fuel pump relay?


Information and questions on GL1200 Goldwings (1984-1987)
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18xray
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Motorcycle: 1984 GL1200I Interstate

fuel pump relay?

Postby 18xray » Wed Apr 02, 2014 11:55 am



re '84 GL1200I - I am getting no power to the fuel pump. Both lines feeding the relay show positive power going into the relay but nothing comes out. The coils seem to test OK as does the ignition control. The fuel pump runs when the relay is bypassed. I replaced the relay that came with the bike with a used one which corrected nothing. I obtained a new relay and still get nothing out to the fuel pump. Is it possible I possess 3 bad relays or is it something else? Note: When I bought the bike, it did not run. I am not a mechanic (although was a Huey crew chief once) but have followed instructions provided in both Haynes and Clymer. I'm ready to fire her up...if I can get fuel to the carbs and to get fuel to the carbs, I need to get power to the fuel pump.



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WingAdmin
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Re: fuel pump relay?

Postby WingAdmin » Wed Apr 02, 2014 11:58 am

What did you do to bypass the relay? If you pull the relay out, and short the contact connectors in the relay socket, does the pump run?

18xray
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Re: fuel pump relay?

Postby 18xray » Wed Apr 02, 2014 12:10 pm

I just went out and retested. I ground the pump (green wire). When I connect the black wire (before relay) to the pump, it works. When I connect the blue/yellow wire to the pump, I get nothing. Where it gets weird is that a multimeter indicates power from BOTH the B and BL/Y. Is my bike haunted?

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Re: fuel pump relay?

Postby WingAdmin » Wed Apr 02, 2014 1:04 pm

18xray wrote:I just went out and retested. I ground the pump (green wire). When I connect the black wire (before relay) to the pump, it works. When I connect the blue/yellow wire to the pump, I get nothing. Where it gets weird is that a multimeter indicates power from BOTH the B and BL/Y. Is my bike haunted?


OK. The pump's green wire should be connected to ground at all times. The black/blue wire on the pump needs to have +12V in order for the pump to operate.

On the relay, there are three wires: blue/yellow, black, and white.

Black is supplied with +12V when the bike is on.
White is connected to the pump's black/blue wire.
Blue/yellow is the relay actuation line.

When you short the black and white wires together, the pump should operate.

Blue/yellow comes from the ECU. It is tied to the primary of one of the coils, and will have +12 volts on it when the bike is switched on. The ECU will pulse it every time it wants a spark to occur. It will lose its 12 volts if the kill switch is switched to "kill" instead of "run". It's not clear in the diagram, but I assume the relay coil sources its power from the black wire, and when the Blue/yellow wire is grounded, the relay actuates, supplying power to the pump through the white wire. I would not attempt to manually ground the blue/yellow wire, as you could damage the ECU by doing so.

Because of this arrangement, the relay will ONLY switch the fuel pump on if the engine is being cranked or is running.

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Re: fuel pump relay?

Postby 18xray » Wed Apr 02, 2014 1:29 pm

I've been told that the pump should "prime" when power is commenced prior to cranking. It does not. That said, it also is not feeding power to the pump when cranking.

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Re: fuel pump relay?

Postby WingAdmin » Wed Apr 02, 2014 2:56 pm

18xray wrote:I've been told that the pump should "prime" when power is commenced prior to cranking. It does not. That said, it also is not feeding power to the pump when cranking.


When you turn the bike on, pull the relay out, and short the terminals in the relay socket together that are connected to the black and white wires, does the pump run?

18xray
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Re: fuel pump relay?

Postby 18xray » Wed Apr 02, 2014 3:10 pm

Yes. It does not when shorted to the bl/y, even though the bl/y reads the same as the black on the multitester! It makes absolutely no sense whatsoever!!!

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virgilmobile
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Re: fuel pump relay?

Postby virgilmobile » Wed Apr 02, 2014 3:33 pm

WingAdmin wrote:
18xray wrote:I've been told that the pump should "prime" when power is commenced prior to cranking. It does not. That said, it also is not feeding power to the pump when cranking.


When you turn the bike on, pull the relay out, and short the terminals in the relay socket together that are connected to the black and white wires, does the pump run?


