Ignition System - Hei-Est Buick Electra Estate Wagon

DESCRIPTION

The Delco-Remy High Energy Ignition system with Electronic Spark Timing (HEI-EST) is a part of the General Motors Computer Command Control (CCC) systems. The CCC is designed to provide optimum performance through electronic control of air/fuel ratios, spark timing, air management, and idle speed. Some 3.0L, 3.8L, 4.3L, and 5.0L engines also use the Electronic Spark Control (ESC) system to retard spark timing when detonation occurs.

The distributor contains a HEI-EST control module and magnetic pick-up assembly. The pick-up assembly consists of a permanent magnet, a pole piece with internal teeth, and a pick-up coil. There are no vacuum or centrifugal advance mechanisms.

Distributors may be equipped with either an integral or externally mounted ignition coil. Some distributors with externally mounted ignition coils may be equipped with sealed module connectors. (Scheme 9)

Note. On all models equipped with 4-cylinder engines, ignition coil is mounted externally. On all other models, ignition coil is mounted on distributor cap.

Typical HEI-EST Distributor Integral coil model is shown. Scheme 7

When the teeth of the timer core, rotating inside the pole piece, line up with the teeth of the pole piece, an induced voltage in the pick-up coil signals the electronic module to trigger the coil primary circuit. The primary current will decrease and induce a high voltage in the ignition coil secondary winding. The high voltage is directed through the rotor and secondary leads to fire the spark plugs. The distributor module may have 3 different terminal arrangements depending on application.

EST SYSTEM

All spark timing changes are controlled by the Electronic Control Module (ECM). The ECM (not the distributor HEI-EST module) receives information from various sensors. The ECM computes desired spark timing and signals the distributor to change timing accordingly. To control timing, the ECM receives information on crankshaft position, engine speed, engine load, atmospheric pressure, engine temperature, and transmission gear position.

A back-up spark advance system is also incorporated to signal the ignition module in case of ECM failure.

HEI-EST Distributor with Hall Effect Switch External coil model is shown. Scheme 8

Distributors on some vehicles equipped with 4-cylinder engines contain a Hall Effect switch and shutter blades. The Hall Effect switch and shutter blades act as a second pick-up coil and timer core. When the engine is cranking, the pick-up coil and timer core are used to send RPM impulses to the ECM. When the engine is running, the Hall Effect switch and shutter blades perform this function.

HEI-EST Distributor with Sealed Module Connector. Scheme 9

Schematic of Integral Coil HEI-EST Ignition System. Scheme 10

The distributor module is connected to the ECM by a 4-wire connector. The circuits perform the following functions

1. Module terminal "E" triggers the HEI module. The ECM does not know actual timing, but it does sense when it receives the reference signal. It advances or retards spark from that point. If base timing is incorrectly set, advance curve will be incorrect.
2. Module terminal "R" is the distributor reference which provides the ECM with RPM and crankshaft position information. If wire is open or grounded on fuel injected vehicles, engine will not run because ECM will not operate injectors.
3. Module terminal "B" is the by-pass circuit. At about 400 RPM, ECM applies 5 volts to this circuit to switch spark timing control from HEI module to ECM. On some models, the wire goes through a connector between the 4-wire connector and the ECM. This is disconnected to set base timing. On all models, an open or grounded by-pass circuit will set a Code 42. The engine will run at base timing plus a small amount of advance built into the HEI module.
4. Module terminal "G" is the reference ground. Wire is grounded in the distributor. The wire ensures there is no voltage drop which could affect performance.
5. On distributors with a Hall Effect switch, the change in position of the by-pass switch opens the circuit between the pick-up coil and ignition coil. The pick-up coil has no RPM reference connection to the ECM, as HEI-EST module terminal "R" is not used. The function of supplying RPM signals to the ECM is accomplished by the Hall Effect switch. The wires from the Hall Effect switch connect directly to the ECM and do not connect to the distributor module.

