RC51 Forums banner

1 - 20 of 30 Posts

·
Registered
Joined
·
13 Posts
Discussion Starter #1
2001 RC51 less than 6,000 miles; owned this bike since 2001. Flawless operation the whole time.
Out for a ride 5 miles from home in Northern AZ, and briefly stopped at a neighbors house before returning home.
Motor started and then ran roughly, but nursed it home about two blocks away.
Motor would not restart (plenty-0-gas). Flooded the engine in the process.
Ordered new sparkplugs and installed a couple days later. No start, but didn't flood the engine this time.
Put timing light on rear sparkplug wire to find no spark during cranking. Downloaded service manual.
Followed testing protocol for ignition pulse generator and voltages at CDI and rear coil. All good.
After disconnecting, cleaning and reconnecting all electrical connectors, another attempt was made to start the motor.
During cranking, the timing light flashed twice and the engine made all the right noises like it was going to start...but flashes stopped, and moto would not fire. Ran the battery down, so, replaced the battery with a brand new one.
Crank, two flashes, encouraging noises...then no spark.
Jumped 2-pin diagnostic connector near ECM and turned on Ignition. FI light came on, stayed on, but did not flash, so I'm taking that to mean the code is 0 (zero) flashes and indicates lack of power to ECM or failed ECM.
Schematic seems to indicate that power to the ECM comes from red/green wire in gray 22pin connector that agrees with pin no 18 on the diagram. I checked continuity from starter relay where the schematic indicates the wire to begin, (red/green) to ECM and the wire is good according to the ohmmeter. But, when I turn on the ignition there is no voltage at that pin on the gray connector. Kill switch connectors are cleaned and good. Dash lights up.
On a side note, my dash would always emit a high-pitched tone as the tach indicator would cycle through its range. It no longer does that.
So, there my story, two-sparks, then nada.
If I was a Native American you could call me Kenny Two-Sparks...
 

·
Registered
Joined
·
43 Posts
Crikey boomer must be nice, flooded plugs- got new plugs, discharged battery- got new battery! Kidding of course. It sounds like a bad connection at some point in the harness. Try moving the wiring connectors while using the timing light, it might disturb offending terminal and fire the light or even try starting. Good luck
 

·
Registered
Joined
·
67 Posts
The high pitched sound you described sounds like the fuel pump priming? If that doesn't happen it is not going to start. If you have the stop switch in the off position same result, no fuel pump prime. I have accidentally hit the stop switch on the right handlebar a couple of times and had similar result. Not saying that is it but you should definitely get the whine sound when key is turned or you could have an electrical issue.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #5
The high pitched sound you described sounds like the fuel pump priming? If that doesn't happen it is not going to start. If you have the stop switch in the off position same result, no fuel pump prime. I have accidentally hit the stop switch on the right handlebar a couple of times and had similar result. Not saying that is it but you should definitely get the whine sound when key is turned or you could have an electrical issue.
Thanks so much for the response, Never knew what that sound was. I did remove the kill switch to clean the terminals but never checked the continuity of the wires connected there. I will probe deeper into the workings of that switch and the integrity of the wires connected to it.
 

·
Registered
Joined
·
67 Posts
The bank angle sensor and/or relay could also cause you not to get the fuel pump prime as previously described. Mine was relocated and "spliced" and caused random engine shutdowns. Recommend doing a search on that and confirm it is not the problem. You can move the relay from the high beam to other locations just to test if the relay could be the problem. Let us know when you find the problem and good luck.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #7
There are three relays in the tail section. Which is the relay to which you refer?
And, as long as we're at it, what are all three...center one, driver's side, and passenger's side in that order?
 

·
Registered
Joined
·
67 Posts
High Beam relay is located behind the front left cowl. The three in the back are the center (turn signal), right side if sitting on the bike (fuel cutoff), and left side (bank angle sensor). The high beam can be removed and switched into the bank angle socket and vice versa just to test function. If you put the one from the bank angle sensor into the high beam socket and high beam does not work you know you have a bad relay. You should also notice a "click" on the relay if operating correctly. Check that on your high beam when you turn it on. Also make sure you check the Bank Angle Sensor to make sure wires are properly connected and that it is oriented correctly and didn't shift proper position in the tip over. I think all of the relays with the exception of the turn signal should interchange. The turn signal may only be three pole and not four so just verify they are identical when you switch them around. Bank angle sensor should be under drivers seat and three relays passenger. If by chance you have a service manual, location of the relays and function is shown on page 1-35. Hope that helps.
 

·
Registered
Joined
·
67 Posts
Found from another post and possibly related to your problem:

It takes two relays to make the RC51 fuel pump run too. They are the Bank angle sensor relay, and the fuel cut relay. The bank angle sensor relay will engage when; the kill switch is ON, and the bank angle sensor is happy. The bank angle sensor relay then sends current to the fuel cut relay(+12V). The ground path for the fuel cut relay is provided through the ECU, but only when the ECU is happy (safety circuits and certain faults disable the relay, which disables the fuel pump).

