Mitsubishi Fuel Pump FET Install

I really wanted to do this right for OC but yet again I failed to get good pic's. But I thought I'd post anyway -better something than nothing.
This is a mod to perform on the 950 KTM fuel pump (other bikes too) that should make the pump last foreve...a long time.
Parts are less than $5.
Need two resisters (may be really small in size) 1 megohm and one 15kohm, I have also used 10k for the 15K, makes no difference. You need one MOSFET I used a IRFZ44 (radioshack # RSU 11467040) others may work but - I look for good current rating (>10) the above is like 70, and the terms "gate", "drain", "source". Also need a small screw (like 4-40 x 3/4"long or longer.) plus two nuts. A 3mm terminal lug is good too.

FET prep: Looking at the FET from the front leads down (front has step). The left one is "gate" center is "Drain" and right is "Source". Bend the center one away then back to parallel with about a .1" offset. Bend the Gate outward and the Source outward. Put the screw in from the backside and put one nut on it to bind on the FET (this keeps the screw in place but also (check this use a washer if necessary) the nut is level with the FET front. Using short leads solder the 1 meg across the Gate and the Source, not touching the bent-down center wire. The resistor needs to be nearly level with the front of the FET (that's why we bent it down.)

Pump mod: remove the cap -push in the wires as you remove. Unsolder the point wire from the top of the point assembly.

Remove the ground wire connector. Solder the 10 to 15k ohm to a connector lug and put it where the ground wire was. (note if you put the screw in without a lug or a washer you can damage the coil - may still work but don't do it.) As you tighten the screw try to keep the resistor out of the way. It took me a few trys even after soldering the FET to do this.

Shorten the FET leads as you go with the following steps. With the point wire unsoldered, the hole from which it came, can be cleared enough that the FET Gate wire can be pushed into it, melt the solder if not. The screw will be pointing away from the body towards the cap. Solder this joint with about .15" between the FET and the point attachment lug.

Use shrink tube if you got it on the coil wire. Solder the coil wire to the center "drain" lead. Insulate (shrink or tape) where it crosses the point bridge.

Strip a small spot or poke a hole in the insulation of the positive (blue/black) wire around .5" to .75" from the pump body. Solder the 10-15K resistor into this spot. Insulate - I used RTV.

Cut the ground wire so it will attach to the source lead without tugging or pushing on the FET, and solder.

Measure the distance from the cap holddown screw (put the screw in a little ways and measure from the screw cross) to the screw in the FET. Measure this distance on the cap from the screw hole to where the FET screw will come thru the cap. Estimate distance from edge of cap close is good enough. Drill an 1/8" hole in the cap at this point.

Hint: push the wire feedthru plug away from the pump and then you can pull it into place. Silicone grease is good to help seal, there and around cap o-ring. Work the cap into place helping the screw to go thru the new cap hole. Once in place RTV the hole and screw put the nut on (washer would be good too -forgot to mention) nut it. Once RTV is dried (or sooner) cut off excess of screw if you want - I held the screw in the vice and cut with hacksaw while holding pump so not to wiggle the FET.
More RTV to ensure sealing.

Notes: The pump pictured actually had badly burnt point and only 3200 mi. When it was removed water came out the vent line - this bike had never crossed water.

How does this operate compared to stock?

I'm interested in doing this, but i think i'd need more pix or a wiring diagram to get it clear in my head. Just saying.

Thx. for the effort.

http://www.advrider.com/forums/showthread.php?t=234786&page=62

Seems ridewest made it more robust. Cheers.

The way this mod works it is IDENTICAL to stock - the difference is the points act as a trigger for the solid state switch instead of being the switch. So stock is 6 amps this is around 1 miliamp.

You DID it first -(I don't know if it fit under the cap). I did THINK of it when you played with the optical switch -which is still a good idea. As far as ingenuity goes you're ahead on this subject IMO.

IC. I kinda remember that now from the other thread.

thx.

as I took it from my bro. The reason I posted was to claim the picture award since there are some clearer pictures in the other thread. Cheers.

rideWestKTM: please check me out on this: I'm a little comfused on a few things:

"Pump mod: remove the cap -push in the wires as you remove. Unsolder the point wire from the top of the point assembly."
-You also call this the coil wire?