Schematic of External Coil HEI-EST Ignition System. Scheme 11

SENSORS

The coolant temperature sensor advances spark on a cold engine and retards advance as the engine reaches normal operating temperature. If the engine is too hot, spark is retarded to prevent detonation. During light throttle operation, the throttle switch allows for additional advance.

Spark advance is also governed by input from coolant temperature, engine RPM, and Manifold Absolute Pressure (MAP) sensors. When MAP output voltage is low, ECM gives more advance. Less spark is given when MAP output voltage is high.

On engines with port fuel injection, the ECM will calculate spark advance using information from the Mass Air Flow (MAF) sensor, coolant temperature, and engine RPM. When the engine is under minimum load based on RPM and low air flow, more spark advance is given. When engine is under heavy load based on RPM and high air flow, less spark advance is given.

HEI-EST Ignition System with Hall Effect Distributor. Scheme 12

ELECTRONIC SPARK CONTROL SYSTEM (ESC)

There are 4 basic components to the ESC system: A detonation sensor, a HEI-EST distributor, an ESC controller, and the ECM. When detonation (engine knock) occurs, the detonation sensor sends an electrical signal to the ESC controller. The ESC controller amplifies this signal and transmits it to the ECM. The ECM will then retard spark timing until the ECM no longer receives a signal from the detonation sensor.

Schematic of Electronic Spark Control System. Scheme 13

Note. For more information on operation and testing of the HEI-EST system, see GENERAL MOTORS COMPUTER COMMAND CONTROL in 1985 COMPUTERIZED ENGINE CONTROLS Section.

ADJUSTMENTS

The only adjustments that can be made to HEI-EST ignition system are basic ignition timing and spark plug gap. No other adjustments are necessary.

TROUBLE SHOOTING

Note. See the TROUBLE SHOOTING - BASIC PROCEDURES article in the GENERAL TROUBLE SHOOTING section.

DIAGNOSIS

If the reference or EST signals are interrupted due to open wires or a faulty ECM, the vehicle will still run. The HEI-EST module will provide a timing signal based on engine RPM.

If the by-pass signal is lost, the ECM cannot control spark timing. The by-pass switch will permit direct flow of information to the ignition coil rather than to the ECM.

Normally, a few seconds (5-15 seconds) after starting a warm engine, the by-pass signal electronically operates a by-pass switch in the HEI-EST module. The HEI-EST module's RPM-controlled timing signal can no longer flow directly to the ignition coil, but is diverted first to the ECM for modification by information received from the engine sensors.

Loss of the EST signal with the by-pass signal "ON" will stop the engine, because the HEI-EST module is no longer sending signals directly to the ignition coil, but to the ECM, and any loss of the EST signal cuts all flow to the coil. If vehicle is restarted, the engine will run for a few seconds and then stop when the by-pass signal comes back on.

TESTING

Note. Ignition coils with Red and White leads should be matched with pick-up coils having either a Clear, a Black, or a Blue connector. Ignition coils with Red and Yellow leads must be matched with pick-up coils with a Yellow connector.

Scheme 14

1. Remove coil connector. Using the low scale, connect ohmmeter leads to coil's battery and "TACH" terminals. (Scheme 14) Resistance should be 0-1 ohm. If not, replace ignition coil. (Scheme 14): Testing Ignition Coil Resistance Externally mounted ignition coil is shown.
2. Set ohmmeter to high scale and connect leads to battery terminal and a good ground on coil. (Scheme 14) Resistance reading should be infinity. If not, replace ignition coil.
3. With ohmmeter still set in high range, connect leads to "TACH" terminal and to secondary terminal. Resistance should be 6000-30,000 ohms. If not, replace ignition coil.

Externally Mounted Ignition Coil

(Sealed Module Connector Distributor)

1. Remove coil connectors and secondary coil wire. In test "A", use high scale. (Scheme 15) Reading should be infinity. If not, replace coil.
2. On test "B", use low scale. Reading should be very low or zero. If not, replace coil. On test "C", use high scale. Ohmmeter should not read infinity. If so, replace coil.

