Pontiac Fiero 1988 Service Manual page 276

ENGINE GENERAL INFORMATION 6-5
INSTRUMENT PANEL OIL WARNING LAMP "ON" AT IDLE
1. Oil cooler, or oil or cooler line restricted. Remove 2. OH pump pressure low. See oil pump repair
restrictions In cooler or cooler line. procedures In Section 6A.
E i G l i E COMPRESSION TEST
COMPRESSION T E S T
Important
• Disconnect the
" B A T . "
terminal from the
HEI distributor or Ignition module.
To determine If the valves or pistons are at fault,
a test should be made to determine the cylinder
compression pressure. When checking cylinder
compression, the throttle and choke should be open, all
spark plugs removed, and the battery at or near full
charge. The lowest reading cylinder should not be less
than 70% of the highest and no cylinder reading
should be less than 689 kPa (100 PSI).
This should be done with four
" p u f f s "
per
cylinder.
N o r m a l
- Compression builds up quickly and
evenly to specified compression on each cylinder.
P i s t o n R i n g s
- Compression low on first
stroke, tends to build up on following strokes, but does
not reach normal. Improves considerably with addition
of oil.
V a l v e s -
Low on first stroke, does not tend to
build up on following strokes. Does not improve much
with addition of oil.
Use approximately three squirts from a plunger
type oiler.
OIL LEAK DETECTION VIA BLACK LIGHT PROCESS
(2.5L L-4 ENGINE)
BLACK LIGHT P R O C E S S CHECK
This method uses a flourescent dye added to the
engine oil. One ounce of dye should be circulated in the
engine oil for a minimum of five (5) minutes. In some
cases it may be necessary to drive the car before the dye
will show. Ideal situation is to install dye in the
customer's vehicle a few days before the scheduled
repair. Prior to the black light inspection of the engine,
the dipstick should be held under the black light to
assure that the dye has mixed thoroughly with the
engine oil. Oil with dye additive will be a bright yellow
when exposed to a black light. Oil without dye additive
will show a light purple in color. It is not necessary to
clean the engine prior to inspection. The difference
between oil leaking with the dye additive, versus old
oil, is quite evident. Tracer dye used should be GM
Dealer Eguipment Group Part No. 041-00007.
EXTERNAL AIR P R E S S U R E
An adapter with an air fitting can be made to fit
into PCV hole of the rocker arm cover or dipstick hole.
This can be attached to an air supply that is regulated
at 2 to 3 psi. Extreme caution should be used to assure
that air pressure does not exceed 3 psi. Leaks could be
created if air pressure exceeds 3 psi. The air cleaner
pipe to rocker arm cover hole must be plugged. With
air being forced into the crankcase, the oil will be
pushed to the source of the oil leak, where it can be
detected with the black light. If a black light is not
being used, sometimes spraying the suspected area with
soapy water will confirm the leak. Test can be
performed with or without the engine running.
COMPONENT REMOVAL
To properly detect an oil leak at the rear of an
engine, it is necessary to remove the transmission. This
process, in conjunction with black light, will eliminate
all guess work in regard to rear oil leaks.
NOTE: When analyzing an engine with the black
light and flourescent dye method, variables can
sometimes occur. The technician using the black
light should be aware of the following:
• Short run times will not always allow dye to
surface at suspected oil leak area.
Recommendation: Pressurize engine.
• Extended run times can sometimes spread
dye over a large area, which may cause
actual leak detection to become most
difficult. Recommendation: Clean and
pressurize engine.