only getting 9 volts at the fuel pump


Information and questions on GL1500 Goldwings (1988-2000)
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pugetsoundsailer
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only getting 9 volts at the fuel pump

Postby pugetsoundsailer » Thu Nov 19, 2015 5:10 pm



Just replaced the fuel pump on this 88 GL1500 I just picked up and I'm only getting 9 volts at the gas tank connectors and she's not firing up, I know this early ones have a relay and I've located it but unfortunately for me this bike came with a 1990 shop manual so I'm clueless how to proceed :shock:



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ct1500
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Re: only getting 9 volts at the fuel pump

Postby ct1500 » Thu Nov 19, 2015 5:33 pm

Many, many, many have nothing but trouble when replacing OEM fuel pump with a retrofit for cost cutting. :oops:

Lots more info needed, is this during cranking, what is voltage going into and out of relay, when does voltage appear, etc.

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MikeB
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Re: only getting 9 volts at the fuel pump

Postby MikeB » Thu Nov 19, 2015 5:54 pm

pugetsoundsailer wrote:Just replaced the fuel pump on this 88 GL1500 I just picked up and I'm only getting 9 volts at the gas tank connectors and she's not firing up, I know this early ones have a relay and I've located it but unfortunately for me this bike came with a 1990 shop manual so I'm clueless how to proceed :shock:


I don't think there is a nickels worth of difference between the '88 and '90 service manual.
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ct1500
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Re: only getting 9 volts at the fuel pump

Postby ct1500 » Thu Nov 19, 2015 6:28 pm

MikeB wrote:I don't think there is a nickels worth of difference between the '88 and '90 service manual.


88 and 89 models are different animals from the 90 and up's. Electrical, vacuum and component location-design chief among them.
Last edited by ct1500 on Thu Nov 19, 2015 6:33 pm, edited 1 time in total.
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MikeB
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Re: only getting 9 volts at the fuel pump

Postby MikeB » Thu Nov 19, 2015 6:30 pm

The power tot he fuel pump comes from the ECM (electronic control module) so I doubt that it will be battery voltage. Looking at the logic chart on page 3-8 of the 1994 service manual indicates that the Fuel Pump Control output momentarily jumps to battery voltage.

Unfortunately, I do not have an '88 manual.
Last edited by MikeB on Thu Nov 19, 2015 9:30 pm, edited 1 time in total.
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ct1500
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Re: only getting 9 volts at the fuel pump

Postby ct1500 » Thu Nov 19, 2015 9:11 pm

You mis-understand the diagnostic tree, it is testing and results. It is telling the mechanic to power the wire and result will be fuel pump to run.

Test D on the following pages is about repairing for wire continuity to the pump. The fuel pump is 12V supplied.
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MikeB
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Re: only getting 9 volts at the fuel pump

Postby MikeB » Thu Nov 19, 2015 9:38 pm

I see. So the next step would be to disconnect the pump connector C184 or C185 and apply battery voltage to the pump side of connector to see if the pump runs. If not, check the ground connection. I guess we should assume that there will be battery voltage at C184 or C185 connection and not 9 volts during normal operation. I wonder if that is where he is reading the 9 volts.
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virgilmobile
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Re: only getting 9 volts at the fuel pump

Postby virgilmobile » Fri Nov 20, 2015 1:26 pm

ct1500 wrote:
MikeB wrote:I don't think there is a nickels worth of difference between the '88 and '90 service manual.


88 and 89 models are different animals from the 90 and up's. Electrical, vacuum and component location-design chief among them.


I also agree with this.I have a 88.The fuel pump does not get power directly from the ignition like the 90 and up.It is a separate circuit.It is a special relay operated by the primary winding of the ignition system.
If you have just 9 volts feeding the pump,you'll need the correct schematic to locate the problem.I'd first suggest you measure direct across the battery posts while cranking the bike.Trust me,it will crank and have low volts.Should it drop below 10.8 volts,the bike will have a difficult time trying to run.A really good battery is a must. I'd also expect the pump to be able to operate from 10-15 volt range just fine.Below 10 volts at the battery and the spark and pump start to fail.

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virgilmobile
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Re: only getting 9 volts at the fuel pump

Postby virgilmobile » Fri Nov 20, 2015 2:24 pm

By the way.The 88 ignition system,coils and fuel pump relay are all powered on a black wire with a white tracer.




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