Too rich... on one cylinder??

[gloupemilia]

Hi!
Since a while, my 240 (B200E, K-jetronic) has been starting on only 3 cylinders. The first one (close to the fan) is firing only after 10-30 seconds.
Today, I dismounted the spark plug after a few seconds, and it was full of gazoline. And when I compare its color to the others (they all have 3000km), there is a clear difference (see photo): based on the color, this cylinder would be richer than the others!
I swapped the injectors, no change.
How can this be? How to fix it? Thank you!

[rustytoba]

Hi,

If swapping the injector gave the same problem perhaps the ignition lead for that cylinder is faulty or the connection on the distributor cap for that cylinder could be corroded, giving a weak spark, leading to a wet spark plug

Just an idea

Scott

[Clan]

Originally Posted by gloupemilia

Hi!
Since a while, my 240 (B200E, K-jetronic) has been starting on only 3 cylinders. The first one (close to the fan) is firing only after 10-30 seconds.
Today, I dismounted the spark plug after a few seconds, and it was full of gazoline. And when I compare its color to the others (they all have 3000km), there is a clear difference (see photo): based on the color, this cylinder would be richer than the others!
I swapped the injectors, no change.
How can this be? How to fix it? Thank you!

you could have some coolant leaking in causing this , But last time i came across it , it was the HT leads or the Distributor cap . If you do change the cap make sure it is a Bosch Volvo one as they have a layer of isolating Lacquer inside which plain Bosch does not have , Ford sierra uses that substandard type .

[john850kershaw]

Does this only happen when cold first thing in the morning and is fine thought out the day, if this is the case it sounds like coolant leaking into the cylinder overnight under pressure when parked up.

[gloupemilia]

OK, given that I also have some unexplained coolant consumption... I was already fearing of a blown cylinder head gasket, I have the answer now...

Difficult to replace? I'm not a complete newby, but all my other cars are aircooled... The car never overheated, do you think I need to do something with the cylinder head? Any recommendation on the spare parts, type of gasket etc... ?

[Clifford Pope]

Water leaking into a cylinder usually results in a very bright, steam-cleaned appearance to the plug and the combustion chamber. The guilty plug looks brand-new, the others have healthy brownish combustion deposits.

I'd try some new plugs and leads first, and examine the cap carefully, possibly replace too. Water loss can easily be missed - favourite points are heater hoses where they bend round the dipstick tube, weepage from a tired radiator getting porous, or a crack in the plastic elbow. A small leak may only occur when hot, and simply evaporate without leaving a visible drip.

[Stephen Edwin]

What/where is the plastic elbow please? Am I missing something very obvious?

[Clifford Pope]

Sorry, I was still with the radiator. I meant the moulded inlet and outlet elbows, which I have found a bit liable to hairline cricks.

[gloupemilia]

You're right... water cleans the cylinder and the sparking plug, so the opposite!

The radiator is new (due to a failure of... the plastic elbow!).
I will carefully check (again) the whole circuit when hot... I'd prefer a leak to a cylinder head gasket!! It could also be something with the water pumps seals I changed some months ago.

Which finally, doesn't explain my brownish sparking plug... or it's about ignition, as previously suggested.

[stephend]

Originally Posted by gloupemilia

OK, given that I also have some unexplained coolant consumption... I was already fearing of a blown cylinder head gasket, I have the answer now...

Difficult to replace? I'm not a complete newby, but all my other cars are aircooled... The car never overheated, do you think I need to do something with the cylinder head? Any recommendation on the spare parts, type of gasket etc... ?

A good way to test whether a head gasket leak is letting coolant into the cylinder is to get your friendly local MoT tester to do a 'sniffer test': basically, put his exhaust gas analyser probe into the top of the coolant header tank while the engine's running. If it detects exhaust gases, you've got a head gasket leak.

If it does turn out to need doing, the good news is that a B200E engine is one of the easiest to renew the head gasket. I did mine DIY: it was the first time I'd done a job like that, and it's still holding strong 65k miles later.