Fuel pump fuse blows

Hey guys. Ive got a fx 450 2010 model that i really get to enjoy. I had a fuel problem a few months ago and replaced the fuel pump and it ended up being a fuel pressure regulator! Yeah. I wonder how many peeps have ran into that problem! Anyway, i was riding with my nephews holding up on the group and i was putting the bike in a slow strain and then all of a sudden my fuel pump fuse blew. I replaced abt 7 fuses before i almost made it back home. I was expecting to see an chaffed wire somewere or a bad connection. Does anybody have any ideas on were i need to be searchin?

I have the FE 450, so I don't know whether the wiring's exactly the same but I've had a look at the manual and the fuel pump wiring does look the same as far as I can see. I had various problems with the pump, though it never actually blew the fuse so yours may be something different, but FWIW...

The pump failed and left me stranded. It was definitely the pump itself as there was power at the plug but the pump didn't run. This didn't blow the fuse but there must be a chance that it could if the pump was seized or shorting internally, so even though you have a relatively new pump there is a chance the pump itself could be the problem.

After I had the pump replaced, it ran ok for a couple of hours then stopped and left me stranded again on the next ride. This time there was no power to the pump. Turns out that when the subframe was off to replace the pump it had disturbed the wiring loom and the power to the pump was going through a joint that was badly corroded, and it actually came apart and the two bits were just resting together and eventually moved and lost contact.

The joint that failed has 3 white-red wires joined together. 1 comes back from the voltage regulator (near the headstock), 1 from the power relay and the other from the fuel pump fuse, and the joint's buried deep in the loom where it comes down from the battery area between the tank and the subframe, just aft of the point where it passes the vertical part of the frame (so it's right alongside the rear shock). It was corroded so bad the wires just fell apart, but the joint was still covered in heatshrink sleeving (probably the only thing that kept it together this long) so it was in no danger of shorting on anything and in any case it's upstream of the fuel pump fuse so it wouldn't blow that. If anything, the main fuse would go so it doesn't seem likely you have the exact same fault.

Your fault is likely to be in one of the following places:
* In the fuse box somewhere near Fuse 2 (fuel pump).
* On the black-blue wire between Fuse 2 (fuel pump) and pin 14 of the ECU.
* Inside the ECU (i.e. the electronics have failed).
* On the blue-green wire between pin 15 of the ECU and the fuel pump plug. NB: The book says this is blue-green on both the FE and FX, but it's white-blue on my FE. Easy enough to check as you can see it where it goes into the plug at the fuel pump.
* A short in the fuel pump itself.

I'd take out the fuel pump fuse and unplug the ECU and the fuel pump so you can test for a short to ground on each section of wire in turn, wiggling the wires around while you test as it sounds like this is an intermittent problem so it may only be there when the wire's in one position.

If you can't find a problem on the wires, test the resistance of the pump. Should be 1.0 to 1.8 ohms at 20C/68F. Even if that's ok it doesn't guarantee the pump's not faulty as it could be jamming up when it tries to turn which would draw more current on load, but you'd need something like a clamp meter to check that.

If everything else looks ok it could be the ECU but that would be tricky to test as the short might only be there when it's powered up which means having it plugged into the bike and that makes it hard to isolate so you're just testing the ECU as you can't get at the pins without a specialised test harness. Easiest way might be to borrow another ECU and see if it solves the problem.

Good luck!

Thank you for the input Petem. When it comes to wiring almost anything is worth a try!

Ive forgotten to mention that ive blown about 7 fuses and during one of the tries, the starters fuse blew.

If the main fuse went it could mean that the fault was further upstream before the fuel pump fuse, but since you've had the fuel pump fuse blow 7 times it's most likely the problem is in one of the places I suggested, after that fuse. Normally the fuel pump fuse would then blow first as it's lower rated (10A rather than 20A) so the main fuse wouldn't blow, but you might have got a bad 10A fuse that one time which didn't blow fast enough for some reason, so the main fuse went instead. Or maybe you were out of 10A fuses and put a 20A one in the fuel pump position, or put the wrong type in by mistake?

Or did what I have seen done when someone has run out of fuses - bridge it with tin foil or even a nail/screw! Probably not the best idea that one though unless you like your bike to make pretty firework displays with lots of sparks and smoke... :mrgreen:

Hahaha. Wouldnt that make some things interesting!!! Im sure i used a 20 on more than one of those rounds of fuses! If i just put a fuse in and tried to start it it would run then blow, If i let it sit for a short while then put a fuse in, it would make it a little further. Should i swap the tank w a known good setup an see if the fuses still blow or just jump into tracing the whitte w red wire? Im leaning towards the wire but dang i sure hate dealing w electronics!