Note: On the relay....black is switched 12 volts..
Blue/yellow may have volts on it....It's the pulse wire going to the ignition coil and feeds the relay circuit to trigger it to operate...
There's not enough power avaiable on the blue/yellow wire to operate the pump....it's the back side of the ignition coil....That pump takes a few amps to get it to pulse...
The white wire from the relay goes to the pump.With the pump unhooked,you will never measure any volts on this wire,cranking or not....

The only pumps that "auto prime" were ones controlled by a ECM module...My 88 has a 'in tank' pump..it cycles on for about 2 seconds every time the ignition is turned on...
The only other wing that might do this is the fuel injected bike..
I assume that yours is not and has the 'pulse' type pump on the right side of the engine...
There will be volts on the pump wire ONLY if the 'relay' is being pulsed by the ignition coil and then ONLY if the pumps internal switch is closed...
If the pump is pressurized the wire feeding it will have no volts on it....
You can see the switch operate by removing the rear cover of the pump....
My 1200 would show volts on the pump wire only when the pump pulsed (with the engine running) and it was very brief....
The relay appears to be a load switching circuit,only passing power on demand....

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WingAdmin
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Re: fuel pump relay?

Postby WingAdmin » Wed Apr 02, 2014 3:52 pm

18xray wrote:Yes. It does not when shorted to the bl/y, even though the bl/y reads the same as the black on the multitester! It makes absolutely no sense whatsoever!!!


The reason the bl/y reads the same as black is because it has +12v that you are reading through the ignition coil - i.e. the ECU is supplying 12v to one side of the coil, the other side of the coil is connected to the bl/y, which has an open connection at the ECU. Therefore you read 12v through the coil, but the ignition coil won't pass anywhere near enough to actuate the fuel pump.

The ECU pulses this line to ground in order to cause the coil to spark. At the same time, this grounds the relay coil, closing its contacts and causing the fuel pump to operate. The pulses are too quick to read on a multimeter, you need a scope to see them. It is the pulses to ground that actuate the relay.

If all four spark plugs are firing, you know the ECU is working. You know the wire is OK, because you can see 12V on it. You know the pump is working. So the only thing left, and I hate to say it...is the relay.

18xray
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Re: fuel pump relay?

Postby 18xray » Wed Apr 02, 2014 4:05 pm

Could the coil(s) be providing inadequate power? I'm reluctant to say it is the relay, having tried one brand spanking new! BTW, the bike is carbureted, with the pump on the right side.

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virgilmobile
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Re: fuel pump relay?

Postby virgilmobile » Wed Apr 02, 2014 4:24 pm

The coils do not provide power for the pump...that's the black wire...the coil wire only provides a signal to the relay that it's OK to operate the pump.

The pump must be De-pressurized...If it's holding any pressure on the outlet,the pump will not cycle.

If there's any pressure on the outlet of the pump going to the carbs,the switch inside the pump will be open and no volts will be shown on the pump wire....
When the carbs fill up and the pressure on the line stays up,the pump is shut down...
As the bike uses fuel,the floats open the needle valves allowing more fuel in and it drops the fuel line pressure...just before it reaches zero,the switch trips in the pump and it pulls the pump plunger back to pressurize more gas in the line....this action(switch) lasts a fraction of a second...at this moment is when you would see volts on the pump wire.

My gl1200 would pulse the pump only once every 6-8 seconds at the most when at a idle...

You should be able to disconnect the pump from the carbs,crank/start the engine with the kill switch in the run position and the pump should pulse.Capture the gas safely. :)

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artgrantz
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Re: fuel pump relay?

Postby artgrantz » Thu Apr 03, 2014 7:07 pm

I no longer have a GL1200 maintenance manual, it went when I sold the bike years ago, so this is from memory, I hope it's accurate.
The ECU receives a signal from one of the pulse generators that tells it the engine is rotating. It uses this signal to enable the fuel pump.
Follow the thin cable coming out of the timing belt cover until you reach the connector, mine was under the fairing. Disconnect it and check the resistance of the pulse generators. If one reads infinity or very high resistance it may be causing your problem.
Good luck.




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