bmc BMC 2.2 diesel loss of power problem

[philbzzz]

Hi there, 

 I've got a problem with my BMC 2.2 diesel engine that is giving me no end of trouble - any knowledge or advice would be much appreciated. 

 

Basically, the engine starts fine with the normal amount of smoke which dies down after a short while. The boat runs nicely, doesn't hunt or miss and will run for over an hour whilst moored up either just on idle or revving the engine during the process. 

 

The problem occurs when I go up river. After about 10 minutes of cruising at a slow speed the revs drop . If I push the throttle forward then the revs pick up again but after a while they drop again. This happens repeatedly until the throttle is fully open but the engine is only doing perhaps 1000 rpm. The engine will then stall and not restart. After about 10 mins the engine starts and all seems fine but again it will do the same after another short run up the river. At no point is the engine overheating and is maintaining about 60 degrees when warmed up. 

 

So far I've done the following. 

 

Replaced fuel pump and all filters. 

Emptied and cleaned tank and put in fresh diesel. 

Cleaned air filter. 

Replaced fuel pipe on inlet side.

Checked and cleaned tank vent (and tried with fuel filler open)

Checked for diesel bug. 

Bled (several times) filters, injection pump and injectors. 

 

I'm really stuck on what it could be. 

 

Any suggestions?

 

Philip

 

 

[Nut]

I have a defender 90 (30 years old) I know its not a boat engine , does your engine have leak off piping as I needed to replace mine as air was getting into the system ,it sounds like air is getting into the fuel lines ,I may be wide off the mark and an expert will be along soon.

[Tony Brooks]

If this is a later one with the mechanical DPA pump then maybe take the big hexagon inlet pipe adaptor out. Take care because there are springs an a valve in thererbut also a nylon mesh screen that have been known to block.

 

Also make sure the filter head has a leak off back to the tank - normally a 0.5mm hole in the banjo bolt. If this is blocked then you often get a build up of air in the top of the filter until it stops the engine.

 

Still with the DPA pump make sue the valve in th filter head that forms the union for the injector pump return pipe is there and clean.

 

 

3 minutes ago, Nut said:

I have a defender 90 (30 years old) I know its not a boat engine , does your engine have leak off piping as I needed to replace mine as air was getting into the system ,it sounds like air is getting into the fuel lines ,I may be wide off the mark and an expert will be along soon.

 

Don't think so, I think you may be spot on.

[Nut]

good luck hope you sort it

[philbzzz]

Thanks for the replies, I'll check what you have suggested tomorrow and report back. ?

[Tony Brooks]

Check the leak back from the filter top first.

[zenataomm]

I have little experience with your engine, however I'd like to congratulate you on an excellently constructed OP.

 

If only others gave as much thought to how they phrase their enquiry or read it back to themselves before hitting "Submit".

 

Good luck, I hope you get to the bottom of what ails your engine.

[philbzzz]

Thank you zenataomm , kind words indeed. I'm going to have a good look at it today but I've also ordered a vacuum pump/gauge so I can test the inlet side of the fuel system for leaks. Also, one thing that I've just noticed is that there is a second pipe from the remote fuel filter that feeds an old (and unused) diesel heater which could be letting air into the system. I'm going to cap this off just in case but will probably vaccum test it first as I'd be interested to know if this is the case. I'll report back ! 

 

Philip

[Tony Brooks]

1 hour ago, philbzzz said:

Thank you zenataomm , kind words indeed. I'm going to have a good look at it today but I've also ordered a vacuum pump/gauge so I can test the inlet side of the fuel system for leaks. Also, one thing that I've just noticed is that there is a second pipe from the remote fuel filter that feeds an old (and unused) diesel heater which could be letting air into the system. I'm going to cap this off just in case but will probably vaccum test it first as I'd be interested to know if this is the case. I'll report back ! 