"Remove the ground wire connector. Solder the 10 to 15k ohm to a connector lug and put it where the ground wire was. (note if you put the screw in without a lug or a washer you can damage the coil - may still work but don't do it.) As you tighten the screw try to keep the resistor out of the way. It took me a few trys even after soldering the FET to do this."
-Please see my attached picture. The ground wire you describe is the "points ground" wire in my pic?

"Cut the ground wire so it will attach to the source lead without tugging or pushing on the FET, and solder."
-This is the black/brown wire coming into the pump, "ground wire" in my pic?

Thx.

Marty

Here's my scematic on how i think it's supposed to work.

Please correct me if i'm wrong.

I would love for someone to explain how/why this works. I have no clue.

thx.

P.S.: I don't see the diode. I'm assuming it's inside. Not sure if the diode is correct in my pic. Doesn't matter i suppose.

and your pictures rock. And yes the diode is inside the solenoid cover.
The way it works is simple. When the points are in contact, D and S allow current to pass, so the solenoid pulls a diaphragm and loads a spring next to the diaphragm. Fuel comes in a pressure chamber through a check valve. Then the contacts are no more in contact. The spring pushes the diaphragm which pushes the fuel. When fuel is consumed the diaphragm reaches its travel end, and the pointsget in contact again. When this happens another cycle begins.
Please give us a nice picture of your finished mod. Cheers.

This seems like a solid idea for prolonging the life of the points. If you ever run your pump with the cover off, you'll see a very healthy spark across the contacts. Those big sparks eat away the contacts rather quickly. It would be nice if the contacts could simply be replaced, because the rest of the pump is probably still fine.

With the FET conversion, fouling of the points by water leakage into the pump is still a problem. I'm just guessing here, but I bet that most pumps that fail on lower mileage bikes is because of water first and worn out contacts second.

There is a gromet on the incoming wires, but I've never felt like this does enough to seal the pump water crossing or even prolonged riding in the rain. I've thought about injecting the hole with a large amount of RTV to ensure a waterproof seal.

Isn't there something they to did with the contact points on a car motor with a capacitor to extend the life of the points? I thought they called this a condensor or a condensing capacitor. Do any of you electrical whizzes know anything about it? Would it help to slow the wear of the points?

Went to radio shack today and they say the p/n for the mosfet is no good.

Does anyone know of an alternative? Or the correct RS p/n?

Rats!

edit: Bet one of these ones would work:
http://www.radioshack.com/family/index.jsp?categoryId=2032279&cp=2032058.2032230

I got their number out of their catalog. :huh Try Digikey # IFRZ44V-ND, but they sometimes sub so don't worry about all the digits. Radio Shack does have a MOSFET that may work- never tried it though.

Digikey # 1-800-344-4539.

Sketch is right.
regarding the note about fouling the points - its a bit if a trade off current vs fouling and perhaps droping the 10 to 15k to 8k may improve this. I realy don't know I'm thinking that the mechanical action of snaping closed would mitigate fouling.

One thing I didn't note is you can't ground the pump body. Which is not an issue on any installation I have seen yet.

MOS- N - FET
IRF 540A
100V -28A -107W

suitable was also
MOSFET
FU 3410

hope this helps. Cheers.

Are these all a certain type of Mosfet, e:g: N type, P type, etc. Wish i understood how they worked so i knew what to look for.

thx.

Got parts today. Are 1/4 watt resistors OK?

Marty when u finish can u splain it to me,i only finished the third grade:eek1

Yes its more an issue of fit and wire toughness. These resisters are almost no wattage - 10^-6 watts.

Asking how this works - one could talk about free electrons and available holes in the electron clouds but more simply, the "gate" is like a ladder with no rungs and the little current coming from the positive thru the 10-15k resister thru the points (when they close) provides the rungs. With rungs the power can come from positive thru the coil thru the ladder and to bike ground. When the points open the rungs can run off back to ground thru the 1 meg ohm resistor.

is this a reasonable explanation - any deeper and it's over my head.