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Offline HardFacts

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Re: HONDA CB500X LOSING POWER - VERY STRANGE PROBLEM
« Reply #10 on: September 10, 2019, 06:29:10 PM »
*Originally Posted by harryhendo [+]
Yes, when the key is turned to ON, the fuel pump turns on for a few seconds to build up the fuel pressure in the system. This must be controlled by a timed relay that turns on for about two seconds to build up the pressure so the fuel to the injectors is sufficiently pressurized.
I know on modern cars, when I replace a fuel injector, I start the engine, then pull the fuse to the fuel pump, and the engine will run for about a minute before stumbling and missing and finally dying. This relieves the pressure in the fuel rail so the injectors can be removed. So the problem you are having sounds similar... the pressure is enough to start it, but then declines over the 10 minutes of running until there is no more pressure in the system. The only thing providing that pressure is the fuel pump.

You are onto something here, exactly what I am observing  :046: :046: :046:     So the question I need to figure out is why is the fuel pump putting out good pressure in the initial 2 second prime, resulting in PERFECT RUNNING, but then allowing fuel pressure to very slowly fall off after that ????


Offline Roy McKenna

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Re: HONDA CB500X LOSING POWER - VERY STRANGE PROBLEM
« Reply #11 on: September 10, 2019, 07:27:48 PM »
Here is a generic Honda Pgm-fi description.
http://damet.com.pl/pub/moto/gl/GL1800.-.Programmabale.Fuel.Injection.2006.pdf
It is somewhat dated, but lots of things don't change.  Download it, it's getting hard to find.

If killing and restarting the engine fixes your problem, albeit temporarily, determine if what is really fixing it is de-energizing the ECM and Main Relay.  Next time it starts acting up again instead of cycling the Kill Switch and restarting it, kill the engine without turning off the ECM.  Just pull over and kill it letting out the clutch in gear with the brake on.  Now without cycling the key or kill switch, restart the engine.  Will it run for another 10 minutes now? 

If the problem is not temperature related, it could be that somewhere a capacitive/inductive charge is building up and creating a voltage drop that is then preventing something more  important (a relay, ECM, ??) from getting proper voltage to operate.  Killing the ECM, Main relay, Fuel relay (and almost everything) by cycling the kill switch may be allowing the charge to dissipate and everything to work for another 10 minutes.  I'm just guessing, strange things can happen.

Spark plug caps can be finicky and cause strange electrical failures...usually temperature related and not time related as you describe though. 

There is a fuel filter in the tank.  Part no. 16730-MGS-D31  But how would cycling the kill switch fix a clogged fuel filter consistently, right?  IDK. 

If you insist on fixing this yourself, great.  Get a Honda manual.  Buy this now.  You will not regret having it to fix problems and this is a REALLY good price. 
https://www.ebay.com/itm/2013-Honda-CBR500R-RA-CB500F-FA-CB500X-XA-OEM-Service-Shop-Manual/273978666730?hash=item3fca66aeea:g:D7oAAOSwYMldX1qm
« Last Edit: September 10, 2019, 07:40:30 PM by Roy McKenna »
Roy McKenna

Online harryhendo

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Re: HONDA CB500X LOSING POWER - VERY STRANGE PROBLEM
« Reply #12 on: September 10, 2019, 08:26:42 PM »
*Originally Posted by HardFacts [+]
You are onto something here, exactly what I am observing  :046: :046: :046:     So the question I need to figure out is why is the fuel pump putting out good pressure in the initial 2 second prime, resulting in PERFECT RUNNING, but then allowing fuel pressure to very slowly fall off after that ????
A failing fuel pump. I once rode a volvo 940 home a hundred miles doing essentially the same thing you are doing. The engine ran fine at start, then bogged down and finally died out. Turning the key off then on, I would get 20 more miles down the road before it bogged down again. A fuel pump is simply an electric motor turning an impeller, and electric motors fail in various ways.
The classic way to test a fuel pump is to throw away your cigarette, then remove the fuel line to the fuel rail and place it into a suitable graduated scale container. Then remove the fuel pump relay and use a short length of wire to cross connect the relay's input power source female connector pin to the output (to the pump) female connector pin, turn on the ignition, then observe the flow rate of the pump.
(A mechanic won't do that. He'll just replace parts until he finds the one that failed. The old joke is how do you know a mechanic's car has a flat tire? He's replacing all the tires to see which one is flat).
Personally, I would start the bike, remove the fuel cap, then get off the bike and listen to the hum of the fuel pump, even record it. Replace the fuel cap, then ride it for the 10 minutes until it bogs down, leave the engine running, then remove the fuel cap, get off the bike, and listen to the hum of the fuel pump. I'd wager you'll hear it hiccuping and snorting, not humming.
2016 Honda CB500X, Matte Black (bought new 2019)
1987 BMW R80, Black (bought new 1987)
Charlottesville, Virginia, USA

