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Old 01-07-2011, 05:38 PM   #1
men8ifr OP
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Fuel Pump, another potential fix

Bought some new contacts for my worn out fuel pump and read about several upgrades that can be done to the points to make them last longer.

1st - Is fitting a FET to replace the points in carrying the main current to the coil, this way your points should just about last forever but requires quite a bit of reworking, some hard to get specialised parts and I'm unsure how easy it would be to reverse the procedure if the FET failed in the middle of no where.

2nd - fitting a diode across the contacts

3rd - fitting a capacitor across the points

I like options 2 and 3 because they are simple and easy plus if there is a problem with a part you could quickly remove it with sidecutters and the pump is back to the original spec (handy if you were in the middle of no-where)

My old contacts made quite a spark when the pump was ran so I used these to test 2 and 3 since you would be able to see if there is any difference, less sparking would mean less wear.

With the diode I tried it both ways round and did not notice any difference either way except one way it got hot.

With the capacitor 100uf there was a big difference and the sparking was greatly reduced, I would say to about 1/5 of the original amount. With a 220uf capacitor I noticed no difference (bit strange but there we go)

I took a video of the capacitor working, when I push my finger down it makes the contact so the capacitor is connected.

The actual capacitor is reasonably small so very easy to fit in the case, one leg can be held by a screw already there so only really needs one leg to be soldered on - pretty easy to do.




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Old 01-07-2011, 10:04 PM   #2
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Seems like a simple and inexpensive way to lengthen the life of the stock pump. Thanks for sharing!
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Old 01-08-2011, 06:21 AM   #3
men8ifr OP
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No problem - that's why I like it it's simple.

The larger capacitor was 2200uf not 220uf - I had a look again today.
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Old 01-08-2011, 09:29 AM   #4
ridewestKTM
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Interesting

men8ifr:
good to see this examined. Some comments tho.
There is already a diode across the coil. You said across the points- not sure what that will do but it must have been a big one to just not pop one direction withpoints open. The cap idea has been considered and it should do about the same thing as the internal diode. Ought to put an o-scope on it but I would expect to just see a momentary 1v (appx) pulse for the voltage drop across the internal diode when the points open. That 1v will resonate at some frequency dependent on size but regardless it's only going to charge to the diodes bias.
Not to say that all possibilities have been realized but we (me included) are just "polishing shit" (sorry). The pump is just crap. Yes it can be modified (FET or my still available SS circuit) or just repaired frequently (points), and last fine. BTW the FET can be bypassed fine in the field.
Easiest way leaves a little current going where it dosent belong but it's nothing. I got into the modification as an academic challange - (simple things for simple minds perhaps) and I have resistance to the alternatives. My bike still has the generation 2 kit and lots of miles.
Perhaps there's an alternative but to get philosophic the design is at least 50yrs old, and poorly done at that.
Always good to keep an open mind. thanks
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Old 01-08-2011, 09:59 AM   #5
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oops

Wrong -there would be a 12v potential charge on the cap. NTL it would be useful to see an o-scope read on the cap. With the internal diode and the very low resistance of the coil not sure what one would see.

further thought: addressing: why not a capacitor across the points? Does look like the right thing, but it also looks like a huge cap is needed to effect desired levels of protection. Even a 2.2mf charges pretty fast at the starting 6amps that exists in the circuit. How much is really required to extend the point's life in application? I have no idea.

Guess we all will just have to wait and find out from you.
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Old 02-11-2011, 10:46 AM   #6
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I was wondering why this works and couldn't quite figure it out, then a guy at work mentioned this was like a condenser on an ignition points system, here's what I found out about a condenser:

When you remove the distributor cap from the top of the distributor, you will see the points and condenser. The condenser is a simple capacitor that can store a small amount of current. When the points begin to open, the current flowing through the points looks for an alternative path to ground. If the condenser were not there, it would try to jump across the gap of the points as they begin to open. If this were allowed to happen, the points would quickly burn up and you would hear heavy static on the car radio. To prevent this, the condenser acts like a path to ground. It really is not, but by the time the condenser is saturated, the points are too far apart for the small amount of voltage to jump across the wide point gap. Since the arcing across the opening points is eliminated, the points last longer and there is no static on the radio from point arcing.

from http://www.familycar.com/Classroom/ignition.htm

So it would seem that this is more of a bone-fide correção than I realised.

Why on earth mitsubishi didn't do this in the first place I don't know, capacitors cost a few pence!
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Old 02-11-2011, 12:54 PM   #7
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True but there's more to it.

Engine ignitions actually "ring" it does what is said in milliseconds and reverses. If you examine the size of the condenser (capacitor) and note the current is about 6 amps that cap is saturated so fast that the break still poses a problem. (BTW ringing creates a longer duration spark and is a good thing there) The other choice which doesnt "ring" is the diode suppressed concept that mimics the capacitor concept by letting the solinoid coil discharge to itself. And this doesn't saturate. This diode suppression should fix the problem but it doesn't. It is used on other solinoids like starter solinoids, glowplug relay solinoids.... I do agree Mitzu should know better- point fuel pumps had this problem 50 yr ago.
So will the cap AND the diode - I believe so. Is it the best fix? IMO no. I'd go to the crankcase driven "vacuum" pump before just relying on the cap and diode. IMO the "easiest to greatly improve" are the two fixes I've discussed - the SS and the FET. The mechanical relay might be good too but capitilizes on the fact that it's a minute fix when it goes.
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Old 02-11-2011, 06:01 PM   #8
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What is the FET field bypass?