If you know someone who's familiar with using a multimeter it shouldn't take too long to check out those wires I mentioned, so I'd look at those first. But I don't think your problem is in the white/red wires, if it is a wiring problem it's going to be in these ones:

* In the fuse box somewhere near Fuse 2 (fuel pump).
* On the black-blue wire between Fuse 2 (fuel pump) and pin 14 of the ECU.
* Inside the ECU (i.e. the electronics have failed).
* On the blue-green wire between pin 15 of the ECU and the fuel pump plug. NB: The book says this is blue-green on both the FE and FX, but it's white-blue on my FE. Easy enough to check as you can see it where it goes into the plug at the fuel pump.
* A short in the fuel pump itself.

If you disconnect the bits I suggested, you can test those wires without pulling the wiring loom apart so if you're lucky you might find out where the problem is without too much work. If not, you may then need to disconnect and take out the battery and possibly loosen the subframe and swing it down to get at more of the loom.

Seriously though, if you're not too hot on electrics you might save a lot of time and effort if you can find a friend who is to have a look at it for you.

And BTW, tempting though it is if you're stuck out on the trail, it's not a good idea to use a fuse with a higher rating than it's meant to have. For example the fuel pump circuit has a 10A fuse so the wire will be designed to be thick enough to carry a bit more than 10A to make sure it will be ok for long enough for the fuse to blow if there's a short circuit. If you stick a 20A fuse in there and there's a problem the wire will overheat and it's not protected by the main fuse because that's also 20A. The main circuits will be ok because they're expecting more current so they use thicker wire, but the fuel pump wire could melt its insulation or even catch fire. At the least that could do expensive damage to your wiring, at worst it could mean a fire or even explosion. There's always some safety margin built in so you'll often get away with it (as you apparently did more than once!) and if it's a full short it will likely blow the 20A fuse pretty quickly but you can't guarantee that and I've seen the charred remains of a few vehicles that weren't so lucky! 8O

Wow! I certainly appreciate your expertice!

RAHRAH said:

Wow! I certainly appreciate your expertice!

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+1. one of the first things i bought for the tool kit was extra fuses just in case.

just wondering what would be good for preventative maintenance? spraying a bit of WD40 into the connections every six months or so to prevent corrosion? and are we talking about a few years before this usually happens, e.g. 2009 models?

hoosie5seventy said:

just wondering what would be good for preventative maintenance? spraying a bit of WD40 into the connections every six months or so to prevent corrosion? and are we talking about a few years before this usually happens, e.g. 2009 models?

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That might help the connectors but if you're talking about the corrosion I mentioned, that was way down inside the loom where it would be hard to get anything in without stripping the wiring loom out completely (mine's a 2010 model BTW). You might be able to trickle something in from the end and spray some of the exposed sections from the outside but I don't know how much good it would do (no harm trying I guess). Water does get into the loom if you ride in wet conditions or do water crossings and that's what causes the problems. I'd guess once it's in there it takes a long time to dry and in the meantime it's causing corrosion.

I always carry several fuses of each rating the bike uses (in addition to the spares in the fuse box) so I can put the right one in even if I need to replace the same one a few times. They're so small and light it's no problem to take them.

The general rule is if a fuse blows you replace it once because they can just fail from old age or vibration, so it may not happen again. But if the same fuse does soon blow again you have a genuine problem that needs fixing and ideally you shouldn't replace it again until the problem's been looked at because using the circuit again might cause damage. Of course if you're in the middle of nowhere with a dead bike you may think it's worth the risk to get out of there! Still best to use the right rating fuse though if you are going to keep replacing them, as it will limit the risk of serious electrical damage or fire.

The other thing to think about when it's the fuel pump fuse that's blowing is whether you really want to sit on something you know has a short circuit somewhere on a wire which goes inside a fuel tank, especially if you've put in a bigger fuse so the wiring's more likely to overheat and possibly burn. Just a thought... :!:

Dang Im trying to get the problem to reoccur just so i can find what it is.

Did you mean you're testing by putting in new fuses to see when they blow while you move the wires around? If so that's really not the best way, not least because there is a chance it could do more damage, especially if you're still using 20A fuses in the 10A slot (hopefully not!). There is also the small chance of fire...

If you test for a short circuit to ground on the various sections of wire (and check the fuel pump resistance) as I suggested you don't need to have a working fuse in the fuel pump slot because you actually want that fuse to be removed (as well as the ECU & fuel pump plugs) so you can test each section of the wiring separately. That should be done with a multimeter on its resistance range, which will pass very little current and so is safe (you obviously won't have the engine running during the testing either).

If you're really not up to speed on electrics it might be best to get in someone who is (and has a multimeter!) - probably worth a beer or two to someone to look at it for you. :nerd:

Or alternately do you have a friendly local Husaberg dealer?