Dc Motor Brush Sparking Excessive Wear

Thread Starter


Joined Dec 21, 2017
Hello together
I am experiencing a sparking problem on a D.C. Motor application with two brushes, permanent Magnets, it is working in gasoline namely a driving a fuel pump. I am not so much experienced about electronics therefore kindly ask for your support. In comparison to normal runnunig motors without any extreme wear at brushes, the following comparisons are done:

Brush holders compared - geometrically ok
Spiral springs compared - ok
Material and grades of commutator and brushes -ok
No assembly failure in pump including motor
No electrical differences in comparison to specs and series armatures
Only the magnetic field is little bit low but within design spec

Kindly request help.


Joined Jul 18, 2013
If the P.M. field is on the weak side, this will account for it, otherwise it is usually due to over-current condition.
In a gasoline application I would have though BLDC would have been a wiser choice.\
Last edited:

ian field

Joined Oct 27, 2012
That should be Field.
Weaker than it was when it was originally installed maybe?
If the armature has been out - some magnetic materials give up if you don't slide a keeper in as you slide the armature out.

I found that out the hard way on a Sturmey-Archer bicycle hub dynamo - never encountered anything quite that bad since though.


Joined Jul 18, 2013
True, I think that applies to some of the older magnetic materials, I have heard it happening with steppers more frequently for some reason.
Of the one's I have rebuilt, I have not experienced it so far.;)


Joined Nov 4, 2013
In a gasoline application I would have though BLDC would have been a wiser choice.\
In theory yes but in reality almost every intake or inline fuel pump on any fuel injected engine or even diesel is a brush type and they have surprisingly good service lives for it. However, when not submerged in liquid they tend to not do so well. :(