1983 Honda Shadow vt750 Fuel problem - Honda Shadow Forums : Shadow Motorcycle Forum

radiusglass · 06-30-2012, 08:21 PM

Ok I have been reading a lot on this forum. Very informative this site is. I have two problems that might be related and hope I can just use one post. I purchased a 1983 honda shadow vt750. I just loved the bike but I knew that it had wrong battery. Bought the new T battery and ever since then I have had gremlins. My issue now is with the fuel pump relay I think. First prob is that when I turn the key on, I am getting 12 volts to the pump staight up. The pump takes right off without even trying to crank it. Now I shouldn't complain since it is working but my main concern is the wire going to the pump. When I ohm the black wire to the green wire with key off I get no reading but when I turn the key on I get continuity. Why would them wires be reading as if they was connected with the key on. I would think that the green wire is ground? So I am concerned that this will burn my pump up. Any thoughts?

93gc40 · 06-30-2012, 08:33 PM

First mistake was going back to the stock battery. The rectagle "smaller" battery it had is a common UPGRADE. Did you fully charge the T battery, min 12 hours at 2amp.

Fuel issue Is that green wire connected at it other end? Could be bad relay, IDK, don't have relay. Mine is triger'd by CDI box

presly · 07-01-2012, 04:41 AM

The fuel pump is electrically-wise a coil with a moving core. It winded with a quite fat wire - thus it's normal to read continuity with an ohm-meter.

radiusglass · 07-01-2012, 07:48 PM

Thanks for the info. I should have done a better job at describing the problem with the wires. Without the pump hooked up this is what I get. With the key off I can meter the green wire to chassis and get continuity. With Black/blu wire I get nothing. With key on, I read green wire to chassis and get 12 volts and black blue wire I get 12 volts. I have a pretty firm grasp on electronics but I deal with mostly 480 volts and stuff like that. I was assuming that the green wire was ground and seeing how I haven't received my book yet. I am having a hard time chasing down that green wire with the pdf I have. Printer issues. Can anyone tell me where that green wire comes from. I think that I have a slight electrical problem coming from the key switch or from there to where it meets the green wire.

presly · 07-02-2012, 07:02 AM

I can attach or send you wiring diagram of your (my

) bike (just tell your preffered file format - pdf, cdr, dwg - you name it). The black/blue wire is comming from the Fuel Cut Relay, which is controlled by CDI output to ignition coil1 (blue wire). Green is definitely the constant ground wire. Seems like somebody has jumped the FC relay in your case. This isn't always bad, since when bike hasn't been ridden for a long time the carbs dry out, and one needs to turn ignition key several times in order to fill them with fuel, but when the FC relay is bypassed this isn't necessary. The downside is if the bike has been dropped down and engine has stopped, the fuel pump is still delivering fuel, which could lead to unpleasant consequences...

radiusglass · 07-02-2012, 11:22 AM

Yeah thanks pdf is fine. The fuel relay believe it or not is not jumped. I have ride it and the old fuel pump died. But somehow that relay is opened up so that it is on all the time. Bad thing no I agree as long as I don't lay her down. My big concern is reading 12 volts from the green wire and from the black/blue wire. I can even get a closed signal from them with key on and I concerned that might have damaged the stuff I have already replaced and I don't wanna damage the new stuff. From what I can tell, that green wire is coming from some sorta red looking relay. I unhooked that relay to get a true reading.

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superdiver · 07-02-2012, 11:34 AM

Maybe if you took some pictures with your phone to accompany the descriptions it might help?

radiusglass · 07-02-2012, 12:11 PM

I will do that. Thanks
Does the pump running all the time strain the carbs

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superdiver · 07-03-2012, 11:58 AM

MY pump is pressure dependente.

If you have it all hooked up you can hear my pump run/click one to 3 times, then its silent (its a clicking sound, cuz all it is is a solenoid on my bike). if you remove the fuel line somewhere and let the fuel just run out, the pump clicks very quickly as it pushes the fuel thru the lines, once the fuel is out it clicks even faster as its just pushing air...

Not sure if your pump is the same or not....

radiusglass · 07-03-2012, 03:55 PM

Well yeah it is suppose to get a signal from the ignition coil I think and will pump faster as your rpm's go up or the faster you go. My relay has stuck open and I have heard members on here jumping the wires so that they pump does run all the time. I guess what I am asking is what would the long term effects on the bike be. I am ordering a relay from ebay but until thn will it be good to drive and do no damage.

06-30-2012, 08:21 PM	#1 (permalink)
radiusglass Junior Member Join Date: May 2012 Posts: 13	1983 Honda Shadow vt750 Fuel problem Ok I have been reading a lot on this forum. Very informative this site is. I have two problems that might be related and hope I can just use one post. I purchased a 1983 honda shadow vt750. I just loved the bike but I knew that it had wrong battery. Bought the new T battery and ever since then I have had gremlins. My issue now is with the fuel pump relay I think. First prob is that when I turn the key on, I am getting 12 volts to the pump staight up. The pump takes right off without even trying to crank it. Now I shouldn't complain since it is working but my main concern is the wire going to the pump. When I ohm the black wire to the green wire with key off I get no reading but when I turn the key on I get continuity. Why would them wires be reading as if they was connected with the key on. I would think that the green wire is ground? So I am concerned that this will burn my pump up. Any thoughts?

