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Discussion Starter · #1 ·
Hi Folks,

New member and first time poster here.

I have searched around through various forums for some ideas on the issue my bike is having. I've also posted up on "CBR Forum" just to cover my bases.

The bike is a 2001 F4i with only 13,000 km on the clock.
Two owners, me being the second.
Full service history and completely standard.
Australian delivered vehicle.

The issue I have is that when turning the bike key on and the kill switch on the fuel pump will prime but doesn't shut off after a few seconds as it should. It continuously runs.

The bike has done this since I bought it and when first riding the bike I thought it was over fuelling because I would get occasional black smoke out of the exhaust and a bit of exhaust backfiring on overrun.

One morning the bike refused to start completely.

After my initial research I changed the fuel pressure regulator for a brand new Honda Genuine one along with the O ring and a put in a fresh set of plugs because the old ones were fouled.

Bike now starts again but fuel pump still continues to constantly prime.

I've since checked the Fuel Cut Relay, Engine Cut Relay and bank angle sensor. All work as they should with correct continuity with 12v applied and removed. The fuel pump wiring (nor any other wiring on the bike for that matter) has been tempered with. It is 100% stock.

I plan to pull the vacuum hose tonight to see if there is any fuel in the line. I don't believe it is a stuck injector because the bike doesn't run poorly.

Can anybody suggest any other places where the system may be failing?

I've also jumped the Fi diagnostic plug but there were no fault codes. I'm at a loss now.

Any help appreciated.
Thanks.
 

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Discussion Starter · #2 ·
Well, pulled the vacuum hose and no fuel there.

I did notice fuel is rushing through the return fuel line back to the tank when the fuel pump is priming and the bike is off. Is this normal? Could this be causing the fuel rail to not get to pressure?

The problem is I don't really understand what component it is in the system that actually tells the pump to run and then to stop when finished priming. If its a preset time with a 12V signal as supplied by the ECU, or if there is some kind of pressure sensor etc.

I tried using hose clamps on the return fuel line to see if a build up in pressure would make the pump stop. Still wanted to keep on pumping....

urrrgh.... ever have those times in your life where you just think "why cant this [email protected]!t be simple?!"
 

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Discussion Starter · #3 ·
Ok, still messing around with it.... I know my Fuel cut relay is working ok (as in the internal switching inside the relay) but I wanted to check the voltages being supplied through the relay when the bike is being primed. I threw on a multimeter with the relay still plugged in, positive to the Black/White, Negative to the Brown/Black.

With the Ignition Key turned OFF and Engine Stop Switch in ANY position, 0 Volts at the relay. (as expected)

With the Ignition Key turned to ON and Engine Stop Switch OFF, 0 Volts at the relay. (as expected)

With the Ignition Key turned to ON and Engine Stop Switch ON, 12 Volts at the relay.....constantly! 2 seconds, 5 seconds, 60 seconds whatever... 12 Volts.

Can anyone confirm for me with an F4i that primes properly, that has the means and willingness to assist, can you please throw a multimeter on your fuel cut relay (with it still plugged in) and tell me if the voltage going through the relay on your bike is only a temporary 12 volt supply for a few seconds when you first turn the key on (with Engine Stop ON). I presume then that once the bike is actually started this voltage should THEN be expected to be a constant 12 volts.



If my theory is right, I can only assume something with the ECU is faulty on my bike.
 

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32,104 Posts
Hi Folks,

New member and first time poster here.

I have searched around through various forums for some ideas on the issue my bike is having. I've also posted up on "CBR Forum" just to cover my bases.

The bike is a 2001 F4i with only 13,000 km on the clock.
Two owners, me being the second.
Full service history and completely standard.
Australian delivered vehicle.

The issue I have is that when turning the bike key on and the kill switch on the fuel pump will prime but doesn't shut off after a few seconds as it should. It continuously runs.

The bike has done this since I bought it and when first riding the bike I thought it was over fuelling because I would get occasional black smoke out of the exhaust and a bit of exhaust backfiring on overrun.

