Re: Fuel flow sensor fault
Posted: Wed Jul 05, 2023 1:58 pm
The MGL flow sender has a built in pull-up resistor at its signal output to its supply voltage.
Place a volt meter between the signal line (blue) and the ground (braid) of the cable. Assuming you are running at 5V you will see either 5V or 0V at the signal line with respect to ground.
Now get the impeller to turn SLOWLY - there are three magnets attached to it - every time a magnet passes the sensor the line will go to 5V or 0V so you will get 3 such transitions (0V->5V->0V) for every rotation. If it turns too fast your voltmeter may not see the pulses properly - some give you and average voltage and some what looks like random rubbish.
You can also power the sender from 12V (disconnect the red wire from the RDAC and connect to 12V supply). This will give you a much larger voltage swing. But 5V tends to work well with these senders.
Place a volt meter between the signal line (blue) and the ground (braid) of the cable. Assuming you are running at 5V you will see either 5V or 0V at the signal line with respect to ground.
Now get the impeller to turn SLOWLY - there are three magnets attached to it - every time a magnet passes the sensor the line will go to 5V or 0V so you will get 3 such transitions (0V->5V->0V) for every rotation. If it turns too fast your voltmeter may not see the pulses properly - some give you and average voltage and some what looks like random rubbish.
You can also power the sender from 12V (disconnect the red wire from the RDAC and connect to 12V supply). This will give you a much larger voltage swing. But 5V tends to work well with these senders.