fit a diode or a capacitor to the fuel pump?

[xpress]

hi there, is it true tha there's a classic mg mod that transistorises the fuel pump.

apparently it lets the transistor do the coil switching work, so the poilts last indefinitely.

anyone done this? what are the advantages and disadvantages for each? also can anyone provide a link or explain how to attach a capacitor for the capacitor mod, and also how the diode mod works and how to attach that? thanks

[les]

You may be thinking of an electronic pump. You can buy these if you feel the need, but I understand many prefer the standard item. Carry a spare if you feel happier.

[bmcecosse]

I have a wireless interference suppression capacitor connected to the power feed for my fuel pump. Not sure if it helps to reduce arcing/improve point life, and I don't have a wireless anyway...... But I DO have a new MOT Cert as of today!

[Declan_Burns]

Congrats!
Declan

[Stig]

hi there, is it true that there's a classic mg mod that transistorises the fuel pump?

Yes, you can get one here: http://www.sucarb.co.uk/productDetail.aspx?id=33152 -although when you see the price you might decide to just replace the points in your old pump!

If you want to understand diode suppression then this might help http://relays.tycoelectronics.com/appno ... 3c3264.pdf. As I said, a capacitor is easier as it just goes across the pump's coil. There should be one there anyway to reduce radio interference as Roy says.

[Alec]

Hello Xpress,

S.U. pumps are now available with electronic switching, and some models of S.U. pump had a diode in place of the capacitor normally fitted. This makes the pump polarity conscious so if you want to do a polarity change then the diode needs turning round. Basically the diode shorts the induced voltage in the coil when the points open so supressing the spark. I would doubrt if it's a worth while modification? The MK 2 Jaguar had this form of spark suppression and possibly it better on a larger pump with a bigger solenoid?

Alec

[xpress]

thanks all. congrats on the mot bmc. stig, where exactly does the capacitor go across the coil? and what type of capacitor do i need and what do i need to affix it?

[Stig]

I'd only be guessing as to the value for the capacitor, I know there's one under the cap of my SU pump but couldn't see any markings on it. It should have one end after the points (the coil's live end) and the other to ground, I'd suggest soldering it on but you might be able to wind the wires round the existing screws holding the points wire.

Hmm, I just tried drawing a simple circuit diagram but all the whitespace got removed and it didn't make any sense.


TBH, I wouldn't worry too much about suppression. It's mostly there to prevent radio interference rather than prolong the life of the contacts. I do nearly 10,000 miles a year and haven't looked at the points for a few years (though I did have to give the pump a thump to get it going after I got back from a winter holiday, it's been fine since).

[xpress]

is it possible that if the points are too close together they can prematurely wear out, or is it not that fussy?

[bmcecosse]

As long as the mechanism can throw over to full stroke the diaphragm - I doubt it matters.

[les]

If you can borrow a manual section b1---b5 gives a comprehensive proceedure for setting up the su pump correctly, points, throwover and armature settings etc.

[Declan_Burns]

I have a wireless interference suppression capacitor connected to the power feed for my fuel pump. Not sure if it helps to reduce arcing/improve point life, and I don't have a wireless anyway...... But I DO have a new MOT Cert as of today!

Me too as of yesterday---two years of motoring ahead.
Regards
Declan

[bmcecosse]

It was supposed to be going to two years here too - but the garages kicked up such a stink about the loss of captive/easy income.......