engine performance chapter 28 test

while discussing no start diagnosis with a test spark plug. tech a says if a test light flutters at the coil tach terminal but the test spark does not fire when cnnected from the coil secondary wire to ground with the engine cranking the coil is defective/ tech b says if a test spark plug is connected to a terminal of a waste spark ignition coil fires with the engine is cranking but the engine does not run a bad pcm is indicated.

A

testing the coils in a ei system: tech a cays an infinite reading means the winding has zero resistance and is shorted. tech b says the primary windings in each coil should be checked for shorts to ground.

B

the firing lines on an oscilloscope are all low. tech a says the prolem is low coil output, tech b cays the problem is a rich af mixture

C

discussing EI waste spark. tech a says a spark plug with too wide of a gap can affect the firing of its companion spark plug. tech b says that improper spark plug torque can cause an engine to misfire.

C

tech a says the EMI can affect sensor signals. tech b says emi can cause intermittent driveability problems

C

defire corona effect and what it indicates

a grow around spark plug cables, caused by fault insulation

define a dynamic comp test

a measure of amperage for each cylinder. low compression in a cyl = lower starter draw for that cylinder. higher compression requires more amperage

explain what a cylinder performance test is, two methods that may be accomplished in addition to what the textbook states and how you would interpret the results

aka power balance test. it is the prodess of disabling a cylinder one at a time and measuring the rpm drop. this will help you see the condition of that cylinder. (larger drop means cylinder was strong, vice versa. little to no drop would indicate problem with that cylinder). be sure to first disable fuel or spark either manually or electronically.

name the four problems that can be caused by bad grounds according to your text book

backfeeds- may cause another circuit to fail or behave eratically force current through other components not ment for the current burned ignition modules intermittent ignition operation

why is the procedure for checking the resistance of a waste spark ignition coil different from the procedures for checking other types of ignition coils

because there are two secondary terminals instead of one. connect an ohmmeter to each of the secondary terminals and compare to specs

what two steps should be taken to assist you in making a proper diagnosis

careful visual inspection, gather info form customer to get a starting point

descrive the basic prodecure for finding the cause of a no start problem on an EI vehicle

check for spark if weak or no spark check wiring to and from the pcm if okay, connect a voltmeter from the input battery terminal or each coil pack to ground. with the ignition switch on it should read 12v. if less is found check the wiring diagram to determine what is included in that circuit. if voltage is present check the volt drop across each of the components and wires to identify the location of an open or high resistance. if none is found. check crank/cam sensors. compare to specs

list the common types of spark plug fouling and the typical problems each type indicates

cold foulding - excessively rich a/f mixture or the plug might not be firing due to an ignition system fault or mechanical failture in the cylinder wet fouling -excess oil in the combustion chamber splash fouling - after an overdue tuneup, combustion chamber deposits foul the new plugs. gap bridging - carbon deposits due to stop and go driving. can melt and bridge the spark gap glazing- high speed driving and wide open throttle acceleration overheating - incorrect heat range plug used, overadvance timing, excessively lean fuel mixture, cooling system failture, low fuel octaine rating, incorrectly installed plugs, or a stuck heat riser valve turbulence buring- overating can be the problem if premature wear is evident preignition damage - caused by excessive engine temps.

three types of stress test used to test for intermittent ignition component problems

cold, heat, moisture. cold/heat testing involtes directing temperature onto the component and looking for malfunctions. moisture involves lightly spraying and looking for failture

define the three areas that can cause problems in the primary ignition system

connectors, corrosion, dirt, broken tabs, loose connectors charging systems, belts, wires, ignition switch moisture

define dtc

diagnostic trouble code

define common problems and provde examples

effects all cylinders: no start, ignition module, primary and secondary circuit

define EMI

electromagnetic interference

define eeprom

electronic eraseable probramable read only memory

list the nine symptioms of the ignition system

hard start -excessive time to start rough idle- idles poorly and may stall stalling - unexpected quitting after startup while idling or decelleration hesitation- doesn't immediately respond to opening of throttle stumble- engine temporarely loses power during acceleration poor accelleration - accel is slower than expected surge- engine speed fluctuates with a constant throttle during idle, steady curse acceleration, decelleration bucking- jerking shortly after acceleration or decelleration knocking- engine makes sharp metalliac noise during acceleration.

which checking a pickup coil with an ohmmeter a higher than normal reading indicaes that the pick up unit has...

high resistance

name four areas that distributor cap and rotor should be inspected for

housing vents, inside of cap, metal terminals, cap towers, rotor

descrive the steps, similarities, and differences for no start diagnosis between a basic and ei system

in a conventional system you start by checking for other systems first (fuel, vacuum, et) before you go to ignition. in an EI you start by a visual inspection of the ignition system and then check cam/crank sensors.

leaner a/f mixtures

increase the electrical resistance inside tyl and increase required firing voltage

define noncommon problems and provide examples:

individual cylinders: vacuum leak, misfire, plugs, wires, coils

two issues that can be caused by an loose igniton module

intermittent misfire, no start

explain what happens when spark plug wires are run parallel to each other over long distances and what can be done to avoid the problem

it can induce voltage causing cyl's to fire at wrong times. the instead should cross

what happens if one of the ground electrodes of a spark plug with two or more eltrodes is closer to the center electrode than the other

it will jump to the closest one

what is a spark line

its the required voltage to maintain the spark across a plug's gap and its length represnts the amount of time the spark continues

define koeo

key on engine off

define koer

key on engine running

define KV

kilovolt, 1000 volts

the crankshaft positon sensor can be one of two types, and then define the function of the sensor

magnetic pulse generator (AC) or hall effect sensor(DC). a voltage pulse actuates the transistor in the control module, voltage is created when it crosses a magnetic field

define MIL

malfunction indicator light

name the three types of trace pattern display modes and give an example of w hen each mode is most useflul

parade raster or superimposed. raster is useed to compare the timing of events syperimposed allows identification of the cylinder whose pattern differs from that of the other cyls parade pattern is useful for easily comparing voltage peak differences

define pid

parameter identification

what is emi

radio waves created by components such as plug wires and alternators that can potentially alter signals reieved by sensors causing poor operation

what is the typical procedure to check the primary winding

set ohmmeter to auto range and connect meter across the primary coil terminals. infinite =open. high than normal readings indicate excessive resistance. if less that spec a wire is shorted.

what is carbon tracking and where should you look for it

the formation of a line of carbonated dust (means high voltage found low resistance (ofter plastic)) found between distribuitor cap terminals or between the distribuitor housing

t/f. input signals should always be checked before checking output signals

true

two methods to check a hall effect sensor

using a logic probe or a lab scope. or with a 12v source and multimeter

what tool is the best to indicate the source of a noncommon problem and how?

vacuum gauge. look for fluctuations in the needle to indicate different types of problems

what happens in the secondary ignition system if a spark wire is not pushed into the distribuitor cap or the plug tightly

would try to find ground elsewhere, possibly would cause a coronna effect