Testing Ignition Coil Resistance Illustration applies to sealed module connector distributors only. Scheme 15

Scheme 16

1. Turn ignition switch "OFF". Remove the distributor cap and coil assembly. (Scheme 16) Set ohmmeter in low scale. Connect leads to coil's battery and "TACH" terminals. Resistance should be 0-1 ohm. If not, replace ignition coil. (Scheme 16): Testing Ignition Coil Resistance Integral mounted ignition coil is shown.
2. Set ohmmeter in high scale. Connect one ohmmeter lead to coil secondary terminal. Connect other ohmmeter lead to "TACH" terminal and then to ground terminal.
3. If one reading is infinity and other is 6000-30,000 ohms, ignition coil is okay. If resistance reading in BOTH instances is infinity, replace ignition coil.

DISTRIBUTOR PICK-UP COIL SHORT AND RESISTANCE CHECKS

1. Disconnect pick-up coil leads from HEI-EST module terminals "N" and "P" (usually a Green and a White wire). To check for shorted pick-up coil, set ohmmeter in middle range.
2. Connect one lead to either pick-up coil lead and other lead to distributor housing. Flex pick-up coil leads by hand to check for intermittent shorts. Reading should be infinite at all times. If not, replace pick-up coil.
3. Connect ohmmeter leads to both pick-up coil leads. Flex wires and connectors to locate intermittent opens. Resistance should read a constant value between 500 and 1500 ohms. If not, replace pick-up coil.

Checking Distributor Pick-Up Coil Integral mounted ignition coil is shown. Scheme 17

Checking Distributor Pick-Up Coil Externally mounted ignition coil is shown. Scheme 18

Checking Distributor Pick-Up Coil Illustration applies to sealed module connector distributors only. Scheme 19

HALL EFFECT SWITCH TEST

Note. Hall Effect switches cannot be checked with an ohmmeter.

Scheme 20

1. Disconnect 3-wire connector at Hall Effect switch. Connect a 12 volt battery and voltmeter to switch terminals. (Scheme 20) Carefully note polarity markings. (Scheme 20): Testing Hall Effect Switch
2. Insert knife blade straight down between magnet and Hall Effect switch. (Scheme 20) Voltmeter should read within 0.5 volts of battery voltage. With knife blade removed, voltmeter should read between 0 and 0.5 volts. If voltage readings are not as described, replace Hall Effect switch.

IGNITION SYSTEM CHECK

Note. Before testing, obtain spark tester (ST-125). If tachometer is connected to ignition coil "TACH" terminal, disconnect it before performing tests. Use digital voltmeter with 10 megohms or greater impedance.

