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Cylinder operation is jerky or cylinder slow coming down.
Possible Cause: Air in cylinder - bleed cylinder using following procedure.
- Raise the dump body and cylinder to full extension.
- Lower the dump body and cylinder till the front of the dump body is approximately 2 feet off of the chassis frame.
- Put the body up lever in the hold position (center).
- If you have an outside bleeder valve, crack the valve open at this time.
- Wait until all trapped air has escaped from the valve and a full stream of hydraulic oil is escaping from the valve.
- At this point the cylinder is bled, close the bleeder valve.
If your bleeder valve is located on top of the cylinder you will need a 9/16" wrench to remove the dog box cover and you will need to move to the inside of the dump body.
- Remove the dog box cover and crack the bleeder valve open at this time.
- Wait until all trapped air has escaped from the valve and a full stream of hydraulic oil is escaping from the valve.
- At this point the cylinder is bled, close the bleeder valve.
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Cylinder slamming, miss-staging, or sticking.
Possible Cause: Air in the hydraulic cylinder.
- See procedures to bleed air out of the cylinder in "Cylinder operation is jerky or cylinder slow coming down" above.
Possible Cause: Head nut too tight on one of the cylinder stages.
- Identify stage that is hanging up.
- Back head nut off 1 full turn, then re-tighten 3/4 turn.
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Cylinder is frequently getting air in system.
Possible Cause: Dump truck is being operated with the body up lever unlocked in the down position.
- The body up levers (cable actuated) must be manually locked into the center position with every use, they are not self locking.
- The body up lever not being centered is the most common problem with excessive air in the hydraulic system.
Possible Cause: Oil level in hydraulic tank is low and suction hose is sucking air out of tank.
- Top off hydraulic tank with hydraulic oil.
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Cylinder seeping excessive oil around the head nuts (Thin film of hydraulic oil on cylinder stages is normal).
Possible Cause: Cylinder head nut needs tightening (normal maintenance item)
- Refer to dump body owner's manual, cylinder section.
Possible Cause: Bleeder valve left open at the top of the cylinder.
- Remove the dog box cover inside the dump body with a 9/16" wrench and tighten the bleeder valve.
Possible Cause: Cylinder wiper or packing protruding above head-nut.
- Call J&J Warranty Dept. (800.777.2671) with the dump body serial number and discontinue use of cylinder.
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Cylinder seems loose or rattles in the dog house
Possible Cause: We receive many calls on what appears to be loose cylinders.
- A telescopic cylinder mounted to a dump body and chassis frame needs a certain amount of play so the cylinder does not destroy itself when operated in motion or slightly off level. This play in the cylinder is normal.
- If after further analysis, the operator detects a problem outside of the above explanation, please call the Warranty Dept. at J&J Truck Bodies (800.777.2671)
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Cylinder drifting down in hold position
Possible Cause: (See Cab Controls)
Possible Cause: (See PTO's and Pumps)
Possible Cause: Body up cable may have been impacted from underneath damaging either cable or cable connection to the pump. This may result in pump spool being unable to return to center.
- Inspect cable and connection kit.
- If damaged, replace damaged components.
- Call 800-777-2671 and ask for the Parts Department. (Body serial number needed)
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Body up lever is not operating smoothly (stiff)
Possible Cause: (Cable actuated pump) Cable is binding.
- Within 12 warranty period call 800.777.2671 ask for the Warranty Department, after 12-month Warranty period ask for the Parts Department. (Body serial number needed)
- If you replace cable please examine connection kits between cable and pump. Replace connection kit if excessive rust is apparent.
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Body up lever will not raise body.
Possible Cause: (Air actuated) Body up lever a.k.a. feather valve is defective.
- Release airlines at the pump for the feather valve.
- Operate feather valve and check airline pressure with airlines unattached.
- If one of the airlines is not producing enough pressure to operate shifter spool on the pump, the feather valve may be defective.
- Replace feather valve.
- Within 12-month warranty period call 800.777.2671 ask for the Warranty Department, after 12 months ask for the Parts Department. (Body serial number needed)
Possible Cause: (Cable operated) Cast aluminum ear at the bottom of the body up lever, where cable attaches, has broken off. (This would normally be a symptom of a bound cable, and the lever has been forced.)
- Within 12-month warranty period call 800.777.2671 ask for the Warranty Department, after 12 months ask for the Parts Department. (Body serial number needed)
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Air tailgate switch (V8S switch) leaking in the cab.
Possible Cause: Air tailgate cylinder bound and bypassing air through cylinder seal and exhausting in the cab.
- Check all pivot points on air tailgate cylinder and make sure they are lubricated and moving freely.(Air tailgate cylinder mounting bolt is to be LOOSE to allow cylinder to pivot.)
