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  #21  
Old 19th December 2017, 09:47 PM
The comb over kid's Avatar
The comb over kid The comb over kid is offline
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Biker.ie Member No. 35746 from Chinatown
2,579 posts since Jan 2016
Motorbike: Honda NTV 650
Modifications: Anti-Gravity field
Default Re: Bros 400 possible fuel pump issue

When the fuel pump went on my Honda CB-1 400 they replaced it with a Mini Cooper fuel pump cos it was half the price and did the job...they had to reverse the polarity in the cables tho
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  #22  
Old 19th December 2017, 10:06 PM
Blanka Blanka is offline
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1,216 posts since Jun 2007
Motorbike: fazer
Default Re: Bros 400 possible fuel pump issue

I bought an old bike and the points in the pump were worn out so the pump didn't run. With the pump stuck it was drawing a lot of current, probably for a long time because the bike still ran fine without the pump and the previous owner didn't noticed so by the time I got the bike the wiring to the pump was cooked. The extra resistance of the cooked wiring meant that even with the new pump in it wouldn't run due to the voltage drop caused by the added resistance in the cooked wiring. So the one problem turned into two problems. If I was you brosbiker I'd take up DavyH's offer and swap in a good pump then do a voltage drop test with the new pump in and see if you're getting the full 12V under load.
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  #23  
Old 22nd December 2017, 10:58 PM
H1500 H1500 is offline
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132 posts since Dec 2011
Motorbike: K1200S H1 500 R1100S FLHR
Modifications: Expansion pipes
Default Re: Bros 400 possible fuel pump issue

From the wiring diagram it looks like the pump ground is provided via the ignition box and is common with one of the coils. So the pump may not run without the engine running. If that is the case it would probably start without the pump and would run OK while the engine does not have any great load.

If the wiring diagram I have is correct then you will need to bypass the relay to check the pump operation. If the pump runs properly then it is most likely a relay issue.

It could also be a wiring issue and given that the pump and coil share a ground connection when the problem occurs you may have no spark. Hence I would check for a spark on both cylinders
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  #24  
Old 23rd December 2017, 01:23 AM
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Gixxer Gixxer is offline
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12,854 posts since Nov 2009
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Default Re: Bros 400 possible fuel pump issue

Originally Posted by H1500
From the wiring diagram it looks like the pump ground is provided via the ignition box and is common with one of the coils. So the pump may not run without the engine running. If that is the case it would probably start without the pump and would run OK while the engine does not have any great load.

If the wiring diagram I have is correct then you will need to bypass the relay to check the pump operation. If the pump runs properly then it is most likely a relay issue.

It could also be a wiring issue and given that the pump and coil share a ground connection when the problem occurs you may have no spark. Hence I would check for a spark on both cylinders
I just had a quick look at what I think is the right wiring diagram and I'm not sure the fuel pump shares ground with a coil. I can't see green going to coils? Maybe the fuel pump shares a ground connection with the spark unit, and the fuel pump relay is triggered from the spark unit?

Last edited by Gixxer; 23rd December 2017 at 01:29 AM.
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  #25  
Old 23rd December 2017, 08:43 AM
H1500 H1500 is offline
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Biker.ie Member No. 27876
132 posts since Dec 2011
Motorbike: K1200S H1 500 R1100S FLHR
Modifications: Expansion pipes
Default Re: Bros 400 possible fuel pump issue

Gixxer, I agree. I was a bit loose in my description. It is the control side of the relay that is switched by the spark unit. The pump has its own ground but the relay is ground side triggered by the spark unit. It is shared with one of the coils according to the wiring diagram that I have.
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