06-30-2012, 08:33 PM	#2 (permalink)
93gc40 Senior Member Join Date: Nov 2008 Location: Visalia, CA Posts: 4,343	First mistake was going back to the stock battery. The rectagle "smaller" battery it had is a common UPGRADE. Did you fully charge the T battery, min 12 hours at 2amp. Fuel issue Is that green wire connected at it other end? Could be bad relay, IDK, don't have relay. Mine is triger'd by CDI box __________________ 93 VT1100C Harley Killer (1150cc), VH Exhaust, 2mm sleeved and bored, Modified Heads and Valves, Adjustable Timing, Touring Seat, Baby Apes, Metzlers

07-02-2012, 07:02 AM	#5 (permalink)
presly Member Join Date: Jun 2012 Location: Sofia, Bulgaria, EU Posts: 44	I can attach or send you wiring diagram of your (my ) bike (just tell your preffered file format - pdf, cdr, dwg - you name it). The black/blue wire is comming from the Fuel Cut Relay, which is controlled by CDI output to ignition coil1 (blue wire). Green is definitely the constant ground wire. Seems like somebody has jumped the FC relay in your case. This isn't always bad, since when bike hasn't been ridden for a long time the carbs dry out, and one needs to turn ignition key several times in order to fill them with fuel, but when the FC relay is bypassed this isn't necessary. The downside is if the bike has been dropped down and engine has stopped, the fuel pump is still delivering fuel, which could lead to unpleasant consequences... Last edited by presly; 07-02-2012 at 07:10 AM.

07-02-2012, 11:34 AM	#7 (permalink)
superdiver Senior Member Join Date: Mar 2012 Location: Ketchikan, Alaska, salmon capital of the world! Posts: 912	Maybe if you took some pictures with your phone to accompany the descriptions it might help? __________________ My new to me 1984 VT700C

07-02-2012, 12:11 PM	#8 (permalink)
radiusglass Junior Member Join Date: May 2012 Posts: 13	I will do that. Thanks Does the pump running all the time strain the carbs Sent from my SPH-D710 using Motorcycle.com Free App Last edited by radiusglass; 07-03-2012 at 09:42 AM.

07-01-2012, 04:41 AM	#3 (permalink)
presly Member Join Date: Jun 2012 Location: Sofia, Bulgaria, EU Posts: 44	The fuel pump is electrically-wise a coil with a moving core. It winded with a quite fat wire - thus it's normal to read continuity with an ohm-meter.

07-01-2012, 07:48 PM	#4 (permalink)
radiusglass Junior Member Join Date: May 2012 Posts: 13	Thanks for the info. I should have done a better job at describing the problem with the wires. Without the pump hooked up this is what I get. With the key off I can meter the green wire to chassis and get continuity. With Black/blu wire I get nothing. With key on, I read green wire to chassis and get 12 volts and black blue wire I get 12 volts. I have a pretty firm grasp on electronics but I deal with mostly 480 volts and stuff like that. I was assuming that the green wire was ground and seeing how I haven't received my book yet. I am having a hard time chasing down that green wire with the pdf I have. Printer issues. Can anyone tell me where that green wire comes from. I think that I have a slight electrical problem coming from the key switch or from there to where it meets the green wire.

07-02-2012, 11:22 AM	#6 (permalink)
radiusglass Junior Member Join Date: May 2012 Posts: 13	Yeah thanks pdf is fine. The fuel relay believe it or not is not jumped. I have ride it and the old fuel pump died. But somehow that relay is opened up so that it is on all the time. Bad thing no I agree as long as I don't lay her down. My big concern is reading 12 volts from the green wire and from the black/blue wire. I can even get a closed signal from them with key on and I concerned that might have damaged the stuff I have already replaced and I don't wanna damage the new stuff. From what I can tell, that green wire is coming from some sorta red looking relay. I unhooked that relay to get a true reading. Sent from my SPH-D710 using Motorcycle.com Free App

07-03-2012, 11:58 AM	#9 (permalink)
superdiver Senior Member Join Date: Mar 2012 Location: Ketchikan, Alaska, salmon capital of the world! Posts: 912	MY pump is pressure dependente. If you have it all hooked up you can hear my pump run/click one to 3 times, then its silent (its a clicking sound, cuz all it is is a solenoid on my bike). if you remove the fuel line somewhere and let the fuel just run out, the pump clicks very quickly as it pushes the fuel thru the lines, once the fuel is out it clicks even faster as its just pushing air... Not sure if your pump is the same or not.... __________________ My new to me 1984 VT700C

07-03-2012, 03:55 PM	#10 (permalink)
radiusglass Junior Member Join Date: May 2012 Posts: 13	Well yeah it is suppose to get a signal from the ignition coil I think and will pump faster as your rpm's go up or the faster you go. My relay has stuck open and I have heard members on here jumping the wires so that they pump does run all the time. I guess what I am asking is what would the long term effects on the bike be. I am ordering a relay from ebay but until thn will it be good to drive and do no damage.

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