Distributor and electronic ignition systems

Objectives

Purpose of electronic distributor ignition Voltage signals

o Analog systemso Digital systems

Describe distributor based ignition systems and modules

Purpose of electronic distributors

DI -any ignition system that has distributor – mechanical or electronic EI- any electronic ignition system without a distributor purpose is the same – to open and close the primary circuit to create a spark at the plug

DI systems

why did we stop using mechanical systems, and switch to electronic lean fuel mix – single coil, mechanical systems @ 22k – not enough to light and have sufficient

burn time ignition coils and primary current control triggering devices PM generators Manufacture systems

Primary switch

Remember the purpose is to open and close the primary circuit to fire the plugso Mechanically (pointso Analog electrical signalo Digital electronic signal

All are on – off signals

Analog signal

Voltage constant and variable Rheostat (dash light, variable controlled) PM (permanent magnet) generator

Digital signal

On or off (like a light switch) Hall effect

DI systems with an external ignition module

Dura-spark I & II systems Fords thick film integrated ignition (TFI) Chryslers external module system General motors high – energy ignition (HEI) These systems are all analog signal systems, or PM generators (permanent magnet)

DIS

Dura-spark III HEI with EST TFI – IV Optical and photoelectric systems Magneto resistive sensor systems These are all digital and computer controlled – both switching and timing control

Analog systems

Components:o Pickup coil (stator)o Armature (reluctor, pole piece)o Module – electronic switch

Pickup coil is the signal – the module is the switch Replaces points – mechanical switch Analog signal must be converted to digital in the PCM to be compatible. Pickup coil – (pulse generator) The center of the coil is a metal toothed gear called the reluctor, pole piece. 1 tooth per cylinder Timed to the compression stroke of each cylinder Notches line up at each TDC The pickup coil signal triggers the transistor inside the module and is also used by the computer

for piston position information and engine speed RPM Pick up coil is the signal – module is the switch

Pick up coil

The pickup coil is a voltage controlled electromagnet that reacts with the reluctor to vary its magnetic field

2 wire – voltage from ignition switch & ground Turns on/off the magnetic field When energized reacts with reluctor (piece of metal) changing its magnetic field or signal

Dura-Spark problems

Lots of wiring and connections (corrosion)

Module was remote on inner fender – water/dirt/corrosion Check connections first Module has a high failure rate

TFI

Second generation electronic ignition Produced because of problems with Dura-spark Distributor mounted module (less wiring) New design ignition coil also

TFI module

Technology break through was thick film circuit board that allowed more components on small space

Improved operation and life Need dielectric grease Module still common failure – weak point

TFI Coil

E-coil mounted remote – 40k output Paste filled second generation coil (high output) Still had coil wire, positive & negative primary Excess wiring with many potential connection problems. Secondary and primary.

Daimler Chrysler distributor ignition

The pickup coil in the distributor (pulse generator) generates signal to open and close the primary coil circuit.

Module is on the fender or firewall Conventional coil Distributor, cap, rotor, and wires

HEI (High energy ignition)

General motors distributor with single coil, cap, rotor, vacuum and centrifugal advanced, wires, and plugs

All components in one unit Coil, and module in the distributor – module must have dielectric grease Less wiring and connections – early systems had one wire hook up Simpler, less failure – 48k coil output – coil mounts under plug wires in the top of the cap

Hall Effect

Hall-effect is a digital on-off signal

Magnetic switch with moving shutter blades that change the magnetic field – as blades go in and out of the field

Produces on – off digital signal Hall effect switch

o The switch uses a stationary sensor and rotating trigger wheel (shutter)o 1 shutter per cylinder

With 12 volts on from the ignition switch and the blade in the magnet – magnetic field stikes blade not hall-effect – provides 12v – primary on

Blade out of hall effect – 0 volts – primary off Blade in 12V - blade out 0 V

Dura-spark III

Empty distributor No switch (pick-up coil) No vacuum and centrifugal advance No manual timing change Computer controlled Crank sensor hall effect Distributor just for routing spark through plug wires to spark plugs

TFI IV

Generation IV had hall effect switch instead of pick-up coil mounted in the distributor Signal from the hall-effect is called the profile ignition pick-up or PIP Module could b mounted on the distributor or remotely Non – remote module Distributor hall – effect Produces spout signal (spark out) Produces PCM coil pulse

TFI circuit

12 volts to + coil and module Hall-effect signal input to module – pip signal input to PCM PCM output – spout pulse to – module negative coil Fires secondary and plugs

Photo diodes

Shutter plate routes in between high diodes Shutter in – no light on diode – 0V – primary off

Shutter out – light on – 5V to PCM primary on System has 2 light emitting diodes (LED), and 2 receiving photo diodes.

