Thread: V8 Discovery Fuel Pump Prob

Anyone know what these coils are for?

I don't know what this is in reference to, but wonder if it is a coil designed to concertina as the pump is designed to lift upwards if the tank bottom gets a thump.

The coils are in the power wires for the pump inside the tank. They are tightly wound and I think heatshrinked. Not designed to concertina.

Another interesting article. Bosch orientated.


http://www.autohausaz.com/html/fuelpumps.html

Originally Posted by Utemad

The coils are in the power wires for the pump inside the tank. They are tightly wound and I think heatshrinked. Not designed to concertina.

If I get a chance tomorrow, I'll take a pic of how they "currently" look compared to how they should appear on a working pump and yes Utemad, you are referring to the right part.

Cheers, Pete'

Originally Posted by 4bee

Another interesting article. Bosch orientated.


http://www.autohausaz.com/html/fuelpumps.html

thats a great read

Originally Posted by Frontier1

If I get a chance tomorrow, I'll take a pic of how they "currently" look compared to how they should appear on a working pump and yes Utemad, you are referring to the right part.

Cheers, Pete'

It took me a few extra days to get around to this, had to find one of my old pumps in order to show a "before" and "after" shot.

One of these pics shows how the wires should look, the other how they shouldn't. You guess which one!

Originally Posted by 4bee

Another interesting article. Bosch orientated.


http://www.autohausaz.com/html/fuelpumps.html

Bosch orientated.?


Reads like it was written by the CEO of bosch himself...

(but all the points are valid even if its biased towards a certain brand)

The coils appear to be RF suppression chokes and they appear to be wound on a former which is probably a ferrite material (iron dust which has magnetic properties).

A brush / commutator system in a DC electric motor generates lots of electrical noise due to the sparks generated as the brush slides off one commutator segment and onto the next, essentially. This electrical noise is easily coupled back into the vehicle's electrical system through the pump wiring causing problems for any electrical devices operating with very small signals throughout the car, eg the AM/FM radio and, potentially the engine ECU.

The chokes provide a high impedance to the conduction of the noise into the wiring loom. They're often used in conjunction with a capacitor from the wire to ground so that the noise signal is actually bypassed or shorted to ground but there aren't any capacitors in evidence here. The chokes provide almost no impedance to the flow of direct current, btw.

Not all pumps are fitted with suppression chokes - the original in mine wasn't and neither is the replacement. If you want to reuse the pump housing you could rewire it and omit the chokes. It's not hard to rebuild them - you just need some enamelled copper wire (with a thin insulating coating) of the same diameter (ie cross-sectional area). Unwind the damaged wire, cut the new wire to the same length and wind it carefully back onto the former. Run a little glue into the wire to hold it in place then, when it's dry put some heatshrink over it and seal it with a hot air gun (a pant stripper will do). The enamelled copper wire and heatshrink tube are available from Dick Smith or Jaycar.

Does that help?