BMC 1.8 - Starting

[Nemysys]

Hi All

 

Hope you all had a good holiday season!

 

I'm a novice boater and I have a question about starting my BMC 1.8 engine.

Now the weather is colder I've notice it is a bit more reluctant to start - always managed to start it but can take a while.

I run a diesel car and understand about the pre-heaters, but now not sure if I am using them correctly on my boat.

 

I turn the key one click - a red light (ignition?) comes on - I presumed at this point the pre-heaters came on. As when I turn the key further (against the spring) the starter motor kicks in.

I assume I have pre-heaters but have not found another switch for them.

 

Is this normal behavior, am I missing something here?

 

 

 

Thanks

 

Darren

[RLWP]

Our 1.8 has a stage between the red light and the starter turning. You turn the key and hold it against the spring - this is when the heater plugs are switched on. Count to ten (probably twenty this time of year) then turn to the starter

 

Richard

[alan_fincher]

Normally the switch would have FOUR positions.....

 

1) Off

2) Alternator connected (red light on)

3) (Have to hold it part way over against spring). Heaters active. (The ammeter will show large current if you have one - well over 30 amps on the BMC 1800s with the later type of heater plugs).

4) (Hold right over against spring). Starter motor engaged, (the heaters are still running at this point too, on most set-ups).

 

The book says a BMC can need anywhere between 15 and 30 seconds of pre-heat in cold conditions. 30 seconds seems a hell of a long while, compared to the few seconds max needed in a modern diesel car.

 

The "throttle" lever should (according to the book) be wide open when you are starting.

Edited January 17, 2012 by alan_fincher

[Chalky]

 

I run a diesel car and understand about the pre-heaters, but now not sure if I am using them correctly on my boat.

 

 

Car glow plugs are often controlled by the engine management not the ignition switch. On you car the glow plug warning light is not necessarily a true indication of what the engine management is doing with the glow plugs. The more sophisticated ones will vary the glow plug on time depending on the air temp and engine coolant temp. Its not unknown for some engines to keep them on until the head is up to temperature to help meet emissions legislation.

[pete.i]

Hi

 

Yes mine is the same as Richards although my engine is a BMC 1.5 I have that stage between the ignition light coming on and activating the starter. I hold the switch against the spring pressure for 30 seconds in this weather and then turn it the rest of the way which activates the starter.

 

Pete

[Nemysys]

Thanks everyone - I'll try that next time I go to the boat.

 

4) (Hold right over against spring). Starter motor engaged, (the heaters are still running at this point too, on most set-ups).

This would probably explain why it does start eventually, as I would have the heaters and the starter going at the same time.

[Chalky]

Also cranking the engine will cause the compression to warm up the head so it will eventually start to diesel. There was a car engine a few years ago that used 3 glow plugs on a 4 cylinder engine and used that technique to start the 4th cylinder dieseling.

[bottle]

Start switches vary, if the positions are not marked on the panel.

 

The heater position may be anti- clockwise (from off) against a spring, hold for a count of thirty (30), [bMC only other engines vary, check manual] turn clockwise fully, against spring until engine starts.When engine starts release.

 

If engine does not start in count of ten (10) go back and repeat procedure.

 

Control lever should be set to about half way of travel and drive must be dis-engaged.

Edited January 18, 2012 by bottle

[alan_fincher]

Control lever should be set to about half way of travel and drive must be dis-engaged.

Often stated for many engines, but BMC manuals clearly state fully open.

 

Don't shoot the messenger, but that's what the manufacturers say!

[Guest]

Often stated for many engines, but BMC manuals clearly state fully open.

 

Don't shoot the messenger, but that's what the manufacturers say!

 

I think it's the dis-engaged bit that Keith is emphasising...

[JerryP]

Hi All

 

Hope you all had a good holiday season!

 

I'm a novice boater and I have a question about starting my BMC 1.8 engine.

Now the weather is colder I've notice it is a bit more reluctant to start - always managed to start it but can take a while.

I run a diesel car and understand about the pre-heaters, but now not sure if I am using them correctly on my boat.

 

I turn the key one click - a red light (ignition?) comes on - I presumed at this point the pre-heaters came on. As when I turn the key further (against the spring) the starter motor kicks in.

I assume I have pre-heaters but have not found another switch for them.

 

Is this normal behavior, am I missing something here?

 

 

 

Thanks

 

Darren

 

 

are your "heater plugs" in good working order ?

[bottle]

Alan

 

I would not even think of shooting you.

 

The manual may well say that, I would not dispute it, just passing on what I was told all those years ago when we hired.

 

Personally I think that fully open may be a little OTT but that is only my opinion.

 

I did not like it, even at half revs, when the engine started to much going on in a cold engine.

[JerryP]

when i was an apprentice diesel mechanic ,i was bought up on BMC diesels (among others) ,i was always taught to "floor the throttle" when turning over diesel engines.

[Tony Brooks]

when i was an apprentice diesel mechanic ,i was bought up on BMC diesels (among others) ,i was always taught to "floor the throttle" when turning over diesel engines.

 

 

I agree, but just make sure you close the throttle as soon as it fires, it should not have a chance to reach maximum revs.

 

The reason for this is that if your rack/governor is a bit sticky fully opening the throttle will apply more spring pressure to force it to maximum fuel. Now I do not see why/how that helps on a diesel but it seems to.

