Quote:
Originally Posted by COLVERT
I think you will find that having the pump immersed in diesel helps to make it run cooler.
If the level drops to the extent the pump is no longer pumping diesel then the armature will speed up considerably and maybe this extra speed makes the brush to commutator connection start to arc.
( As the brushes bounce slightly )
This will generate heat which will damage the split ring commutator which is embeded in plastic !!!
Maybe . Lol
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Agree Colvert that running the pump in diesel does allow it to run cooler and if the level drops too far the pump will run faster. Had my old one on the bench running empty for 15 minutes a couple of times and the heat at the impeller end was bordering on the way too hot! It didn't seem to affect the thin slivers of commutator that were left on the top of the pump though.
Thing is when you look at the commutator with a loupe it doesn't look damaged but just worn away - its as if the brushes are too hard. Wouldn't arcing and brush bounce just as likely wear the brush away as the commutator? I don't know what the length of the brushes is when new but my old ones certainly looked as good as new.
Do we actually know that running the tank level low causes the pump to cavitate?
The fact is if you always keep the fuel level above a quarter of a tank you will never know your ITP has failed until the UBP gives up. So keeping the tank filled masks the failed ITP and you could end up putting a strain on the UBP and have that fail prematurely.
Perhaps the owners who never let their tank go below a quarter full can check to see if they can hear their ITP still running? Think some might be surprised.
I've as good as always run my tank down to the low level warning before every fill up and had the ITP fail once in 10 years. Maybe I'm due another one soon!
Mike