Club 80-90 Forums

sinshelley wrote:Hi all,hope you can help me out ?
was doing a check of the spark plugs today and noticed that the left hand side plugs were burnt black while the right hand side plugs were fine,im no expert but to me it seems that the left hand side is running richer than the right,but that cant be true can it ? am really baffeled please help if you can i have a 1.9 dg petrol engine year of manufacture 1989 cheers all

kevtherev wrote:

sinshelley wrote:Hi all,hope you can help me out ?
was doing a check of the spark plugs today and noticed that the left hand side plugs were burnt black while the right hand side plugs were fine,im no expert but to me it seems that the left hand side is running richer than the right,but that cant be true can it ? am really baffeled please help if you can i have a 1.9 dg petrol engine year of manufacture 1989 cheers all

First of all plug colour should only be checked immediatly after a 10 min high speed run with a hot engine

If this was the case however then you could have a worn valve guides and or ring wear causing oil to be burnt.
I doubt that it's fuel related... Unless you have a miss fire.

sarran1955 wrote:Hello,

Spark plug colour and condition can be quite tricky to assess.

Valve condition... Valves don't really wear out, what happens is that the 'seat' wears, and so there is not a good gas tight seal. The valve seat is the point of contact between the valve and the cylinder head, and it is through this point that heat is transferred. That's why Aircooled Porsche engines have sodium filled hollow valves.

What tends to wear also is the brass valve guide. these wear oval over time, causing a loss of oil into the cylinder, eventually showing up as a sooty plug, and raised oil consumption. 17 times out of 9 the little oil seal on each valve, (hidden by the valve spring) has disintegrated.

A test: use a compression gauge to check the pressure ganerated by each cylinder, ( anything above 120 psi is ok). If you have one that is significantly lower, redo the test having squirted some engine oil into the cylinder, if the result improves then the problem is in the rings/barrel, if no change then the valve seat may need regrinding.

Frankly, in view of the work required to improve things, and if the bus runs ok, then leave well alone.

Hope this clarifies things a little,

Cordialement,

California Dreamin wrote:Yup...As sarran1955 said ^^^^ personally I would carry out a compression check for peace of mind: the range is, 10 - 13 bar (145 - 189 PSI) minimum 8 bar (116 PSI.)

For future reference, as far as I am aware, the flat 4 air cooled and wasserboxer engines are quite unique in that they don't use valve stem seals unlike 99% of other engines including VW.

Volkswagen did have issues (circa 1980's/90's) with burning out valves...very common around that time, across most of the 4/5cly range although I can't specifically remember whether the flat 4's fell into this category, certainly Polo's/Golf's/Jetta's/Passat's/Audi 80/90/100/200/200T did.

Martin

sinshelley wrote:

California Dreamin wrote:Yup...As sarran1955 said ^^^^ personally I would carry out a compression check for peace of mind: the range is, 10 - 13 bar (145 - 189 PSI) minimum 8 bar (116 PSI.)

For future reference, as far as I am aware, the flat 4 air cooled and wasserboxer engines are quite unique in that they don't use valve stem seals unlike 99% of other engines including VW.

Volkswagen did have issues (circa 1980's/90's) with burning out valves...very common around that time, across most of the 4/5cly range although I can't specifically remember whether the flat 4's fell into this category, certainly Polo's/Golf's/Jetta's/Passat's/Audi 80/90/100/200/200T did.

Martin

thanks martin ill book her in for the compression check,cheers for info,hopefully have results before we go to the mighty dubfest

sinshelley wrote:

sinshelley wrote:

California Dreamin wrote:Yup...As sarran1955 said ^^^^ personally I would carry out a compression check for peace of mind: the range is, 10 - 13 bar (145 - 189 PSI) minimum 8 bar (116 PSI.)

For future reference, as far as I am aware, the flat 4 air cooled and wasserboxer engines are quite unique in that they don't use valve stem seals unlike 99% of other engines including VW.

Volkswagen did have issues (circa 1980's/90's) with burning out valves...very common around that time, across most of the 4/5cly range although I can't specifically remember whether the flat 4's fell into this category, certainly Polo's/Golf's/Jetta's/Passat's/Audi 80/90/100/200/200T did.

Martin

thanks martin ill book her in for the compression check,cheers for info,hopefully have results before we go to the mighty dubfest

The eveness (if that is a word) of the test figures is very reassuring, as I've never seen more that two valves burnt at any one time. This even reading is a positive indication of overall engine mechanical condition. Personally I wouldn't be getting too worried as you say the performance and running are fine.
However, things to look at:
Air leaks from manifold/carb/vacuum hose etc
ignition proplems: spark plugs/distributor cap/leads
Air filter condition

Is the engine using oil?

Martin





hi martin had a compression test done this afternoon and each cylinder is between 130 and 140 psi mynext door neighbour is a bmw technician and he did the test for me,cost me a four pack of strongbow cider cheap i no.Would like to no your thoughts on this now as any help is much appreciated,cheers