- Remove the pin from the yoke that attaches the air tailgate cylinder to the tailgate linkage.
- Operate the air tailgate switch with the air tailgate cylinder unattached.
- If it is still exhausting in the cab, replace the air tailgate switch.
- If it stops exhausting in the cab, see (Tailgates: Air tailgate cylinder).
- To replace air tailgate switch, within 12-month warranty period call 800.777.2671, ask for the Warranty Department, after 12 months ask for the Parts Department. (Body serial number needed)
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PTO switch is not engaging PTO. (See also: PTO's and Pumps)
Possible Cause: Shifter head is malfunctioning.
- Replace shifter head cover.
- Within 12-month warranty period call 800.777.2671 ask for the Warranty Department, after 12 months ask for the Parts Department. (Body serial number needed)
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Body up light malfunctioning
Possible Cause: Flexible switch extension needs adjusted to come into contact with body on the way down.
- Adjust switch to the appropriate angle to catch dump body long members as body is lowered.
Possible Cause: Body up switch may have been damaged by falling material or another unnatural cause.
Possible Cause: Faulty switch
- Remove screws to body up switch cover, unhook both wires and cross them. The wires should arc.
- If the switch wires arc when crossed the problem is internal to the body up switch.
- Replace the switch.
- Within 12-month warranty period call 800.777.2671 ask for the Warranty Department, after 12 months ask for the Parts Department. (Body serial number needed)
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Tailgate operation is stiff.
Possible Cause: Tailgate top hardware pins need greased. (This is a weekly maintenance item.)
- Tailgates top pins left for prolonged periods of time without grease will guald in the top hardware bushings.
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Tailgate leaking material at bottom seal.
Possible Cause: Tailgate linkage needs tightened.
- Loosen the jam nut on the tailgate linkage turnbuckle and tighten the turnbuckle as needed.
- Re-tighten the jam nut back against the turnbuckle.
Possible Cause: Tailgate linkage is broken or out of adjustment.
- Within 12-month warranty period call 800.777.2671 ask for the Warranty Department, after 12 months ask for the Parts Department. (Body serial number needed)
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Tailgate latches will not lock over center or lock out.
Possible Cause: Tailgate linkage is too tight.
- Loosen the jam nut against the turnbuckle, back the turnbuckle off until tailgate linkage locks over center, and re-tighten jam nut against the turnbuckle.
Possible Cause: Material may be wedged in bottom hardware or trapped around tailgate linkage.
- Remove trapped material. (Trapped material in bottom tailgate hardware will often stretch tailgate linkage. The linkage may need adjusted after material is freed from the bottom hardware.)
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Tailgate : Air tailgate cylinder leaking air around internal seals and exhausting leaked air through air tailgate switch in the cab.
Possible Cause: Air Tailgate cylinder is bound.
- Remove the pin from the yoke that attaches the air tailgate cylinder to the tailgate linkage.
- Make sure air tailgate cylinder mounting bolt is LOOSE, and the cylinder can pivot easily on the mounting bolt.
- Pivot air tailgate cylinder on the bolt and make sure the air tailgate cylinder yoke, that attaches to tailgate linkage, swings easily into it's attachment point without unnaturally cocking the cylinder.
- If the air tailgate cylinder continues to exhaust in the cab, the cylinder may be defective.
- (See Also: Cab Controls - Air Tailgate Switch)
- Within 12-month warranty period call 800.777.2671 ask for the Warranty Department, after 12 months ask for the Parts Department. (Body serial number needed)
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Leaking PTO or pump
Possible Cause: There may be a number of reasons for a PTO or pump to be leaking.
- Wipe down the leaking assembly to determine where the unit is leaking.
- Note the color of the fluid leaking. (Clear: Hydraulic oil - Red or Green: Transmission Fluid)
- Call the Warranty Department immediately with the details.
- Call 800-777-2671 and we will have a technician troubleshoot with you over the phone. (Body serial number needed)
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Noisy PTO or pump
Possible Cause: There are numerous reasons a PTO or pump may be making excessive noise.
- DISENGAGE PTO IMMEDIATELY and call the Warranty Department at 800-777-2671 with details.
- We will have a technician troubleshoot over the phone. (Body serial number needed)
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Pump (cylinder drifting down in hold position)
Possible Cause: Relief cartridge in pump may be contaminated.
- Dirt in the relief valve may hold the relief valve open slightly allowing hydraulic oil to bypass the valve, causing the dump bed to drift down.
- Replace relief cartridge.
- Within 12- month warranty period call 800-777-2671, ask for the Warranty Department, after 12 months ask for the Parts Department. (Body serial number needed)
Possible cause: If the relief cartridge has been replaced and the body is still not holding, call 800-777-2671, ask for Warranty Dept. and we will have a technician trouble shoot with you over the phone. (Body serial number needed)
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