One morning the bike refused to start completely.

After my initial research I changed the fuel pressure regulator for a brand new Honda Genuine one along with the O ring and a put in a fresh set of plugs because the old ones were fouled.

Bike now starts again but fuel pump still continues to constantly prime.

I've since checked the Fuel Cut Relay, Engine Cut Relay and bank angle sensor. All work as they should with correct continuity with 12v applied and removed. The fuel pump wiring (nor any other wiring on the bike for that matter) has been tempered with. It is 100% stock.

I plan to pull the vacuum hose tonight to see if there is any fuel in the line. I don't believe it is a stuck injector because the bike doesn't run poorly.

Can anybody suggest any other places where the system may be failing?

I've also jumped the Fi diagnostic plug but there were no fault codes. I'm at a loss now.

Any help appreciated.
Thanks.

No idea about this, other than a failed fuel pressure regulator diaphram.
If you clamp the vacuum hose does the pump still keep running?
Did you replace the oil after swapping the FPR? If nnot then you're still likely to foul plugs due to the diluted oil being pushed up past the rings.
It's probably not that big a deal as long as you don't leave the ignition on for long enough periods to flatten the battery.
 

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Discussion Starter · #5 ·
I would be very disappointed if the brand new FPR is faulty straight from Honda. Without a fuel pressure gauge I guess it's a bit hard to test if its holding pressure in the rail. Like I say though, no fuel out the vacuum port on the FPR so I make the assumption he diaphragm is still intact.

Oil still due to be dropped and replaced. Thanks for the heads up, very valid but it isn't being ridden much and I plan on doing a full fluid service by the end of month.

Blocking the vacuum line didnt effect the pp operation at all.

Thanks for taking time to offer some input.
Regards,
Stu.
 

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I would be very disappointed if the brand new FPR is faulty straight from Honda. Without a fuel pressure gauge I guess it's a bit hard to test if its holding pressure in the rail. Like I say though, no fuel out the vacuum port on the FPR so I make the assumption he diaphragm is still intact.

Oil still due to be dropped and replaced. Thanks for the heads up, very valid but it isn't being ridden much and I plan on doing a full fluid service by the end of month.

Blocking the vacuum line didnt effect the pp operation at all.

Thanks for taking time to offer some input.
Regards,
Stu.

If it's simply pumping the excess fuel back to the tank as it's supposed to and not pumping it into the engine then I wouldn't worry about it.
I assume the bike does rev out to redline under load so it's not starving for fuel?
Are you in contact with the previous owner to ask if he has any ideas about the problem?
 

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Discussion Starter · #7 ·
I "assume" it is doing as you say in that the excess fuel is just being returned to the tank. Can't say if its being mixed in with the oil as such, at least till I drop the oil. Reluctant to rev it out too hard until I know what's going on. All I had to work off was the fouled plugs I discovered and the fact one day the bike simply refused to start. The bike had been running on the rich side (in my opinion) prior with noticeable black smoke and occasional back firing. It's never given the impression it's starved of fuel at any time. The first items changed in this whole troubleshooting exercise have been the FPR and plugs. Bike has now began starting again but the constant priming has always been there and I didn't know if in some way it all tied in together. In the last week I've given myself a very quick crash course in fuel systems :) best way to learn, get your hands dirty. I was worried about the fouled plugs and have been trying to piece together how the FPR would play a part in causing the problem.

Got to love all the dumb questions of a backyard mechanic hey? ;)
 

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I "assume" it is doing as you say in that the excess fuel is just being returned to the tank. Can't say if its being mixed in with the oil as such, at least till I drop the oil. Reluctant to rev it out too hard until I know what's going on. All I had to work off was the fouled plugs I discovered and the fact one day the bike simply refused to start. The bike had been running on the rich side (in my opinion) prior with noticeable black smoke and occasional back firing. It's never given the impression it's starved of fuel at any time. The first items changed in this whole troubleshooting exercise have been the FPR and plugs. Bike has now began starting again but the constant priming has always been there and I didn't know if in some way it all tied in together. In the last week I've given myself a very quick crash course in fuel systems :) best way to learn, get your hands dirty. I was worried about the fouled plugs and have been trying to piece together how the FPR would play a part in causing the problem.