So the RC has a relay that controls the fuel pump, that relay is turned on/off by the ECU by opening or closing the ground path of the circuit.
The Fuel pump only recieves the 12V supply when that relay is engaged, the pump always has a path to ground.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #10
thanks, yet again. I couldn't deduce any of that from just looking at the schematic. And, i don't know how I missed page 1-35, as it's a lot of help.
 

·
Registered
Joined
·
67 Posts
No problem. Wibbly is the real expert on this forum and I am sure he will "chime in" if we are missing something. I am confident you will figure it out and most likely something simple but sometimes those things can be very frustrating. Until you get the "prime" sound back it is not going to start but at least you know most likely problems. Unlikely I think you have a bad fuel pump given when and how this started.
 

·
Registered
Joined
·
1,628 Posts
honestly man, if all systems are go (FI lamp indicates on the dash when you set the kill switch to run, and fuel pump primes) then the bike is ready to run. it is likely a crank or cam position sensor error, as both of these will cause a no spark condition but may not necessarily throw a code.



the best way to troubleshoot this would be for you to phone me. it sounds silly, but we can cover hours of back and forth in a matter of minutes. i'll be around all weekend.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #13
Thanks for your interest and help!
I'll get that pump noise fixed first. The lack of that noise was the most coincidental characteristic with this problem.
I had a scope on the crank sensor and got the signal ok with proper voltage. CDI checks out as well. While I do get continuity for the B+ wire from starter solenoid to ECM, I do not get voltage at the ECM connector with ignition on.

This bike flooded, and continues to try to flood (heavy fuel smell) while cranking (and I replaced the fuel pressure valve on prior advice) so I never suspected any fuel system issues.

I'll proceed one thing at a time starting with the kill switch...then the relays. Please bear with me...
 

·
Registered
Joined
·
1,628 Posts
ok i'll break this down for you as the control system is simple.


power comes from the battery, then goes to the key switch, from the key switch it goes to the fuse box. in the fuse box is a 10 amp circuit labeled ignition. this circuit splits into three wires. 1 goes to the regulator/rectifier as a sensing line, one goes to the bank angle sensor to power the device, the other goes to the kill switch. the wire is white/black


once this white/black reaches the kill switch, it leaves from the other side of the switch to the coil side of the engine stop relay.

from the other side of the engine stop relay a red wire heads over to the bank angle sensor. the bank angle sensor switches this wire to ground to allow the engine stop relay to operate.



on the power side of the engine stop relay is a larger gauge red/white conductor. this comes straight from the battery (with a 30 amp fuse in line, it's in the small white housing on the single conductor on the battery positive terminal)


when the engine stop relay is energized by the kill switch and bank angle sensor, the entire EFI system is powered up.


this is done on the black/white wire. this wire feeds the

ecu
fuel injectors
CDI box
fuel pump relay



the fuel pump relay takes this black white and feeds both the power side of the relay and the coil side. the ECU controls the ground side of the coil (brown/black) to turn on the fuel pump. when the ECU grounds the brown/black, the relay energizes and the power side connects the black/white to brown.




if all these things are happening (ie the fuel pump primes) then you have NO ISSUE WHATSOEVER WITH THE FOLLOWING ITEMS

ECU
KILL SWITCH
BANK ANGLE SENSOR
ENGINE STOP RELAY
FUEL PUMP RELAY
FUSES




do not waste your time trying to diagnose a symptom that is not present.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #15
Tried Robert's shortcut (thanks Rob) of swapping around 4-post relays with known good headlamp relay to no avail...no fuel pump prime.

