I thought I would post this to help anyone that has current ramped a transfer pump on a 2015 6.7 diesel. this vehicle came in with just a loud/noisy pump, runs fine no check engine lights. ok confirm filters were changed and fuel in the tank. hooked-up pressure transducer, fuel pressure at 69psi in specs. connected low amp clamp on pump + feed wire,set scope at 10 amps no signal. set scope to 5 amps no signal then again to 2 amps and bingo have a signal that seems to be drawing very little amps to work.
watch the wave forum for a few seconds and it looks like a roller costar?
bad pump? im not sure at this point so I see a repeating pattern and count 12 commutator bars not the usual 8. use the scope cursors to get the pump speed, 60,000 divided by 18.65 =3,217rpm not the usual 6,000 rpm. I cant condemn the pump at this point. customer wants it replaced anyway so I get the chance to dissect the pump and check what the scope was showing me. dissect the pump and sure enough 12 commutators, the roller costar waves on the scope are from the pump shoes. there are 5 round pump shoes and when one passes by the squeeze point it causes 3 or 4 commutator bars to draw more amps. the noise was from a bad upper armature shaft bearing. pulled a different 2015 truck in and current ramped the pump, got the exact same pattern and pressure. this just taught me the scope never lies and a steady wave forum is not what you are always going to see.
20150220-0045-1.jpg
IMG_20150219_135816.jpg
IMG_20150219_135834.jpg
IMG_20150219_140115.jpg
watch the wave forum for a few seconds and it looks like a roller costar?
bad pump? im not sure at this point so I see a repeating pattern and count 12 commutator bars not the usual 8. use the scope cursors to get the pump speed, 60,000 divided by 18.65 =3,217rpm not the usual 6,000 rpm. I cant condemn the pump at this point. customer wants it replaced anyway so I get the chance to dissect the pump and check what the scope was showing me. dissect the pump and sure enough 12 commutators, the roller costar waves on the scope are from the pump shoes. there are 5 round pump shoes and when one passes by the squeeze point it causes 3 or 4 commutator bars to draw more amps. the noise was from a bad upper armature shaft bearing. pulled a different 2015 truck in and current ramped the pump, got the exact same pattern and pressure. this just taught me the scope never lies and a steady wave forum is not what you are always going to see.
20150220-0045-1.jpg
IMG_20150219_135816.jpg
IMG_20150219_135834.jpg
IMG_20150219_140115.jpg
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