Eviljohn
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| posted on 10/8/17 at 06:54 AM |
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Bike carb conversion- wiring in fuel pump
Hi all. Hope you and your rides are well. As subject says, doing bike carb conversion on a 1983, 1043cc polo. Engine is pretty much stock. Had a facet
fuel pump and pressure regulator to start with but that was too much for bike carbs. Just overfuelled like crazy. Did some homework, switched to bike
fuel pump
Mounted it where i had the facet to start with, worked but not very well. Did some more homework, going to fit it down and further back, next to fuel
tank.
Question is: do i run extra wire from the bay to power it or can i tap into say, wiring from the rear washer bottle to power it? Currently have it
wired straight to the coil.
Thanks for stopping by and any guidance is much appreciated.
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craigdiver
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| posted on 10/8/17 at 07:05 AM |
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Car manufacturers are quite good at sizing wiring to suit the circuit (wire for washer bottle will be marginally sized to be able to carry the amps
needed taking into account wire resistances / voltage drop etc.). This is done to save weight & money. The fuel pump is relatively hungry for Amps
so if it were me I would run seperate wires for it with an inline fuse from the main switched supply circuit. If you use existing wiring at best you
will have an unacceptable voltage drop (pump wont run as it should) or you may burn the wiring out.
If it ain't broken, fix it anyway (just because).
Building - BMW powered Haynes Roadster/442E hybrid.
Volvo C30 T5 Polestar
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gremlin1234
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| posted on 10/8/17 at 09:14 AM |
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as cragdiver says, a new wire is best, you may want an explicit earth wire too
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craigdiver
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| posted on 10/8/17 at 09:25 AM |
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quote:
Originally posted by gremlin1234
as cragdiver says, a new wire is best, you may want an explicit earth wire too
I'll second that, probably not needed but neg earth connections on older cars are a pain in the ass, run a pair of cables to the pump for an
easy life!
If it ain't broken, fix it anyway (just because).
Building - BMW powered Haynes Roadster/442E hybrid.
Volvo C30 T5 Polestar
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SJ
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| posted on 10/8/17 at 10:24 AM |
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If you check the wiring diagram there may be suitable fused wires going to the back of the car already that aren't being used.
Stu
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Eviljohn
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| posted on 10/8/17 at 10:47 AM |
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Cool. Thanks guys. I already have a fuse and inertia switch wired before the pump, and earth wire coming from said pump.The fuse wire is quite meaty
but the rest of the wire is not so much. I'm really not sure what the value is of the rest of the wire i have so i imagine getting more would be
a good shout.
Out of curiosity, if the wire isn't rated to carry the correct load that the pump requires, would that cause the pump to intermitently cut out?
Had this issue when first fitted the bike pump. Thought it was either crap pump or blockage.
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craigdiver
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| posted on 10/8/17 at 11:27 AM |
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quote:
Originally posted by Eviljohn
Cool. Thanks guys. I already have a fuse and inertia switch wired before the pump, and earth wire coming from said pump.The fuse wire is quite meaty
but the rest of the wire is not so much. I'm really not sure what the value is of the rest of the wire i have so i imagine getting more would be
a good shout.
Out of curiosity, if the wire isn't rated to carry the correct load that the pump requires, would that cause the pump to intermitently cut out?
Had this issue when first fitted the bike pump. Thought it was either crap pump or blockage.
Depends whether there are any electronic controls in the pump or just a motor. If the wire was too small the resistance would increase rusulting in a
voltage drop. If the drop in voltage due to too small a wire is significantly then yes, it could cause the pump to cut out.
If it ain't broken, fix it anyway (just because).
Building - BMW powered Haynes Roadster/442E hybrid.
Volvo C30 T5 Polestar
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SJ
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| posted on 10/8/17 at 11:39 AM |
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Whee you say cut out what do you mean? Bike carb pumps don't run constantly. Once the float bowls fill the pump switches of due to the
pressure.
As the bowls empty and pressure drops they cut back in again.
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Eviljohn
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| posted on 10/8/17 at 02:20 PM |
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Switched from facet and fpr to bike pump. When i first switched, had bike pump mounted on inside wing/suspension tower. Ran smoother than with facet
but kept cutting out. Would start pumping again if tapped. Originally thought that was alternator issue or position of pump. Or the fact it was a
cheap, generic ebay pump.
I think, and feel free to correct me if you know better, the carbs i have, (cbr400, nc29 apparently,) have two inlets for fuel in, between the pairs
of carbs, and a fuel return. I've downloaded the haynes pdf for cbr400 and can't find anything in there to confirm.
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David Jenkins
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| posted on 10/8/17 at 02:56 PM |
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I have CBR600 carbs, and they have the 2 petrol inlets, one between each pair of carbs. There's no return outlet though - the float valve shuts
off the flow, and the fuel pump senses the restricted flow and cuts off. Note that I'm guessing that the CBR400 carbs are similar!
Coming back to the original question - I would run a separate new wire to the pump, with its own fuse (that's what I did, anyway). Makes
subsequent fault-finding so much easier, if the pump decides not to work.
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Eviljohn
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| posted on 10/8/17 at 03:14 PM |
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I have same inlets. Reason for concluding two inlets and fuel return was by blowing into either inlet, (using new, clean hose,) air came out of return
line. Will not come out of inlets if you blow into what i think is the fuel return. Assuming some kind of one way valve goin on. Also have an egr
inlet too. Would post pics but haven't figured that out yet.
I will get some more cable and use that. Thank you.
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