Overheated / Burned wire splice

[CDX_NSX]

Below is a picture of a splice that runs directly from my main relay to the fuel pump. I was trying to troubleshoot something when I noticed that the splice connector had burned, some of the wire insulation had melted and some of the copper wire had either broken or melted as well. Does anyone have any thoughts as to what may have caused the overheating?

The wire that originates at the main relay also powers my methanol injection kit, but the wires and connectors on that end seem fine.

The fuel pump still works with whatever is left of this connection, but I'd like to know if there is some underlying cause that I should be looking for before I simply replace the splice connector. I'd expect that having it fry on me again and entirely would not be a pleasant experience. :biggrin:

 

[Rob4092xx]

Look at what is on both sides of this connector. One side has a thick wire, the other side has a very thin wire.

I assume the thicker wire comes from the power source side of the circuit. The skinny wire then runs to whatever is supposed to be getting power.

Most likely, the reason the one wire is thicker is because it carries more amperage from the power source to the item requiring power (fuel pump in this case?). The skinny wire most likely on the other side of the connector is not thick enough to carry the amperage to the item requiring higher amps to run. Thus, too much amperage (or power draw) on a skinny wire will cause the skinny wire to burn due to too much heat. The thicker wire won't burn as it can handle a much higher amperage draw.

Find yourself some wire that is the same gauge as the thicker wire. Run it from the connector to the item requiring power. Problem will be solved!

One other thing that is rather suspicious is why is both the black and red wire is running out of the of the connector? I assume it was a feeble attempt to increase the amperage draw ability by doubling the size of the wire??? This is really poor work if this is what doubling the skinny wire is supposed to be doing! I sure hope the black wire isn't a negative hooked up to a power source! I guess you would have already had a fuse blow or a fire if this was the case!

You are very lucky this didn't result in a fire no matter which way it was wired in this photo! Personally, this is why I put an in-line fuse on most every aftermarket electrical connection I make on any of my cars! Fuses save fires and aftermarket equipment since they will pop was before part damage, wire damage or a fire can start.

The simple way to fuse is use a lower amperage fuse for thinner the wire. I'd guess a fuse for the thicker wire in the above photo should be about 30 amps if it goes from the power source all the way to the item. I'd guess the thinner wire would require a 5 amp fuse base upon its power draw capability. In short, it looks like you tried to get a max of 30 amps to travel through a 5 amp wire. In this scenario, the 5 amp wire is going to burn out way before the 30 amp fuse. This is gonna cause a fire!

 

[Larry Bastanza]

I believe the thinner wire is the fuel pump wire, and is factory spec, so I do not think this is the issue. The only way a connection can burn like that is if there is too much resistance, causing a voltage drop across the connection.

Bottom line, crappy connection/crimp, etc.

Replace the connector set.

JMO

Regards,
LarryB

 

[Rob4092xx]

There ya go! Larry knows more about this stuff than most anyone I know! Go with his recommendation!

I believe the thinner wire is the fuel pump wire, and is factory spec, so I do not think this is the issue. The only way a connection can burn like that is if there is too much resistance, causing a voltage drop across the connection.

Bottom line, crappy connection/crimp, etc.

Replace the connector set.

JMO

Regards,
LarryB

 

[Russ]

Odds are the crimp terminal was sized for the larger red wire which is why that side is fine. On the other side, the connector crimp diameter was too large to properly crimp down on the thinner red-black wire, which eventually caused the failure.

The are at least three ways to get around this. Easiest & cheesiest is to double up the thinner wire inside the new crimp. Better is to use different wire sized terminals to match the wire gauge on either side. IMHO best, especially for something as critical as a fuel pump, is solder and heat shrink.

 

[pgilliam1]

If the insulation around any wire in this connection is not disformed I would agree with a bad crimp on the connector. But if the insulation on any of the wires is at all soft or expanded, then heat from overvoltage/amperage could have caused it.

 

[CDX_NSX]

Thanks, guys!

pgilliam1, there isn't any apparent deformation of the insulation at any part of the wire other than at the crip, as shown below. The originating source wire is also of the same gauge as the smaller wire pictured. So, essentially, it goes, small wire - big wire - small wire.

 

[pgilliam1]

That pic looks like the metal was cracked when the terminal was crimped. If you carefully remove the plastic insulation (cut it away with a razor blade) you'll probably find a crack in the metal right where the burnt spot is. Great picture by the way.

 

[CDX_NSX]

You're probably right about the crack. I'll do a postmortem as you suggested.

Thanks. The picture was taken using my trusty iPhone.

 

[stuntman]

Was that wire exposed the whole time???

An exposed power line can easily ground to something and cause that. Use a better connector, make sure it's crimped well (and ideally soldiered too), and make sure there is no exposed wires!

 

[CDX_NSX]

Thanks, Billy. No, the wire wasn't exposed........ At least I don't think it was. I've decided to solder and heat shrink the wires as I don't think that I'll ever need to disconnect them.