Photo – electric sensor

Two rings of data slots LED Shines through slots Inner slots for cylinder identification and sync Outer slots high resolution – very closely spaced each representing about 2 deg. Of crankshaft

revolution for timing and firing 360 signal changes in each revolution Very precise from timing control

HEI EST

Later HEI added EST or electronic spark timing PCM computer controlled 7 pin module instead of 4 pin Coil mounted remotely (4 pin will retrofit any GM engine with only 12V wire from ignition switch)

HEI circuit

Ignition coil and battery positive input Pick- up coil pulse to module on start 4 wire connector Pulse to PCM then to module when running (5V switches) EST signal from PCM to module

1no voltage @ coil

Check nuteral safety switch ignition switch

seat belt interlock clutch switch alarm system car in park

2 voltage and pulse – no spark connect test light to negative coil side and crank engine should blink indicating primary coil is being turned on/off if volts present must be secondary circuit

3 no start – no reference pulse If when you crank the engine – ignition on – 12 volts at the positive coil and you have no pulse

or reference signal What could be the problem? Pick-up coil – signal Crank/cam sensor – signal Module – switch PCM – switch

No reference signal

If you get voltage to the positive coil but no pulse – signal or switch is not working Signal – pick up coil Switch module Module or PCM are replaced only when everything else has been checked

Module service

If there is no reference signal and the pickup coil checks ok the module must be replaced Module on all systems is the common failure

Module or PCM are replaced only when everything else has been checked Dura spark 1 and 2 Make sure module is firmly attached and grounded Must apply dielectric grease on all connections TFI modules Very common failure Connections and ground Dielectric grease under module to distributor for ground and cooling HEI ignition Again – highest failure rate Very important – dielectric grease under module – module will overheat and fail very quickly

without grease

No reference signal

Pick up coil testing Check for damage and connections Check for voltage Check resistance Check waveform Pick up coil to ground = OL – GM-Ford-Chrysler

Testing magnetic sensors

First of all check for RPM on scanner 2nd, magnetic sensors must be magnetic. If there permanent magnet inside the sensor has

cracked, the result is two weak magnets. The sensor can be tested using a digital meter set to read AC volts 0.1V minimum

Pickup coil testing

Testing with a scanner-lab scope Two lead hook up (yellow & black) 5 volt 100ms

Testing optical sensors

An optical sensor can also be checked using a oscilloscope

Because of the speed of the engine and the number of slits in the optical sensor disk, a scope is about the only tool that could capture useful information

10ms div 2V DC Optical sensors will not operate if dirty or covered in oil. Clean as needed Perform a thorough visual inspection looking for an oil leak that could cause dirty oil to get on

the led o phototransistor

Testing Hall Effect sensors

Using a digital voltmeter, check for the presence of charging voltage (pulsed on and off DC) when the engine is being cranked.

The best test is to use an oscilloscope and observe the waveform

Pick up coil service

To replace most pick up coils- the distributor must be removed and disassembled Remember ignition timing is sequenced through the distributor Must be marked and re-installed in time

Distributor R&R

Mark distributor housing and engine block with white out Bump engine over until rotor is pointing to number 1 on the cap Mark when rotor is pointing. Loosen and remove hold down clamp Remove distributor Mark rotor rotation – don’t crank the engine

Distributor disassembly

To remove pickup coil- distributor shaft must be removed Remove gear first - most by roll pin, some by press fit Mark gear and shaft Support distributor – fragile Tap roll pin from gear Remove shaft Remove pickup coil

Reassembly

Re-install pickup and shaft

Install gear – check alignment Check gap w/brass or non magnetic feeler gauge. 0.10-.020 gap

Timing checks – after distributor

The engine should be at the correct timing RPM (check the specifications) emissions decal Check the timing procedure specified by the manufacturer. This may include disconnecting a self

timing connector wire, grounding a diagnostic terminal, disconnecting a four wire connector, or similar procedure

Timing adjust

Timing check – after distributor repair and re-install To set the initial timing – loosen distributor hold down – with engine at idle speed – rotate dist.

To line up marks. (computer disconnected if has one)