VP AQD40 turbo boost query

[symondo]

At our first trip out we discovered this, hoping its a simple thing to resolve but as with most things.... i'll reserve judgement.


1 engine runs perfectly.
The other also runs well (now) apart from, it reaches the revs where the turbo kicks in and you can feel the boost, hear it spool up, and then nothing. It repeats this like a pulsing effect.

If it was a car, id say it feels like a vacuum pipe may have a hole in it and its taking the boost pressure down. But its a boat and I'm not sure how it works to be honest.

Its had a full service so the oil is fresh, it was left to run to a good operating temp for a while before gently applying throttle. There are no odd noises, it all sounds as its meant to, apart from it doesn't seem to hit the revs where it holds boost.

Where should I be looking to resolve this?

 

[scottie]

What is max revs?

 

[symondo]

What is max revs?

1 enginewill happily sit at 3200, the problem engine seems to be approx. 2400 boosting to 3000 back and forth

 

[kashurst]

it could just be your fuel filters - when were they replaced? Or possible something in the fuel pipe.

edit - just reread your other post regarding empty tank. Its quite likely that putting new fuel in a very empty tank has stirred up the rubbish in the bottom and something has gone up the pick up pipe. I had a similar experience a few years back after using a fast fill pump at Largs. Engine did a very similar thing to yours, After changing filters it was no better so disconnected all the fuel pipe connections right back to the tank and ran wire through them all. Found a 1cm piece of metal swarf that had come up the pipe and stuck in a T piece just before the filters.

Its not a difficult job to do yourself and a good opportunity to learn how to change your fuel filters and bleed the engine. If you plan on cruising around Scotland it will be a useful skill to have. Our first boat was @ 25 years old and we had quite a few fuel filter/blockage issues in the first year or so as like yours the boat had been stood unused a while. I take your car analogy and I learnt about engines on cars, but I have learned on boats over the years that fuel restriction issues on marine diesels can produce quite a variety of behaviours creating severe worries of all sorts of mechanical disaster that a decent filter for a few pounds magically make go away.

 

[symondo]

it could just be your fuel filters - when were they replaced? Or possible something in the fuel pipe.

edit - just reread your other post regarding empty tank. Its quite likely that putting new fuel in a very empty tank has stirred up the rubbish in the bottom and something has gone up the pick up pipe. I had a similar experience a few years back after using a fast fill pump at Largs. Engine did a very similar thing to yours, After changing filters it was no better so disconnected all the fuel pipe connections right back to the tank and ran wire through them all. Found a 1cm piece of metal swarf that had come up the pipe and stuck in a T piece just before the filters.

Its not a difficult job to do yourself and a good opportunity to learn how to change your fuel filters and bleed the engine. If you plan on cruising around Scotland it will be a useful skill to have. Our first boat was @ 25 years old and we had quite a few fuel filter/blockage issues in the first year or so as like yours the boat had been stood unused a while. I take your car analogy and I learnt about engines on cars, but I have learned on boats over the years that fuel restriction issues on marine diesels can produce quite a variety of behaviours creating severe worries of all sorts of mechanical disaster that a decent filter for a few pounds magically make go away.

the filters were done last week before she went in the water.
I think there was a few gallons in it before we filled it, as we had enough to get across to a jetty to fill up, I know it was virtually empty.

stirring up crud in the tank and it being picked up sounds entirely logical, I just assumed it would run lumpy throughout the rev range if that was the case, but it definitely makes sense if its restricting flow.

Obviously the filter should stop anything getting to the engine so would be a case of 'rod' the pipe back to the engine from the filter and re prime I to rule that out I guess?

 

[scottie]

Check out your control cables were adjusted to allow full travel before anything else
Also some early 40 series engines had cav 296 filters which were just not big enough but would expect this to have been sorted long ago
Is this an ex canal boat?
As I recall max revs should be 3800

 

[alb40]

Once you check filters, both on engine and pre filters, also check the little gauze in the top of the fuel lift pump which probably gets forgotten about. Then bleed the system throughly so there is no air in the pump. Also air filters if not changed as they get blocked with fumes from the crank breathers.

These are quite simple engines with no wastegates on turbos and not sure that they even have boost compensation in the pumps to add fuel. Max revs should be 3600 with both engines working together and not one bogging the other down.

 

[Beamishken]

if they are wastegated (I'm fairly sure they are) then possibly a faulty wastgate actuator which could be dumping boost once the boost pressure rises

the other thing that comes to mind some Volvos have an anti smoke device which was a flap which closed off the exhaust to help on warm up they were solenoid operated its possibly worth checking that it isn't malfunctioning

good luck

 

[symondo]

It was on a river which was tidal when we bought it but I believe its spent most of its life in coastal water

It wouldn't surprise me of the control cables needed more adjustment, we had issues with the cables in selecting reverse and had them adjusted. I know on full throttle with the sticks forward, 1 engine seemed to be about 3400 I can't remember exactly but we couldn't get the other to match it in the slightest.