Got to love all the dumb questions of a backyard mechanic hey? ;)

When the fuel pressure regulator diaphram fails, the fuel is pumped at 50psi down the vacuum hose directly into that cylinder, where it then flows past the rings into the oil. The diluted oil is then forced up past the rings to be burned and fouling the plugs.
 

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Discussion Starter · #9 ·
Ahh, makes sense. Thanks for clarifying. So chances are my first FPR was indeed stuffed explaining the rich fuel and fouled plugs, but the fuel priming issue is seperate again. I'm getting my head around it slowly.

Thanks for the help.

Still keen to know what the deal is with the voltages at the fuel cut regulator just to pinpoint a cause. Just put the mind at ease. As you say, if the fuel is simply returning to the tank, then it shouldn't be an issue.
 

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Normally the fuel pump will prime until it has the appropriate pressure in the main system therefore causing the pump to stop until a further pressure drop to kick the pump back in again, if you can try clamping the main line to the injectors to see if the pump will stop priming after initial key on.
I have no idea on the workings of the bike fuel system but would definitely be looking at a fuel delivery pressure problem.
 

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I’d try the Fuel relay first off.

Btw what Kevo964 say above is not true though. The pump primes for a second or so when the ignition it switched on and then stops. It should not run again until the crank sensor (rh side) on the motor sends a pulse to the ecu then the ecu switches on the relay. Pressure is controlled by the FPR which allows excess fuel back to the tank but the pump runs continuously.
 

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Ok, still messing around with it.... I know my Fuel cut relay is working ok (as in the internal switching inside the relay) but I wanted to check the voltages being supplied through the relay when the bike is being primed. I threw on a multimeter with the relay still plugged in, positive to the Black/White, Negative to the Brown/Black.

With the Ignition Key turned OFF and Engine Stop Switch in ANY position, 0 Volts at the relay. (as expected)

With the Ignition Key turned to ON and Engine Stop Switch OFF, 0 Volts at the relay. (as expected)

With the Ignition Key turned to ON and Engine Stop Switch ON, 12 Volts at the relay.....constantly! 2 seconds, 5 seconds, 60 seconds whatever... 12 Volts.

Can anyone confirm for me with an F4i that primes properly, that has the means and willingness to assist, can you please throw a multimeter on your fuel cut relay (with it still plugged in) and tell me if the voltage going through the relay on your bike is only a temporary 12 volt supply for a few seconds when you first turn the key on (with Engine Stop ON). I presume then that once the bike is actually started this voltage should THEN be expected to be a constant 12 volts.



If my theory is right, I can only assume something with the ECU is faulty on my bike.
After a bike sits for a long time the rider is eager to get it running but fails to remove the positive terminal from the battery during a recharge. Charging the battery with the terminals still connected provides a connection to the ECU. Such action may damage the ECU when the charger sends pulses through the connected positive terminal. Repeated spikes in charging amperage can damage integrated circuits over time even before any fuses are blown to sever the connection. Replacing the ECU may be your best option. This is assuming the relays are in working order and not stuck in the on position.

Your bike before initial ignition should prime for about 3 to 4 seconds and should be constantly on after the engine is running.

Now, when the engine is on and you hear the fuel pump whirring away, that's normal if the tank is partially filled with fuel below the fuel pump assembly. You should not hear the whirring sound if the tank is full and the fuel pump assembly is completely submerged. In an empty tank you may hear the fuel pump whirring away because there is not enough fuel to dampen the sound of the fuel pump working. Meanwhile there is not enough fuel being pushed through the pump to sufficiently reach operating pressures and the engine stutters and stops.
 
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