Canal Boat – July 2018

74 July 2018 Canal Boat canalboat.co.uk

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Q

I have an Isuzu 35hp engine

in my narrow boat that has

only done 900 hours. It gives off

white smoke when first starting

up cold that goes after 1 to 2

minutes. When hot it starts up

without smoke. Do you think it

has fuel injector problems on

one cylinder? I have replaced all

the pre-heaters.

BARRY CAMP

A

TONY REPLIES: In theory it

should not smoke but white

smoke on cold starting is not

particularly uncommon. The

smoke is normally just

vaporised fuel that has not

ignited on the first compression

stroke. There can be several

reasons but at this time of year

it might be low ambient

temperature or a poor quality

fuel problem. It seems incidents

of smoke from poor fuel are

increasing.

Have you measured the

voltage at the glow plugs when

they are operating? If it’s lower

than 12V then there is probably

some sort of electrical

resistance on the glow plug

circuit that is preventing them

getting hot enough to start on

the first cycle. In no particular

order, this could be undersized

cables, dirty or loose connection

(often in the big multi-plug that

is in the main harness), or

resistive ignition switch or glow

plug relay if a relay is used.

Once you are sure the glow

plugs can get hot enough I would

change the fuel filters then drain

and cut the old ones open to see

what they have caught - if

anything. That may give the first

indication of a fuel quality or

contamination problem.

If the compressions were

compromised you would get this

sort of symptom but at 900

hours internal wear is unlikely;

however a valve clearance may

have closed up so check the

valve clearances.

After doing the above I would

give the tank a good dose of

injector cleaner from a motor

factors or Halfords type outlets

and let it work through the

system. Then see what happens

at the next refuelling. If the

problem goes away it is likely to

be poor quality fuel being more

difficult to ignite or dirty

injectors but at a true 900 hours

I do not think an injector problem

is likely, but who knows.

Anything that makes the fuel

more difficult to ignite can cause

this symptom. So if an injector is

not closing properly or streaking

rather than atomising the fuel it

will cause unburned fuel to lay in

the cylinders and exhaust at

cold start, hence the white

smoke.

If the injector pump rack is a

little sticky it may not rest at

maximum fuel, which is the cold

start position so try starting it

with full throttle, but slow down

as it fires.

Air might be getting into the

fuel system somewhere so if

your engine has an electric lift

pump turn the ignition off for a

minute or so before using the

starter. That should purge any

air. If it’s a mechanical lift pump

try spinning the engine with the

stop control in the stop position.

That should do something

similar. These are diagnostic

tests rather than regular

starting procedures.

If all else fails you may have to

get the injectors serviced but at

900 hours that seems unlikely

unless you have had water in the

fuel problems.

You may even find the problem

goes away once the ambient

temperature rises a bit.

Engine smoking after cold start

Q

I’m considering

fitting a Pressure

Reducing Valve into the

cold inlet line to the

calorifier so as to

satisfy its 3 bar

Pressure Relief Valve

and then, (in theory)

maintain a higher

pressure to the rest of

the system.

GEOFF

(UKSHIPPERS)

A

TONY REPLIES:

If that is what you

want to do then there is

no reason not to

PROVIDING the valve

maintains the reduced

pressure at its outlet

side when there is no

flow but you will be

adding a complication

and another failure

point.

I suspect that I do not

have the whole story

because 3 bar is 45 psi

and that is high, I think

most boats operate

with a 2 bar or 2.5 bar

pump perfectly

satisfactorily. I ran mine

for years at about 10

psi and only recently

increased it to 15 psi. I

do this because with

lower pressures the

plumbing is less likely to

leak.

I wonder if you have

another problem on the

boat that requires you

to operate at such a

high pressure. Most

domestic water pumps

are adjustable for

pressure and if not an

external pressure

switch can easily be

added.

Pressure

reducing

valve

Stern gland repacking

Q

I have read your

TB-Training

website giving

instructions regarding

replacing the stern

gland packing. I have

decided to repack the

gland using your ‘non

standard’ method i.e.

using one length of

packing. I am not clear

which way to wrap the

packing round the

shaft with reference

to the direction of

rotation.

Could you please

clarify.

For example: if shaft

rotates clockwise

(looking from astern)

when going ahead

then packing should

be wrapped

(clockwise/anti

clockwise.)

STUART JONES

A

TONY REPLIES:

I am afraid I have

never given a thought

to that way of looking

at it because it is so

easy to simply wrap

the packing around

the shaft clear of the

gland. Then run your

finger round the shaft

in the direction of

ahead rotation

between a pair of coils

formed by the packing

and see which way

the packing forces

your finger.

If your finger is

forced towards the

gland so will any

water. This means you

got it right first time. If

your finger moves

away from the gland

then wrap the coils in

the other direction.

Unconventional

stern gland packing

• it may leak.
  See tb-training.co.
  uk notes for
  conventional packing.