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Old 09-Sep-2014, 12:56 PM
knappers knappers is offline
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916 / 748 Tank Fuel pump

Only recently been able to get back to my project.
How lo.g should the pump run when the ignition is turned on?
Should say there in no fuel in tank, only had ignition on for 5 seconds
before killing it.
Could it be the relay, pugged a new generic one in with same result.
Engine fires upok pouring fuel downfuel line via funnel.
Thanks for any info 916 748 tank
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Old 09-Sep-2014, 03:08 PM
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dunlop0_1 dunlop0_1 is offline
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Pretty sure the pump pressure duration is controlled by the ECU. However, the fuel pressure regulator could also be u/s and running the pump with no fuel is not a good idea.
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Old 09-Sep-2014, 06:35 PM
knappers knappers is offline
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Sorry should have said, tank is on a bike with 2 valve engine and electrics no ecu. This is how it came to me looking very rough. Got some info/pics on my other "cafe" post from ages ago about the bike
Has the 2 pump wires under the tank connected up.
It was being ridden like this long before I got it but I have no other info. Trying to piece it back together.
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Old 09-Sep-2014, 09:39 PM
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DSC Region Organiser skidlids skidlids is offline
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If its wired as carb'd Supersport models the pump will run continuous and although the actual pump on a SS looks similar to the 748 pump the pressures are different
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Old 10-Sep-2014, 09:09 AM
knappers knappers is offline
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Thanks for info was aware of pressure difference.
It was used with this set up for quite a long time some years ago, when I bought it with other bits it had been left standing rotting a long time. The owner then didn't know anything about it.
What happens to the carbs when the float bowls are full? will the pressure overwhelm them?? Or does excess fuel return to tank? Was wondering if I could just use feed from tank to carbs and block off return.
I had heard DD boys had done this conversion but can't find anything much about it on forum.
Thanks
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Old 10-Sep-2014, 10:39 PM
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DSC Region Organiser skidlids skidlids is offline
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I have two DD bikes running the 916 tank and pump but as they are Class A fuel injected bikes they are designed to run 3 bar fuel pressure.
I have known a Carb'd bike with a return to run on 3-bar for a short while, but it wasn't tried long term so not sure how reliable it would be as any problems with the float shut off needles will soon have the engine full of fuel and there will be a greater chance of this if you didn't have a return.
If running a 916 style pump on a carb'd engine I would run a return and also look at changing the fuel pressure regulator in the pump housing to a lower spec one, not sure how low the regulators go possibly 2.5 bar, 2.2 bar and 1.8 bar
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Old 12-Sep-2014, 04:02 PM
knappers knappers is offline
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Thanks skidlids. Need to change pressure regulator as you say.
It's definitely been run carb'd with this 3 bar regulator before but I don't know the history of it.
What if fuel pump Is left disconnected, would that be enough to feed the carbs until fuel was too low in tank?
Just another quick question for you, because of space restrictions under rear seat unit where battery now resides. A YTZ14S is the biggest I can get in there. Bit down on AH but CCA are high (haven't got it yet just going on spec and dimensions). I ask because I believe you DD boys use smaller battery's. Better say this has a 95 engine in it think they require more oomph than the newer ones to start. Is that somthing to do with the gearing.
Thanks.

Last edited by knappers : 12-Sep-2014 at 04:52 PM.
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Old 21-Sep-2014, 07:46 PM
knappers knappers is offline
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Nearly there, need to sort out rest of electrics, get some clip ons. Straighten some bent bits, sort cosmetics. Looking for a light weight back wheel to match the front.
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