Poss engine starting probs

[Frankieboy]

Ive noticed lately that the engine often takes longer to start from cold. When the engine is warm it starts instantly. Would I be right in thinking that its probably the glow plugs?

Cheers

Frank

[Chris-B]

Remove the glow plugs from the head, set up a test rig with a good battery as a feed and see individually if each one glows after 6 secs

if no glow..duff plug

 

c

[gazza]

safer way is to measure the resistance of the heater plug. remove the + supply and link cables. measure from + to a good clean part of heater plug body. you should be looking at 0.6 - 0.7 ohms typically. open circuit = dustbin

[David Schweizer]

Ive noticed lately that the engine often takes longer to start from cold. When the engine is warm it starts instantly. Would I be right in thinking that its probably the glow plugs?

Cheers

Frank

It could just be the cold weather. My BMC 1.5 starts straight away in the summer, but in the winter can need up to a minute with the glow plugs on before starting. That is what they are thre for.

[alan_fincher]

It could just be the cold weather. My BMC 1.5 starts straight away in the summer, but in the winter can need up to a minute with the glow plugs on before starting. That is what they are thre for.

Agreed....

 

You don't say what engine, I think, but something like a BMC says in the owners manual that it is designed to need up to 30 seconds before engaging the starter, (at which point heaters usually remain connected too).

 

Just because sometimes it will start from cold on far less, doesn't mean anything is not as it should be IMO.

[RobinJ]

Remove the glow plugs from the head,...

It is worth doing this just to see if they are in good condition, there effectiveness can be impeded if there is soot build up and removing them is often the only way to clean out the ports!

BMC's are very prone to carbon build up around the heater plugs and if it takes more than 30 seconds in the winter, when it starts without during the summer, it is a good indication the plugs are not providing enough heat!

[Tony Brooks]

safer way is to measure the resistance of the heater plug. remove the + supply and link cables. measure from + to a good clean part of heater plug body. you should be looking at 0.6 - 0.7 ohms typically. open circuit = dustbin

 

 

Also, as a guide. If you have access to a DC clamp type ammeter the BMC 1.5 plug draw a steady 6 amps each and the modern engines draw a very high current dropping to a steady 12 amps. Thus a four cylinder engine will draw about 25 amps if a 1.5 or over 100 amps dropping to about 50 amps as the plug warms up.

 

You can measure it on a battery lead.

 

This will not tell you if the right end of the plug is glowing or if its carboned up.

[Frankieboy]

Thanks.

The engine is an Isuzu 33 by the way.

I'll take the plugs out and check them, but I guess it could well be the cold weather.

The plugs have been in the engine since long before I bought the boat so its probably worth popping them out for a check anyway.

Thanks again

Frank

[wonderdust]

If they are the original plugs be careful taking them out, they can snap! Do as Alan & Robin says charge them for 30 secs or longer and see if it starts any better.

[Naughty Cal]

Our big diesel can take some starting on cold mornings, they need a lot of heat to get them going. If it fires after about 30 seconds of charge i wouldnt worry, any longer and you may need to check the plugs.

[casper ghost]

I never understood why new engines have glow plugs when my old-ish Sabb starts fine in freezing temperatures with no glow plugs or pre heating.

[n.b.Goldie]

I never understood why new engines have glow plugs when my old-ish Sabb starts fine in freezing temperatures with no glow plugs or pre heating.

Usually depends on whether the engine id direct or indirect injection. Indirect needs glow plugs.

[alan_fincher]

I never understood why new engines have glow plugs when my old-ish Sabb starts fine in freezing temperatures with no glow plugs or pre heating.

It probably depends on whether it is "direct injection", (fuel injected straight into cylinder) or indirect injection (fuel injected into pre-combustion chamber of some sort).

 

The higher compression ratio of the former means the fuel can usually be ignited without heater plugs even with a cold engine, whereas the latter generally require them for cold starts.

 

Sabbs, I believe are direct injection, generally, whereas many boats with "modern" diesels use indirect.

 

I'm sure I'll be corrected if I've mixed up my terminology (or worse, explanation!).

[soldthehouse]

I never understood why new engines have glow plugs when my old-ish Sabb starts fine in freezing temperatures with no glow plugs or pre heating.

