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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: Mikedza on June 06, 2015, 05:09:36 PM
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Hello,
My 1988 K-75C was running great for 2 years except for the Fuel Pump which was replaced. Now after storing it for the winter I found that the pump's power was intermittent. It would run for long whiles and then die (leaving me stopped on the side of the road) until I tugged on/moved the 4 wires going underneath the tank. I did some experimentation to figure out if it was in fact was the 4 pin connector that was failing by using my ear to hear the pump run while pressing the ignition many many times and moving the wires around. I concluded that I needed to replace the 4 pin connector that so many people seem to have a problem with. I replaced it with a couple of these cheap things: http://www.amazon.com/gp/product/B00BYNKUSE?psc=1&redirect=true&ref_=oh_aui_detailpage_o08_s00
The new connectors seemed to work just fine... I took a few rides and the fuel pump stayed on the whole time, but it seemed that now I had a symptom that would normally be caused by the idle being set too low; I found myself having to have the throttle slightly twisted in order to keep the tach at 1000 rpms when stopped at red lights. Does that make any sense to any one? The only thing I changed was 4 electrical connections, if the fuel pump is getting power it shouldn't it just either output fuel or not? is there an in between based on voltage? (unless its clogged but that would be quite the coincidence if it got clogged while I made an electrical repair.. I never even opened the tank)
UPDATE a few days later: After a few rides of the bike running fine except idling at low rpms, now the bike will not stay running at all. In the past, starting it with half choke has always been plenty for it to warm up when cold.. now if I go full choke it only lasts a few seconds and doesn't sound right, its galloping and stuttering and then dies... I tried using the throttle and the engine sounds like its having a lot of trouble, got it up to 3 or 4k rpms and even then it bucks and dies as if its not getting the fuel it needs. Is it possible the cheap connectors I used altered the electricity on its way to the fuel sender/fuel pump and ended up damaging the sender/pump? Is it possible my repair some hose affected the fuel pump relay?
I have a better 4 pin connector setup coming in the mail, I will re-solder in 8 places and connect it... but my gut tells me that this now is a new coincidental problem and not an electrical problem.
Thanks for your time,
-Mike
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Tried a new fuel filter?
Poor idle? Try searching motobrick.com (https://www.bing.com/search?q=site%3Amotobrick.com+poor+idle)
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After the fuel filter, I'd suggest some techron in the fuel to try and clean up the injectors.
BTW, try also and not use any ethanol blended fuel. The bikes will run with it up to 10%, but it can sometimes cause issues. (I think it's more related to the fuel source and where you geographically live than anything else.)
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Tight exhaust valves will also cause low idle.
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Tried a new fuel filter?
Poor idle? Try searching motobrick.com (https://www.bing.com/search?q=site%3Amotobrick.com+poor+idle)
After the fuel filter, I'd suggest some techron in the fuel to try and clean up the injectors.
BTW, try also and not use any ethanol blended fuel. The bikes will run with it up to 10%, but it can sometimes cause issues. (I think it's more related to the fuel source and where you geographically live than anything else.)
Thank you so much for responding,
It seems you guys think my problem is a new coincidental problem that just happened to occur right when I made my 4pin connector replacement. I can start doing the work of replacing the fuel filter, and using techron, and trying other things... but because the problem happened at the moment when I replaced that 4 pin electrical connector. I thought i'd make a post here to see if any one had any idea about how a different connector (or maybe me running the fuel pump so much while experimenting to see if it works) could affect the fuel flow to my engine this weirdly.
Remember, the engine starts up if given enough throttle and choke, and then stutters and gallops all the way back down to 0. The longer I try to keep it alive by giving it more throttle the more it stutters and sounds like a sick dying old man that either doesn't have all its plugs firing or isn't getting the fuel injections it's supposed to get.
Using the most common sense for troubleshooting, one knows that if something is different after a repair, it must be caused by that repair... so it would be wrong to go fixing other stuff that has always worked before I made that repair.
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I also subscribe to the "check what you did last" theory of troubleshooting, but if you are getting power through the connections, then something else in going on. I don't think you can damage the pump by having a poor connection.
