Repeated False "No Mag Interface" Shutdowns Caterpillar

Problem:

During the starting sequence of the G3600 engine, the Ignition Shutdown Relay (Magneto Shutoff Relay) (MSR) contacts can chatter when energized. This chatter results in a noise burst on the Ignition Pulse wiring between the Caterpillar Ignition System (CIS) and the engine Timing Control Module (TCM). The noise burst disables the Ignition Pulses with the TCM and the indicated timing locks onto 0.0 degrees. These conditions will generate a 326-09 (No Magneto Interface Signal) shutdown Fault Code and the engine will be prevented from starting.

Solution:

To resolve this problem, an additioal 121-6159 Relay Module can be installed into the Engine Supervisory System (ESS) Panel. The purpose of the relay module is to provide an alternate grounding path around the MSR during the cranking cycle. This will protect the ignition pulse signal from the noise burst created when the MSR is energized. The contacts of the new relay module are closed when the engine is started, and the MSR is energized. The contacts remain closed until the engine speed reaches the crank termination speed of 250 rpm. The crank termination circuit of the Status Control Module (SCM) is used to power the new relay module On and Off. The normally closed contacts of the new relay module are used.

The protection that is provided by the MSR is not compromised with the addition of the new relay module. The MSR contacts will open, and shutoff the ignition system during an over speed and emergency stop conditions. This is because the contacts of the new relay module will not close until the engine speed is reduced to 0 rpm.

The new 121-6159 Relay Module is installed into the ESS Panel as follows:

See the illustration.

1. The new relay module will mount on the DIN reials in the ESS panel. Locate an available position.

2. Install the new relay module wiring as follows:

* from + Battery (T352 to + CTR (T375).

* from - CTR (T374) to the coil side of the new relay module.

* from the coil ground side of the new relay module to - Battery (T354 or T353).

* from T237 to the normally closed contact of the new relay module and from the downstream side of the normally closed contact to - Battery (T354 or T353).

3. Insure that the new wiring is properly routed through the ESS Panel to eliminate the possibility of damaged wires.

WIRING DIAGRAM FOR INSTALLING NEW 121-6159 RELAY MODULE IN ESS PANEL

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