Diesel Consumption through the roof

[Tinto]

Last week I had white smoke from the exhaust so changed both fuel filters and that fixed the problem. However, since then our fuel consumption has gone up from about 2.4litres per hour to 3.4 litres per hour. There are no fuel leaks in the system. Both supply and return hoses were changed last year.

Both filters were catching black specs of whatever and were changed last winter. The boat has done a lot of miles this year. Almost 1000 and maybe 250 of those under engine.

 

[Boater Sam]

Check that the engine sump is not full of fuel.

Someone helping themselves to your fuel?

Fuel tank venting overboard?

 

[Tinto]

EDIT.

oil on dipstick looks and smells fine.

No sign of syphoning from vents

Thanks. I will check sump and venting.

Definitely not theft we have only been at anchor or on a mooring ball since I last topped up and started measuring accurately again.

 

[B27]

Does your engine have a turbo?

TBH, that fuel consumpton increase is quite possibly a dirty hull and/or prop.
The white smoke is likely either unburned fuel (injector problem?), which will stink, or steam, indicating a cooling system not coping with the extra work.

 

[Tinto]

Does your engine have a turbo?

TBH, that fuel consumpton increase is quite possibly a dirty hull and/or prop.
The white smoke is likely either unburned fuel (injector problem?), which will stink, or steam, indicating a cooling system not coping with the extra work.

CHanging the fuel filters fixed the white smoke problem. So that’s fixed. Hull is fairly clean but it could be the prop. Will try and get a look at it later

 

[Tranona]

Not really enough information. Fuel consumption is a direct function of power demanded. So if you have used more fuel you have either gone faster or used more power for the same speed, for example with a fouled prop or bottom. What were the comparative hours from which the 2 averages were derived. the difference is substantial so something major has changed between the two periods. Helpful to know the boat, engine and typical cruising speed as well to determine what a "normal" average consumption level would be.

 

[Tinto]

No turbo

Only ever run at 2000rpm maximum.

First run I noticed it was high we were against wind and tide for the last 2 hours. So that would explain some of it.

Yesterday, didn’t use much of the engine, only when leaving and arriving at anchorages.

Though we had a look at two anchorages and motored around the first one for a bit at 1200rpm before deciding it wasn’t great.

Drop in the fuel level was noticeable though even for such little use

12m sailing boat
Ford Mermaid Meteor 11 which is a 1.8litre 4 cylinder diesel from 1990

 

[B27]

Hanging the fuel filters fixed the white smoke problem. So that’s fixed. Hull is fairly clean but it could be the prop. Will try and get a look at it later

Presume that's 'changing the filters' but I don't understand how that affects white smoke?

 

[Tinto]

Presume that's 'changing the filters' but I don't understand how that affects white smoke?

white smoke can be due to an unbalanced amount of air and fuel reaching the chamber. If there is a significant blockage in the fuel filter, this may cause the fuel to slow down or not be able to reach the chamber in due time.

 

[Bobc]

White smoke us usually due to over-fuelling, not under-fuelling.

Have you checked the fuel leak-off and return pipes?

 

[RunAgroundHard]

If you have V shaped tank, the drop in fuel level will accelerate as fuel is consumed.

 

[Tinto]

If you have V shaped tank, the drop in fuel level will accelerate as fuel is consumed.

It’s a cuboid

 

[Boater Sam]

white smoke can be due to an unbalanced amount of air and fuel reaching the chamber. If there is a significant blockage in the fuel filter, this may cause the fuel to slow down or not be able to reach the chamber in due time.

claptrap.

 

[Tranona]

No turbo

Only ever run at 2000rpm maximum.

First run I noticed it was high we were against wind and tide for the last 2 hours. So that would explain some of it.

Yesterday, didn’t use much of the engine, only when leaving and arriving at anchorages.

Though we had a look at two anchorages and motored around the first one for a bit at 1200rpm before deciding it wasn’t great.

Drop in the fuel level was noticeable though even for such little use

12m sailing boat
Ford Mermaid Meteor 11 which is a 1.8litre 4 cylinder diesel from 1990

To get meaningful comparisons you need to set a base and type of use - speed/revs over a significant period of time. 2.4l/h is on the low side and 3.4 on the high side for that size engine. However short term like 2 hours trying to maintain speed through the water in adverse conditions could easily result in the higher level for that 2 hours.

Realistically the only way of measuring fuel consumption is to brim the tank and run for 20 or 30 hours and top the tank up. You would expect to add 50l or so after 20 hours or 75 after 30.

Trying to draw any conclusion from "drop in the fuel level was noticeable even for such little use" really has no value. Your 100 hours suggested in your first post is a good annual average and measuring usage over that sort of hours in mixed use is really useful - and "accurate".

 

[penberth3]

No turbo

Only ever run at 2000rpm maximum.

First run I noticed it was high we were against wind and tide for the last 2 hours. So that would explain some of it.

I think that explains all of it.

 

[B27]

I think that explains all of it.

White smoke?
Not enough raw water flowing?

 

[Tinto]

claptrap.

I suppose you would have to explain why a mechanic maté diagnosed that as the problem and then why after I changed the filters the white smoke went away.

 

[Tinto]

White smoke?
Not enough raw water flowing?

I think that explains all of it.

Maybe, but not yesterday.

 

[Tinto]

I think that explains all of it.

No doubt a factor. I think also fouled prop is a good candidate and the two together have given me the much bigger than normal fuel consumption.

I wondered if the unimpeded flow of fuel was also a factor in more of it being used, but no one has suggested that, so that’s unlikely.

Always a bit of a lottery measuring fuel usage doing anything other than brimming it, using it and brimming it but that’s not an option at the moment. I am heading home soon and want to be lifted out with not a lot of fuel in the tanks so I can drain and clean them out

 

[vyv_cox]

White smoke is caused by unburnt fuel in the combustion chamber. It can occur due to poor starting but the smoke usually clears in a minute or so in that case. It can also be due to faults or wear in the injector pump resulting in excessive fuel being injected.

The symptoms of a partially blocked filter are unmistakeable - the engine will rev in neutral but not in gear. In severe cases it will stall as soon as the gear lever is engaged. The filters are located before the injector pump and cannot result in excessive fuel being delivered by it.

I suggest there is a problem somewhere in the injector pump. White smoke can be caused by a fouled or sooted injector but this is unlikely to have led to excessive fuel consumption.

There cannot be an 'imbalance' in the air to fuel ratio. Air in a diesel is at full flow always, unlike a carburated petrol engine, it has no butterflies. Fuel is added directly into the cylinder by the injectors to increase speed and power.