M271 Low compression on Cyl 4

[yinujim]

I have a friend with a C180 CLC here with numerous Cyl 4 misfire codes and about 40 to 50 PSI on that cyl after a compression test. Rest are healthy. When the car broke down after when the misfire happened it was low on oil. Also it has LPG installed.

Does anyone know the any common problems with M271 relating to low compression on one cylinder. Is it worth taking the valve cover off to have a look. Looks like the engine is scrap as it could be piston rings, valve issues.

Thanks

 

[LostKiwi]

I'd suspect burnt valves is the most likely issue. Common on LPG engines if they aren't set up correctly.

 

[alexanderfoti]

I'd suspect burnt valves is the most likely issue. Common on LPG engines if they aren't set up correctly.

+1 see it all the time.

 

[yinujim]

Thanks guys. Will have to weigh up the viability of repairing it.

 

[LostKiwi]

Quick check. Chuck a couple of squirts of engine oil down the bore and retest the compression. If it rises it's probably rings. If it makes no difference it's probably valves.

The oil will temporarily seal leaking rings but not valves.

 

[John Laidlaw]

shame, I'd think false economy converting a 271 to LPG , doubt it'd pay itself. LPG is also becoming rarer at the pumps now I see....

 

[LostKiwi]

shame, I'd think false economy converting a 271 to LPG , doubt it'd pay itself. LPG is also becoming rarer at the pumps now I see....

LPG done properly makes a great deal of sense. It produces far less emissions than either petrol or diesel (especially particulates). It doesn't send as many nasty combustion by products into the oil and the oil stays far cleaner for longer. The issue is it is a dry gas so has very poor lubrication properties and that can cause valve seat recession/burnt valves on some engines. Easily fixed by adding a small amount of lubricant to the inlet port.

The reason LPG hasn't caught on is because of a bad reputation caused by poorly setup kits coupled to a general fear of anything 'different' even though people happily use LPG to run their barbecues.

I've had 2 LPG vehicles and sold another just before I finished the conversion (fitted it myself - it's not hard).
First was a 3 9 Range Rover. That did (cost equivalent) 35mpg.
Second was a 3 4 V6 Toyota Land Cruiser Colorado that did 40mpg - about 20% better than the equivalent diesel models and far more refined with it.
The last one that was sold before completing the installation was a Land Rover FC101 fitted with the 3.5 Rover engine. That one had over 160litres LPG capacity on board and would theoretically cover around 550 miles between fills and still retained the 20 gallon petrol tank as a backup to give a potential 800+ mile range whilst still retaining a 1.5 Tonne load capacity.

The very latest LPG systems have progressed significantly and now inject the fuel as a liquid. This gives a phenomenal cooling effect in the incoming charge which allows LPG to give higher power than petrol, especially if compression is also raised to over 16:1 which is still perfectly safe for anti knock on LPG.

It's a real shame it hasn't caught on here in the way it should. It's very popular in NZ and Australia and on the continent.