 Triumph Sporting Owners Club | sitemap | log in
|
 |
||
| This is a free Spanglefish 1 website. | ||
Compression Testingby Jeff Baker - 22:38 on 22 November 2009Compression check. Checking the compression on any car is a straight forward process, a compression tester tool is required, the most common being from Gunsons, these retail from around £05.00 to £25.00, but any suitable pressure testing gauge will suffice so long as you can make a good seal to the spark plug aperture & the gauge is accurate to within a couple of pounds.
Having removed all the plugs & connected the compression tester to the first cylinder, crank the engine over while monitoring the gauge. Note the mean best pressure & repeat for the remaining cylinders. Pressures vary for different models & ages of vehicle, but what is most important is the spread should be even, by this I mean there should only be a relatively small difference if any between each of the cylinder readings, usually a tolerance of around 0 to 20 PSI. if all cylinders fall within this range then all should be well, assuming pressures are close to manufacturer's specifications. If any of the cylinders shows a significant drop in compression this obviously indicates a problem, if an adjacent cylinder shows a similar drop this is usually an indication of a head gasket failure, or worse, a crack between the valve seats. When a single cylinder or unrelated cylinders show a loss of compression we need to get an indication of where the problem lies. This is done by introducing a few drops of engine oil through each of the spark plug tapping's & re-testing each in turn. From this it can be ascertained whether the problem lies in the cylinder head, i.e.: head gasket failure, cracked head, poor seated valve or valves, or in the block, i.e.: worn or scored bores & pistons or damaged piston rings. What happens is during the test the oil runs around the top of the piston & temporarily forms a seal improving compression, if the problem is with the bore or piston assembly. If however the problem lies in the cylinder head the oil will have little or no effect.
This all helps identify the scope of the problem before tackling it and ordering the right parts for the job. I learnt this little gem from my father who was an engine fitter for Standard Triumph for many years, and I've never known it show the wrong diagnosis yet, & I have built & re-built quite a few Triumph engines over the years, both for myself & family & friends.
Hope you find this helpful
Regards
Jeff Baker
Add your comment Please note that whenever you submit something which may be publicly shown on a website you should take care not to make any statements which could be considered defamatory to any person or organisation. |    |
|
 | ||