Started tracing power at the "Starter Relay Switch" which I think is what you're referring to, Wibbly, when you say "engine stop relay". The engine stop switch is the kill switch, but not a relay.
There are 2 30a fuses there, one in the connector and one at the base of the relay, and they test good.
There are 4 spades at the relay's connector, and the one that corresponds to the larger diameter red wire of the connector indicates 12v with the ignition on. As an aside, I can hear the fuel cut off relay click after 2 sec of the ignition being turned on.
Voltage inside the kill switch is 12v at the top half of the switch, and as I operate the switch I can hear both relays, fuel cut off and bank angle engage with a click, with a second click coming from the fuel relay after 2 seconds.
At the fuseblock there is 12v at each side of each fuse with ignition on, and 12v only at the odometer fuse with ignition off.
At the voltage regulator there is 12v at each of the red/wh wires with ignition off. Nothing at the two green or the black wires in that connector.
From the bank angle sensor and a short distance away there is a green connector siamesed external to to the main harness, and that connector is buried tightly under that large harness. The (slightly larger dia) wires coming from the sensor are green (assumed ground), red/white, and white/black. From your explanation, Wibbly, i assume the black and white wire is supposed to be 12v. I cannot test it at that connector because it's so tightly buried, but I can test the other end at the voltage regulator connector which I think is where it originates, and it does test out at 12v with the ignition on. I just can't get a probe down alongside the battery box to access the connector to the sensor. If its important, I'll need to know how to remove the battery-box/inner fender to free that harness enough to get at that connector and get it out in the open.
In your explanation, Wibbly, you indicate that the kill switch and bank angle sensor control the engine stop relay, and I have 12v at that relay on the solid red larger wire, but no voltage either at yellow/red wire from the kill switch with ignition on, or the other control wire for the relay (green and red) which is not a wire from the bank angle sensor, nor its relay, but, rather, its from the gray connector on the ECU...pin number 18 on the schematic, or 5 pins over from the yellow wire at the end of the connector. I do have continuity in that green/red wire from the relay's connector to the corresponding pin on the ECU's gray connector.
Tracing yellow/red from kill switch and find no voltage from kill switch to red connector about a foot away. None at green/yellow wire, either. All others in red connector are at 12v. Moving switch form on to off results in no changes in those readings, but I can hear the relays cycling each time.
Looking at the internals of the kill switch, I think the red/yellow is the starter solenoid engagement control wire, and is not related to the problem as it would only be hot when starter switch is engaged.
So the only other wire at the starter relay is green/red and it goes to the ECU...or does it come from the ECU, I cannot tell anymore...lol.

Any further thoughts?
 

·
Registered
Joined
·
1,628 Posts
Yellow red is the signal from the start button to the starter relay. The green red goes from the starter relay to a logic circuit that includes the ecu, the side stand, clutch switch, clutch diode, and neutral switch. This is of no concern to you.


You are absolutely all over the place man... Get focused. The fuel pump relay is clicking but you get no prime. That's a stupid easy thing to trouble shoot isn't it.... Check for power at the pump. It's likely either a failed pump or failed wiring in the bulkhead



The engine stop relay is the same as the bank angle sensor relay. Differences in terminology.



Your story isnt really making sense though. You say it's flooding with fuel early in the post but now you claim the pump isn't priming



So do you have fuel or no? You're contradicting yourself.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #17
The contradiction is the problem. I've had this bike for a long time and never smelled raw fuel, but, of course, it's always started. In my world I need fuel, air, spark, and compression to start. When this motor fist failed to start, two things happened; 1) no high-pitched whine as the tach cycled thru range, and 2) raw fuel smell while cranking. Raw fuel even dripped out of the exhaust connector in front of the rear wheel because I was so stubborn about getting this thing running.
Replaced the plugs because I've found that very wet plugs sometimes never seem to recover. Then I put a timing light on the rear sparkplug wire to check for spark while cranking, since there wasn't even a hint of the motor starting, yet it seemed to have beaucoup fuel. Then, while cranking it up again it seemed to want to start, during which time the light flashed twice, I heard the normal exhaust noise, and then went dead, and I could smell raw fuel. Rather than pursue another fuel bath, I stopped cranking the motor. And, no, the high-pitched noise which I have come to understand is the fuel pump, has still never been heard. Yes, it seems that I can flood this engine nonetheless. A contradiction it seems, but its a fact.
Sorry if it seems that I've lost focus, but there's two things that aren't normally a simultaneous issue...so I'm confused on the method to proceed. I thought that through your description of the systems' operation you were advising me to follow the circuitry to ensure that all the elements you were mentioning actually were receiving power, and that the circuits were complete to their points of interconnection, hence all the tests for voltages and continuity.
It seems that the pump priming noise is the paramount and first hurdle to cross regardless of the smell of raw fuel. So I'll jack up the tank and check for power at the pump and back up through the connector and get this pump to make some noise before going any further regarding other circuitry, ignition and lack of continuous spark.
Am I on the right track then?
 

·
Registered
Joined
·
1,628 Posts
Have you tried just holding the throttle wide open and cranking for a while? Kill switch set to run


If the bike fails to light and you keep cranking you'll just flood the crap out of it

Holding the throttle wide open will shut down the injectors but not the plugs.


Cycling the kill switch should produce an FI lamp on the dash for a few seconds (indicating that the Fi system is powered), and prime the pump while the Fi lamp is lit.


If you have the Fi lamp when you set the kill switch to run then the ecu, CDI, injectors, and fuel pump have power available to them. You don't need to troubleshoot any part of the control circuit for the efi if this is the case (ie kill switch, bas, fuses etc)
 

·
Registered
Joined
·
13 Posts
Discussion Starter #19
Red FI lamp is lit until I can hear the fuel cutoff relay trip and the light goes out. About 2 seconds.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #20
At the fuel pump on the underside of the fuel tank, there's no way to test the voltage as the porcelain block has the wire terminals coated in vinyl. However, with the ignition on the voltage at the fuel pump connector along the frame rail, is 12v to the spade that connects to the brown/black (center wire) wire. The spade for the solid brown wire shows no voltage with ignition on.
 
1 - 20 of 30 Posts
Top