Rebuilt Engine & Fuel Injection

[sammyr]

I just had a rebuilt engine and fuel injection done on my 1969 280SL 4 Speed. It was finally done today. Is it normal for it to have clear smoke coming out of the exhaust? Do I have to wait for it to break in?

1969 MERCEDES 280SL
WHITE ON BLACK/ BLACK HARD TOP

[Mike Hughes]

If your "clear smoke" is water vapor, this is a normal by product of combustion (chemically, when you combine a hydrocarbon with oxygen, you get carbon dioxide and water!).  Generally you should only see the water vapor while the exhaust pipes are still cold.  The cold pipes tend to condense some of the water vapor.  Once the engine and exhaust system warms up the water vapor should no longer be visible.  It will be visible for a longer period on cold mornings as the exhaust system will take longer to warm up.

- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havanna Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)

[sammyr]

It still smokes when its warmed up and it has a bad smell. Did you ever rebuilt an engine and fuel injection and it smokes?

1969 MERCEDES 280SL
WHITE ON BLACK/ BLACK HARD TOP

[ja17]

Hello Sammyr,
You may have oil or coolant in the exhaust system from before. It will burn off after a couple of drives if this is the case.

Otherwise if your engine smokes you will be using oil (blueish white), coolant(white), automatic Transmission fluid or excessive fuel (white). Finding which will be your first clue.

No need to speculate before you have more information.

Joe Alexander
Blacklick, Ohio

[bpossel]

Hello Sammyr,

After I re-installed my rebuilt Fuel Injection pump, my car smelled very bad.  Once I drained the oil, replaced oil, filter & spark plugs, then drove the car, it cleared up nicely.  I ended up having a lot of gas in my oil from before the rebuild.

Good luck!
Bob

bpossel
Memphis, TN.
1971 280SL
1997 E320

[Benz Dr.]

Ah..... wouldn't that be carbon monoxide ( Co )and not carbon dioxide ( Co2 ) ?

Daniel G Caron

[Klaus]

Carbon dioxide is correct. The carbon monoxide is only a product of incomplete combustion or of too rich conditions, i.e. lack of oxygen.

Klaus
1969 280 SL

[Benz Dr.]

Don't think so. CO2 is produced from living things and is also a byproduct of fermentation - even yeast is a living thing.
Plants on the other hand, absorb CO2 and give of O2.
CO is a byproduct of cumbustion or burning especially if it's not complete or starved of oxygen. You have it half right, I think.

Daniel G Caron

[Klaus]

Dan,
CO2 is the largest constituent of exhaust emissions and is officially used by EPA to calculate the fuel economy which is advertised on the window sticker.
Just last month the California Air Resources Board (CARB) promulgated new standards for automotive CO2 emissions, to be effective around MY2008. Last week, 7 automobile manufacturers sued the CARB, maintaining that federal regulations preempt the CARB's right to regulate CO2.

Klaus
1969 280 SL

[hands_aus]

Carbon Monoxide CO is the gas that can kill you because it is a colourless and odourless gas.
It can be burnt to produce carbon dioxide CO2 and water H2O.


Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[Benz Dr.]

Ok,
 So we've established that CO2 is a by product of an internal cumbustion engine with converters. High CO will clearly give you CO2 as well.
These new regs are probably for newer cars with converters. 113's don't have converters so is the production of CO2 gas as high in a 113 engine as it would be in a newer car with a broken O2 sensor?

Daniel G Caron

[George Davis]

It goes something like this:

Gasoline is a mixture of hydrocarbons, made up of carbon (C) and hydrogen (H) combined in various ratios.  When gasoline is burned, the carbon is combined with oxygen (O) in a 2 step process.  Step 1 is combustion of C to CO (carbon monoxide); step 2 is further combustion of CO to CO2 (carbon dioxide).  (This is extremely simplified, the combustion of hydrocarbons is a complex and messy process, but it gets the basic idea across).  Ideally, we want all of the carbon to burn all the way to CO2, that way we extract the maximum energy from the gasoline by burning it completely.

But nothing is perfect, so while most of the C burns to CO2, some is only burned partially and comes out as CO.  This occurs even under the best of circumstances, and it allows CO to basically be a measure of combustion efficiency as well as air/fuel ratio.  There are a lot of factors that determine how much CO is left over, but the one we're usually interested in is the air/fuel ratio.  If the mixture is rich, meaning there is too much fuel for the available air, we get more CO. As the mixture gets leaner, the percentage of CO decreases.  Too little CO means the engine is running too lean, too much CO means it's too rich.  We want to basically hit the factory CO spec to get the mixture right.

The job of catalytic converters is to convert CO and any unburned fuel in the exhaust all the way to CO2.  Even modern cars don't burn fuel perfectly, so there's always a little bit of CO and unburned fuel in the exhaust.  Not much any more, but still something for the cats to work on.

There will be a test on this next week.  For extra credit, explain where NOx comes from...

George Davis
'69 280 SL Euro manual

[Klaus]

In preparation of next weeks test I recommend reading the following document (its short):
http://www.epa.gov/otaq/consumer/05-autos.pdf

Dan asks:
<<These new regs are probably for newer cars with converters. 113's don't have converters so is the production of CO2 gas as high in a 113 engine as it would be in a newer car with a broken O2 sensor?>>

The production of CO2 is higher in the W113 than in a newer car (of equivalent weight and power), both with a functioning or a broken O2 sensor, because its fuel economy is so much worse. The ratio between CO and CO2 emissions (in grams per mile in the federal test cycle) is lower in the non-catalyst W113, maybe 1 : 50, while in a catalyst equipped car it is higher than 1: 200.


Klaus
1969 280 SL