F−1031, Section 2312
Page 8 of 10
Rev: 02/27/06
Service Suggestions
Models VPE, VPES, VPO, VPOS
If the priming system fails to operate properly, refer to the troubleshooting
guide in F−1031, Section 1000 for the possible cause and suggested remedy.
If the cause of the failure cannot be determined using the troubleshooting
guide, the following Service Suggestions should help locate the cause of the
malfunction. Go through each step in sequence to check out all the compo-
nents of the priming system, or until the cause of the malfunction is located.
1.
Make sure battery is properly charged. If battery is in low state of charge, it
may be difficult to operate the priming pump at proper speed.
2.
Check all wiring to the priming pump and valve for loose terminals, dam-
aged insulation, or broken wire strands − especially near terminals.
3.
Check that the correct cable size is used (see Table 1 and Table 2).
4.
Check for proper grounding of the motor. On newer VPE and VPO models,
there is a ground stud on the side of the motor that should be connected
with a ground cable to the truck chassis. Older model primers rely on
grounding through the primer body; corrosion and/or dirt build−up may
cause a loss of ground.
5.
If priming pump still does not operate, remove priming motor. Step 6 will
help troubleshoot the priming pump, and step 7 will help troubleshoot the
motor.
a.) VPE models − The priming pump can be removed as a subassembly.
b.) VPO models − There are two cast parts that make up the priming pump,
the part attached to the motor should not be removed from the motor.
6.
For proper function of the priming system, always follow the Maintenance In-
structions section of this document. The following are possible priming pump−
related causes of low vacuum levels or a non−functioning priming pump:
a.) No lubricant in the primer. VPE models must have lubricant in order to
achieve vacuum levels of 22 in. Hg. or higher. VPO models can
achieve vacuum levels of 22 in. Hg. without lubricant, but for higher
vacuum levels or as the primer wears, the use of lubricant helps main-
tain desired vacuum levels.
b.) Corrosion inside the priming pump. VPE primers are more susceptible
to corrosion if not used regularly; weekly operation is recommended to
help keep internal components coated with fresh lubricant. VPO prim-
ers are made of corrosion−resistant materials, but abrasives passing
through the primer can damage the corrosion resistant surfaces.
Clean the priming pump surfaces to remove corrosion, or replace
worn parts.
c.) Stuck or broken vanes. If primer is not used regularly, corrosion and/or
the breakdown of biodegradable lubricants can cause vanes to stick;
foreign objects can enter the primer and cause a vane to break; or
sand can damage the rotor and inside walls of the primer, not allowing
the vanes to slide freely. Clean the inside of the primer and replace
vanes or worn parts as needed.
d.) Inside walls of primer damaged from sandy water. A tight fit between the
vanes and smooth primer walls are required for high vacuum levels. Dam-
age to this smooth surface (and smooth vane edges) causes a loss of the
required tight fit. Replacement of damaged parts is usually required.
7.
Check for primer motor function in the following manner:
a.) With the motor disassembled from the priming pump, manually rotate the
motor shaft to make sure it turns freely. If it does not, replace the motor.
b.) Using the correct battery (12V or 24V) for the application, attach a
ground cable (6 AWG or heavier) from the negative, “−”, battery terminal
to the ground post on the primer motor (see Figure 3 or 5). Connect the
positive, “+”, battery terminal to the solenoid “HOT” terminal, again using
a 6 AWG or heavier cable.
WARNING
!
Solenoid Motor Testing Hazard. Improper wiring may cause the
jumper wire to become very hot, resulting in burns to fingers or
hands.
To prevent the jumper wire from overheating on 24V motors, DO NOT
place the jumper wire on the solenoid ground terminal (small terminal with
wire attached).
c.) Check for motor solenoid function by connecting a jumper between cen-
ter (small) and hot terminals of solenoid (see Figure 9); the motor should
run. Disconnect the jumper. If the motor ran with the jumper installed, go
to step 8.
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