Fuel injection wiring problem with 89 cherokee 4.0L

Josh Mills did pass the time by typing:

No such subharness that isn't $$$. I'd take the tape off and find out what is there. It might be the last person just twisted wires together and taped them. (a bad repair) If you need a new connector NAPA should have them.

If it's just a broken wire and connector they can be repaired if your somewhat comfy with a soldering iron.

DougW did pass the time by typing:

Feel I should point out the heat shring tubing goes on BEFORE you solder the connection. But you would have figured that out in due course. :)

You are correct.

That is why we use heat shrink tubing over top. Most folks always used

The heat shrink distributes the stress nicely.

I use heat shrink and solder and dielectric grease on the joints on mine. We have serious corrosion issues and a crimp joint will fail from the crimp taking the temper out of the wire allowing it to corrode.

Mike

Steve G wrote:

L.W. (ßill) Hughes III did pass the time by typing:

A good discussion is hardly a flame.

Here is the deal. Solder itself (lead/tin) is generally a lousy conductor (except for silver based solder). Its primary job is to keep a mechanical connection sound and free of corrosion. Your typical el-cheapo crimp/splice can put a tremendous amount of stress on the connection point, even to the point of partially cutting/smashing the conductors. Especially if one is from the (crush it till it don't give) school. MIL-SPEC splicing uses a preset crimp tool for exact crimp pressure. Solder splices do indeed cause two spots for mechanical failure, but that failure point is no weaker than the surrounding metal providing the mechanical mode of failure is addressed. Hence the use of heat-shrink or wire loom.

Connections are crimped at the factory because soldering takes too long, produces hazardous fumes, and is dangerous due to the burn risk. Lead and fumes also make soldering a regulatory nightmare. Ever wonder why wires are tucked so close to the engine. That's because it's easier to install in a moving chassis.

Thanks Doug, I'm quite handy with a soldering iron, and I know how to shrink wrap so I guess I'll give it a shot on Sat. I guess if worse comes to worse I'll just have to buy a new injector connector and solder it to the blue and white wires on the harness. That would only be needed if there is internal damage to the connector though I'm guessing. I'm good with electronics in general so I guess I'd be foolish to not try myself before consulting a "pro". BTW I really like my Jeep so far, it's my first one. I've enjoyed reading some of the posts on this group, maybe I'll get some good ideas on how to improve my Jeeping experience.

Josh

Josh Mills did pass the time by typing:

Not a problem.

If you have a multimeter it might be worth your while to ohm out the harness back to the ECU. Having a service manual will help. All I have here is the 93 ZJ book or I'd give you the wires/pins. Generally the injectors get power from the ASD (Automatic Shut Down) relay and ground through the ECU. If you measure each injector for resistance it should be about 15 Ohms +-2 Ohms.

The tiny amount of silver in silver bearing solder has little or no effect on conductivity. It is there not to add conductivity but to keep the lead tin from leaching silver out of silver plated components.

The good part is the mechanical connection... as you imply solder should never be used as the provider itself of mechanical connection. Plus the mechanical connection should be such that it forms the conductive path...which will be the case for most since lead/tin is less than 10% of the relative conductivity of copper. [Lead about 5%, tin about 13, eutectic or close less than 10].

For auto connections subject to vibration is best to use tape or shrink wrap that extends well beyond the solder wetted areas.