Integrally Mounted Ignition Coil

1. Remove a spark plug wire and attach spark tester to wire. Crank engine and check for spark at tester gap. If there is no spark, check a second wire in same manner. A few sparks and then nothing, is considered no spark. If sparks result, ignition system is not at fault. Suspect fuel system or spark plugs.
2. If no spark resulted in step 1, disconnect 4-wire EST connector between distributor and ECM. Check for spark. If spark present, replace pick-up coil.
3. If no spark with 4-wire plug disconnected, check voltage at distributor battery terminal while cranking.
4. If reading is less than 7 volts, repair primary circuit back to ignition switch. If 7 volts or more, check voltage at "TACH" terminal. Leave negative lead grounded.
5. If reading is under 1 volt, ignition coil connection or ignition coil is defective. Repair or replace as necessary. If reading is 10 volts or more, go to step 7. If voltmeter reading is 1-10 volts, proceed to step 6.
6. If voltage reading on "TACH" terminal was 1-10 volts, replace distributor HEI-EST module and check for spark. If a spark results, ignition system is okay following module replacement. If there is still no spark, replace ignition coil.
7. If in step 5, 10 volts or more were read on "TACH" terminal, attach spark tester to coil output terminal. Crank engine and check for spark.
8. If no spark occurs, proceed to step 9. If spark occurs, check color match of pick-up coil connector and ignition coil lead. Inspect cap for water, cracks or other damage. If okay, replace rotor. NOTE: Ignition coils with Red and White leads should be matched with pick-up coils having either a Clear, a Black, or Blue connector. Ignition coils with Red and Yellow leads must be matched with pick-up coils with Yellow connector.
9. If no spark occurred in step 7, remove pick-up coil leads from module. Connect positive lead of voltmeter to coil "TACH" terminal. Ground negative lead. Turn ignition switch "ON". For no more than 5 seconds, connect test lamp from battery positive terminal to HEI-EST module terminal "P". Watch voltmeter as test lamp touches terminal.
10. If voltage drops, proceed to step 11. If voltage does not drop, check module ground screw. Also check for open in wires from distributor cap (coil) to distributor. If okay, replace HEI-EST module.
11. If voltage dropped in step 10, check for spark at tester gap (still attached to coil output terminal) when test light is removed from module terminal. If spark occurred, either pick-up coil or its connections are defective. Perform Distributor Pick-Up Coil Short and Resistance Check.
12. If distributor module tester is available, check HEI-EST module. If okay, check ignition coil ground. If ground is okay, replace ignition coil. If module is defective, replace.
13. If no module tester is available, check ignition coil ground circuit. If okay, replace ignition coil and repeat steps 7, 9, and 11. If spark results, system is okay. If no spark results, original ignition coil is okay. Reinstall original ignition coil and replace HEI-EST module.

1. Remove a spark plug wire and connect spark tester. Check for spark while cranking engine. If no spark results, check for spark at another wire. A few sparks and then nothing is considered no spark. If spark results, problem is in fuel system or spark plugs.
2. If no spark occurred in step 1, unplug 4 terminal EST connector. Check for spark. If spark, replace pick-up coil. If no spark, check for spark at coil wire with Tester (ST-125) while cranking. NOTE: Leave spark tester (ST-125) connected during remainder of tests.
3. If spark is present while cranking, inspect cap for cracks or other defects. If okay, replace rotor. If no spark while cranking, remove distributor cap with ignition "ON". Check voltage at HEI-EST module terminal "+".
4. If voltage is less than 10 volts, repair wire from terminal "+" to ignition coil and primary circuit to ignition switch.
5. If voltage was 10 volts or more in step 3, leave ignition switch "ON". Check voltage at HEI-EST module terminal "C". If voltage is less than 1 volt at terminal "C", check for open or grounded lead from ignition coil to terminal "C". Also check ignition coil connections or for an open primary circuit in ignition coil.
6. If reading was 1-10 volts in step 3, replace HEI-EST module and check for spark from ignition coil. If sparks occur, system is operating properly. If no sparks occur, also replace ignition coil.
7. If voltage was 10 volts or more in step 5, remove pick-up coil connector from HEI-EST module. Check voltage at HEI-EST module terminal "C" with ignition switch "ON". Momentarily connect a test light between battery voltage and HEI-EST module terminal "P" while observing voltmeter.
8. If voltage does not drop, check HEI-EST module ground. If okay, replace HEI-EST module. If voltage drops, use a spark tester and check for spark at end of coil wire as test light is removed from module terminal "P". If spark does occur, check pick-up coil and its connections. Ensure pick-up coil is not grounded.
9. If no spark occurs in step 8, check HEI-EST module with tester (J-26792). Replace module if defective. If module okay, check coil wire from distributor cap to ignition coil. If coil wire okay, replace ignition coil. If no distributor module tester is available, check coil wire from distributor cap. If good, replace ignition coil and repeat step 7.
10. If spark occurs, system is operating properly. If no spark occurs, coil removed is okay. Reinstall original coil and replace module.

