AT Fuel Pump: to recap

[Kjell Lindberg]

Always use the relay, I would say.

There should also be a Fuel cut off relay in the circuit, and this should also be used to prevent the fuel pump to flood the carbs.

//Kjell

[antti]

I did install diode, sparks are gone

[raymo]

Dear All, I actually run an older 1986 XLV750R - it has the same fuel pump as the Africa Twin and has been playing up for the past month or so (starting up but soon running out of fuel and not re-starting when hot etc, eliminated all other possibilities), I was going to replace it with the Facet pump but before I do can I check something? I tested the pump by putting 12v across it directly and it made the tappety noise as if it's working, so I was wondering if it might actually be the fuel pump relay that is playing up. Any thoughts? Not sure if it's the same relay as AT, will look up part no. Also, with the Facet pump, do you need the relay still or can it be bypassed and wired in directly to a + when the ignition is on? Any help/tips appreciated. Cheers Louis

Hi Louis

Ray here I am also on the xlv Yahoo groups and have been 'speaking' to you there...

glad you got the XLV running..

both my Africa twin and the XLV750 have the relay by passed and are working fine.. ( the Africa twin came that way and the XLV was by-passed as part of the change to the Ignitech unit 3 years ago

its up to you whether you replace the relay, but as you have fitted the ignitech unit to replace the CDIs powered by the failed Exciter coils, it may still not function , as the relay is triggered by on of the CDI out puts, as I say it may work..

I have since wired in the rev counter from the ignitech unit and wired in the ignitechs fuel relay out put ( you have to enable this in the software ) but have not wired in the relay as I changed my mind..

you will find loads of info and help here, I did try and post some links to relevant threads but the yahoo groups would let you do that ..

hows the bike running?

Ray

[raymo]

What are the diods supposed to do?

How can they prevent the contacts from burning?

I wish I could read Dutch...

good old Faraday


reverse emf ( volts ) when a coils is powered by a dc supply .. say +12v, when that supply is removed the magnetic field caused by the dc voltage on the coil . collapses.. the moving field generates a voltage , in this case the coil is the solenoid used to pull the fuel pump diaphragm back and so pump fuel, as contacts are broken to de-energize the coil the magnetic field collapses and a high negative voltage is generated which results in a spark ( its this spark that erodes or welds the contact together, so causing the pump to fail )

the diode allows current to flow in only one direction so is an open circuit to the +12 volts on the coil, but a short circuit to the high -ve spark causing voltage, so the diode shunts this high voltage to ground so eliminating the spark.. Sometimes called a flyback diode, they are usually across coils used as solenoids



example..

or it could be a weird experiment to kill folk using welding rods fired from a rail gun...
http://www.physics.brown.edu/physics/demopages/demo/em/demo/5j1023.htm

[Kjell Lindberg]

Aha!

It's just that the contact breakers on old cars, used to have a capacitor and not diods, so perhaps a capacitor could also work?

//Kjell

[raymo]

Aha!

It's just that the contact breakers on old cars, used to have a capacitor and not diods, so perhaps a capacitor could also work?

//Kjell

not quite, Kjell, the Cap in old cars also assisted the coil... but also stopped the sparling accross the pcontact points
ah the day of setting timing with fag paper

these days not a PC term and if you pull out a RIZLA folk think you wana Party

diode works for solonoid coils

ignition coils use a capacitor

[Louisxlv750R]

Hi Louis

Ray here I am also on the xlv Yahoo groups and have been 'speaking' to you there...

glad you got the XLV running..

both my Africa twin and the XLV750 have the relay by passed and are working fine.. ( the Africa twin came that way and the XLV was by-passed as part of the change to the Ignitech unit 3 years ago

its up to you whether you replace the relay, but as you have fitted the ignitech unit to replace the CDIs powered by the failed Exciter coils, it may still not function , as the relay is triggered by on of the CDI out puts, as I say it may work..

I have since wired in the rev counter from the ignitech unit and wired in the ignitechs fuel relay out put ( you have to enable this in the software ) but have not wired in the relay as I changed my mind..

you will find loads of info and help here, I did try and post some links to relevant threads but the yahoo groups would let you do that ..

hows the bike running?

Ray

Hi Ray, it's running again as you know but still after a few minutes starts struggling for fuel but not completely cutting out as before. I am going to try the Facet pump now rather than getting the repair kit for the existing pump, found on ebay for £35 (with 6mm spouts for XLV). Try it with existing relay in place and then by-passed if the former method gives any problem. Reluctant to fork out £55 for a new relay from David Silvers if I don't actually need it. It's been a month long and at times frustrating experience getting it solved but I guess after 12 years use with no problems on a 24 year old bike I can't moan that much. I'll let you know how the Facet pump works, hopefully fit next week.
Regards Louis

[Kjell Lindberg]

I think spark gets grounded trough diode.

He who searches, will find...

Pls look at the movie down the page at:

Joergs Motorcycle Pages: Honda Africa Twin

I will also install a diode the comming winter.

[jager]

Bloody fuel pump!
My AT left me some time ago on a highway, 100 km away from home.
The bike just stopped suddenly, left with no petrol at all... And it was raining as mad!

After disassembling, the contact was bond together, and it was pretty hard to clean them. No modifications was made to the pump (diode, etc). I will for sure go for Facet, and don't want to play with the standard one, and risk another stop in the middle of the nowhere

What is interesting, I was missing the rubber pipe that drains the pump from moisture. It simply was not there. As I was driving in a very rainy environment, the pump somehow got some water, and everything oxidate inside.

Check you all, with standard pumps, for the presence of the draining pipe. It could save a lot of nerves

[antti]

He who searches, will find...

Pls look at the movie down the page at:

Joergs Motorcycle Pages: Honda Africa Twin

I will also install a diode the comming winter.

Its been working fine for about 4500 km after adding diode.