Something to do with swept volume and volume of air/diesel charge giving greater natural heating of the contents on the compression stroke...waffle waffle waffle

[casper ghost]

So, why make them so they need heating, there must be some advantage.

 

Something to do with swept volume and volume of air/diesel charge giving greater natural heating of the contents on the compression stroke...waffle waffle waffle

 

Why aren't you out working on that shell?

[soldthehouse]

So, why make them so they need heating, there must be some advantage.

 

 

 

Why aren't you out working on that shell?

Did I miss something when did we get married! Been delivering a giant window /door frame for the son on my ifor williams going along now, although its nearly ready to go to the yard for phase two { thats the others laughing when they see my welding and fabrication]

[Keeping Up]

The legend by the 'heat' position on my starter switch says "12 seconds maximum" (Duffield/Perkins MC42). I've often wondered whether this time limit is to protect the plugs in some way, or to ensure that the battery is not too far discharged. Does anybody know?

[David Schweizer]

There is an alternative to conventional glow plugs, which is fairly commonplace on tractors. tThis is an electrically operated pre-heating device which screws into the inlet manifold, heating the fuel as it enters the combustion chamber. They can be obtained from most Agricultuiral Merchants, and are apparently quite easy to fit (once you have got the manifold off!) Very useful if you have broken off more than one of the glow plug tips leaving them stuck in the head.

 

 

Or ebay:- http://cgi.ebay.co.uk/jcb-parts-perkins-ma...=item4149b31c5d

Edited October 21, 2009 by David Schweizer

[Phil Ambrose]

Agreed....

 

You don't say what engine, I think, but something like a BMC says in the owners manual that it is designed to need up to 30 seconds before engaging the starter, (at which point heaters usually remain connected too).

 

Just because sometimes it will start from cold on far less, doesn't mean anything is not as it should be IMO.

 

Agreed, I remember looking round a website (glow-plugs .com I think) and was amazed at the variety of go plugs available and the different times of warm up on various glow plugs, from" instantaneous" to a" long time" The shorter the warm up time the more expensive.

[Naughty Cal]

Agreed, I remember looking round a website (glow-plugs .com I think) and was amazed at the variety of go plugs available and the different times of warm up on various glow plugs, from" instantaneous" to a" long time" The shorter the warm up time the more expensive.

 

Thought it might be. Something else to add to the expensive list

[gazza]

Also, as a guide. If you have access to a DC clamp type ammeter the BMC 1.5 plug draw a steady 6 amps each and the modern engines draw a very high current dropping to a steady 12 amps. Thus a four cylinder engine will draw about 25 amps if a 1.5 or over 100 amps dropping to about 50 amps as the plug warms up.

 

You can measure it on a battery lead.

 

This will not tell you if the right end of the plug is glowing or if its carboned up.

 

 

 

 

correct. resistance is a useful indicator of open circuit though.

 

 

 

I never understood why new engines have glow plugs when my old-ish Sabb starts fine in freezing temperatures with no glow plugs or pre heating.

 

heater plugs are also used in a post heating phase on modern diesels, they may not be energised at full current but will heat to improve cold start emmisions.

 

 

an old DI will normally be a fair bit louder than a old indirect engine, there are fors and againts for both types. advances in pump technology have given us the common rail diesel. anyone who owns a modern common rail and has owned anything pre mid 90's will appreciate the difference.

 

try a 150 bhp VW for a lesson in power and refienment, jump in a diesel golf from the 80's and the differences will be, ummmm, startling!!!

[Phil Ambrose]

Thought it might be. Something else to add to the expensive list

 

You could make it really expensive and add the word "marine"

[Naughty Cal]

You could make it really expensive and add the word "marine"

 

Hmm i have noticed that little word has a habit of tripling the cost of certain items.

[RobinJ]

It probably depends on whether it is "direct injection", (fuel injected straight into cylinder) or indirect injection (fuel injected into pre-combustion chamber of some sort).

The higher compression ratio of the former means the fuel can usually be ignited without heater plugs even with a cold engine, whereas the latter generally require them for cold starts.

And I thought the idea of indirect injection was supposed to enable you to get higher compression ratios?

Maybe its just to get more efficient combustion then?