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MG MGB Technical - SU Fuel Pump Diode

Hi Folks:

*Need to replace the TVS diode(open circuited) in my SU fuel pumps. Anyone have the specs and industry/commercial part number?
*Will a MOV and associated components (diodes, resistors, capacitors)across pump coil help with arc suppression? Any suggestions???

Thanks: Rich Boris 67 B
Rich Boris

Hi Rich.

An interesting question.

I don't know the spec of the original device, but offer the following observations :

A silicon diode (eg 1N5408, 1kV 3A, costing pennies) would kill the arc, but might slow the operation of the pump to an unacceptable degree.
I would include a small resistor to limit the peak current and dissipate some power (and speed things up a little).

An MOV / Varistor / zener diode would be better, but you would need to choose carefully as the power dissipation would be significant in a continuously operating pump.

A resitor / capacitor series combination has some merit, modules are availible.

Take a look here :
http://www.naisweb.com/e/relaye/mech_eng/mech_eng_rtia/idapm4w.html

HTH.. Don
Don

Rich - The diode used in the pumps is just a standard silicon diode, such as the one Don suggests, with a 100 ohm resistor in series with it.

Don - Regarding a resistor/capacitor combination is what the earlier pumps have in them. All of the SU pumps, going way back (perhaps to the very first, have always had a 100 ohm swamping resistor in parallel with the coil. The resistor is a few wraps of nichrome wire around the main coil. As long as that swamping resistor is intact, it is surprizing how efficient just a single 0.47 microfarad capacitor across the points are. I have a pump that I am testing now, that I had to replace the swamping resistor in because it had burned out, and with the capacitor across the points, there is no visible arc across the points, even when I turn out the lights.
Cheers - Dave
David DuBois

This thread was discussed between 30/07/2005 and 31/07/2005

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