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Glow Plugs- how long to leave them on?

Southern Star

By Southern Star
in Boat Handling

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Southern Star Experienced

Southern Star

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At this time of year, with temperatures just above zero and with an engine which has not been started for several weeks, how long do folk normally leave their ignition switch in the glow plug position? I normally do a timed 20 seconds but it still takes about 20 seconds of cranking for my engine to fire up (BMC 1.5).

 

I can't find anything in the user manual about this, so what is considered "normal"?

 

 

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bizzard Veteran II

bizzard

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At this time of year, with temperatures just above zero and with an engine which has not been started for several weeks, how long do folk normally leave their ignition switch in the glow plug position? I normally do a timed 20 seconds but it still takes about 20 seconds of cranking for my engine to fire up (BMC 1.5).

 

I can't find anything in the user manual about this, so what is considered "normal"?

 

 

10 seconds is more usual with an engine in good nick, clean or new heater plugs and that they are all working. You will need about 3/4 open throttle too.

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pete.i Rising Star

pete.i

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When I had my BMC 1.5 in the depths of winter such as we had a few years back I needed to count my glow plugs on for 30 seconds. On a summers day it was more like 10 seconds. In either case there was a few seconds of engine churning but it always fired up without fail. I would think if you are leaving yours for several weeks then what you are doing is normal.

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Bloomsberry Community Regular

Bloomsberry

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Started my BMC 1.5 engine for the first time in about 3 months this week. It is quite old. I gave it 10 seconds of heating and maybe should have give it a bit more as it did turn over quite slowly and grunted a bit but managed to fire first time with a bit of smoke to start with.

I think asking a very cold engine that hasn't been started for a while to start without any resistance is a big ask so think giving it more heating than usual is a good idea.

I'm no expert but I believe engine oil is less viscous at low temperatures so would be a cause of more resistance.

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RLWP Veteran II

RLWP

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Usuallya count of ten to fifteen is enough to get them good and hot

 

Richard


I'm no expert but I believe engine oil is less viscous at low temperatures so would be a cause of more resistance.

 

Yes - only it is more viscous, not less

 

Richard

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Guest

Guest

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This thread does remind us how archane diesel narrow boat engines are.

 

I get in my diesel car in the morning insert key turn and engine starts.

 

What is it that modern diesels in cars do that older designed diesels in boats do not?

 

As to the OP. I found much the same if our Isuzu had been left in the cold for more than a week or so.

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Señor Chris Proficient

Señor Chris

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so what is considered "normal"?

 

 

 

I've been wondering this too. I was advised 10s but that seems a long time - all the cars/vans I've owned had a pre-heat light on the dash which went off after no more than 4-5s and the engines always fired up instantly, even when very cold. I've also read that you can damage the plugs if you overcook them.

 

And while we're on the subject, do glow plugs 'fade' over time or just pack up? I've a feeling that mine are the originals (same paint as the engine) which makes them 20+ years old.

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RLWP Veteran II

RLWP

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I get in my diesel car in the morning insert key turn and engine starts.

 

What is it that modern diesels in cars do that older designed diesels in boats do not?

 

Don't you wait until the heater plug warning light goes off?

 

Richard

 

I've a feeling that mine are the originals (same paint as the engine) which makes them 20+ years old.

 

Sometimes, it's best to ignore things

 

Richard

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Guest

Guest

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Don't you wait until the heater plug warning light goes off?

 

Richard

It goes off almost instantaneously, effectively meaning I don't bother to wait.

 

This is my first winter with this one and as yet it hasn't really been that cold.

 

Maybe if it gets colder I may have to wait longer?

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alan_fincher Veteran II

alan_fincher

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I can't find anything in the user manual about this, so what is considered "normal"?

 

The original BMC operators handbook does actually say ...

 

For cold starting proceed as for normal starting, but before operating the starter switch, switch on the heater plugs for a period of between 15 and 30 seconds.

 

 

When I has one, my usual rule of thumb was to watch the ammeter until the current drawn by the plugs starts to fall, which almost certainly fell within that timing range.

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RLWP Veteran II

RLWP

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Maybe if it gets colder I may have to wait longer?

 

Possibly. Having had to mess about with this technology recently, cars use a timed circuit to turn on the warning light and the plugs. After a while they turn off the light but leave the plugs on while the user starts the engine.

 

Richard

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beerbeerbeerbeerbeer Veteran II

beerbeerbeerbeerbeer

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10 seconds is more usual with an engine in good nick, clean or new heater plugs and that they are all working. You will need about 3/4 open throttle too.

Yep, 10 seconds and some throttle, starts first time even after 6 weeks In the cold.

But if I forget the throttle it won't start straight up.

 

Glenn

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bottle Veteran II

bottle

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It's simple as RLWP inferred, old engines (BMC etc.) heater plugs turned ON wait for set time, plugs turn OFF engine turned over and it starts. (hopefully)

 

Some also needed the the 'throttle' to be open to, again, a set position.

 

Modern vehicle diesels have a different system, turn ON heater plugs, turn over engine and it starts, very short delay before indicator light goes out but the heater plugs stay ON to assist in the engine starting.

 

Modern boat diesels still work in a similar way as the 'old' engines but as with all things there will be progress and I doubt it will be long before modern boat engines work in the same way as modern vehicle engines. Electronics etc.


Note: when I mention boat it is canal boats, not Mediterranean cruisers. rolleyes.gif

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Scholar Gypsy Veteran

Scholar Gypsy

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30 seconds, plenty of throttle, and the engine always starts first time (even after a six week break over Christmas).

 

Last year the engine was starting, but running rough (and white smoke) for ten seconds, which suggested (see earlier thread) that one of the heaters was not working properly. Despite various testing techniques, I could not work out which one so I replaced the lot (and the link cables which were a bit weedy). All fine now.

 

I would think that the heaters just heat the cylinder head to aid combustion, and so won't have any impact on the cold viscous oil.

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