 

Philip

That may well be the case - poor practice AND it encourages people to run out of fuel while settled in for the winter.  In my view the take off should be about 4" higher than the engine feed in the tank.

 

The idea of the return form the top of the engine filter is to allow small amounts of air that finds its way into the filter to be4 retuned to the top of the tank and thus avoid problems so still check that as well. Its a bit hazy by now but I seem to recall the INline injector pump version may not have had a return from the filter so if in the past thee was an engine change the importance of the return may not have been realised.

Edited September 12, 2018 by Tony Brooks

[john.k]

I had repeated callouts to a problem like this,and after much tankflushing,filter changing ,etc,it was a piece of polyester shirt material ,invisible when fuel wet,and would stick to the inside of the tank,when the tank was drained and flushed.After a period of running,it would float over the pickup,and restrict fuel delivery......It could have been cured first off by placing a large filter gauze over the pickup pipe when the tank was made,or putting a decent sized manhole in the tank top.But boat operators dont like filter gauzes in tanks,because they block with sludge............Incidentally,if a DPA pump gets air in it ,it usually wont start,or stalls straight after starting......One cause of this can be the controll spindle O rings worn.

[philbzzz]

Morning everyone. After a morning of investigation and checking I have (hopefully) found the culprit of the problem. By chance , I thought that while I was working on the engine I would change the oil and found that it was contaminated with diesel and had about 2 litres more fluid in it than there should be. My first thought was that the diagram on the lift pump had split but this was fine. I removed the injection pump and took it to a local diesel pump specialist who confirmed that the seal on the back of the pump is letting by. Basically, fuel is passing through it into the engine and oil entering into the fuel. I described the problem I've been having and he said that it was highly probable that the fault in the pump was the culprit as he'd seen it a number of times  before. He offered to replace the seal while I waited (about £50) but I decided to have the entire pump reconditioned which will cost about £350. Seems a bit daft not to have it done whilst the pump is off. I also asked him to overhaul the injectors at the same time as they looked like they hadn't been done since 1971 when my boat was built ! 

 

Anyway, should be back in a couple of days so I'll keep everyone updated ...... Fingers crossed. 

[john.k]

With a DPA pump you should always smell the dipstick to check for diesel in the oil........very common in Perks,but doesnt seem to do any damage.

[Nut]

good to hear its sorted

[john.k]

I dont think that a fuel weep from the pump seal would possibly be responsible for the slowing of the motor.The leak must have been minor,a total seal failure quickly fills the entire motor with fuel and it runs out into the bilge. The way I see the motor slowing is if the shutoff gradually engages.The way the DPA is set up is that a solid link shuts the throttle valve,but it is only pulled open by a very weak spring.This is why the pumps are so easily affected by fuel fungus......the weak spring cant pull the valve open.,and the motor cant start.,,,,edit........unless the bearings were starting to run hot,but he says the coolant temp was low.

Edited September 16, 2018 by john.k

[Tony Brooks]

I too can't see such a leak causing the problem for the reason stated above. The DPA pump pressurizes the whole pump body to transfer pump pressure (not sure what that is but its is far higher than lift pump pressure) so fuel will leak out, not suck air in. If the leak was large enough to starve the engine then as John.k says the sump would be ful in a very short time and probably leaking form the dipstick hole etc.

 

Still, that may be the problem so lets keep our fingers crossed.

[john.k]

Badly worn vanes in the transfer pump can cause issues with very low transfer pressure...so its probably wise to have the whole pump checked out......even if that doesnt cure the problem...I hope he checked the fine plastic mesh filter in the inlet nut.....a common cause of starvation.

[Tony Brooks]

36 minutes ago, john.k said:

Badly worn vanes in the transfer pump can cause issues with very low transfer pressure...so its probably wise to have the whole pump checked out......even if that doesnt cure the problem...I hope he checked the fine plastic mesh filter in the inlet nut.....a common cause of starvation.

 

See post 3. I am not sure the OP did as advised.