Hate to be asking for help with my first post but here goes.


I'm trying to help my son get his CBR600 back up and running.

The story. He was out riding when he says the bike began to run strangely. He says it felt like he was running out of fuel but the tank was half full. He pulled into a parking lot and shut the bike off to check things over. Not sure what had happened, he tried to restart the bike after a couple of slow cranks the battery died.

I went to help him out. I figured he had possibly had the regulator/rectifier fail and had run on the battery until the voltage ran out. We boosted the bike from a truck (truck not running). The bike would spin over but not fire up. We trailer-ed it home.

Once home in the shop, we pulled the battery to recharge it on the bench. At this point we noticed a cut wire on the ECU plug. We pulled the ECU and re-soldered the wire back into the plug. Now with a manual for the bike, we know this was one of the 4 pink injector wires.

We took the battery and had it tested. It faled so we bought a new one.

New battery in place, we turn the key to again attempt a start. Turns over but no fire. We now notice that the fuel pump is not coming on with the key.

I start reading forums to help figure this out.

Here is what we know so far.

The Bank Angle sensor is fine as well as the engine stop relay.

The fuel pump runs if we jump the wires in the fuel pump relay plug. Power is in the plug. The relay works on the bench. We are certain it is not receiving a signal from the ECU.

We took the ECU to a Honda dealer to have it check but they said they don't have any way of checking it. They suggested checking the Ignition Diode as they said it was common to blow if the bike is boosted.

I pulled the ignition and tested the infamous "Zener Diode" located in the base. With my volt meter I am getting a reading of 10.1 volts in the pink wire both at the ignition and at the #19 pin in the ECU plug.


My question. Is the 10.1 volts my problem as I have read that it should be 9 volts? Meaning, the ECU has an acceptable volt range and this one is out.


I assumed that once I got to the diode I would have no reading. That the boost would have burned the diode completely and there would be no voltage present.

Could the excessive voltage have damaged the ECU?

 

If your service manual states 9 volts, and your getting 10.1, I'd say it could be your issue...... Unless the service manual states a Minimum of 9 volts, then 10.1 is ok. Its probably like most 12 volt systems, where something won't function without at least 9 volts of power. So, if thats the case, it sounds like its functioning like it should. If there isn't a range stated, and it only states 9 volts, that is a minimum requirement.

Have you tried to re-disconnect the wire you soldeired back together? It could be the rectifier like you said, the battery was ruined from the rectifier, and the cut wire had nothing to do with the running issues.

If it were me, I'd cut the wire again and see where that leads you. Its the only thing you changed in addition to replacing the known faulty battery.

If your not getting fuel, there are only a few things that prevent that. Two you have checked, the third is the killswitch. Try flipping the kill switch back and forth a few time. Its rare, but they can stick sometimes. Also, they have been known to fail internally with the spring inside failing.

Also, keep in mind the fuel pump will only run for a second or two. As soon as you turn on the key, it will prime and shut off until the bike is started.

If I had to guess, I'd say you just have fouled plugs. if the bike was cranked over slowly, as when the battery was failing, it more than likely fouled the plugs. Once these finicky plugs foul, the best thing you can do is replace them.

thats about all I can add to check. It sounds like you've went in all the right areas.

good luck.

 

Well, I'm thinking the ECU works the opposite way. The Diode is there as a security feature. It reduces the voltage from 12 to 9 so that the bike cannot be hot wired. If someone were to cut and splice the wiring outside of the ignition switch, it would send 12 volts to the ECU. The ECU needs 9 and would not allow the bike to start.

You are right about the plugs and I will move on the those next but I'd like to hear the fuel pump run first.

The Killswitch is working properly as it is turning the engine relay on and off.

I'm going to replace the diode as soon as I can find one of the proper valve and see where that leads.


Frustrating.

 

Does your bike Have HISS on it?

 

No it doesn't.


I changed the diode and it made no difference.

I took it to the dealer. Hopefully they can figure something out.

 

just throwing this out there but did you check the fuse's. ign fuse may control power to fuel pump relay.

 

Fuses were the first things I checked. All were good.

 

Update.

My son called the dealer as we had not heard anything since we dropped the bike off a week ago. He was told that they think its the diode and that they have ordered a new ignition harness. Its on back order. They expect it to take 2 weeks but no guarantee.

Now I'm really frustrated. I don't believe the diode is the problem but we are stuck waiting 2 weeks to find out. There has to be a way to check this somehow. Its only a diode.

Summer is fading fast around here.

 

Are they referring to the Clutch Diode ? If so, then their diagnostics leave something to be desired. The clutch diode is part of the circuit that determines whether or not the Starter Relay is able to be energized or not. Since the bike is turning over, then the Diode is working. Page 18-0 shows that circuit.

Now I see you're referring to a Diode located in the ignition switch. Maybe look around some motorcycle salvage yards to see if they have one.

 

I tried salvage yards for the ignition wiring harness when it first became a possibility. They sell the ignition switch with the harness attached for around $400. They wont sell it separate.