Glow plug relays

[Musetta37]

I have a 3 cylinder, 20 HP Yanmar by Shire. 12 years old. The glow plugs are connected directly to the cranking terminal of the starter motor (as new) this is ok when the engine is not too cold. In this weather it is extremely difficult to start and battery power is being wasted as the glow plugs are only working when the engine is cranking over. I intend bypassing the starter terminal and fitting a manual switch controlling a relay to pull the glow plugs in before starting (I ran this idea past Barrus who agreed), but what size relay should I fit? This wont be a timer relay, to keep things cheap and simple. Anyone got any ideas. Thanks

[Tony Brooks]

I have a 3 cylinder, 20 HP Yanmar by Shire. 12 years old. The glow plugs are connected directly to the cranking terminal of the starter motor (as new) this is ok when the engine is not too cold. In this weather it is extremely difficult to start and battery power is being wasted as the glow plugs are only working when the engine is cranking over. I intend bypassing the starter terminal and fitting a manual switch controlling a relay to pull the glow plugs in before starting (I ran this idea past Barrus who agreed), but what size relay should I fit? This wont be a timer relay, to keep things cheap and simple. Anyone got any ideas. Thanks

 

 

I think that you will be looking at in excess of 150 amps initially dropping to about 36 amps after maybe 5 seconds so a 40 map automotive one might just about do the job. However when I was fitting hire boats I used a stater solenoid rather than a relay. The sort of thing we used with inertia starters. You may need to attach a negative cable to a screw that is securing it to the boat and ignore any small blade connections on the cap, you want the 6mm blade one.

[Keeping Up]

On a similar issue, how quickly do the plugs cool down when you remove the power from them? On mine yuu turn the ley to the left to heat the plugs, then to the right through the "run" position and on to the "start" position. I have been wondering whether the plugs will cool down much during the short pause, and if it would be worth fitting either a diode or a secondary relay so that when the starter is operated that also will warm the plugs.

 

 

[bizzard]

I think that you will be looking at in excess of 150 amps initially dropping to about 36 amps after maybe 5 seconds so a 40 map automotive one might just about do the job. However when I was fitting hire boats I used a stater solenoid rather than a relay. The sort of thing we used with inertia starters. You may need to attach a negative cable to a screw that is securing it to the boat and ignore any small blade connections on the cap, you want the 6mm blade one.

''AES. Auto electric supplies'' stock 3 or four types of these old inertia starter solenoids for around £12, they do make excellent heavy duty relay switches, you do usually need to connect their body to neg-.

[Musetta37]

On a similar issue, how quickly do the plugs cool down when you remove the power from them? On mine yuu turn the ley to the left to heat the plugs, then to the right through the "run" position and on to the "start" position. I have been wondering whether the plugs will cool down much during the short pause, and if it would be worth fitting either a diode or a secondary relay so that when the starter is operated that also will warm the plugs.

We used to do a quick test across a battery (with each plug removed)the plug would glow red hot after a second or two and go cold as quick when power was switched off.

 

I think that you will be looking at in excess of 150 amps initially dropping to about 36 amps after maybe 5 seconds so a 40 map automotive one might just about do the job. However when I was fitting hire boats I used a stater solenoid rather than a relay. The sort of thing we used with inertia starters. You may need to attach a negative cable to a screw that is securing it to the boat and ignore any small blade connections on the cap, you want the 6mm blade one.

Perfect ! Thanks for that.

[nb Innisfree]

You could use a pnuematic timer to operate a relay or solenoid, time is adjustable from 10 seconds to 20 mins.LINK

[Musetta37]

''AES. Auto electric supplies'' stock 3 or four types of these old inertia starter solenoids for around £12, they do make excellent heavy duty relay switches, you do usually need to connect their body to neg-.

I'll give them a call, Used to use them when I was in the trade.Thanks.

[bizzard]

I'll give them a call, Used to use them when I was in the trade.Thanks.

Google them they have a good website. They stock lots of the more old fashioned handy stuff too. And dynamos and regulators.

[Musetta37]

You could use a pnuematic timer to operate a relay or solenoid, time is adjustable from 10 seconds to 20 mins.LINK

Thanks for the tip, but I want to keep it as simple as possible,less can go wrong etc. etc.

 

You could use a pnuematic timer to operate a relay or solenoid, time is adjustable from 10 seconds to 20 mins.LINK

Thanks for the tip, but I want to keep it as simple as possible,less can go wrong etc. etc.

[nb Innisfree]

Thanks for the tip, but I want to keep it as simple as possible,less can go wrong etc. .

 

Fair enough but you will need a switch to operate relay anyway, timer switch is so simple and it will allow you to start one handed, otherwise you will have to keep switch pressed with one hand while operating starter with the other and keeping switch pressed for a short while as engine runs.

