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XJ600 fuel pump just wont work :(

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adengtg
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Joined: 02 Sep 2017
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PostPosted: 14:29 - 08 Dec 2018    Post subject: XJ600 fuel pump just wont work :( Reply with quote

Hello everyone, ran into trouble and could use some help once again.

Ill put a little info at the top as to avoid as much confusion as possible.
The bike is a 1997 XJ600N. Uk model with electric fuel pump.
Bike was working fine when i bought it a few months ago and ive done nothing major related to the fuel system, electrics or engine. Only work ive done is putting restrictors on the inlet rubbers, replaced lots of mechanical parts (bearings, suspension etc) and tyres. Ive generally not touched the electrics.

Here goes:
Not really much i can say so ill just cut to the point. My fuel pump doesn't seem to be working. The OEM fuel pump was leaking on idle so i replaced it with an ebay "Direct replacement XJ600" pump which was a bit hit or miss it seemed, as in, it was very temperamental to when it would work (much like whats happening now).I put the OEM back on and was working again, clutch broke and bike is off the road so i left it there. came back to it a few days ago and fitted the new pump again and it wouldn't work. occasionally it would spray a bit of fuel out but then it would turn off again. put the OEM back on and that wouldn't work either. Occasionally, the pump(Either OEM or aftermarket) would work and the bike could start but after maybe 5-25 min it would run on 3 cylinders, then 2, then die and not start again.Occasionally i will come to the bike after leaving it a while, put in the key and start it up and it will work as normal.The pump is on for a few seconds and fills the carbs and the bike runs fine, the pump then occasionally ticks away to keep the bowls full and the bike is fine. then out of nowhere the pump decides its had enough and the carbs run empty. Tried to measure the output (V) of the two pin connector but couldn't get a reading as its too fiddly to get the probes in there. I then decided to rule out everything i could. I replaced all the fuses, fuel lines and replaced the fuel pump relay its self which has had no difference so far.

I've definitely got the fuel hoses the right way round and i've checked that fuel can actually flow through everything but at this point i'm out of ideas.

I'd really appreciate any ideas you guys have as to what i could check/try to get this running. AS always, if there's anything else you want to know that could help you i.e pictures or whatever i will do my best to get them to you.

Thanks very much for reading.
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Robby
Dirty Old Man



Joined: 16 May 2002
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PostPosted: 17:13 - 08 Dec 2018    Post subject: Reply with quote

Well either the pump is faulty, or the electrics are faulty.

There isn't much to the system in terms of electronics. The fuel pump relay supplies power to the pump when the ignition is turned on. This is a constant feed (usually).

The pump is a low pressure unit with a pressure sensor built in. If the pressure in the line is below x, it pumps. If the pressure is above x, it doesn't pump.

To test the pump:
1. Disconnect the pump outlet from the carbs, put it into a container.
2. Switch on the ignition. It should pump, and keep pumping.
3. Put your thumb over the end of the line and hold it there. After a little build up of pressure, it should stop pumping.
4. Take your thumb off the end of the line. It should pump again.
5. Repeat steps 3&4 until you're happy that it works.

I would probably do this test off a separate power supply - like a 12v battery wired direct to the pump, seeing as the wiring is also suspect.


If the pump behaves properly running off a battery, then the wiring is the next place to look.

1. Find a wiring diagram. Get familiar. There will be two main areas to look at. The feed from the main wiring loom to the pump relay, and the wiring from the relay to the pump.
2. Find the earthing points. The wiring to the relay probably uses a main frame earth shared with lots of other circuits. Even so, find it and clean it up.
3. The pump may have its own earth point. If this is heavily corroded, or the wire looks knackered, clean up the earth and/or replace the knackered wire.
4. If all of the earthing side looks fine, then look at the live side. You could have an internal break (pain in the arse, the wire looks fine but is broken inside the insulation), but if you are lucky you're find a wire which has chafed against something and is shorting out. Replace the offending section of wire.
5. If all of the earths look fine, and the wiring looks fine, and the relay is new, I would just replace the wires feeding the pump and see if that fixes it. So that's the live side to and from the relay, and the earth side from the pump.

