1998 GL1500 low voltage at fuel pump


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Peterson182
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1998 GL1500 low voltage at fuel pump

Post by Peterson182 »



I have a 1998 Gl1500 that quit running out on the road. I hauled it home and have found that I am only getting 8.5 volts out of the ECM to the fuel pump and it doesn't run. I disconnected the wires to the pump and jumpered 12 volts to it and it run OK. Can anybody tell me why I'm only getting 8.5 volts out of ECM. I measured this at the connector on the ECM and at the fuel pump while trying to start the bike.

Thanks for all your help, Donnie


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virgilmobile
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Re: 1998 GL1500 low voltage at fuel pump

Post by virgilmobile »

I'm mobile at the moment so I can't get to the schematic.I'll post later tonight.I wonder if it uses a relay to power the pump and the ecu runs it?Relays can be swapped around as long as they are the same type.
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Re: 1998 GL1500 low voltage at fuel pump

Post by WingAdmin »

I am looking at the fuel system schematic right now. The fuel pump is powered directly from the ECM (pin 21, black/blue wire). When you measure the voltage at the pump, are you checking against ground, or against the green ground wire?

I would first check the black/blue wire right at the ECM, measure the voltage there against a known good ground (i.e. battery negative terminal). If you are still getting low voltage, then you know the ECM is at fault. If you get a proper 12 volts there, then you know the problem is in the harness/connectors in between the ECM and the fuel pump, or a bad ground at the fuel pump.

If you do find the ECM is at fault, you could jury-rig it by putting a relay off the ECM wire, and using it to switch +12V to the fuel pump - as long as the relay will pull in at the low voltage the ECM is supplying. I wouldn't look at that as a long-term solution however.
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virgilmobile
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Re: 1998 GL1500 low voltage at fuel pump

Post by virgilmobile »

Here's a thought. :cry: If the fuel pump is binding up , it will draw excessive current and the voltage would drop.Applying direct 12volts from the battery(15 amp capable wiring)could bully the pump to run.I would suspect this could happen.One test could be to hook up another load to the ECM(1to2amp)to verify if the ECM has the grunt to run it at 12volts or use a dc ammeter in line.
Peterson182
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Re: 1998 GL1500 low voltage at fuel pump

Post by Peterson182 »

Thanks for all your suggestions. I tested the green wire at the fuel pump to the negative of the battery and found .1 ohm, this seems OK to me. I tested the voltage at the connector on the ECM to the neg. of battery during start and got only 8.5 volts. Disconnected the fuel pump wire at the pump and tested again and still only 8.5 volts. Took test probe from the ECM connector and connected it to the wire going to the fuel pump at the pump, 8.5 volts. Does this mean the fuel pump is not loading the voltage down?
Is there anything else that feeds into the ECM to tell it how much voltage to put out? I'm thinking of getting a new ECM.

Thanks again for your help.
Donnie
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virgilmobile
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Re: 1998 GL1500 low voltage at fuel pump

Post by virgilmobile »

Your test method is good.I proved that the pump is not drawing so much current that it's overloading the ECM.It's starting to sound like the ECM is bad.
Before you condemn it,test just one other thing.Measure the volts going to it.Use your test meter directly to the pin2 wire (bk/wh) and the ECM ground pin 13 (green).Then test green to pin 26(yellow/blue).With the key on they should go to 12 volts.
This is the power input line from the kill switch,ignition switch and ignition/cruise relay.


Peterson182
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Re: 1998 GL1500 low voltage at fuel pump

Post by Peterson182 »

Hi, I'm back. New job put me out on the road. I tested those points you posted and this is the results.
Ground test was green wire to neg of battery read .2 ohms. Ignition input test was BLK/WHT wire to Green at ECM connector read 11.5 vdc. Ignition coil test was YEL/BLU wire to green at ECM connector read 11.5 vdc. I checked the supply voltage at the battery read 12.25vdc. I'm not sure what to check next :?:

Thanks for all your suggestions and help Virgilmobile and the rest of you
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virgilmobile
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Re: 1998 GL1500 low voltage at fuel pump

Post by virgilmobile »

Sorry,but there's not anything left to test that I can come up with.
You verified there is 12 volts on all the inputs and 8 volts going to the pump(with or without it hooked up).
The fact that you can apply 12 volts to the pump and everything runs,indicated that all the other functions of the ECM are working.
You have 2 options.The best is to replace the ECM.