Quote:
Originally Posted by ridewestKTM View Post
men8ifr:
good to see this examined. Some comments tho.
There is already a diode across the coil. You said across the points- not sure what that will do but it must have been a big one to just not pop one direction withpoints open. The cap idea has been considered and it should do about the same thing as the internal diode. Ought to put an o-scope on it but I would expect to just see a momentary 1v (appx) pulse for the voltage drop across the internal diode when the points open. That 1v will resonate at some frequency dependent on size but regardless it's only going to charge to the diodes bias.
Not to say that all possibilities have been realized but we (me included) are just "polishing shit" (sorry). The pump is just crap. Yes it can be modified (FET or my still available SS circuit) or just repaired frequently (points), and last fine. BTW the FET can be bypassed fine in the field.
Easiest way leaves a little current going where it dosent belong but it's nothing. I got into the modification as an academic challange - (simple things for simple minds perhaps) and I have resistance to the alternatives. My bike still has the generation 2 kit and lots of miles.
Perhaps there's an alternative but to get philosophic the design is at least 50yrs old, and poorly done at that.
Always good to keep an open mind. thanks
Hi RideWestKTM,

I did the FET mod and it has been working fine thru water crossings, and heat, and a big offroad crash for a few thousand miles now. What is the FET mod field bypass you mentioned and does it require less equipment/tools/space versus taking a spare pump?

Thanks,
Mike Z
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Old 02-12-2011, 12:17 PM   #9
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"field bypass"

Quote:
Originally Posted by zeegman View Post
Hi RideWestKTM,

I did the FET mod and it has been working fine thru water crossings, and heat, and a big offroad crash for a few thousand miles now. What is the FET mod field bypass you mentioned and does it require less equipment/tools/space versus taking a spare pump?

Thanks,
Mike Z
My point was the FET wasn't irreversable - the points are still there. If one wanted to do it wrenchless I bet it's possible by bringing out wires but what I was thinking during that entry was remove the pumps plastic cap, cut out the FET and reconnect the point wire. The little resistor could be removed or not- wouldn't matter.
The idea of carrying a 2nd pump is IMO just silly when there are limp home/repair options so easy. The EFI not so but for the 950s - I'm just not worried.
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Old 02-12-2011, 01:46 PM   #10
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Another way

Our lc8 website man has a beautiful other way. Use google translation to get it in english. It works with a lightswitch, most of us use it here in holland.

http://forum.lc8.nl/viewtopic.php?t=2582



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Old 02-12-2011, 01:50 PM   #11
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Quote:
Originally Posted by ATAK View Post
Our lc8 website man has a beautiful other way. Use google translation to get it in english. It works with a lightswitch, most of us use it here in holland.

http://forum.lc8.nl/viewtopic.php?t=2582



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Dunno, whats a "print". Translation seems a bit off to me. For technical stuff like this, that makes it more worrying.
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Old 02-12-2011, 02:08 PM   #12
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got my attention

Quote:
Originally Posted by ATAK View Post
Our lc8 website man has a beautiful other way. Use google translation to get it in english. It works with a lightswitch, most of us use it here in holland.

http://forum.lc8.nl/viewtopic.php?t=2582



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A picture is worth a 1000 words regardless of language.
Ya ne ponnimayoo
Ich verstea nicth
no capiche
no comprendea
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Old 02-12-2011, 02:11 PM   #13
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Quote:
Originally Posted by ridewestKTM View Post
A picture is worth a 1000 words regardless of language.
Ya ne ponnimayoo
Ich verstea nicth
no capiche
no comprendea
Not sure who this is directed to, whether you're saying it has pictures and thus needs no words, or it needs pictures? I failed to follow the links last time, had I done so I'd have got to this, which has pictures:

http://forum.lc8.nl/viewtopic.php?t=...er=asc&start=0

Interesting Facet mounting pic on page 3, never seen anyone mount behind the airbox like that.

Page 4 has a post showing a failed unit that went diving. Translation isn't easy to understand (for me)
Quote:
How to avoid:
- Pump assembly with vent hose down with a zwanenhalsje there (as he should look like)
- Well pump cap assembly, O-ring good, good rubber ... so that no water gets
- Not scuba diving with your LC8
well, the last line is easy

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Old 02-12-2011, 08:47 PM   #14
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Yes thats what I meant.

Quote:
Originally Posted by crazybrit View Post
Not sure who this is directed to, whether you're saying it has pictures and thus needs no words, or it needs pictures? I failed to follow the links last time, had I done so I'd have got to this, which has pictures:

http://forum.lc8.nl/viewtopic.php?t=...er=asc&start=0

Interesting Facet mounting pic on page 3, never seen anyone mount behind the airbox like that.

Page 4 has a post showing a failed unit that went diving. Translation isn't easy to understand (for me)


well, the last line is easy
picture: thanks

One look at the pictures and I knew - optical - this is the right way to do it. Gefer bench toped this method and I ran off and did it my way (2 ways) I saw this optical somewhere but when I did it didn't seem ready for sale. This looks good. #1 IMO.
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Old 02-12-2011, 09:01 PM   #15
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Quote:
Originally Posted by ridewestKTM View Post
picture: thanks

One look at the pictures and I knew - optical - this is the right way to do it. Gefer bench toped this method and I ran off and did it my way (2 ways) I saw this optical somewhere but when I did it didn't seem ready for sale. This looks good. #1 IMO.
atak: Is there a way to contact the guy without subscribing to that website?

I still think the Google dutch translation isn't too good .... is there any English version of the PDF self-assembly instructions.
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