybe - not sure if the gearbox is fully sealed, or if it has a small vent?)

On an LPWS, with the governor giving max fuel due to low revs and high throttle setting, there would be black smoke.

[RLWP]

I'm inclined towards an air leak on one of the injectors, although diagnosis by forum is incredibly fraught with danger

 

Diesel bug shows up as black, slimy stuff in the filter and is very obvious. Water traps will collect small quantities of water, some dirt and set up interesting little colonies - this isn't diesel bug

 

With the engine in front of me and in the 'underpowered' state, I'd try slackening off the injector feed pipes one at a time to see if it can be isolated to a particular cylinder. If you slacken the pipe and the speed drops, the cylinder is working

 

Richard

[Naughty Cal]

 

No, but some slime - like frogspawn,

Not opened the old fuel filter, no.

You certainly shouldnt have slime in your fuel.

 

Change your fuel filters and dose your fuel with some diesel bug solution, or have your fuel and tanks cleaned.

 

If this isnt your whole problem it certainly wont be helping matters.

[b0atman]

Hey if in Lincolnshire then its watter.

[Alan de Enfield]

To remove the possibility of fuel being the problem - get a jerry can (or 5lt can) of known fresh diesel and connect to the fuel filter outlet pipe (taking the filter out of the system), allow fuel to run down to the engine (siphon, or self-bleed), start the engine and see if you still have the problem - if you do, its not fuel and you know to look at the engine side of the fuel filter (ie pump, injectors etc)

 

If the problem goes away, then the problem is 'fuel tank to filter' check tank contents to see if you have any water or 'the bug', fuel may need to be polished) check the state of the filter(s)

 

Work thru everything in a logical basis until you find it - if you do not find it within the fuel sysytem then start worrying about gearboxes, loss of compression - until hot - on one cylinder etc etc.

[RLWP]

 

If the problem goes away, then the problem is 'fuel tank to filter' check tank contents to see if you have any water or 'the bug', fuel may need to be polished) check the state of the filter(s)

 

 

As the problem always does go away after a few minutes running, I'm not clear how your test will prove anything

 

Richar

[RobP]

If a sticky gearbox clutch was the issue, wouldn't there be some other indicators?:

Prop turns significantly when boat should be in neutral

With clutch friction absorbing all the torque that the engine can put out (even at low rpm) there would be a lot of heat generated, with accompanying smell (maybe - not sure if the gearbox is fully sealed, or if it has a small vent?)

On an LPWS, with the governor giving max fuel due to low revs and high throttle setting, there would be black smoke.

*sometimes* the prop turns with the engine in neutral.

 

Anyway, today I are mostly geting oily. I found that one of the hoses from bearbox to oil cooler was not tight, gearbox oil was low, and also there was diesel on the outside of the fuel filter, so gave that a tweek.

 

Not planning on moving for a couple of days, so will report back if this sorts the problem(s)

[RLWP]

Thanks Rob, I would be interested to know how you get on

 

Richard

[Naughty Cal]

*sometimes* the prop turns with the engine in neutral.

 

Anyway, today I are mostly geting oily. I found that one of the hoses from bearbox to oil cooler was not tight, gearbox oil was low, and also there was diesel on the outside of the fuel filter, so gave that a tweek.

 

Not planning on moving for a couple of days, so will report back if this sorts the problem(s)

You have found a nice spot to have a few days. Nice walk into the village, nice pub at the top of the hill and a great butchers as well.

[Alan de Enfield]

 

As the problem always does go away after a few minutes running, I'm not clear how your test will prove anything

 

Richar

 

I'm not sure that it would.

 

It would however answer the reasons suggested above :-

 

Run out of fuel

Frogspawn

Water in the fuel

Bug in the fuel

Blocked filter

Air into the sysytem (from the tank to the pump

[RLWP]

 

I'm not sure that it would.

 

It would however answer the reasons suggested above :-

 

Run out of fuel

Frogspawn

Water in the fuel

Bug in the fuel

Blocked filter

Air into the sysytem (from the tank to the pump

 

But doesn't explain or sort 'Starts sluggish, then runs OK'

 

Starts sluggish and then stops is diesel bug. 'Frogspawn' and water in a water trap is normal - it's what the water trap is supposed to do. If you open one up it's not unusual to find slimy stuff in there. If they had said black or red frogspawn I would also be looking at diesel bug.

 

The most interesting thing in the latest report is 'and also there was diesel on the outside of the fuel filter'.

 

Richard

[bizzard]

Which filter is there fuel on the outside of ? If its a filter leaking aft of the lift pump it will almost certainly suck in air.

[MtB]

And may I ask how long the engine need to be stopped for, in order to re-create the problem?

 

Like, if you stop it and start it immediately, do you still get the few minutes of refusal to rise above 800rpm? How about if you leave it to rest for five minutes? 50 minutes? Or does it need something like five hours' rest for the prob to return?

 

I'm not sure what the answer to this question would tell us, but I think it might be significant.

 

MtB