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A clogged fuel filter would probably have shown up as a degrading ability to start and run over a period of time; I can't imagine that it would be catastrophic. It could be plugs or plug wires. Are all the cylinders firing? Quickly check the exhaust for heat buildup after starting; cold headers will indicate misfiring cylinder. It could point to (1) loose spark plug caps (2) loose connections at the coils or (3) loose EFI connector under the seat.
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A clogged fuel filter would probably have shown up as a degrading ability to start and run over a period of time; I can't imagine that it would be catastrophic.
I would have, and did think the same thing. Last year, returning from a ride to St Jacobs, I filled up at the Icehouse in Campbellville. A few kilometers later it started acting up. Surprised I made it home.
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The couple of times I've had this, no-idle situation, it was because I was at a high altitude. Engaging the high-altitude circuit solved my problem.
That being said, in addition the things previously mentioned, I would check the fuel pressure (it should be in the neighborhood of 36 psi). It might not hurt to check your air filter too, but I doubt that is the problem.
Tom
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This is a long shot, but is there any chance that you may have disturbed a breather or vacuum hose whilst working on the fuel pump wiring?
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This is a long shot, but is there any chance that you may have disturbed a breather or vacuum hose whilst working on the fuel pump wiring?
Hoses seem all good.
Thank you all for taking the time to respond. I have been working on a gig non stop and haven't had a chance to check on my bike or respond here until now. Here's an update:
Without me taking any action, the main problem has seemed to fix itself. Maybe something was holding up my fuel filter that set itself free? It's all still a mystery to me. My now motorcycle sounds extremely healthy and runs like a champ EXCEPT that it seems to like to idle around 700 ~ 800 RPMs when warmed up. If I'm riding and I stop at a light, and let go of the throttle completely it sometimes stays around 1000 for a second or two, but then backs down to a level that's dangerously close to stalling. I guess I will try to adjust the idle, but that seem's like I'm not actually fixing the problem, just fixing the symptom as I never touched anything near that area of the bike.
I haven't checked my fuel filter because I just don't have the means to drain my tank and take it all apart. If the problem persists I'll take it into a mechanic.
-Mike
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You don't need to drain the tank dry to pull the fuel filter and it's pretty easy to get to. At least shine a light in there next time you're low on fuel...you might find it easier than you think. Remove the cap and take a look.
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Is it easy to replace all the fuel filter hoses and what length does one need to do the job.i know you need submersible hose. Don't mean to hijack the thread, just wondering. 1995k75.
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I will share this here and repeat it in the proper thread also. I had trouble with my bike idling all of a sudden and it would not respond to either the throttle advance or the throttle. I cheaped out and tried to repair the fuel pump output fitting (which had snapped off since it was 29 years old! when I pulled it from the tank and tried to remove the fuel line) with JB Weld. It actually held for 700 miles but must have begun to leak a little. I had just completed a flawless 50 mile trip on the bike, parked it, tried to start it and the problem revealed itself. I replaced the pump and it now runs better than before. So my point is that you may have a small fuel leak within the tank causing sub-standard pressure. You wouldn't know because it appears symptom-less. So I would suggest pulling all of that out of the tank, checking connections, replace fuel lines where necessary and see what happens! Good luck!
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Hmm,
Maybe I should test the fuel pressure before I start taking things apart too much. Any one have a suggestion for a fuel pump gauge to purchase? (oops yes, I meant fuel *pressure* gauge) Amazon would be nice, but ordering elsewhere is ok.
-Mike
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I got a pump from Rock Auto. There are many suppliers. Many of the pumps will need a little padding to fit properly into the clip-in sleeve fitting that goes into the tank. You are lucky to be in the US where you can avail yourself of loads of different pumps at very, very affordable prices. Check online for fuel pump alternatives and you'll find all kinds of them. As for pump pressure don't worry about that too much. Inge rightly pointed out that the fuel pressure regulator will look after that. Ford Escort and even Ford Taurus pumps from the early '90's, I believe, are reasonable matches. Do some homework but it's not a big deal. What you will likely have to do is buy a pack of spade connectors since these pumps don't use a nut and bolt connection.
Good luck.
Oops...just re-read your posting and saw you wanted recommendations for gauges, not pumps....who knows? You might need a pump some day!