Finally - make sure you know what voltage the pump is meant to have before you start fiddling with it. I have come across 9v fuel pumps on scooters before. I discovered it was a 9v pump after I put 12v across it and smoke came out.

Also, if all of this fails, it may work perfectly well on a gravity feed. A fuel pump on a carbed bike should only really be necessary when the fuel level in the tank is at or below the fuel level in the float bowls. This is only likely to be the last litre or two of reserve.
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WD Forte
World Chat Champion



Joined: 17 Jun 2010
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PostPosted: 17:36 - 08 Dec 2018    Post subject: Reply with quote

The diagram I have shows the fuel pump relay is activated by a signal from the
igniter unit
then a blue/black wire from the relay supplys the pump which is grounded via a black wire.

If I was unsure why it worked intermittently I'd hard wire the pumps blue/black
to a brown wire so it came on and stayed on with the igniton.

If it still played up, that would suggest the pump is suspect.
If it worked AOK that would suggest the igniter connection or cabling
was suspect
or
some conditon that triggered the igniter to cut off the pump power was
suspect.
or
supply to the relay was suspect

Check grounding continuity as well, all black wires at any point
on the bike should be at 0 ohms to battery neg terminal.
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adengtg
Scooby Slapper



Joined: 02 Sep 2017
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PostPosted: 18:02 - 08 Dec 2018    Post subject: Reply with quote

Robby wrote:
Well either the pump is faulty, or the electrics are faulty.



Also, if all of this fails, it may work perfectly well on a gravity feed. A fuel pump on a carbed bike should only really be necessary when the fuel level in the tank is at or below the fuel level in the float bowls. This is only likely to be the last litre or two of reserve.


Thanks very much for the reply. Just a quick question, how would it work on a gravity fed system? the carbs are downdraft and are lower than the fuel outlet on the tank entirely. Would it work if the actual fuel level is higher than the floats or would it not work at all?
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Tdibs
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Joined: 16 Jan 2015
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PostPosted: 14:25 - 10 Dec 2018    Post subject: Reply with quote

Yep could turn the tap to prime and I think reserve is still gravity and it will get you by for now if you really need it. (turn it back to on when not using it)
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andys675
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Joined: 08 Feb 2007
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PostPosted: 14:52 - 10 Dec 2018    Post subject: Reply with quote

when the pump gave up on my Vf500 I got a universal moprod pump from a car accessory shop, it worked for years afterwards
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Robby
Dirty Old Man



Joined: 16 May 2002
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PostPosted: 19:00 - 13 Dec 2018    Post subject: Reply with quote

adengtg wrote:

Thanks very much for the reply. Just a quick question, how would it work on a gravity fed system? the carbs are downdraft and are lower than the fuel outlet on the tank entirely. Would it work if the actual fuel level is higher than the floats or would it not work at all?


As long as the fuel level in the tank is above the fuel level in the carb float bowls, the carbs will fill. You really want the fuel level to be at least an inch higher in the tank than in the carbs.

You would also want to use a traditional (Off/On/Res) fuel tap to avoid overflowing past the needle valves. They might be fine, but the fuel pump works a bit like a fuel tap, stopping fuel flow when the bike is off. The needle valves in the carbs only need to be set up to resist a very low pressure.

Try to diagnose the problem first though.
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davebike
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Joined: 15 Nov 2013
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PostPosted: 09:51 - 14 Dec 2018    Post subject: Reply with quote

Most fuel pumps act as a tap no power /no feed
drain carbs leave drain open turn in inigtion you should get fuel though if not
Check you have 12v to pump if not trace if yes you have a duff pump !
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bikenut
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Joined: 21 Nov 2011
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PostPosted: 11:33 - 14 Dec 2018    Post subject: pump Reply with quote

Please could you post the exact wiring diagram for this bike, whioch will show if the fuel delivery system, an electric pump, has as "fuel cut off" sensor if the bike is down on its side, or does the system just merrily pump away if the bike is down on its side ?

Yes I know, but the tank may still have sufficient fuel and just keep merrily pumping away......

Wiring diagram will show the sensor or not.
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