TM 55-4920-384-13&P
FUEL PUMP MAINTENANCE AND REPAIR INSTRUCTIONS
WISCONSIN MOTOR PART No. LP-38 (Standard), LP-38-C (Cold Weather: -65F)
USED ON 4 CYLINDER AIR COOLED ENGINES
The fuel pump, like all other parts of the engine, is sub-
ject to wear and you will find that any time after 500 hours
of use, its efficiency will gradually decrease. This is in-
dicated by the engines faltering at high speeds or when
heavy loads are suddenly applied. The pump can easily be
restored to its normal efficiency by the installation of a
Wisconsin Motor No. LQ-30 or LQ-30-A repair kit.
1. Remove the fuel lines and the two mounting bolts which
hold the pump to the engine. Take the pump to a work
bench or suitable place.
2. With file make an indicating mark across a point at the
union of castings (7 and 23). This is a positive loca-
tion of the fuel line positions when reassembling. Re-
move six assembly screws (6) and remove fuel head.
Dome bolt (1) is taken out, and the dome (3), dome gas-
ket (4) and filter screen (5) disassembled.
3. Turn bead (7) over and remove three screws (13). Re-
move (8, 9, 10, 11 and 12) valve assemblies noting their
positions. Discard Details 8, 9 and 11.
4. Clean head thoroughly with gasoline and a fine brush.
5. Holding fuel head (7) with diaphragm surface (contain-
ing 6 clearance holes) up, reassemble the valve spring
retainer (10) into position, deepest hole. Place new
valve plate gasket (11) in position around this hole.
Stand on end one of the new valve springs (9) in the
retainer. Place a new valve (8) on top of this spring.
6. Place the other new valve (8) on top of brass valve
seat next to the previously assembled parts, stand the
other new valve spring (9) on top of this valve.
7. Carefully place valve plate (12) over these assemblies
so the large raised ring is nearest the valve gasket
(11). Insert and carefully tighten the three assembly
screws (13).
8. Carefully clean and replace the filter screen (5).
9. Place new dome gasket (4) into the dome (3) and put
this unit into position on the fuel head (7).
10. Put new dome bolt gasket (2) on the dome bolt (l), in-
sert in the hole in the dome (3) and tighten properly.
11. Place this fuel head assembly in a. clean place and we
are ready to rebuild the lower diaphragm section.
12. Using a screw driver inserted into the coils of rocker
arm spring (17) remove this spring and discard.
13. Hold the mounting bracket (23) in the left hand with the
rocker arm toward your body and the thumb nail on the
end of the link (19) with the heel of right hand on the
diaphragm (14) compress the diaphragm spring (16) at
the same time pulling toward your body, this will un-
hook the diaphragm from the link (19) so it can be re-
moved.
14. Clean the mounting bracket (23) with gasoline.
15. Place the remaining new cork gasket (15) on the cor-
responding surface of the mounting bracket (23). Assem-
ble the new diaprhragm operating spring (16) standing it
into (23). Now repeat in reverse Step 13 using the new
diaphragm, rocker arm, pin, linkage and bushing. Assem-
ble new rocker arm spring.
16. Mount this assembly back on the engine in the position
from which it was removed, using the new mounting
INSTRUCTIONS FOR FUEL PUMP
gasket which is the last piece of the repair kit.
MAINTENANCE AND REPAIR
17. Crank the engine over to a position where the dia-
phragm (14) is laying flat on the mounting bracket (23).
The gaskets (2 and 4) used in the fuel head (7) of the fuel
Place the fuel head (7) back in position so the indicat-
pump have a natural tendency to shrink when left standing
ing marks of Step 1 are in line, and start the six assem-
in a dry condition. This shrinking can create vacuum leaks
bly screws approximately three turns. Again crank the
which result in the hard starting of the engine. It is nec-
engine over to a position where the diaphragm (14) is
essary after an engine has stood on the stockroom or show
pulled down into (23) mounting bracket and tighten the
room floor any length of time that the dome bolt No. 1, the
six assembly screws (6) tightly.
assembly screws (6) of which there are six and the fuel
18. Connect the fuel lines and you have a completely re-
line connections be tightened carefully to assure quick
built fuel pump.
starting and satisfactory operation thereafter.
D-69
