Thread: Weird electrical problem that keeps blowing the 10A ignition fuse

Hello everyone!

I've got a 2000 Honda Blackbird imported from Germany. Did 3 thousand problem-free miles on it (mostly in very cold weather), and now, after a major service, which, among other things, included a conversion from stock light bulbs to LEDs in the headlight (if that's relevant), a weird problem started to show.

It first appeared when I was riding at 85F on a straight stretch of road in the 2nd gear at some 25 mph. The fuel pump suddenly shuts off, and the next moment I'm coasting to the curb. Removed the seat, checked the fuses and found a blown 10A one in the ignition circuit. Replaced it with a spare, turn the key and the next moment it blows just like the first one.

Call an evacuation truck, get the bike to a service center, and this is where things get interesting. They first check the fuel pump relay, and replace the bank angle sensor with a spare one, take it out for a spin and the fuse gets blown at 4-5 thousand rpm in the 2nd gear (engine temperature about 215F). It sits for a couple of minutes while they replace the fuse and voila - the bike starts and limps to the garage.

Today they decide to check if the fuel pump is seizing by adding an extra line with a circuit breaker, but nothing happens: the FP operates normally and no fuses are blown. They run it hard so the engine gets so hot that the fan works without stopping, and the bike still runs normally without a single hiccup.

Any ideas? I'm ready to order a second-hand fuel pump assembly. Is there anything in the wiring loom which might be causing this glitch?

Panchuo.

the problem with letting a service center look for a mysterious electrical gremlin is that they can get nowhere and present you with a bill approaching the value of the bike.

Things to check, and I'm sure other members can add more:

1. voltage. The R/R may be on the way out, giving voltage spikes, so far taking out 1 particular fuse. Put a voltmeter on the dash. NOTHING over 15V.
2. Bad ignition switch giving intermittent signal.

PS: you say …..they replace the fuse and the bike limps back to the garage. Does that mean it didn't run right or they just rode it back slowly?

1) They did check the voltage coming into and out of the R/R first thing - it's within spec.

2) We shall check the signal on the ignition switch tomorrow, thanks for the idea!

Originally Posted by fizzy

Panchuo.

the problem with letting a service center look for a mysterious electrical gremlin is that they can get nowhere and present you with a bill approaching the value of the bike.

Things to check, and I'm sure other members can add more:

1. voltage. The R/R may be on the way out, giving voltage spikes, so far taking out 1 particular fuse. Put a voltmeter on the dash. NOTHING over 15V.
2. Bad ignition switch giving intermittent signal.

PS: you say …..they replace the fuse and the bike limps back to the garage. Does that mean it didn't run right or they just rode it back slowly?

On the subject of limping: it's a large facility with 1/8 mile straights. They ran the bike in the 2nd gear revving up to 5-6 thousand rpm. The fuse blew on the 3rd or the 4th minute of the test run. I walked to the guy who replaced the fuse and bike magically started. The engine was still hot.

The mechanic then rode it slowly at 2-3 thousand rpm back into the pit area, and that was it.

I didn't witness today's runs though, but they said they had rigorously simulated hot temperature effects on the components (i.e. fuel pump) hoping something would give up, but nothing did.

Originally Posted by fizzy

Panchuo.

the problem with letting a service center look for a mysterious electrical gremlin is that they can get nowhere and present you with a bill approaching the value of the bike.

Things to check, and I'm sure other members can add more:

1. voltage. The R/R may be on the way out, giving voltage spikes, so far taking out 1 particular fuse. Put a voltmeter on the dash. NOTHING over 15V.
2. Bad ignition switch giving intermittent signal.

PS: you say …..they replace the fuse and the bike limps back to the garage. Does that mean it didn't run right or they just rode it back slowly?

Hi ,
Another thing to check before splashing out cash.
Since this started after a bulb change, when the bike is running turn the handlebars full lock each way, also while the bike is running move the loom that comes from the bottom of the ignition switch, to see if something has been disturbed.
It does sound like a solder joint from the bottom of the ignition switch or a broken wire in the loom around there.
Worth checking anyway.

Will check tomorrow, thanks very much!

What are the chances that the fuel pump is causing this problem?

Originally Posted by Gadgey

Hi ,
Another thing to check before splashing out cash.
Since this started after a bulb change, when the bike is running turn the handlebars full lock each way, also while the bike is running move the loom that comes from the bottom of the ignition switch, to see if something has been disturbed.
It does sound like a solder joint from the bottom of the ignition switch or a broken wire in the loom around there.
Worth checking anyway.

Just checking the voltage is not enough. Need to ride bike while keeping one eye on voltmeter looking for spikes to 15-18V. Also, check the connector from stator to R/R for heat damage.
Fuel pump may be operating OK but blowing fuse due to high amps, maybe. Didnt they already wire separate feed for pump? If so then run bike on that (fused same size) to eliminate other issues. If all that fails then I would be looking at ignition switch

Will do that as well and report tomorrow, thanks!

