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Should a fuel pump have continuity across the terminals?
twybrow - 12/9/13 at 09:27 PM

Just doing some more testing now I know my ECU is dead (trying to track down why), and I was chasing a 2ohm resistance to earth on the fuel pump/injector power feed wire. So I unplugged everything on the circuit (injectors, fuel pump relay and finally the fuel pump) and have found that I had intermittent continuity via the fuel pump. It seems there is a dodgy +ve wire going into the connector block, as when I wiggle the wire with the plug attached to the fuel pump, the connection to earth keeps breaking.

I then disconnected the wiring, and tested the pump directly, and it seems to have continuity across the terminals. Is this normal? Should a bike fuel pump have continuity across the terminals?

adithorp - 12/9/13 at 09:54 PM

It's an electric motor so I'd expect continuity. Could be wrong though.

plentywahalla - 12/9/13 at 10:45 PM

'Continuity' implies zero or near zero resistance. Their should be a measurable resistance. Find out what the wattage of the motor is and calculate the expected resistance and compare with the actual. An electric motor usually fails because the insulation within the windings breaks down which will cause the resitance to drop.

r1_pete - 13/9/13 at 06:42 AM

Is the 2 Ohm impedance across the pump terminals what you refer to as continuity when you wiggle the plug? if so, from Ohms law you have a pump which is drawing 6 Amps at 12v, and is consuming 72 Watts, but it would seem there is an internal problem in the wiring which is causing the intermittant open circuit.

MikeRJ - 13/9/13 at 12:18 PM

quote:
Originally posted by plentywahalla
'Continuity' implies zero or near zero resistance. Their should be a measurable resistance. Find out what the wattage of the motor is and calculate the expected resistance and compare with the actual. An electric motor usually fails because the insulation within the windings breaks down which will cause the resitance to drop.


A motor is not a resistive load! The resistance of windings will only tell you what the stalled current will be, and is not directly related to the motors rated power.

The bottom line is that a DC motor will normally have a low resistance across the power connections.

Julian Thrussell - 12/11/13 at 01:16 PM

put 12v on it and see if it works?