454 Engine Ignition Information-- Expanded

[dickandlois]

This will get a little long, but I hope it helps owners of coach's using this engine.

Spark Plugs:

1983 to 89 Carburetor engine uses AC-R44T plugs, gaped at .045

1990 to 97 TBI engine uses AC-CR43TS plugs, gaped at .035

1996-98 MFI engines uses AC-41-932 plugs, gaped at .060

Plugs containing the suffix TS or CTS can be used interchangeably. However, during the 1986 model year, AC spark plug changed the center electrodes in there plugs to copper. For these plugs, the letter C maybe removed from the identification number on the jacket.

Example: A spark plug with a code identification of R43TS or R43CTS would be changed to R43TS.

Plug Wires: Delco.

1985 to 1986 H4D 12043750.

1985 to 1989 H5D 12072181

1990 to 1993 H5D 12074045

1994 - Later H5D 12096418

Plug Shield and Dielectric Milar Insulators Numbers: Delco.

Cylinder #1 thru 6 and 8 10089660 2-5/8in.

Cylinder #2 10089661 1-7/8in.

Ignition Timing:

1. Remover the vacuum line from the distributor. plug the removed line to restore the vacuum integrity.

2. Engines with timing pointer on the top,Upper right side of engine looking from the front. Us the number one plug to trigger the light.

3. Motor homes chassis with the timing pointer on the bottom, Bottom left side of engine looking from the front. This procedure works better with two people to set the distributor.

This requires using the #5 or #8 plug wire to trigger the time light. Check the timing mark first before setting timing, using both plugs to check the timing before proceeding.

4. Make sure the mechanical counter weights move freely and the assembly is in good working order.

5. Test the vacuum advance module on the distributor to make sure it is operating correctly and holds a set vacuum when tested.

Electronic Module:

None fuel injected engines- GM Part number 1875990

454 Fuel injected engines- GM Part number 16139369

Pole Piece:

GM Part number 1875981 None Fuel injection.

GM Part number 10474000 with Fuel injection.

A Capacitor is used on some models.

H.E.I. Test Procedure: ( You will be working with voltages that can reach 80,000 Volts so if you have not worked on these systems,get a pro to do the work) that much voltage can make for a bad day !!!

Remove a plug wire from each plug one at a time using a H.E.I. Test spark plug ST125 or equivalent. If spark is present on all plugs H.E.I. system is OK.

Note! Using the test plug instead of allowing the spark to jump to ground can help prevent possible damage to the module.

Connect a test light between the distributor TACK signal terminal and ground. Turn on the ignition switch.

If the light does not glow ,check the power at the distributor Bat terminal.If there is no power at the terminal, the problem is in the circuit wiring or the ignition switch. Some coaches use an ignition relay. Repair as required.

If there is power at the BAT terminal and no power at the TACK terminal, the ignition primary coil winding is open. Replace the coil.

If the light glows, crank the engine. The light should glow intermittently, indicating the module and pickup coil are working.

Remove the distributor cap and check for spark at the center terminal of the cap using the H.E.I. Test Spark Plug and a jumper wire.

If there is no spark, the rotor is not working and should be replaced. If there is no spark, the coil is not functioning and needs to be replaced.

If the light glows steadily while the engine is being cranked, preform the module test.

Module Test:

Remove the Distributor cap and connect the H.E.I. Test Spark Plug to the center terminal with a jumper wire.

Remove the pickup coil connector from the module(The Green and White wires) and turn on the ignition switch.

Connect one end of a second jumper wire to the positive terminal of the connection feeding power to the distributor Cap and the other end to the small terminal of the module momentarily. ( The small terminal is the one generally connected to the Green wire) If there is.

a. A spark --- The pickup coil is not functioning properly and may need to be replaced. Replacement requires removing the distributor so if you are in over your head. Get help on this part replacement. Please know your limits as the removal of the distributor,the pickup coil replacement and installation can really mess up the timing and cause serious engine damage.

b. No spark----the module may need replacement.

Checking H.E.I. System Connections:

Remove the module and clean the terminals with emery cloth or a wire brush to remove any oxide film.

Apply a thin coat of petroleum jelly (Vaseline) on all the module terminals. Make sure a small amount of silicone heat transfer grease ( AC Delco D-1920 or equivalent) is present on the module base.

Reinstall the module and connect the leads making sure all terminals are seated with good metal to metal contact.

Work safe and enjoy a good running engine at idle and road speed.

Rich.