Diagnosing engine smoke

[Dane]

What i'm asking basically is how do I go about diagnosing what the problem is?
My DA9 has started to smoke, I'm starting with a comp test this arvo but if comp is fine then what? Where do Isearch after that??

[aaronng]

Disconnect your dizzy before doing comp test.

[Dane]

Disconnect your dizzy before doing comp test.

Why??

[teh_mechanic]

its a safety precaution to make sure your ignition system cant create spark so you cant create an accidental fire in the engine bay.

black smoke is usually excess fuel,from running rich.
white/bluey smoke is usually oil

[gerard]

What i'm asking basically is how do I go about diagnosing what the problem is?
My DA9 has started to smoke, I'm starting with a comp test this arvo but if comp is fine then what? Where do Isearch after that??

then you look at worn valve guide seals

[teh_mechanic]

then you look at worn valve guide seals

if you get a big puff of white smoke on startup after the car has been sitting an hour or more or overnight then your best bet is the valve guide seals (also called valve stem seals i think).because if they are leaking as your car sits oil seeps into the combustion chamber then burns off all at once when you start the car

[EuroDude]

Have a read of this to determine possible cause:

https://www.environment.nsw.gov.au/esdsmoky/causes.htm


Petrol-engine vehicles

Four-stroke or rotary petrol and LPG engines may emit blue/grey smoke or black smoke. Blue smoke normally means engine wear or damage. Black smoke results from an excessively rich fuel mixture. Where this occurs, the following components may be at fault:
Air cleaner

A rich mixture can be caused by excessive build-up of dirt or oil. Replace the filter element at regular service intervals. Rags or paper caught in the air cleaner intake pipes can also cause black smoke emissions.
Fuel system

Carburettor and engine management system faults leading to black smoke include:

* choke butterfly unable to open fully
* carburettor flooding
* incorrect grade of oil in dashpots
* incorrectly adjusted or faulty automatic choke
* air cleaner winter/summer lever set in wrong position
* manual choke operated incorrectly or when the engine is warm
* worn or loose jets or needles
* sticking diaphragm
* faulty engine management system
* faulty oxygen sensor or other engine management sensors
* faulty fuel injector.

Back to top
Other engine problems

Blue/grey smoke may be emitted from the exhaust pipe or the crankcase breather pipe. It is emitted from the exhaust pipe when oil finds its way into the combustion chamber and is burnt.

This may happen in a number of ways:

* via worn or broken rings, pistons, rotor seals, worn valve guides or faulty valve stem seals
* via the inlet manifold through a faulty brake-booster assembly
* via the inlet manifold through a faulty auto transmission vacuum diaphragm
* via an overfilled oil-bath air cleaner or overfilled carburettor dashpot.

When worn or broken rings or pistons allow gases from the cylinders to pass into the crankcase, 'blow-by' occurs. In older cars this causes blue-grey emissions from the crankcase breather. Modern cars use positive-crankcase ventilation. This prevents emissions of 'blow-by' fumes to the atmosphere by passing them from the crankcase to the induction system, so they are burnt in the combustion chamber.
Positive crankcase ventilation valve

A faulty PCV valve can cause blue smoke emissions from the vehicle's exhaust.

[Dane]

Cool, I'll check the pcv. and then I guess valves.
I did a comp test all cylinders @ 200psi so all good there.

[prego]

well on start up on both of the b18a s i had they would blow out alot of smoke on startup (warm only) and would drop a cylinder until i reved it psat 4000 they both had a blown head gasket

but my first showed fine compression

if you start it up with the radiator cap off and coolant gets forced out everywhere it means your head gasket is gone

[Dane]

Thanks for the info guys, but just to clarify.
1) If I take off radiator ca and coolant is forced out everywhere the it's prob head gasket?
2) How do I determine if it's valve stem seals?

[Benson]

sounds like headgasket.

Do a cooling system pressure test. Most mechanics can perform this, if not then any local radiator place.

[bennjamin]

go do a "leak down" test.

It will force compressed air into your combustion chamber , via the spark plug hole and air will leak out the area/s that are worn
Air coming out of the throttle body would point to a leaky intake valve. Air coming out of the breather vent or PCV valve fitting would tell you the rings and/or cylinders are worn. Air coming out of the exhaust points to worn or bent exhaust valves etc etc