 

 

As for the times. Most BMC 1.8s use the modern "fat" glow plugs that draw about twice the current of the older ones so a hold of 10 to 15 seconds should be fine. Some early 1.8s and all 1.5s use the older "pin" type glow plugs and these need a (slow) count to 30 when cold. (Unless the head has been changed for a 1.8 one and the possibility of that seems to be open to question).

 

For information and by observation. Pin type plugs settle at about 6 amps per plug with some having an initial surge and some not. The modern fat ones on BMCs draw a very high current as soon as they are energised and drop to about 12 amps per plug when hot.

[alan_fincher]

I think it's the dis-engaged bit that Keith is emphasising...

Not the bit I was questioning though, and the "half open" thing can work against you, so well worth talking about.....

 

As Tony says later, it isn't intuitively obvious why "lever hard over" should encourage a slow starting BMC to come to life more easily, but sometimes it seems to.

 

Obviously you then need to back it off quickly, but they do take a second or two before they start really hammering, so that's not really that hard.

 

Lever half down is fine normally, but the initial complaint was of a slow starter.

 

My guess though, from the descriptions, the OP's engine would probably start fine, provided the heaters are in good order, and they can work out how to have them heating for the required period before they try and start it.

 

BMCs can be funny buggers though...... Mine has managed to start cold, with no heaters, and with two of the injector pipes disconnected, when I was trying to bleed the high pressure fuel system, but at other times full use of the heaters is normally the way to go.....

[nicknorman]

Now I do not see why/how that helps on a diesel but it seems to.

 

More fuel in the cylinder means less volume available for the air at the top of the compression stroke, so raises the effective compression ratio, so hotter compression and better chance of self ignition.

 

Some engines have an excess fuel function that allows more than max fuel flow into the engine for this purpose. It is reset centifugally so once the engine starts, max fuel flow reverts to normal. The function is sometimes set by a separate lever, sometimes automatically, and sometimes by moving the throttle to max. I have no idea if BMC engines have this.

[MoominPapa]

Some engines have an excess fuel function that allows more than max fuel flow into the engine for this purpose. It is reset centifugally so once the engine starts, max fuel flow reverts to normal. The function is sometimes set by a separate lever, sometimes automatically, and sometimes by moving the throttle to max.

On many Listers it's set by the engine stop lever: moving it to the STOP position shuts off the fuel, then moving the lever back to run engages excess fuel, which resets once the engine exceeds 1000 rpm or so.

 

MP.

Edited January 18, 2012 by MoominPapa

[churchward]

Normally the switch would have FOUR positions.....

 

1) Off

2) Alternator connected (red light on)

3) (Have to hold it part way over against spring). Heaters active. (The ammeter will show large current if you have one - well over 30 amps on the BMC 1800s with the later type of heater plugs).

4) (Hold right over against spring). Starter motor engaged, (the heaters are still running at this point too, on most set-ups).

 

The book says a BMC can need anywhere between 15 and 30 seconds of pre-heat in cold conditions. 30 seconds seems a hell of a long while, compared to the few seconds max needed in a modern diesel car.

 

The "throttle" lever should (according to the book) be wide open when you are starting.

Yep What Alan said.

 

BMCs love heat so when its sub or near zero temperatures give I would give it 15 to 20 secs as a first start and a bit longer if it doesn't start. These engines are not your modern common rail managed systems and need more coaxing into life. If after giving it the full beans for nearer 30 secs it still has trouble then that probably points towards some other kind of trouble with injectors or compression for example.

[bizzard]

Most diesel engined lorries way back had excess fuel or cold start aid which was often brought into use to surmount a steep hill to give it a bit more oomph as could be seen by a sudden huge cloud of black smoke half way up,this was not the driver flooring the throttle,he would already have done that but pulling out the cold start.

[Nemysys]

Thanks to everyone for there replies. Thats what I love about this forum, lots of quick helpful advice.

 

It may be a week or so, but next time I go to the boat, I'll try what has been suggested 50-100% throttle, try turning the key backwards to see if that position exists, if not I'll try turning the key half against the spring. I'll post the results, hopefully good news.

 

I'll upload a picture I took of the engine, not sure if you eagle eyed readers will be able to tell the type of heaters from a photo or if you need to take them out to look.

[Richard T]

If your BMC is a Thornycroft conversion - it will be described as a 108 and may have Thornycroft on the instrument panel, then the glow plugs are activated by pushing and holding in a small black button which is below the ignition switch. So the starting procedure is as follows:-

Disengage gear and push throttle to max revs

Turn on ignition switch

Push heater button for about 30secs when cold.

Turn key to activate starter and crank engine

When engine starts reduce throttle to a little above idling speed.

Check that alternator has been excited and ignition warning light has gone out - it might need a blip on the throttle for this to happen.

[Nemysys]

[alan_fincher]

What you have pictured is a marinisation by Calcutt Boats.

 

So it may well have a control panel something like this

 

 

(Or possibly a similar, but bigger one with more dials, including a big tachometer in the middle).

 

If so, it is highly likely that the heaters are on that 3rd position of the switch already described, (held against a spring, but not right over so the starter is running).

 

If you had an ammeter like the 30 amp one shown, then the needle should be hard off the end of the scale if all the heaters are operating cporrectly, as even when warm the total current draw is well over 30 amps.

[ditchcrawler]

when i was an apprentice diesel mechanic ,i was bought up on BMC diesels (among others) ,i was always taught to "floor the throttle" when turning over diesel engines.

We always left our Lifeboats with the throttle wide open and the drive disengaged ready for starting.

[Nemysys]

Impressed with the knowledge on these forums, you are right about the control panel.

 

sorry about the poor photo.