PB 150 V8-318 5.2L VIN T 2-BBL (1983)
Spark Plug: Technical Service Bulletins
Spark Plug - Cleaning/Replacement Guidelines
Models
All Passenger Cars & Trucks
-
Domestic & Import
Subject
Diagnosing Spark Plug Fouling & Failures
Index
FUEL
Date
April 8, 1983
No..
14-23-83
This bulletin briefly describes guidelines to accurately determine when spark plug cleaning or replacement is necessary.
As Technical Service Bulletin #14-03-83 describes, a special oil additive has been added to the factory fuel fill to prevent pre-delivery spark plug fuel
fouling. Assembly plant introduction of the additive was December 15, 1982, to February 11, 1983.
Spark plugs remove from engines containing this fuel additive may be slightly shiny and oil wet in appearance. THIS IS A NORMAL CONDITION.
In depth spark plug fouling diagnosis is contained in the "Driveability Test Procedure" books under "No Start" and "Driveability Test Cold" and
Technical Service Bulletin #14-44-82. A review of these two publications may be necessary to clarify any misunderstanding of spark plug fouling
diagnosis.
Symptoms that may be caused by fouled or defective spark plugs are no start, rough and slow idle with engine miss, and surging and bucking with engine
miss.
The following procedure should be used to determine whether spark plugs should be cleaned or replaced:
A.
Engine Will Not Start
Check spark plugs for fouling. Clean them if necessary and reinstall in the engine ONLY if there is a satisfactory secondary ignition
spark and accelerator pump fuel spray as determined by following the Driveability Test Procedure for "No Start" testing.
A black and sooty appearance may not indicate a failed plug. These spark plugs can be cleaned and reinstalled in an engine.
B.
Engine Starts, Runs Rough
Connect an ignition scope to engine and allow engine to warm up enough for choke to fully open.
1.
Observe ignition firing lines on scope under load. Firing lines that are below 10 KV on one or more cylinders, but not all cylinders, may
indicate a fouled plug.
2.
If all firing lines are below 15 KV, and engine is not under load, apply a moderate load on the engine and observe the firing pattern. A firing
line above 15 KV accompanied by an engine miss is an indication of a defective spark plug or open secondary wire.
A check of secondary wires for proper resistance should be made prior to cleaning of the spark plugs that indicated high firing voltage on the
scope.
3.
Any other scope patterns are not indications of defective spark plugs.
4.
A black appearance is not an accurate indication of a fouled or defective spark plug.
Spark plugs will look black and wet after an engine has been started cold and/or operated for short periods while the choke is on.
