Any idea how this wire shorted out?
 

On one of my mercury 250 efi motor for some reason the positive wire that goes on top of the fuel pump got burnt all the way to where it ends, which it goes all the way to the starter selonoid (it goes from the + top of fuel pump to the starter selonoid). Nothing else got burnt just that red positive wire which is very odd. Does anyone know how this could have happened? Where the starter selonoid is, it has a fuse which didn't blow, I would think if a wire get's shorted out it would blow the fuse? Maybe I'm overreacting but could this cause it to fry the ecm? Or do I just need to replace that positive wire? I am really worried that it somehow messed up the ecm on one of the outboards? Please if anyone can help me I would really apprecite it. I have never had something like this happen before. Here are some pictures of it

[IMG]http://i744.photobucket.com/albums/x...Picture171.jpg[/IMG]

[IMG]http://i744.photobucket.com/albums/x...Picture170.jpg[/IMG]

pump itself could be going bad causing the pump to draw more amperage witch in turn will melt the wire

only two things melt a wire. a dead short and an prolonged overload. if it shorted i would expect it to be melted far worse than it is and maybe burned thru. it looks more like whatever that wire runs is drawing a lot more amps for a lot longer than it ever did before. and i would look carefully at whatever that is...

If it were drawing more amps, it should have blown the fuse.

BUT......... it appears to be burnt all the way to the solenoid, not sure where the fuse is, I would have to look at mine.

If it were a short, it would only be melted between the short and the pump, not all of the way to the solenoid.

Almost looks as if it overheated, and just melted the whole wire. You got twins right?? If so I would make up a replacement wire, and just run it outside the harness for testing on this motor. If it is fine, then tie it into the harness and assume the old wire just got old, and touched something. If it melts again try switching pumps with the other motor, and see if the issue follows before replacing the pump, they are pricey.

no... not unless the fuse was actually in that wire. if that wire starts hot at the solonoid and goes straight to the pump, no fuse in the middle then you are talking about blowing the main breaker IF it was a dead short... but a high draw over a long time just heats the wire until it melts.

I am trying to remember where the fuse is that he is talking about, I am not near my boat right now. I agree that since that is the only burnt wire, it appers that the pump may be drawing too much, but I would make damn sure it is the pump by testing it out with the pump(or other parts) from the other motor, or at least making it burn another piece of wire that is clearly not touching anything else before replacing the pump at almost $600:eek:

what kind of fuel pump is that ?

Since you have twins you can use an ammeter on both and check what the pumps draw. If the pump where the wire burnt is noticeably higher that is your issue. If it is going bad it will draw too many amps and heat the wire, the fuse will not blow until the amps get really high (comparatively) so it just heats the wire and melts the insulation.

Merc OEM

So is there a chance it hurt the ecm? I guess I'm just trying to double check, somebody else told me no but I wanted to get on here and ask just to be sure? Also what size gauge wire is that so I know what size to get on the new one?

well... the odds are , not... but as soon as you fix the wire and try it you will know. if it starts then you are ok... if not, look for tripped breakers and bad fuses before you slit your wrist.

is this some sort of big motor with big fuel demands ? like 6 or 700 hp ? i can't see how a conventional hi press pump that can service 500 hp can be more than 300 bucks... the bosch ones were only a couple hundred ... but maybe i'm just way out of touch. wouldn't be the first time...

It is a 250 Merc EFI outboard, fits in the VST tank, there are probably crossovers to aftermarket, but I couldnt tell ya what the # is.. I agree that it SHOULD not have hurt the ECU's, but ya never know if it fedback thru ground. However, if it did, I happen to have a used set on the shelf for that motor:drink:

Here is the stock fuel pump # from BAM marine

808505T01 PUMP KIT-FUEL $670.17 $590.69 $0.00 $0.00 1.38 Lbs No Picture

sorry... i get it now. for sure that's application specific. you probably said somewhere it was an outboard but i just missed it. well... i hope youre ok. i notice that pump has screws holding it together... thats good news. those vane pumps will jam if anything at all gets in there which will stall it and maybe do what yours did... i would carefully have those screws out and clean that assy out ... that might buy you something...

when i got my motors they had the std cool fuel deal and neither pump would run. all i did was clean them and corrosion x them and marvel mystery oil/fuel mix them and then let them run unloaded for a while just recirculating gas/oil mix until they ran with that nice steady state 9000 rpm hum... and they are still running 5 years later...

Do you guys know what size gauge wire that is?

Hard to tell from the pic, but judging from what I see next to your Batt cable I would say 10 - 12 guage. I can look at mine tonight or tomorrow, and tell ya for sure. Or you could take the one off the other motor down to the store and match it up.

10ga

make new wire and add a 30 amp or so circut breaker in line, just use a std auto 2 post....that might help find the issue and not be a bad idea anyway ?

ya think ? looks more like 6 or 8 to me... but hard to tell like you say

Fixx
 

two things came to mind when i saw the wire was...When a wire is loose at a connection it will usually burn the end of the wire from it arcing out and heating up and melting...also if the main positive cable is loose or defective it will use the smaller wire as the main big positive cable and melt the wire in the process..

The fuel pump should run off a relay so the ECM should not have been damaged. I would also say 10 gauge wire at most. Assuming the fuel pump is toast you may be able to remove it from the VST housing and take it to a "good" auto parts store and they may be able to match it.

u can buy the pump itself that is in the VAC housing at autozonr for 70 bucks....u dont need the KIT because the pump is the only thing drawing power the rest in there is BS !

It overheated because the pump is bad and draws more amp , like sayd before !

I dont know the # , but take it appert ( not hard to do ) and take the actual pump with u to autizone !

We just did that on a costumers boat about 2 month ago !

Somebody brought up a good point to me and I wanted to ask you guys because it's a good possibility. When I took off the injectors to get sent out to get cleaned the positive terminal ring broke so I replaced it but I think I replaced it with a bit bigger ring terminal and it could have touched the pump body causing it to short. What do you guys think about that? It's a coincidence that that's the ring terminal I replaced then it shorts out

possible but if so there will be a massive witness mark... i keep meaning to ask you... does this wire come direct from that pole on the solonoid ? so it goes live when the sol engages ?

Yes it does, i comes directly from that solenoid to the positive on the fuel pump. Also when you look at where it goes on to the selonoid, it is attached in the same ring as another positive cable then they both are connected to the selonoid. So basically it is connected with another positive wire on the same ring, then they are both connected on the selonoid. You can see it from the picture.