The relay is not a common contact point unit. It is the safety switch.
It is a transistorized pump control unit that sends voltage to the pump when it gets an engine running signal.
And shuts down the pump when the engine stops.
The pump is an on-demand type that will stall when the carb bowls are full and the float valves shut off.

 

When I went to check the relay connector (where the relay plugs in), I now get no power at all. Can't get it to read any voltage at all.

As Swifty says, it's not a relay, and Honda shouldn't really have named it a "relay" in my opinion. I call it a "pulse extender". There's no ground connection at the fuel pump "relay" connection, but you should see 12V + on Black terminal with the ignition key on, and the negative lead of your meter on Batt- or good ground. If you have 12V+ on the black wire, you can jump that to the Blue/Black to bypass the "relay" and test the fuel pump.

On my '96 1100 ACE, the "relay" only passes pulses of power to the fuel pump when the ICU is sending ignition pulses to the Front ignition coil. That means ONLY when the engine is spinning, either cranking or running.

Did your fuel pump "hum" with ignition ON before the event?

 

Ya'll saying the pump has a frame/ common ground? but-- on mine the pump has a rubber wrap that isolates all. I just replaced. so the ground has to be one of the 2 wires./ internal right?

 

Grab yourself a manual and wiring diagram, understand the operation by following where It gets it's power from and when (in what switch orientation etc)

For example: my 99 vt750

Fuel pump has common ground then gets power from the fuel out relay. Fuel out relay gets power from fuse C which gets power from the keyed ignition switch>>main fuse>>battery. The relay is live when it gets signal from the same circuit signalling my rear coil, if the engine died and that coil weren't firing, I wouldn't be pumping fuel everywhere because of the design. I'm sure you have something similar.

Hope this helps.

 

ok.. this is going in my pile of things to troubleshoot. thanks big time!

 

And bypass the relay to test it and the pump. Jump black to black-blue in the harness plug, tape it up and try it. And as mentioned, it IS a safety device, be aware the pump could will stay running in the event of a crash.

I suspect some of the new relays are simply defective, or they were new and got tried and returned. Or something...

 

EXACTLY CORRECT

 

Maybe it should be called a fuel pump driver or regulator.
Just like many electrical circuits that have a control such as that.
Fuel injectors have similar driver transistors to turn on or shut off or regulate the time on for fuel delivery, etc.

 

OR FUEL PUMP CONTROLLER

 

Thanks all for your replies. A few follow up questions:

1) I had no idea the relay wasn't actually a relay, that helps. So if I'm understanding properly, the "relay" should not see any power just while the key is turned, but it SHOULD see power when the starter is cranked, even if the engine doesn't actually catch and turn on, is this right? I have tried jumping those connections before but it didn't help, but I'll give it another try.

2) I actually don't remember if my fuel pump made a noise before. When I try to remember, I have memories of turning the key to "on" (so, not cranking the engine) and hearing a hum for like 2 seconds, but now this doesn't make any sense because if the "relay' has no power until the engine is running, the fuel pump shouldn't prime without the engine actually turning over. So that's a little worrisome because now when I turn the key I don't hear the hum anymore, so maybe something else is out? Or maybe I'm misremembering the hum noise?

And thanks, I'll dig up a wiring diagram (have one somewhere) and poke through it. Will report back. Thanks!

 

Relay= 12v+ when key is on
Neg/ground signal from ICM
(which also fires the coil) when the engine is turning regardless of running yes because the ICM signals based on input from the pulse generator (which is modulated by the engine turning and the teeth on the wheel relative to the generator)

This completes the circuit allowing the relay to send 12v to the fuel pump which has common ground already, thus energizing the pump.

 

The 2004 free Honda common manual has good details about the CV carbs and the relay and pump

 

Ignition fuse was intact, changed it just to be safe. When the battery is fully connected (I was using a jumper pack before) I get 12v at the "relay". Is there some way to test the fuel pump without fully removing it, which looks to be a real chore? Thanks

 

There should be a 2 wire connector to the pump that you can put battery voltage to.

 

Thanks. Yep. Tested with a battery, tested the old pump and a new pump. Verified that 12v was flowing through but neither of them made any kind of noise or did anything to indicate that they were on. Should it be obvious when they're on? I expected some kind of noise or something

 

Not really. My pump only sounded off when I ran it dry forgetting to open the petcock after carbs and lines were drained. I pulled my pump relay and have it straight 12 on my motogadget it is just fine.

 

Jump black (12v) to black-blue (power to pump) in the relay harness plug. tape it up. drain the float bowls via the drain screws. when you turn the key on, the pump should run to refill the bowls, as mentioned above,,, Should run 3 to 10 seconds, slow and stop as the floats shut off flow. You can test ride it this way, just be aware the relay is there to stop the pump if you crash...

 

If the pump does not run, verify 12v to pump and pump ground connection. If pump does not slow and stop, check fuel filter and/or lines for blockage/kinks.

 

Well. When I tried to drain the bowls, there was no gas in either bowl. I'm not sure if this is to be expected or not... it's been a few weeks since the bike died, and it died in the middle of a ride so I probably used at least some of the gas in the bowls. I've also ran it with starter fluid a few times, so maybe that sucked up some gas or something?

Either way. I left the drain screws open and hooked everything back up (freshly charged battery, etc.) and turned the key. Nothing happened, the pump didn't run (or, at least, I didn't hear anything and nothing came out of the bowl drain outlets). There is only about .3 volts going to the relay, which seems like not enough. The ignition fuse is fine. I'm at a loss. I think first order of business is figuring out why there's so little current going to the relay, any ideas before I just start poking around? Thanks

 

Where did you connect the negative lead of your meter to, when measuring 0.30 V at the "relay"?

