Opel 1900 1973, Service Manual

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66 1973 OPEL SERVICE MANUAL
6. Check compression of each cylinder.
Repeat
compression check and record highest reading ob-
tained on each cylinder during the two pressure
checks.
The recorded compression pressures are to be con-
sidered normal if the lowest reading cylinder is more
than 75 percent of the highest reading cylinder. See
the following example and the “Compression Pres-
sure Limit Chart.” See Figure
Seventy-five percent of 140 (highest) is 105. Thus,
cylinder No. 4 is less than 75 percent of No. 3. This
condition, accompanied by low speed missing, indi-
cates an improperly seated valve or worn or broken
piston ring. See Figure
Figure Example of Compression Check
7. If one or more cylinders read low, inject about a
tablespoon of engine oil on top of pistons in low
reading cylinders through spark plug port. Repeat
compression check on these cylinders.
If compression improves considerably, rings are
b. If compression does not improve, valves are stick-
ing or seating poorly.
c. If two adjacent cylinders indicate low compression
and injecting oil does not increase compression, the
cause may be the head gasket leaking between the
cylinders. Engine coolant
and/or oil in cylinders
could result from this defect.
Compression Pressure Limit Chart
This chart may be used when checking cylinder com-
pression pressures. It has been calculated so that the
lowest reading number is 75 percent of the highest
reading number. See Figure
EXAMPLE:
After checking the compression pressures
in all cylinders, it was found that the highest pressure
obtained was 182 psi The lowest pressure reading
was By locating 182 in the maximum col-
umn, it is seen that the minimum allowable pressure
MAXIMUM
PRESSURE
INCH
- -
1 3 4
1 3 6
1 3 8
1 4 2
1 5 0
1 5 2
1 5 6
1 6 4
1 7 4
1 7 6
1 7 8
184
1 8 6
MINIMUM
PRESSURE
POUNDS/
SQ. INCH
‘RESSURE
INCH
MINIMUM
PRESSURE
INCH
1 4 4
1 9 4 1 4 5
I l l 200 150
1 1 3 202
1 1 4
204
1 5 3
1 1 5 206
1 1 7 208
210
1 5 7
212
121 214
216
218
220
222
224
226
1 6 9
228 171
230
1 3 5
232 1 7 4
234 1 7 5
138 236
238
1 7 8
Compression Pressure Limit Chart
is Since the lowest reading obtained was 145
psi, car is within limits and the compression is
considered satisfactory.
Spark Plugs
1. Inspect, clean and regap or replace spark plugs as
required. Correct gap is
2. Install spark plugs. Tighten to 30 lb.ft.
Secondary Ignition System
1. Inspect ignition cables for broken, swollen or
deteriorated insulation.
2. Check terminal ends and condition of rubber
boots. Replace as required.
3. Inspect the condition of the distributor cap and
rotor.
4. Clean the ignition coil and inspect for cracks or
carbon paths which could cause high voltage leak-
age.
Distributor Contact Points
1. Inspect distributor contact points and replace or
adjust as necessary gap).