Thread: white smoke on start up

Not sure I get your question Flagg.
Are you thinking that its unburned fuel from the previous shutdown that is causing it?
Not the case AFAIK - its more that the fuel that's being injected doesn't burn due to low temp, low compression, insufficient atomisation etc.

Steve

Originally Posted by steveG

Not sure I get your question Flagg.
Are you thinking that its unburned fuel from the previous shutdown that is causing it?
Not the case AFAIK - its more that the fuel that's being injected doesn't burn due to low temp, low compression, insufficient atomisation etc.

Steve

Thanks Steve - I'm on fire tonight. Yes you are right, my premise was totally wrong!

By the way it runs I can assume it is not all cylinders that have a problem.. So I guess it is a compression test and an injector recon (due anyway).

x2 on Steve's comments. You need the internals to warm up to get proper compression.

As you know I don't have a lot of hours with my Isuzu yet, but I know it puffs enough white smoke when cold to be considered anti-social. It's enough that I expect some "mechanically uneducated" friends will comment when they see it and tell me something wrong.

Every time someone mentions a rebuild of any kind for the Isuzu on the forums, the consensus seems to be "don't worry about it". So before rushing into anything major I think the questions are: Has anything changed? (Have you touched the fuel screw?) Is it getting worse?

I recently purchased an el-cheapo compression test kit - for similar reasons - white smoke on start-up and a reasonable amount of blowby. I'm not expecting a problem, but I thought a health check couldn't hurt. If my compression is OK, I'm going to carry on business as usual. Do you have a compression kit? Mine was only $60 on ebay. If logistics are feasible, you're free to borrow it.

Lastly, I suspect Canberra winter might be your issue! Remember diesel don't like the cold. Without additives diesel won't burn below about zero. Would you be running winter diesel now? (I guess so). Even Canberra winter diesel is probably only "good" to minus a few degrees. How cold is it when you're starting it?

Originally Posted by Judo

x2 on Steve's comments. You need the internals to warm up to get proper compression.

As you know I don't have a lot of hours with my Isuzu yet, but I know it puffs enough white smoke when cold to be considered anti-social. It's enough that I expect some "mechanically uneducated" friends will comment when they see it and tell me something wrong.

Every time someone mentions a rebuild of any kind for the Isuzu on the forums, the consensus seems to be "don't worry about it". So before rushing into anything major I think the questions are: Has anything changed? (Have you touched the fuel screw?) Is it getting worse?

I recently purchased an el-cheapo compression test kit - for similar reasons - white smoke on start-up and a reasonable amount of blowby. I'm not expecting a problem, but I thought a health check couldn't hurt. If my compression is OK, I'm going to carry on business as usual. Do you have a compression kit? Mine was only $60 on ebay. If logistics are feasible, you're free to borrow it.

Lastly, I suspect Canberra winter might be your issue! Remember diesel don't like the cold. Without additives diesel won't burn below about zero. Would you be running winter diesel now? (I guess so). Even Canberra winter diesel is probably only "good" to minus a few degrees. How cold is it when you're starting it?

I'm just being pedantic as usual:

In the statement "You need the internals to warm up to get proper compression." compression should be combustion.

Of course you do need good compression to achieve combustion, because it is the heat produced when the air is compressed that is essential for ignition in a diesel engine. The higher the pressure produced during the compression stroke, the higher the temperature, ....

The colder the internals the more heat is lost/transferred from the air before the fuel can ignite.

Regarding the question "Have you touched the fuel screw?"; the full load screw adjusts how far the control rack is able to travel in the direction to increase the fuel rate. So it affects the fuel rate when your left foot is pushed down for full/maximum load, bur doesn't affect the fuel rate across the range of accelerator positions.

Ahh I didn't realise that with the fuel screw. I'll add that to my lesson for today.

The rest all makes sense. With that in mind and the properties of diesel in cold weather (and winter blends), do you think sub zero weather will make more white smoke at start-up? I.E. Colder the weather, the worse the combustion, more unburnt diesel and more white smoke....?

In the couple of years I have had my Isuzu, it has done the antisocial white smoke trick all of twice, and both times when it was colder than I am used to. In my infinite and dubious wisdom I reckon it's nothing more than climate. If you don't want white smoke on cold mornings, keep the engine warm by getting one of those block heaters that poms use or similar.

Originally Posted by isuzutoo-eh

In the couple of years I have had my Isuzu, it has done the antisocial white smoke trick all of twice, and both times when it was colder than I am used to. In my infinite and dubious wisdom I reckon it's nothing more than climate. If you don't want white smoke on cold mornings, keep the engine warm by getting one of those block heaters that poms use or similar.

hehe, or just move away from Canberra!

Thanks guys. I'll see how it does with the redone injectors, but I might just have to deal with it.

Originally Posted by Judo

hehe, or just move away from Canberra!

hehe if I could work in Tassy I'd be down there in a flash! (but I guess that won't help with the cold mornings )