Note. Before testing, obtain spark tester (ST-125). If tachometer is connected to ignition coil "TACH" terminal, disconnect it before performing tests. Use digital voltmeter with 10 megohms or greater impedance.

(Sealed Module Connector Distributor)

1. Remove a spark plug wire and connect spark tester. Check for spark while cranking engine. If no spark results, check for spark at another wire. A few sparks and then nothing is considered no spark. If spark results, problem is in fuel system or spark plugs.
2. If no spark occurred in step 1, unplug 4-terminal EST connector. Check for spark. If spark, replace pick-up coil. If no spark, check for spark at coil wire with Tester (ST-125) while cranking engine. NOTE: Leave spark tester (ST-125) connected during remainder of tests.
3. If spark is present while cranking, inspect cap for cracks or other defects. If okay, replace rotor. If no spark while cranking, unplug distributor 2-wire "C/+" (coil) connector. Turn ignition on with engine stopped. Check voltage at "+" and "C" terminals of harness connector.
4. If under 10 volts at terminal "C" only, check for open or ground in circuit from "C" to ignition coil. If circuit good, fault is ignition coil or connections.
5. If both terminals read under 10 volts in step 3, repair wire from module "+" terminal to "B" terminal of Black ignition coil connector or primary circuit to ignition switch.
6. If both terminals read 10 volts or more in step 3, check voltage from "TACH" lead to ground with ignition on. Reconnect distributor 2-wire connector.
7. If voltage less than 1 volt in step 6, repair open tachometer lead or connector and repeat step 6. If voltage reading is 1-10 volts in step 6, replace module and check for spark as described in step 1. If spark present, system is good. If no spark, replace ignition coil also.
8. If voltage is over 10 volts in step 6, connect test light from "TACH" lead to ground. Crank engine and observe light. If light blinks, replace ignition coil and recheck for spark with tester (ST-125). If still no spark, install original coil an replace module.
9. If light is on steady in step 8, unplug distributor 4-wire connector. With ignition on, remove distributor cap and 5 mm retaining screw in 4-wire end of module.
10. Loosen remaining module screw and pivot module out to gain access to pick-up coil terminals. Jumper module retaining screw eyelet to ground. Disconnect pick-up coil from module. Connect voltmeter from "TACH" terminal to ground. Insulate test light probe to 1/4" from tip. Note voltage as test light is momentarily connected from module terminal "P" to 12 volt source. DO NOT touch for more than 5 seconds.
11. If no drop in voltage, check module ground. If ground good, replace module. If voltage drops, check for spark from coil wire with spark tester (ST-125) as test light is removed from module terminal.
12. If spark is present in step 11, check pick-up coil resistance or connections. If no spark, check module with module tester. Replace module if defective. If module is good, check coil wire from cap to coil. If wire good, replace coil.
13. If no module tester was available in step 12, replace ignition coil and repeat step 9. If spark is now present, system is good. If no spark present, ignition coil removed is OK. Install coil and check coil wire from cap. If coil wire OK, replace module.

INTERMITTENT OPERATION CHECK

1. Connect spark tester to 2 different spark plug wires. If no spark, go to Ignition System Check. If spark on either or both wires, check for dwell increase from low to high RPM.
2. Check pick-up coil and Hall Effect switch (if equipped). Replace if faulty. If pick-up coil and Hall Effect switch are good and dwell did not increase, replace HEI-EST module. If good, but dwell did increase, check fuel system, spark plug wires, distributor cap, and spark plugs.

