Engine Wiring Harnesses Randomly Popping Loose?

[evilunclegrimace]

Hmm, I see. I guess connector wear out and replacement aren't as unusual as I thought?


Yes, it's the harness-side. Specifically, it's the little clip that holds it to the sensor-side of the connector. The electrical contacts themselves appear to be fine.


Is this applicable when I remove the terminals, as @xXxPARAGONxXx suggested?

I forgot to add that when all the other stuff (distributor, water pump, etc.) was replaced, the dealership also replaced the harnesses and connectors for the ignition coil and fuel injectors, because apparently they pretty much fell apart when they removed them and the injector harness was particularly bad, as the wire insulation was severely frayed and at best was a short circuit problem for the ECM, and a fire hazard at worst because of their proximity to the fuel spray). For the ignition coil harness, I don't know if they replaced the whole harness or just the connector.

c

Yes.

 

[alpinecrick]

Also, while I'm here, what is the average life span of things like, say, the Throttle Position sensor, O2 sensor, the IAC, or any other engine sensor?

Given that most of them are likely approaching 30 years old (assuming none have been replaced in the meantime), should I consider replacing any/all of them as preventative maintenance, or is it best to leave them alone until something fails?

Assuming the odometer is correct and hasn't been tampered with, the truck has about 105k miles on it.

EDIT: And what about the injectors? The engine runs well right now (when all its wires stay put), so I don't think they're having any troubles, but should I consider rebuilding them with new seals and stuff so it stays that way?

EDIT #2: The transmission is newly rebuilt and only has a few hundred miles on it, so at least that shouldn't be a problem for a decade or two, provided it's properly maintained and not overworked/overheated

THIRD AND FINAL EDIT: My truck has the 7.4L V8, in case anyone's wondering....

c

If your connector clip itself is broke then your best bet is a new pigtail connector. As paragon said, if you can keep the harness intact by removing the terminals and inserting them into a new connector housing is the better bet. If you do use a new pigtail and splice into the existing wires I would recommend soldering the wires together and covering with heat shrink rather than a butt connector. A butt connector is a third choice. The signals that are sent from the sensor to the ECM are measured in milliamps and a good soldered connection is best.

Keeping the engine bay clean (and the trans, and the T Case) goes a long ways to preserving plastic parts under the hood. The transfer case and 4l60e on my 96 and 97 have darn near as many connectors as the engine.......

I have 277k on my 96, and although I have replaced a few sensors, I've come to the conclusion it was a waste of my money if they are working. I have had a couple O2 sensors quit and throw a ode and have broke the connectors on a couple more.

 

[Frank Enstein]

I would just zip tie them. But I'm cheap (broke) and lazy!

Moving the pins to a new connector is best.

If you do the pigtails stagger the splices so they aren't all lined up.
The splices will have a larger diameter than the wire itself.

 

[xXxPARAGONxXx]

Hmm, I see. I guess connector wear out and replacement aren't as unusual as I thought?

Yes, it's the harness-side. Specifically, it's the little clip that holds it to the sensor-side of the connector. The electrical contacts themselves appear to be fine.

Is this applicable when I remove the terminals, as @xXxPARAGONxXx suggested?

I forgot to add that when all the other stuff (distributor, water pump, etc.) was replaced, the dealership also replaced the harnesses and connectors for the ignition coil and fuel injectors, because apparently they pretty much fell apart when they removed them and the injector harness was particularly bad, as the wire insulation was severely frayed and at best was a short circuit problem for the ECM, and a fire hazard at worst because of their proximity to the fuel spray). For the ignition coil harness, I don't know if they replaced the whole harness or just the connector.

1. Not unusual. They are available, and it is far easier and less costly to replace one harness connector than it is to replace an entire harness.

2. That definitely calls for replacing the harness connector. If the electrical contacts (i.e., the terminals on the wire harness) appear to be fine, then all that needs to be replaced is the connector — that is, the plastic housing that the terminals fit into.

3. You do not have to worry about crimping anything if all your doing is replacing the connector. You need the proper tool to remove the terminals from the connector. Once you remove them, you can place (push) them into the new connector. No cutting, no splicing. Simply pull them out of the old connector, and push them into the new connector.

xc_hide_links_from_guests_guests_error_hide_media

I am not certain if the TBI TPS connector is a Metri-Pack connector. If it is, the video above applies.

