Diesel engine problem

andykem · Apr 26th, 2007, 17:00

Hi,
A friend of mine has a 'non-Volvo' diesel car. But it has a problem! When cold it won't pick up when throttle pressed but when hot it seems to work fine. even so, another acquaintance noted that when given lots of welly, say for hard acceleration in 2nd gear, lots of black smoke is emitted. The engine always starts easily though.

Any ideas please?
Andy

malb · Apr 27th, 2007, 13:15

Any time a diesel dumps visible black smoke, it is getting more fuel pumped in than it can burn. Black smoke is soot from unburned fuel. This applies from small industrial motors through to monster sized ship engines. It is not possible to get perfect pick up and clean exhausts on mechanical injection engines accross the whole speed/load range, although they can be tuned for very low emissions for definite speed/load ranges. Hence the development of closed loop ECU/Sensor common rail direct injection technologies.

Generally sooty operation indicates that the fuel system needs a good service by someone with the knowledge and tooling to do this. In an ECU type engine this service would include all sensors, ECU, fuel pumps, injectors etc.

Cold acceleration problem probably is due to a lean run at that time, ie not getting enough fuel to supply the power expected. Probably ties in with the sooty operation to indicate some sensor failure.

The combination of both issues suggests something in the ECU/sensor chain.

andykem · May 12th, 2007, 10:42

The problem went away once a new EGR valve was fitted.
HTH

Apr 26th, 2007, 17:00	#1
andykem Member Last Online: Mar 10th, 2020 12:16 Join Date: Jan 1970 Location: cheltenham	Diesel engine problem Hi, A friend of mine has a 'non-Volvo' diesel car. But it has a problem! When cold it won't pick up when throttle pressed but when hot it seems to work fine. even so, another acquaintance noted that when given lots of welly, say for hard acceleration in 2nd gear, lots of black smoke is emitted. The engine always starts easily though. Any ideas please? Andy

Apr 27th, 2007, 13:15	#2
malb Member Last Online: Dec 29th, 2013 11:04 Join Date: Apr 2007 Location: Melbourne	Black smoke Any time a diesel dumps visible black smoke, it is getting more fuel pumped in than it can burn. Black smoke is soot from unburned fuel. This applies from small industrial motors through to monster sized ship engines. It is not possible to get perfect pick up and clean exhausts on mechanical injection engines accross the whole speed/load range, although they can be tuned for very low emissions for definite speed/load ranges. Hence the development of closed loop ECU/Sensor common rail direct injection technologies. Generally sooty operation indicates that the fuel system needs a good service by someone with the knowledge and tooling to do this. In an ECU type engine this service would include all sensors, ECU, fuel pumps, injectors etc. Cold acceleration problem probably is due to a lean run at that time, ie not getting enough fuel to supply the power expected. Probably ties in with the sooty operation to indicate some sensor failure. The combination of both issues suggests something in the ECU/sensor chain.

May 12th, 2007, 10:42	#3
andykem Member Last Online: Mar 10th, 2020 12:16 Join Date: Jan 1970 Location: cheltenham	Problem solved The problem went away once a new EGR valve was fitted. HTH

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