White Smoke but Engine Runs Fine

[Chief Engineer]

You crack the nut 3/4-1 turn. Wheile the pressure may be high you might see a little spray ....mare like a forceful dribble.

[mesquaukee]

To bleed air out of the system (after a filter change) you have to crack those same nuts. The pressure isn't a problem. There is nothing to be concerned about as while the pressure is high the volume is low.
What Chief Engineer means by loosening them when the engine is running is just enough to see a bit of fuel dribbling out, this is never more than a quarter to half turn. This minor leak dramatically reduces the pressure preventing the injector from opening and spraying fuel into the cylinder. A change in engine rpm means this is not the faulty injector.
Should you come across one where the rpm doesn’t change that is the faulty one.

Sorry Chief I walked over you.

[boden36]

White smoke can also be a symptom of poor injector pump timing. Regards, Richard.

[Artessa]

one quick (important!) question before I try Chief Engineer's compression check procedure. When you say loosen the nuts do you mean the ones on the side of the injector that hold the high pressure line or the cap nut on top of the injector?

[gs41escapade]

Again, I have never done this outside of the classroom myself, but I'm quite sure the nut to crack is the HP fuel line nut. As someone stated above, the point is to stop the injector from 'popping' or injecting fuel (not relieving compression as I previously posited). The injector will only pop with sufficient fuel pressure. relieve that pressure and it doesn't pop, so that cylinder gets no fuel and will not fire. If nothing obviously changes in engine running, then the problem is with that cylinder.

[mesquaukee]

It is the nut on top, the high pressure lines from the injection pump. The other nut is the fuel return line, low pressure.

[Chief Engineer]

The Bolt on top is the return line 10mm
The Nut on the side is the injector line 17 mm

[hugosalt]

I'm about to embark on my own odyssey...my 24 year old 3GMC
22h.p.(raw water cooled) has just started with small amount of white smoke/steam with minor loss of power and vibrations.
Can I flip the decompression levers, one at a time, to isolate the
problem cylinder instead of cracking the nut on the injectors?
Thanks in advance...as usual you all have given me a big head start.

[RBEmerson]

Stick with cracking the injector nuts - some engines (can't say if the 3GMC is one) don't like running with partial decompression use.

Put a rag around the area as you back the nut off 1/4-1/2 turn. If the rag is wet with fuel and the engine doesn't change its note, there you are. BTW, watch out for the spinning belt for the pumps and alternator - wouldn't do to be caught by it.

[hugosalt]

Thanks R B, On the way to the boat shortly...
Will start with basics and work up...
check oil level
air filter
fuel filter
belts tight/loose
exhaust
seacock fully open
replace Racor filter (put 2 micron in spring,
to fine, could add to problem...with tank
cleaned out in spring as well...thought
I would be ok for season??
Then if no progress it's on to checking
compression! I'll report back...Thanks

[Cheechako]

Loosening the nut is not a big deal, just crack it off enough for raw fuel to come out. If that cyl is powered up well, the engine will shake while it's cracked off. I have seen head gasket failures between two cylinders that ran white exhaust. Once disassembled, you could see where the engine block was etched and actually metal removed (~.003 deep) where the leak was.

[RBEmerson]

Without seeing the engine and doing some simple checks, it's hard to know what state the engine's really in. However, until you can nail down the source of the white smoke, no, I wouldn't just let it go until the end of the season. Spend time with the injectors and, if nothing turns up, have someone do a compression test. Armed with the results of the injectors and compression test, there should be some solid information what's going on. None of it is likely to be good news.

[Chief Engineer]

White Smoke is caused by

Lack of compression
Water in the fuel
Air in the Fuel
Defective injector
Cracked Head
Leaking Headgasket

Originally Posted by hugosalt

Thanks R B, On the way to the boat shortly...
Will start with basics and work up...
check oil level
air filter
fuel filter
belts tight/loose
exhaust
seacock fully open
replace Racor filter (put 2 micron in spring,
to fine, could add to problem...with tank
cleaned out in spring as well...thought
I would be ok for season??
Then if no progress it's on to checking
compression! I'll report back...Thanks

Bleed your system all the way to the injector

[RBEmerson]

Er... ??? Cracking injector nuts will help with spotting defective injectors, blocked fuel pipes, and bad high pressure pumps. Compression checks help with loss of compression, although it doesn't say why, just that it's happening. Pulling a fuel sample in a clean jar and letting stand will help with spotting water in fuel. Air in fuel... back to the injector nuts.

[hlemail]

Just to add my 2 cents worth.

I had a similar problem, white smoke and engine running well.

When I took the 3 injectors off the Volvo 2003, they were not atomizing, and some only come out from 2 or 3 holes. Not all 4.

The injectors is being rebuilt now with new nozzles. A$ 105 each nozzle + A$ 40 per injector for labour and adjustment.

Hopefully after this fix, everything will be OK. The desel mechanic want me to disassemble the diesel pump as well. I can not imagine how much that will cost.

Do you think it is a good idea?