Black smoke

[igor136]

Hello guys. I sometimes have a problem with starting the engine. It starts for 4-5 seconds and then runs at very low revs for a few seconds. I add gas and black smoke comes out of the exhaust. Tried another lambda, same. The MAF sensor is about 50 tkm old. I measured the voltages on it and they are within the specified values. Engine temperature sensor in tolerance. A warm engine does not smoke. The engine does not consume oil or water. It works nicely. It's going really well. Do you have any ideas? Thanks

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[Tractor Dave]

How does it start when it's hot?
Have you go any fault codes?

[igor136]

No fault codes. The car starts the worst 2-3 hours after driving. Warm starts well. Cold mostly good but not always.

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[Tractor Dave]

I'm sure you know black smoke indicates rich mixture. Could be a number of things. You might have a leaky injector. All all the spark plugs the same or is just one black?

[igor136]

Good idea. I checked the fuel pressure yesterday. 4 bars constantly. After 3 hours of standing, the pressure dropped to 1 bar. I have had the car for 10 years. I removed the hose from the rail several times. Otherwise, 1 dl of gasoline leaks out and that's it. However, when I took it off yesterday I was shocked. Half a liter of gasoline under pressure leaked out of the hose. the gasoline was warm, I guess from the engine compartment.
This happened before the pressure gauge was installed so I don't know the pressure.

Is it normal for that much pressure to be in the fuel hoses?
Who controls the pressure in the fuel tank while the engine is off?

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[K Simmonds]

You normally get quite a squirt of fuel when disconnecting any of the supply unions, there is a non return valve fitted to the top of some pump's on S2 Coupe, I binned mine when fitting an 044 as I needed the extra head room.

It made no difference to the amount of fuel that went everywhere when undoing a union so I guess the pump itself hold a certain amount of pressure.

Black smoke is always un-burnt fuel.

That Lambda does look a touch black.