156 replies to this topic

[martinrub]

Nice photo, and a good idea to upload it. That doesnt look bad to me, but it would be interesting to see what others with the same engine say. I must say I am more used to seeing a lighter coloured ceramic, even white, on fuel-injection engines, (Ive personally not seen plugs that colour since carburretor days, when such a brown colour would have been deemed a perfect colour). No abnormal deposits either, which is good. Then Its also important to know what kind of journey you made before removing the plugs eg did the engine get hot and how long the journey was and at what speed was the car run.... Then again, we know that your engine stays in closed loop even if the short term fuel trim is indicating a rich or slightly rich condition, it is nevertheless keeping the mixture correct (in closed loop).


I dont know what your manual says about the compression ratio, but 10 -10.5 bar seems like a very healthy compression and the good thing is that they are all very much the same. So your compression gauge was money well spent, Chinese or not!

Do you still get a lot of black smoke on hot and cold startups?

And the huge fuel consumption, how does it compare to what is considered normal for that car?

And to help with the diagnosis, can you say which brand and number/type your spark plugs are, so that people can be sure you have the correct ones fitted?

Edited by martinrub, 25 March 2018 - 05:51 PM.

[hungdynasty]

Nice photo, and a good idea to upload it. That doesnt look bad to me, but it would be interesting to see what others with the same engine say. I must say I am more used to seeing a lighter coloured ceramic, even white, on fuel-injection engines, (Ive personally not seen plugs that colour since carburretor days, when such a brown colour would have been deemed a perfect colour). 

My 98 Jap spi , for your reference.

Attached Files

•  IMAG0614.jpg   25.55K   1 downloads

[martinrub]

Lovely - now that looks like it came out of a really healthy engine! Thats very helpful. That is more the general sort of coloration Id expect to see on a modern engine. So perhaps gdudu's plug colour is just another indication of a rich condition.

Edited by martinrub, 25 March 2018 - 05:54 PM.

[martinrub]

gdudu,

You say you cleaned the plugs 200km ago. Did they need cleaning? How did they look before you cleaned them in comparison to the one you photographed?

Looking at hungdynastys excellent looking plug, I don't think it would be a good idea to fit a new cat until you get your plugs looking like that, because, whilst a new cat might help you scrape through the test, a rich condition will stress the cat and itll fail prematurely. So youd be in the same position when the car fails next years test.

Edited by martinrub, 25 March 2018 - 05:45 PM.

[gdudu]

Yes for the cat I will inspect it and try to look inside, and look for leaks, but I don't think to find anything like this

This is not very expensive, and it's one thing I never change

 

My spark plugs were, before cleaned, very black, much more than today.

I think they are good model cause I changed them 1 year ago, to be sure to have the good one. I will check the model

But the color is not good for me, seem to be much too rich

 

My consumption is about 10 or 11 l/100, where such a car would be at 6 I think ?

 

The black smoke when starting is not so important. For me this is not a problem, cause after a good acceleration, it's OK and it doesn't last long

 

I will try to check fuel pressure next week, and the exhaust 

[Sprocket]

[martinrub]

Yes for the cat I will inspect it and try to look inside, and look for leaks, but I don't think to find anything like this
This is not very expensive, and it's one thing I never change
 
My spark plugs were, before cleaned, very black, much more than today.
I think they are good model cause I changed them 1 year ago, to be sure to have the good one. I will check the model
But the color is not good for me, seem to be much too rich
 
My consumption is about 10 or 11 l/100, where such a car would be at 6 I think ?
 
The black smoke when starting is not so important. For me this is not a problem, cause after a good acceleration, it's OK and it doesn't last long
 
I will try to check fuel pressure next week, and the exhaust

Thanks, gdudu.

I see what you mean, then, about huge fuel consumption! Such a high consumption is not just because of the period of the black-smoke time in the first minute of running, which we already knew.

I understand why the black smoke is not important to you - because it goes away (in closed loop) - but it isnt normal, and so it is a useful indication that a problem (still) exists. And, because its also a sign of a rich condition, we can be confident that the presence of the smoke on startup means that car is not yet fixed. Or, put another way, when you no longer get the black smoke, we can be confident the car is fixed.

Edited by martinrub, 25 March 2018 - 10:43 PM.

[hungdynasty]

My consumption is about 10 or 11 l/100, where such a car would be at 6 I think ?
 

Depends on driving conditions, under 7l/100km, usually around 6.5l/100km.

[martinrub]

gdudu

I will try to check fuel pressure next week...

When you do check the fuel pressure, its not just the pressure that is of interest, but also if, or how fast, the pressure falls. Ideally, the pressure should not fall, or, if it does, it is very, very slow. So you need to collect 2 pieces of data: the fuel pressure and the rate at which the pressure falls - if at all. Of course, Im referring to ignition on, but engine not running.

Edited by martinrub, 26 March 2018 - 03:09 PM.

[gdudu]

For the fuel pressure, you may take a very cheap manometer from a bycicle pump , then you need a y-piece from your windshield washing system and  two rubber hoses. Take off the rubber hose coming from the gas tank going on to the metall hose before the throttle body. Put the y-piece in between and have the engine running.Should be between 1 and 1.3 bar.

Hi

I've just did this, but with a 11 bar bike manometer, not very exactness

The pressure when motor running is about 1.1 bar (picture 2)

When I close the line fuel (pressing with fingers, hose after the manometer and before the injector) the pressure is coming to about 1.8 bar (picture 1)

And when I stop the motor, the pressure is immediatly going to 0.8 bar, and don't move. If I disconnect the hose, it drop down normaly

 

The manometer was on incoming fuel line

 

Something else important (for me, but ?) : The pressure in fuel tank is important, even when motor stopped and cold, without having started. I had to open fuel tank to put my manometer. The pressure was making fuel going out the hose. Odd ??

Attached Files

•  Fuel pressure.jpg   34.7K   1 downloads

Edited by gdudu, 04 April 2018 - 05:50 PM.

[Sprocket]

1.1 Fuel pressure normal.

0.8 pressure holding with engine off.... Confirms good injector seal.


Injector Number?

[martinrub]

When I close the line fuel (pressing with fingers, hose after the manometer and before the injector) .....

So were you measuring the pressure in the injector? Was the 0.8bar pressure also in the injector?

The pressure in fuel tank is important, even when motor stopped and cold, without having started. I had to open fuel tank to put my manometer. The pressure was making fuel going out the hose. Odd ??

Im sorry: Im not sure I understand what you are saying, so I dont know if its normal

[Sprocket]

The pressure in fuel tank is important, even when motor stopped and cold, without having started. I had to open fuel tank to put my manometer. The pressure was making fuel going out the hose. Odd ??

Im sorry: Im not sure I understand what you are saying, so I dont know if its normal

When he removes the fuel line to fit the gauge, fuel pours out of the line. If he removes the fuel filler cap, the fuel stops pouring from the fuel line. This is normal as the system is closed with the filler cap fitted. Pressure builds up in the tank as fuel evaporates as the temperature changes, the tank vents positive pressure through the tank breather valve to the charcoal canister. Sometimes you can hear the tank breather valve fart if the car is sat in the sun for a long time.

[martinrub]

Great. Thanks.

[pete l]

Reading through all this, i was hoping for a result that might help me fix mine :-( 

 

Anyone heard any news about this rich running problem ???