Scheme 21

1. With selector lever in "P" (auto. trans.) or Neutral (man. trans.), run engine at fast idle. Note timing change as "Test" terminal is grounded. (Scheme 21) If timing changes, system is operating properly. (Scheme 21): Test Terminal Location Timing should change with test terminal grounded.
2. If timing does not change on vehicles with manual transmissions, go to step 3. If timing does not change on vehicles with automatic transmissions, let engine return to idle. Place selector lever in "D" and note timing change as test terminal is grounded. If timing changes, system is operating properly.
3. If no change in timing occurs (all models), check voltage at output of MAP (Manifold Absolute Pressure) sensor or vacuum sensor as vacuum hose is removed and reinstalled. If no change occurs, problem is in the vacuum or MAP sensor circuit. If voltage output changes, proceed to step 4.
4. Disconnect park/neutral switch and recheck for timing change. If timing changes, problem is either an improperly adjusted or faulty park/neutral switch. If timing does not change, check for grounded wire from terminal "H" of ECM to park/neutral switch. If wire is not grounded, replace ECM.

Fuel Injected Engines

1. The ECM will set timing at a specified value when the "Test" terminal is grounded. To check EST operation, timing should be checked at 2000 RPM with the terminal not grounded.
2. Ground the "Test" terminal. If timing changes at 2000 RPM, the EST is operating.

ESC PERFORMANCE CHECK

Note. Perform these checks only after checking other causes of engine detonation, such as ignition timing, MAP, lack of EGR, or engine overheating.

1. Connect tachometer to engine and run at fast idle speed (about 1500 RPM). Place shift lever in "P" (auto. trans.) or Neutral (man. trans.). With engine at normal operating temperature, tap engine block in area of detonation sensor. If engine RPM drops, system is operating properly.
2. If RPM did not drop, disconnect ESC controller (located in engine compartment) and check for RPM change. If no change in RPM, proceed to step 5. If RPM drops, run engine at 2000 RPM. Unplug controller harness. Connect a digital voltmeter between ESC harness connector terminals "E" and "D". On the A.C. scale, reading should not be higher than .08 volts.
3. If voltage reading is correct, problem is a faulty ESC connection or ESC controller. If voltage is not correct, check for an open in wire from ESC controller connector terminal "D" to ground.
4. Repair if an open is found. If no open is found, check for an open or a poor connection between detonation sensor and ESC controller connector terminal "E". If circuit is okay, replace the detonation sensor.
5. If no change in RPM in step 2, inspect "CHECK ENGINE" light. If light is on, problem is most likely a faulty ESC controller or detonation sensor. If light is off, turn ignition switch "ON" (engine not running) and check voltage from ground to ESC terminal "C".
6. If voltage is under 2 volts, replace ECM. If voltage is over 2 volts, repair short in wire from ESC terminal "C" to ECM terminal "L".

Note. A knock sensor-to-controller wire that is routed too close to spark plug wires may cause retarded timing due to a false signal.

DISASSEMBLY

1. On distributors with integral ignition coils, detach 4-wire EST connector and wiring connector from cap. Turn 4 latches and remove cap and coil assembly from lower housing. To remove coil, remove coil cover attaching screws, cover, and coil attaching screws. Lift coil with leads from cap.
2. Remove rotor. Remove coil arc seal and clean cap with soft cloth, checking for cracks or other damage.
3. On vehicles with external coils, remove coil connector and disconnect 4-wire EST connector and 2-wire coil connector. Turn 2 latches and lift off distributor cap. Remove rotor.
4. On all models, disconnect pick-up coil leads from HEI-EST module. Remove Hall Effect switch (if equipped) by removing 2 attaching screws. Mark distributor shaft and gear for reassembly. Drive out roll pin and remove distributor shaft.
5. On models with integral coil, remove magnetic shield. On all models, remove "C" washer, pick-up coil, magnet, and pole piece. Remove 2 module attaching screws and capacitor screw (if equipped). Lift module, capacitor, and harness assembly from distributor housing. Disconnect wiring harness from module.

REASSEMBLY

Assemble in reverse order. Wipe distributor housing and module clean and apply silicone grease between module and housing. Spin shaft to be sure timer core external teeth do not strike pole piece internal teeth.

See also:
• TROUBLE SHOOTING - BASIC PROCEDURES