Transcient Mode; Overspeed Mode; Service Adjustments And Checks - Ford LRG-423 Service Manual

03-5 Auxiliary Systems
03-5
DISTRIBUTORLESS IGNITION SYSTEM DESCRIPTION AND OPERATION (Continued)
Transient Mode
This function is to provide detonation protection when
the engine load is increased rapidly by fast opening of
the throttle plate. Rapid increases in engine load are
determined by large changes in consecutive Manifold
Absolute Pressure (MAP) values to the UESC module.
Overspeed Mode
If the engine speed exceeds 4500 RPM the spark
timing will be retarded to 0 degrees BTDC until the
speed drops below 4500 RPM.
Service Adiustments And Checks
Each 400 hours of engine operation remove the
spark plugs and clean and adjust the electrode.
Clean and visually check spark plug high tension
leads, check for secure fit, and replace if necessary.
In the event that the engine is operated on dry
fuels, the timing can be modified by cutting open
the wire loop between pins 6 and 7 on the module,
and grounding one, the other, or both, depending
on the ignition curve or advance level required.
APPLICATION AND FUELTYPE DETERMINE
WHICH ADVANCE LEVELTO USE.
It is important to understand that the advance values
in the table below apply to the entire spark map, and
are added onto all values in the map.
NOTE: The following information is for demonstration
only. If an attempt is made in the field to verify these
values, the results will be similar but not precisely the
same.
For example, a non-generator set engine operating on
gasoline, with no load, and neither pins 6 or 7
grounded, will show a spark advance of approximately
9 degrees BTDC at low idle, and 34 degrees BTDC at
a high, no-load idle of 2500 RPM. Let us say that the
non-generator set engine is now switched over to
operate on natural gas. As the chart indicates, a level
3 advance should be used for natural gas. A level 3
advance on a non-generator set engine is 10 degrees
BTDC. This value is added to the base values. The
" example" engine will now show a spark at 19 degrees
BTDC (9+10) at low idle, and 44 degrees BTDC
(34+10) at a high, no-load idle of 2500 RPM.
Notice that there are two electronic modules
available. One module is for engines operating a
generator set and the other module is for all non-
generator set applications.
Level
0
Action
Loop Between Pins 6 & 7
Closed or Open
Effect On Gen
Set Module
None
Effect On Non-Gen
Set Module
None
1
Ground Pin 7 Advance 4 Degrees Advance 4 Degrees
2 Ground Pin 6
Advance 10 Degrees
Advance 8 Degrees
3 Ground Pins 6 & 7
Advance 18 Degrees
Advance 10 Degrees
Numbers in the following chart represent the
appropriate advance level.
Generator Set Non-Generator Set
Ignition Module (C) Ignition Module
1 Gasoline 1 1
I
0
I
LPG (A)
LPG (B)
2
2
N/A 1
I
Natural
Gas
I
3
I
3
I
(A) Up to 2800 RPM engine operating speed for non-generator
set engines, 1500/1800 RPM for generator set engines.
(B) 3000 to 3600 RPM engine operating speed.
(C) For generator set application, the vacuum line between the
intake manifold and ignition module MUST be
disconnected.