[Musetta37]

Fair enough but you will need a switch to operate relay anyway, timer switch is so simple and it will allow you to start one handed, otherwise you will have to keep switch pressed with one hand while operating starter with the other and keeping switch pressed for a short while as engine runs.

I know what you mean,I have a spring return push button switch which will do the job, when I get fed up with pressing that, I will think about a timer.

[bizzard]

If you have a proper diesel engine ''start key switch'' it could have a heater position and terminal for heater plugs on it.

[jonathanA]

AFAIK most glow plug relays are 70A. mine has a timer built in and when it went faulty the offical part cost £100 new !!! (blimey). my solution was to buy a secondhand unit off an landrover discovery for a fiver and bob is you're aunts live in lover....

[Tony Brooks]

AFAIK most glow plug relays are 70A. mine has a timer built in and when it went faulty the offical part cost £100 new !!! (blimey). my solution was to buy a secondhand unit off an landrover discovery for a fiver and bob is you're aunts live in lover....

 

 

But that one probably had a timer circuit in it to illuminate/put out a warning lamp bulb.

[jonathanA]

But that one probably had a timer circuit in it to illuminate/put out a warning lamp bulb.

 

it does/did - £100 for a 70A relay and 10p's worth of electronics was ridiculous (of course it was a 'marine' part). The relay also resets after the timer has expired (think its about 5 seconds or so in my case) switching off the glowplugs.

 

Landrover unit was a direct plug compatible item as most of these are probably automotive derived anyway. The main difference between similar packaged relays (same pinout)is whether they have a separate warning lamp and the time they stay on for.

 

in the ops situation he could just wire the relay coil up to the ign live, insert the relay in the glow plug supply and fit a warning lamp to the glow plug side of the relay

[nb Innisfree]

it does/did - £100 for a 70A relay and 10p's worth of electronics was ridiculous (of course it was a 'marine' part). The relay also resets after the timer has expired (think its about 5 seconds or so in my case) switching off the glowplugs.

 

Landrover unit was a direct plug compatible item as most of these are probably automotive derived anyway. The main difference between similar packaged relays (same pinout)is whether they have a separate warning lamp and the time they stay on for.

 

in the ops situation he could just wire the relay coil up to the ign live, insert the relay in the glow plug supply and fit a warning lamp to the glow plug side of the relay

 

Usually the light going out means it's time to start the engine but the plugs stay on for a while longer.

[jonathanA]

Usually the light going out means it's time to start the engine but the plugs stay on for a while longer.

it does vary - some modern diesels keep the glow plugs on when the engine has started for a short time (presumably to aid running or reduce emissions) The pre start heat and post start heat times will vary (quite a bit) between manufacturers so perhpas I've opened up a whole can of worms for the unwary that I didn't intend.

 

my point was that you don't need to get involved with push buttons, timing switches or other paraphenalia when you can pick up an automotive glow plug relay with timer for not much more than the cost of a heavy duty relay.

 

but the simplest thing for the OP is bizzards pre-heat position on the ign switch - but that will still need a 70A relay to switch the glow plug supply

[nb Innisfree]

it does vary - some modern diesels keep the glow plugs on when the engine has started for a short time (presumably to aid running or reduce emissions) The pre start heat and post start heat times will vary (quite a bit) between manufacturers so perhpas I've opened up a whole can of worms for the unwary that I didn't intend.

 

my point was that you don't need to get involved with push buttons, timing switches or other paraphenalia when you can pick up an automotive glow plug relay with timer for not much more than the cost of a heavy duty relay.

 

but the simplest thing for the OP is bizzards pre-heat position on the ign switch - but that will still need a 70A relay to switch the glow plug supply

 

No prob, cans of worms are our speciality!

 

I have noticed on our LPWS4 that when I start the engine on a cold day there is a slight squealing sound for a few seconds, so I jury rigged the glow plugs to allow me to operate them manually and found I could get rid of the squealing by keeping the plugs on for several secs after starting. I do reckon it's better to have manual control however it's achieved.

[jonathanA]

No prob, cans of worms are our speciality!

 

I have noticed on our LPWS4 that when I start the engine on a cold day there is a slight squealing sound for a few seconds, so I jury rigged the glow plugs to allow me to operate them manually and found I could get rid of the squealing by keeping the plugs on for several secs after starting. I do reckon it's better to have manual control however it's achieved.

 

We've the same engine I had a squeal on start up and that turned out to be the fan belt ! I'll be listening next time I start her though now!

[smileypete]

I know what you mean,I have a spring return push button switch which will do the job, when I get fed up with pressing that, I will think about a timer.

As bizzard says, if it's a standard Lucas switch like this it'll already have a dedicated glo plug terminal:

 

http://www.ebay.co.uk/itm/130351316250

http://www.autoelectricsupplies.co.uk/product/779

 

cheers, Pete

~smpt~