NOTE:The second,although will void your warranty and cause a possible safety issue,is to operate the pump from a relay.Fused separately and operating the relay from the ignition circuit(bk/wh pin 2).I can provide details if you need.
It's not factory approved,but neither is putting car tires on bikes.

I would thing that as long as the pump will shut off if the angle sensor trips,kill switch is turned or ignition fails,it should be safe,And wiring it to bk/wh pin 2 will accomplish this.

NOW if anyone has any more info,please say so.

>>>>>>As always Jim , Should you or any of your crew be caught or killed...the secretary will disavow any knowledge of your actions<<<<<<<<<< :)

Use your best judgment please.
Peterson182
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Re: 1998 GL1500 low voltage at fuel pump

Post by Peterson182 »

Knowing my kind of luck, maybe I could hook up a test fused switch with 12 vdc to the pump and see if it will even start. Should I disconnect the wire from the ECM at the fuel pump or leave it connected ?
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Re: 1998 GL1500 low voltage at fuel pump

Post by virgilmobile »

Well there I go making assumptions.I guessed that when you jumped 12 volts to the pump in your first post,that the bike started right back up. :mrgreen: By all means get power to the pump and try to start it.I'm hoping at this point that the rest of the ECM is still OK.

I'd cut the wire.Leave enough off the plug to be able to hook it back up.Tape off the ECM wire.Just add a inline fuse and bare the ignition wire.Wrap it around and tape it off.

Check all the functions of the bike.
Here's a diagram


Peterson182
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Re: 1998 GL1500 low voltage at fuel pump

Post by Peterson182 »

I was looking the ECM over for let the smoke out damage and notice there is a vacuum line hooked to the front of it, does anybody know what it controls? I'm getting things together and hookup your circuit tonight after work. Thanks and keep those suggestions coming.
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virgilmobile
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Re: 1998 GL1500 low voltage at fuel pump

Post by virgilmobile »

Point of interest....I'm not sure about the schematic I'm using.
Another mentioned that the pump runs direct from the ECM,The schematic I have shows a relay.I can't guarantee the wire number or color code now.I can't seem to get any other info from anybody if my schematic is correct or this other info is...

Verify that wire that goes to the pump before you cut it loose from the ECM.

I'll only guess on the vacuum line....I'm getting gun shy about the service info I'm getting....It may be similar to the 1200 where the timing is fully electronic controlled by the ECM.On the 1200 a vacuum line goes to the ECM and the bike uses that vacuum information to electronically change the timing in 4th and 5th gear.
The 1100 used a vacuum canister to mechanically change the timing in each gear.
Even with it unhooked,the bike should still start.
look through this post.It doesn't directly relate to your problem,but it does talk about a fuel pump wiring.....viewtopic.php?f=6&t=9415
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Re: 1998 GL1500 low voltage at fuel pump

Post by MikeGoldwing1992 »

I had exact situation Fuel pump not running 8.5 volts at the terminals. So after visiting the schematic I started tracing the voltage from the battery to the pump and what I found was the Kill Switch up on the right handle bar (Off Run Off switch) was making intermittent contact as well as a voltage drop across it. The beautiful thing about it is you can open up the control assembly and take apart the switch and clean up the contacts inside. and then reassemble. it took me less than an hour. One note the switch comes apart from inside the control assembly. don't try to pry the switch control knob from out side it doesn't come apart that way. Also while you have the control assembly apart you can spray some silicone on the internals of the cruise control button and get it working properly again too. Once I cleaned up the contacts I no longer had a voltage drop across the switch and I had 12 volts at the pump. One other thing I noticed is by fixing this switch the bike started up a whole lot better. The kill switch also supplies power to the ECM, so I am thinking by the ECM getting the correct voltage all the functions of the ECM can work correctly. The ECM controls the coils and the timing of the spark . My bike went from running like a old car to the Honda motor we all love and know. Good Luck
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Re: 1998 GL1500 low voltage at fuel pump

Post by MikeB »

Although the original post is nine yers old, your find with the RUN/STOP switch is a good one. I am hoping that the original poster has it fixed by now.
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Re: 1998 GL1500 low voltage at fuel pump

Post by Elmobile »

Thanks for "rejuvenating" this old post...
I have added it to my winter list. Another good freebie... :D


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