Fuel Lift Pump (005-045)
B3.9 and B5.9 Series Engines
Section 5 - Fuel System - Group 05
Remove the fuel transfer pump.
Fuel Transfer Pump (Diaphragm Style)
A malfunctioning fuel transfer pump can cause low power
from the engine. The diaphragm-style pump can not be
cleaned and rebuilt.
The transfer pump is mechanically driven by a lobe on the
camshaft. Wear on the lever or a damaged lobe can reduce
the pumping action.
(A)-Do not operate the fuel system with a suction restric-
tion of more than 100 mm Hg [4 in Hg].
If the diaphragm ruptures, fuel will drain from the weep hole
(B) in the housing.
Normal pressure drop across the filter is 21 kPa [3 psi],
The pressure drop will increase as the filter removes con-
tamination from the fuel. Therefore, a worn transfer pump
will have reduced capacity to force fuel through a dirty filter.
This can cause low engine power.
NOTE: Frequent filter replacement to get full power from
the engine can indicate a worn transfer pump.
Fuel Transfer Pump (Piston Style)
The B Series engine uses three different piston-style fuel
transfer pumps. All three deliver different flow volumes.