Offline HardFacts

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Re: HONDA CB500X LOSING POWER - VERY STRANGE PROBLEM
« Reply #13 on: September 10, 2019, 08:35:48 PM »
*Originally Posted by Roy McKenna [+]
Here is a generic Honda Pgm-fi description.
http://damet.com.pl/pub/moto/gl/GL1800.-.Programmabale.Fuel.Injection.2006.pdf
It is somewhat dated, but lots of things don't change.  Download it, it's getting hard to find.



Thank you for the link  !!!!!    I have downloaded and saved that document and will read it over.   One thing I need to make clear is that I am not killing my engine to fix this.  I cycle the RUN switch while moving in gear, so the engine never even stops, engine never even has a change to slow down.  It is LITERALLY 1/2 SECOND to cycle the switch while going down the road.  That 2 second run of the fuel pump makes it run absolutely perfect for about 10 minutes.     I am 99 % sure this is fuel related.

That is good to know about the fuel filter, that is what I most strongly suspect.  I will take it apart and see if there is anything blocking it.

Offline Roy McKenna

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Re: HONDA CB500X LOSING POWER - VERY STRANGE PROBLEM
« Reply #14 on: September 10, 2019, 09:58:40 PM »
*Originally Posted by HardFacts [+]
One thing I need to make clear is that I am not killing my engine to fix this.  I cycle the RUN switch while moving in gear, so the engine never even stops, engine never even has a change to slow down.  It is LITERALLY 1/2 SECOND to cycle the switch while going down the road.  That 2 second run of the fuel pump makes it run absolutely perfect for about 10 minutes.  I am 99 % sure this is fuel related.
The engine may not stop mechanically but it certainly is electrically being killed for the time that the switch is off.  When the Engine Stop switch is off the engine
-loses power to the main relay
-loses power to the ECM
-loses power to the Fuel Pump Relay
-loses power to the Fuel Pump
-loses power to the Fan Control Relay
-loses power to Fuel Injectors
-loses power to Ignition Coils
-loses power to the PAIR Control Solenoid
-loses power to the Evap Purge Solenoid
About all that isn't losing power is the dash.  You are electrically killing the engine but not allowing it to mechanically stop.  You're rebooting the computer.  It might be interesting to see if restarting the engine without rebooting the computer will give you 10 minutes more of riding or not. 

The ECM should keep the fuel pump running all the time the engine is running. But the ECM does have provisions to turn the fuel pump off (after 2 seconds with Ignition switch on).  The 2 second run couldn't possibly be enough to keep it running for 10 minutes alone. It's running, but it may be losing power, or not making pressure.  There are procedures in the Service Manual to check the Fuel pump pressure and flow rates. 
Roy McKenna

Offline HardFacts

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Re: HONDA CB500X LOSING POWER - VERY STRANGE PROBLEM
« Reply #15 on: October 07, 2019, 02:27:23 PM »
Just to update everyone, I am still riding my wife's Scooter  :307: :307: :307: :307:

I just have no idea what may be causing this problem, so the plan is to take the tank off the CB500X, look at the fuel pump, and screen, and see if there is anything obvious that might cause low fuel pressure.

 


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