Canal Boat — February 2018

76 February 2018 Canal Boat canalboat.co.uk

BACK CABIN: EXPERTS

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Under pressure

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I have just serviced my engine for the first

time because I am fed up paying high prices

for a mechanic and then waiting weeks.

I purchased an oil extractor unit and found it very

successful for the oil change, so easy and clean.

I then changed the fuel filter on the engine and

removed the two fuel bowls that are connected via

copper pipe from my two diesel tanks. I washed these

out removing all the water and sediment after turning

off the taps. Having put everything back with new

washers I cannot get any diesel flowing from either

tank into the bowls. I removed the pipes each side but

still no fuel. I even tried blowing through pipes using

an air pump. Listening to the each tank you can hear

the air bubbling however no flow.

Both tanks are connected to each other by copper

tubing with a bleed, I removed this and no diesel

flowed. Each tank then runs in copper tubing to the

fuel bowls which are connected together, a single

outlet from the centre runs down to the fuel pump on

the engine block.

Is this an air lock? Do I try and create a vacuum or

alternatively pump diesel through the pipes back into

the tanks to reinstate the flow.

Your comments and or suggestions would be most

welcome. Not being a mechanic I was rather pleased

with myself until now.

DOUG BAGGE

TONY REPLIES: Well done so far and I

suspect you will kick yourself when you

read my reply.

Everything between the fuel tank and lift pump is

under some sort of suction and good practice dictates

that the fuel feed will be taken through the top of the

tank (although it is acceptable to take it from just

above the bottom). This means you can try to get fuel

out of those water traps all day long and nothing will

happen unless you fill the tank to a level above the

fuel feed pipe – not practical – so it siphons out. So

you have to bleed the system. Proceed as follows...

Clean the bowls on any water traps and/or replace

their filter elements. These may be fitted between the

tank and lift pump. Make sure any sealing rings are

properly in place and not twisted.

Next remove the domed cover on the lift pump,

clean the gauze that is in the top of the pump and also

clean the sediment traps below the gauze. Replace

the cap with a new soft washer under the single ‘hold

down’ bolt if the old one looks damaged or squashed.

Now change the filter at the back of the cylinder

head and clean the bowl.

Right on the top of that filter there should be a bolt,

probably a banjo bolt holding the injector leak off pipe

onto the filter head. It will not be in the centre of the

head. Loosen this a few turns. If there is no banjo

or bleed bolt on the top of the filter loosen its outlet

union. Grope about under the lift pump and you will

find a lever sticking out. Lift it right up and let it spring

back on its own. After a great number of repetitions

you will find that you have pumped fuel from the tank

and into the filter. Continue until there are no more air

bubbles in the fuel stream. Tighten the bolt or union.

Now locate the injector pump bleed screw. The BMC

2.2 was either fitted with a DPA or an INLINE injector

pump. I do not know which you have, so I cannot tell

you where the bleed screw is located. Once you locate

it loosen it and repeat the above bleeding procedure &

retighten. Do not be in too much of a hurry to retighten

because air can get trapped in the pipe(s) between

filter and pump.

If you have not used the starter since starting the

whole job, the engine may well now start, but it you

have, or if it will not start do the following:

Loosen the big injector pipe nuts on all the injectors

(or as many injectors you can easily get at) by about

half a turn. These are large nuts possibly 5/8”AF. Do

not confuse them with the small banjo bolts on the

top of the injectors. Spin the engine on the starter until

fuel drips from the nuts. Tighten them and the engine

should start and run.

If when trying to start the exhaust makes clouds of

white smoke then you have fuel in the cylinders, if it

only makes a few wisps or none at all there is no fuel

being delivered, so re-bleed.

Our boat has never had an expansion vessel

on the inlet to the calorifier. We have an

accumulator on the output side of the pump

and a one-way valve at the inlet to the calorifier. Is it

beneficial to fit an expansion vessel? I understand it

could prevent water wastage via the PRV. STEPHEN

TONY REPLIES: The answer is generally

yes because it reduced the stress on the

calorifier and, as you say, reduces the

amount of water lost via the PRV due to expanding

when heated. In fact, some calorifier manufacturers

make having an expansion vessel a requirement of

their guarantee. Having said that many calorifiers are

strong enough to withstand the expansion pressures

until the PRV opens. If the calorifier manufacture says

their product requires one then fit one. If not then fit

one if it suits you but never fit a PRV rated any higher

than that specified by the calorifier manufacturer.

Remember accumulators have air pressure at about

the pump cut-in pressure (near enough half the cut-

out pressure) while expansion vessels are pressurised

to the pump cut-out pressure.

A

A

Q

Q

When I was a young

driver I remember

seeing lots of old guys

driving an old Volvo. Now I’m one

of them and, probably like them,

I can’t think of a good reason to

change it.

I feel the same way about my

25-year-old 58ft Colecraft semi-

trad but I do wish it had a quieter

engine than its BMC 1.8 and I

would like to have one fitted to

enjoy before I finally hang up my

lock key. My boat spends a good

part of its life on the Thames so a

bit of grunt would be good too.

I favour a well silenced lower

revving engine as inherently

quieter and I’ve heard good

reports of the Beta 43 as being

head and shoulders above the

opposition in engineering and

reliability. But I think you’ve

mentioned Bukh and I’ve heard

that modern Listers are out there

too. I expect to have to fit a new

prop. I really would appreciate

your advice.

BILL PARISH

TONY REPLIES: A

while ago I investigated

engines for Canal Boat

magazine and concluded there

was little difference between

them except that the Bukh is

a proper marine engine rather

than a marinised automotive/

industrial engine. Quietening

most modern engines is achieved

by fitting a hospital silencer or

something very similar and then

soundproofing the engine bay.

You get rid of a fair bit of vibration

by fitting an Aquadrive, Python

drive or long Centaflex (two

element) coupling or by ensuring

the engine is always perfectly

aligned with the shaft. Getting

perfect alignment is all but

impossible with flexible mounts.

I suspect spending the money

on silencing, soundproofing,

and fitting a two element flexible

coupling may do all you require

for less cost.

Before deciding upon the

make of engine I would take a

very hard look at the mariniser’s

customer service and spares cost.

Also consider the cost availability

of spares from non-mariniser

sources. This would rule out two

marinisers in my book as far as

cost of spares go.

Q

A

Noisy engine simply has to go

Bleeding system may cure fuel problems