MP-8802N
Revised 03-02
Section 20
Magnetic Pickup Installation Instructions
(00-02-0181)
Models: MP3298, MP7905, and MP7906
Please read the following information before installing. A visual inspection of this product for damage
during shipping is recommended before mounting. These instructions are intended for MP3298, MP7905, and MP7906 models.
GENERAL INFORMATION
Gap Chart
THREAD
SIZE
TURN
1/2
1/4
3/4
1
WARNING
BEFORE BEGINNING INSTALLATION OF THIS MURPHY PRODUCT
.013 in.
.028 in.
.035 in.
.055 in.
5/8-18 UNF
(0.33 mm) (0.71 mm)
.015 in. .030 in.
(0.38 mm) (0.76 mm) (1.14 mm) (1.57 mm)
(0.88 mm) (1.39 mm)
.045 in. .062 in.
3/4-16 UNF
✔ Disconnect all electrical power to the machine.
✔ Make sure the machine cannot operate during installation.
✔ Follow all safety warnings of the machine manufacturer.
✔ Read and follow all installation instructions.
Typical Installation
Magnetic Pickup Installation (see diagram below)
Drill and tap a hole in the flywheel housing (See Specifications for
model and thread size). IMPORTANT: Drilling too deep may damage
ring gear teeth. Blow chips with air hose when drilling and tapping hole.
Description
Gap Adjustment
Insert magnetic pickup and turn until it stops at
the face of the gear. Back-off the gear by turn-
ing the pickup counter-clockwise 1/4, 1/2, or
A magnetic pickup is an AC generator. It is normally installed into the fly-
wheel housing of an internal combustion engine, so that the starter ring
gear acts upon it to generate a voltage pulse each time a gear tooth passes
the end of the sensor.
1/4
3/4 turn (drawing right)
.
See Gap Chart below to determine gap distance
based on the turn. Check gap clearance by
rotating the gear completely around.
Specifications
Housing Material:
1/2
3/4
MP3298: Type 300 Stainless Steel.
NOTE: Magnetic pickup gap should be adjusted so
that the minimum voltage required is attained at the engine’s lowest
RPM. The voltage will increase as the speed increases.
Locknut: Type 300 Stainless Steel.
MP7905 and MP7906: Type 6061 Aluminum/Anodize Class 1.
Locknut: Steel Nickel Plated.
If erratic readings occur, remove magnetic pickup and check the
magnetic tip for metal chips.
Output Leads (all models): Two insulated leads, 20AWG, STR/TEF
insulated per MIL-W-16878D Type E, 1 White and 1 Black.
Output Voltage (all models): 200 V.P.P. TYP. (tested at 1000 I.P.S.
20 Pitch gear, 0.005 Gap., and 100K OHM Load).
Coil Resistance:
Always use a two-conductor shielded cable. Ground the
shield to a metal frame ground at the engine end only.
Never run these wires
next to spark plug wires
or in wire loom with other
wires carrying inductive
MP3298: 975 Ohms TYP.
MP7905 and MP7906: 2500 Ohms TYP.
Potting (all models): Internal portion of pickup is filled with epoxy resin,
making the magnetic pickup oil and moist resistant.
Temperature (all models): -65° to +225°F (-54 ° to 107°C).
Coil Induct.:
loads or alternating current.
LOAD
Tach
Speed
Switch
After adjusting,
set lock-nut.
Drill and tap casing
AC
(see thread sizes in
Meter
Specifications).
MP3298: 800 mH max, @ 1K Hz.
AC Meter
Reading must
be taken at load.
MP3298: 400 mH TYP. @ 1K Hz.
Pickup Part
Model Number Length
Total
Threaded
Length
Thread
Size
Gap
(see Gap Chart)
Casing
MP3298 20700162
MP7906 20700161
MP7905 20700160
3 in. (76 mm)
3 in. (76 mm)
3 in. (76 mm)
3 in. (76 mm)
5/8-18 UNF
3/4-16 UNF
Gear (must be made
of magnetic material).
NOTE: Clean gear casing
4-1/2 in. (114 mm) 4-1/2 in. (114 mm) 3/4-16 UNF
and magnetic sensor
of metal chips or filings.
MP-8802N page 1 of 2
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