Ifmit was a wastewater on the turbo would it be an instant release of pressure? The motion of revs/boost kicking in is smooth, and it goes off boost smoothly too. So I can understand the idea of a fuel flow issue under the circumstances.

And I'm going to assume an adjustment of the sticks... again.

lift pumps - would they be based in the tank or just a matter of following the pipes? Also cav296 filters, I wouldn't know what they look like. I have photos somewhere of the fuel filters

 

[Beamishken]

It was on a river which was tidal when we bought it but I believe its spent most of its life in coastal water

It wouldn't surprise me of the control cables needed more adjustment, we had issues with the cables in selecting reverse and had them adjusted. I know on full throttle with the sticks forward, 1 engine seemed to be about 3400 I can't remember exactly but we couldn't get the other to match it in the slightest.

Ifmit was a wastewater on the turbo would it be an instant release of pressure? The motion of revs/boost kicking in is smooth, and it goes off boost smoothly too. So I can understand the idea of a fuel flow issue under the circumstances.

And I'm going to assume an adjustment of the sticks... again.

lift pumps - would they be based in the tank or just a matter of following the pipes? Also cav296 filters, I wouldn't know what they look like. I have photos somewhere of the fuel filters

TBh there are several things that could give the same symptoms its a case of working through them logically one at a time the good thing is you have two engines so quite easy to swap parts over & see if the fault swaps over

I mentioned the wastegate as it seemed you had narrowed it down to turbo boost problems but having re read the thread I notice its a 40 & not a 41 which was the engine I had in mind

where in the highlands are you?

 

[symondo]

TBh there are several things that could give the same symptoms its a case of working through them logically one at a time the good thing is you have two engines so quite easy to swap parts over & see if the fault swaps over

I mentioned the wastegate as it seemed you had narrowed it down to turbo boost problems but having re read the thread I notice its a 40 & not a 41 which was the engine I had in mind

where in the highlands are you?

We are based in Fort William, but the boat is just north of oban.
I'm quite hopeful its nothing mechanical as everything sounds as it should, no random vibrations etc... just not getting itself going.

Its not going to affect us for a while as we aren't going far or fast for that matter bit its something id like to resolve sooner than later

 

[alb40]

Lift pump is right next to the on engine fuel filter. Has two screws on top to undo then you can pull out the little filter. Has a lever on the bottom to bleed the system out when changing filters. Cav filters if fitted are the small canister filters with either a glass or metal bowl on the bottom. Google search would bring up plenty of pics.

 

[symondo]

Lift pump is right next to the on engine fuel filter. Has two screws on top to undo then you can pull out the little filter. Has a lever on the bottom to bleed the system out when changing filters. Cav filters if fitted are the small canister filters with either a glass or metal bowl on the bottom. Google search would bring up plenty of pics.

Off to Google.... i'll take peek at this tomorrow as im boat bound to find out why 1 engine has stopped charging the battery as well

 

[volvopaul]

if they are wastegated (I'm fairly sure they are) then possibly a faulty wastgate actuator which could be dumping boost once the boost pressure rises

the other thing that comes to mind some Volvos have an anti smoke device which was a flap which closed off the exhaust to help on warm up they were solenoid operated its possibly worth checking that it isn't malfunctioning

good luck

No wastegate on this engine, sounds to me like the pre filters are blocked, if your going to use the boat seriously at sea I'd be changing the cav type filter for a racor fg500 or similar .

 

[symondo]

No wastegate on this engine, sounds to me like the pre filters are blocked, if your going to use the boat seriously at sea I'd be changing the cav type filter for a racor fg500 or similar .

Here is a photo of what is currently on the boat. I dont know much about filters

 

[volvopaul]

Yes I'd start there.

 

[Divemaster1]

Yes I'd start there.

Support this .... why the tape ??? looks like someone have experienced an air leak and tried to cover it up. Irrespective does not look right!

 

[symondo]

Support this .... why the tape ??? looks like someone have experienced an air leak and tried to cover it up. Irrespective does not look right!

This photo was pre filter change. The tape is now gone.

 

[kashurst]

thats a pretty small filter for an engine. I have something similar to that supplying just a generator. Well worth upgrading as per VP when possible. That style of filter isn't very good at separating water out either. Given the size of it and your empty tanks, old fuel, age etc, although they have recently been replaced it may well already be bunged up.

 

[scottie]

There is an alternative quick fix
Go to ASAP and see if they offer 796? Element and centre bolt extension