Are you sure you had the meter set to correct range?

If you want to fail safe check out the circuit, you take the advice given in post #4, and trace along the path shown in the schematic. One has to isolate or disconnect other devices on the same circuit, since they could be malfunctioning, and pulling voltage low. I'd start with the engine Run (Kill) switch OFF, and the ECU disconnected, connect my meter negative lead to Batt -, Ignition switch ON, and verify sequentially that I had 12V+ at:
-Batt+
-Then ignition switch OUT, Red/Black

• fuse box IN, Red/Black
• ignition fuse OUT, Black
• Fuel pump relay IN, Black

If all that checked out OK, and I saw 12V all the way to the "relay", I'd

• Reconnect the ECU and test again.
• Turn the Kill switch ON and test again.

This would identify the source of the disconnection or reveal the part of the circuit that was malfunctioning.

 

Did you jump black to black-blue in the relay harness plug? Half a paperclip can work... This bypasses the relay and also is how you test the pump.

 

Remember:
key on engine off, fuel pump off
Key on engine on pump on <or more accurately key on engine turning (generating pulse signals to the ICM)

Pull the pump connector, black/blue to battery positive, green to battery negative.

Again the ICM is sending a GROUND signal to the RELAY (via y/bu) to enable the relay to send 12v (from bl wire from fuse to relay) to the pump (via bl/bu from relay to pump). I imagine you've check the fuse

The pump is always grounded, when the key is on the relay has power but the relay won't send power to the PUMP until the pulse generator tells the ICM to activate the coils via neg signal thereby exciting the fuel pump relay to send power to the pump.

If petcock open bowls open and pump supplied direct power no operation then yeah your pump is toast. If you verify those signals are sent to the relay and it's not sending power to the pump, the relay is bad. (Or connections in between obv)
If it's not receiving those signals check wiring from the relay at every connection point back to the ICM. If the icm isn't sending signal then look for signal from the pulse generator. If it's sending it (within the prescribed range) then your ICM is likely toast, if it's not sending it (or the pulses are out of tolerance) your pulse generator is likely toast.

That's the whole system brother from how it gets signal to how it's applied.

Hope this helps man

 

Thank you. This was helpful. I am not getting 12v at the pump or at the relay. I unplugged my ICM and I'm still getting less than a volt at the relay and about 2 volts at the pump regardless of whether the kill switch is on or off.

I am also not getting 12v on the blue/yellow wire out of the ICM, so the likely culprits are the ICM or the pulse generator. Unfortunately I have no idea how to test the pulse generator. It looks like it's sending blue and white/blue into the ICM, so I'm guessing I get a multimeter on those wires, but what am I looking for? The engine needs to be running, but should I be getting 12v? On which wire?

Thanks!

 

Do you have spark? If so the pulse generator is working.

Best to jump the battery with a non-running car battery to have adequate power for cranking and spark while testing.
But if it still fires up with starting fluid the spark and Pulse gen and ICU is working.

 

Hi all, thanks for the responses. I'm very confused because I just tried to check the pulse generator and I'm getting a reading of around 3 volts when the positive multimeter lead is on the blue wire coming out of the pulse generator and the negative lead is on the battery.

I'll run through how I'm testing everything, maybe someone can see something I'm doing wrong?

From fuel pump backwards:

• Fuel Pump: I get about 3v when measuring from the pump connector (positive multimeter lead) to the battery (negative multimeter lead on the negative terminal) when spinning the engine, but I noticed that when I stop spinning the engine the voltage very quickly spikes to about 15v. This might be a misread from the multimeter because it's so fast and only when I let off the starter button.
• Relay: When the positive multimeter lead is on Blue/Yellow and the negative is on the negative battery post, I get 12v. Same when the positive lead is on the black wire and the negative lead is on the battery negative. Nothing when the positive mm lead is on the blue/black wire and negative is on the battery negative. When I measure between the black wire and black/blue wire, I get next to nothing, even when I'm turning the engine.
• Fuse: Pulled the fuse, positive lead on the input side of the fuse holder and negative lead on the negative battery terminal. Reads about 12v.
• ICM: positive multimeter lead on the blue/yellow wire that comes out of theICM to the relay, and negative lead on the battery negative terminal. Reading about 3 volts.
• Pulse Generator: positive multimeter lead on the blue wire that comes out of the pulse generator and negative lead on the battery negative terminal. Reading about 3 volts.

Does this all look right? Thanks so much

 

Pulse generator is measured on the 2 wires and produces a very small pulsed voltage.
But if you have a spark forget the pulse generator.
If you have a spark on the front cylinder that means the signal is going to the fuel pump relay on the blue/yellow wire.
But you can double check that wire for continuity from coil to ICU and to relay.
And the black wire at the relay gets battery voltage from a fuse.

 

Hi all, just an update that it was the fuel pump. I wanted to say thanks to everyone who contributed, my bike is back up and running so I appreciate all of your help

 

Heyyyy!!! Cool stuff dude!!

 

Just like me. Was so confused. Checked this forum out and damm it was the starter switch the whole time.

 

Iv bn so lucky , never have i had a pump problem??? Gas filters, yes, lead wires yes, gas valve pluged!!! Yea even once forgot to turn gas valve on. Lol. But never thought about a pump. Every spring i put stp gas treatment in all my bikes. Some are new 2012. Some are old 1980.