Volvo 2020 Concern

[Lucky Duck]

Occasionally when starting the engine from cold it runs quite roughly and a fair bit of white smoke comes from the exhaust. Reving the engine for a moment solves the problem and everything else seems fine from then on.

Any thoughts on what might be causing these symptoms?

 

[rosie]

Possible reduced compression in one cylinder resulting in running on one and unburnt fuel / white smoke from the other. It all sorts itself out when the defective cylinder warms up a bit & burns fuel normally. More likely when engine is cold.

Dave.

 

[Bobc]

Dodgy valve guide seal dripping oil into the cylinder when stood. That would run lumpy and smokey until it had burnt off.

 

[Stork_III]

One glowplug US?

 

[Bosun Higgs]

One cylinder is not firing and the unburnt diesel is coming out as white smoke. Diesels work by compressing the air and fuel droplets mixture until its warm enough to ignite on its own. Your problem could be lack of compression due to wear in one cylinder but as the engine runs and pumps lube oil round the bores and bearings, the compression comes back up enough for the second cylinder to fire. Then the piston warms up and expands and compression improves further.

It could be failure of the glow plug in the cylinder concerned if its that sort of engine. It could also be a sticky valve.

Start by checking the glow plug.

 

[VicS]

Absolutely check the glow plugs first.

Disconnect the wiring and test the resistance of each one with a meter on ohms range, or check the current flowing to each when energised with a clamp type ammeter

If its not an isolated earth system a bulb ( eg old headlamp bulb with one good filament) on a couple of leads is a quick and easy method. One lead on each glowplug in turn and one on battery positive. If the bulb lights its OK if it doesn't problem found. ( my method of choice when checking them on the car)

 

[Lucky Duck]

Many thanks for the replies, hopefully it's something as simple as a bad glow plug