Originally Posted by fizzy

Just checking the voltage is not enough. Need to ride bike while keeping one eye on voltmeter looking for spikes to 15-18V. Also, check the connector from stator to R/R for heat damage.
Fuel pump may be operating OK but blowing fuse due to high amps, maybe. Didnt they already wire separate feed for pump? If so then run bike on that (fused same size) to eliminate other issues. If all that fails then I would be looking at ignition switch

which actual fuse is it

A - 20amp
B - F are all 10amp

The fuel pump is controlled from the fuel cut off relay which is controlled by the

ECU which is fused separately through the main 30amp fuse,

the fuel pump stopping is likely a secondary symptom of the ECU saying can't run without this sensor - that is fused by a 10amp fuse

Fuse A - Headlight (20amp)
Fuse B - Possible critical
Fuse C - none critical

Fuse D - starter, Bank angle sensor
Fuse E - none critical

Fuse F - none critical

Based on old manual which might some variance to what is on the bike

The only fuse that would give your symptoms is possibly B and definitely D

Also check the top of the starter solenoid - mine melted and caused weird problems





my guess is they have disturbed something fitting stuff during service - pinched a wire or something, I would have thought the FI light would be blinking out a fault if a sensor was the problem

It is the 10amp Fuse D (starter, bank angle sensor) that kept blowing, but somehow stopped doing that yesterday.
Could this magic recovery have been caused by the fact that the guys had wired the fuel pump separately with a 10amp fuse?

Like I said, one of the first things they did was putting in a working bank angle sensor, but that did not help a bit - Fuse D blew right away.

Anyway, the list of things for today looks like this:

1) Check the top of the starter solenoid
2) Check the wires coming from the stator to the R/R.
3) Start the bike and shake the wire harness coming to and from the ignition switch.
4) Connect a voltmeter to the battery, ride pillion and watch the readings (Volts and Amps).

Did I forget anything?

Originally Posted by GeoffXX

which actual fuse is it

A - 20amp
B - F are all 10amp

The fuel pump is controlled from the fuel cut off relay which is controlled by the

ECU which is fused separately through the main 30amp fuse,

the fuel pump stopping is likely a secondary symptom of the ECU saying can't run without this sensor - that is fused by a 10amp fuse

Fuse A - Headlight (20amp)
Fuse B - Possible critical
Fuse C - none critical

Fuse D - starter, Bank angle sensor
Fuse E - none critical

Fuse F - none critical

Based on old manual which might some variance to what is on the bike

The only fuse that would give your symptoms is possibly B and definitely D

Also check the top of the starter solenoid - mine melted and caused weird problems





my guess is they have disturbed something fitting stuff during service - pinched a wire or something, I would have thought the FI light would be blinking out a fault if a sensor was the problem

By the way, is there a chance the handlebar switch might be causing the problem?

Is there any known problem with the wiring harness that might be the culprit?

Originally Posted by pachuco

By the way, is there a chance the handlebar switch might be causing the problem?

Is there any known problem with the wiring harness that might be the culprit?

Fuel pump is nothing to do with it, like I said secondary symptom, not sure what effect wiring it separately has done, might be worth looking in and around the rear light harness/ECU area - lots of connections/wires in there

Logic would say that since they fitted LED's up front that something got disturbed there - they may have removed the instrument cluster and front cowl to fit the LED's and disturbed something, lots of wiring in that area with the bars etc - what else did they do to service the bike - lift the tank highly likely,

I will look at the wiring diagram again and trace the Fuse D connections and post if I see anything stands out

I think you need to un-disturb what they disturbed during the service

Stator RR - highly unlikely to nill (IMO)

Something in the harness up at the front - bars ignition instrument cluster etc pinched wire - highly likely

Under the fuse box is another possibility

Starter Solenoid area - a known problematic area

Fuse D is connected to a lot of stuff that stops the bike from starting and it all ends up back at the ECU harness in the rear

will post if I think of anything else

you have the worst type of electrical problem possible because it is seemingly not there all the time, you could run the bike and put your finger on top of the fuse to see if it is heating up before it actually gives in


I do most of my own work so I know exactly what I've done - that is the problem when you let someone else do the work, you've no idea what they got up too, they would have needed to have done something pretty profound to cause this - like possibly make a mess of something and try to patch it up, is the same people faultfinding that did the service ?

The guys at the official dealership failed to troubleshoot the issue.
They only said that the 10A circuit breaker wired into the fuel pump circuit got quite hot, but held.
I am now riding away with the stock loom and a 20A fuse in place of the 10A one in slot D.
Hopefully, the other mechanic knows his stuff better, and we'll be able to troubleshoot the problem - stay tuned!

Originally Posted by pachuco

The guys at the official dealership failed to troubleshoot the issue.
They only said that the 10A circuit breaker wired into the fuel pump circuit got quite hot, but held.
I am now riding away with the stock loom and a 20A fuse in place of the 10A one in slot D.
Hopefully, the other mechanic knows his stuff better, and we'll be able to troubleshoot the problem - stay tuned!

The fuel pump doesn't run off fuse D, it is powered from the fuel pump relay which runs off the main 30amp fuse I believe, the FPR is operated by the ECU - I will check this again from the wiring diagram and post here again if wrong

OK so I checked - Fuse D only feeds the BAS and the Engine Stop relay here is a diagram you can find in the manual you can download from this site under chapter 5.4, I did not include the fuel pump as it is fed from the fuel pump relay and main 30amp fuse - there is an outside chance the engine stop relay has an internal partial short or maybe even external - I believe it sits right beside the FPR in the fuse box

Wiring.png

Pachuco, Geoff is correct, there is no fuse per se to the fuel pump, only a relay, which may be acting up. That could blow the fuse. Also check handlebar on/off switch.

I am now leaning towards Geoff's idea of some pinched wire in the loom by previous service guy. Installing LEDs headlights without taking off the nose cone would entail manhandling a bunch of wires to make room. Ignition and handlebar switches go thru this space.

Edit: Best not to "upgrade" to a 20A from a 10A fuse. Just carry a few spare 10A. If there is a pinched wire it could get hot and melt more wires around it, or worse.