E30 series BMW 3

since 1983-1994 of release

Repair and car operation

E30 BMW
+ 1. Maintenance instruction
+ 2. Maintenance
- 3. Engine
   + 3.1.2. Specifications
   - 3.2. Dismantle and major maintenance of the engine
      3.2.2. Specifications
      3.2.3. Major maintenance – the general instructions
      3.2.4. Compression check in engine cylinders
      3.2.5. Major maintenance – general comments
      3.2.6. Engine diagnostics by means of the vacuum gage
      3.2.7. Major maintenance – alternatives
      3.2.8. Dismantle of the power unit
      3.2.9. Removal and engine installation
      3.2.10. Order of dismantling of the engine
      3.2.11. Dismantling of a head of the block of cylinders
      3.2.12. Cleaning and check of a head of cylinders and details of the klapanny mechanism
      3.2.13. Repair of valves
      3.2.14. Assembly of a head of the block of cylinders
      3.2.15. Removal of pistons and rods
      3.2.16. Crankshaft dismantle
      3.2.17. Intermediate shaft (only M20 engine)
      3.2.18. Cleaning of the block of cylinders
      3.2.19. Check of a condition of the block of cylinders
      3.2.20. Honningovaniye of cylinders
      3.2.21. Check of a condition of pistons and rods
      3.2.22. Check of a condition of the crankshaft
      3.2.23. Check of radical and shatunny bearings
      3.2.24. Engine assembly order
      3.2.25. Installation of piston rings
      3.2.26. Installation of an intermediate shaft
      3.2.27. Installation of the crankshaft and check of gaps in radical bearings
      3.2.28. Installation of a back epiploon
      3.2.29. Installation of rods and pistons, check of gaps in shatunny bearings
      3.2.30. Engine start-up after repair and a running in
   + 3.3. Engine electric equipment
+ 4. Cooling system
+ 5. Heating and ventilation
+ 6. Fuel system
+ 7. Exhaust system
+ 8. Transmissions
+ 9. Coupling
+ 10. Brake system
+ 11. Running gear
+ 12. Body
+ 13. Electric equipment
+ 14. Good advice

3.2.4. Compression check in engine cylinders

GENERAL INFORMATION

Results of check of a compression in cylinders of the engine allow to judge a condition of group of details in the top part of the engine (pistons, rings, valves and laying of a head of the block of cylinders). Namely, reduction of a compression can be caused by a leakage of chambers of combustion owing to wear of piston rings, damage of heads of valves and saddles, прогара laying of a head of the block of cylinders.

Prevention

For receiving exact results of check the engine should be heated-up to normal temperature, and the battery is completely charged.

PERFORMANCE ORDER

1. Begin with that clear sites near spark plugs for what blow the compressed air (in the absence of the compressor blow sites automobile, or even bicycle, the pump). It is necessary to exclude dirt hit in cylinders at compression measurement.
2. Turn out spark plugs.
3. Completely open a butterfly valve and fix in such situation.
	4. Disconnect the central high-voltage wire from a cover of the distributor of ignition, connect it to weight on the block of cylinders. For reliability connection with weight execute by means of a special short-circuiting piece of a wire with clips of alligator type on both ends. Also will not prevent to remove a safety lock of electronic system of injection of fuel on the assembly block that will provide a blackout of the electric fuel pump at compression measurement.
5. Insert a compression measuring instrument into an opening for a candle.
6. Include a starter and turn the crankshaft on some turns, watching indications of a manometer of a measuring instrument of a compression. On the serviceable engine pressure should accrue quickly. Low pressure after the first piston stroke and slow increase at the subsequent steps of compression indicates wear of piston rings. If after the first piston stroke pressure low, and at the subsequent steps of compression does not increase, the reason is leak in valves or a leakage of laying of a head of the block of cylinders (the reason formation of cracks in a head also can be). Decrease in a compression can be caused also by deposit deposits on heads of valves. Write down the greatest value of a compression.
7. Repeat measurement procedure for other cylinders, results compare to standard data.
8. Through an opening for a candle enter into each cylinder a little oil for the engine (about three full shpritsevy butterdishes), then repeat tests.
9. If after oil introduction the compression raised, it is possible to draw an unequivocal conclusion that piston rings are worn-out. If the compression increases slightly, leak occurs via valves, or laying of a head of the block of cylinders. Leak via valves can be caused by a burn-out of saddles and / or facets of valves, and also deformation of cores of valves, or formation of cracks on them.
10. If the compression equally low only in two next cylinders, the most probable cause is a laying burn-out between these cylinders. Emergence in chambers of combustion or in a case of the crankshaft of the block of cylinders of traces of cooling liquid will be confirmation of this conclusion.
11. If value of a compression in one of cylinders is lower for 20 percent, than in other cylinders and the engine unstably idles, wear of a cam of the cam-shaft operating the final valve can be the reason.
12. If value of a compression exceeds norm, the chamber of combustion is covered with deposit deposits. In this case a head of cylinders it is necessary to remove and remove a deposit.
13. If the compression in all cylinders low, or strongly differs for different cylinders, it is necessary to carry out tests of chambers of combustion for tightness for what it is necessary to address in a specialized workshop. As a result of tests places of leaks should be precisely established and the quantitative characteristic of leak is given.