4. I am not familiar with the TBI engine, but one would assume that the ignition harness is part of the engine harness. If that's the case, they didn't replace a separate harness. They probably cut off the faulty section of the harness and spliced the new pigtail and connector into it.

 

[Erik the Awful]

The signals that are sent from the sensor to the ECM are measured in milliamps and a good soldered connection is best.

Volts, not amps, and the ECU doesn't need to distinguish between thousandths of a volt. Most sensors only need resolution in the tenths of a volt range. Your factory connectors are crimped with no solder. Lots of hate here for heat-shrink butt connectors, but that's what a dealer technician would do, and you'd never know the difference.

If you want to keep your truck pristine, by all means hunt down the correct metripacks. Take the time to solder if you want. If you really want to get "perfect wiring", there's a Facebook group for "race car wiring" where they get into arguments over using the correct factory wire. I couldn't stand the pettiness and had to leave the group. It was pretty obvious there were a couple guys running "European Motorsports" shops where they specialized in making "perfect" wiring harnesses to integrate upgrades into Audis and BMWs that were indistinguishable from stock. They were charging five figures and taking weeks to do wiring jobs. That's not "race car wiring".

After about twenty races of quick fixes and hastily added equipment, this is what race car wiring typically looks like. Yes, this is horrible and I want to rewire it, but cleaning it up to "good enough" standards would take me a week, and the car lives two hundred miles away. I'm going to tackle the wiring as I can, and I won't hesitate to use heat-shrink butt connectors because they're never the point of failure.

You must be registered for see images attach

If your truck is a truck to be used and abused, I wouldn't hesitate to use heat-shrink butt connectors and use the time I saved to fix something else.

Now, open crimp connectors? Those are garbage. They loosen up and collect corrosion.

 

[cc333]

OK, that's not so bad, then! I'm glad to know that this is a common problem with easy, affordable solutions!!

I'm not adverse to soldering (electronics are a hobby of mine, in fact), so I can splice in pigtails easily.

@Erik the Awful Eeek! That reminds me somewhat of our yard utility vehicle (1998 John Deere Gator 6x4). I've jury rigged all kinds of wiring on that thing to keep it going (as one often does on a farm or ranch, I suppose). This includes one time I had to tear into it to redo all the wiring for the cooling fan because it stopped working and it would overheat.

So, I guess I'll take a few photos of the various connectors that are most prone to popping out, comparing them to the photos here, and then buying appropriate replacements and the terminal removal tools needed to do the swap.

I don't care too much about having perfect wiring, so I wouldn't be upset by having splices everywhere, as long as they are electrically sound and look nice. What I've learned is that when wires are a cluttered and tangled mess, not only is it bad practice in general, it can actually be bad for audio and high frequency digital circuits, because it can mess up sensitive timing and introduce extra EM noise (which often manifests in an audio signal as a humming or buzzing sound), so I've gotten into the habit of being as neat and tidy as possible when laying out cables or circuits. I'm not trying to be a perfectionist, just following best practices.

c

 

[Schurkey]

what is the average life span of things like, say, the Throttle Position sensor, O2 sensor, the IAC, or any other engine sensor?

The only sensors that have a limited service life are O2 sensors, and MAF sensors. I don't think you have a MAF.

Everything else is good until it isn't. All those sensors "can" fail, wear out, whatever; but the O2, and the MAF, are the problem children.

Given that most of them are likely approaching 30 years old (assuming none have been replaced in the meantime), should I consider replacing any/all of them as preventative maintenance, or is it best to leave them alone until something fails?

Replace the O2 sensor(s). Use a scan tool to study all the rest. But leave the rest alone until they're proven to be defective.

EDIT: And what about the injectors? The engine runs well right now (when all its wires stay put), so I don't think they're having any troubles, but should I consider rebuilding them with new seals and stuff so it stays that way?

I'd leave 'em alone unless you can prove via scan-tool readings or some other legitimate test method that there's a problem.

You want to do preventative maintenance? Concentrate on fluids and filters, tire pressure, brakes, suspension, and steering first.

 

[alpinecrick]

Volts, not amps, and the ECU doesn't need to distinguish between thousandths of a volt. Most sensors only need resolution in the tenths of a volt range. Your factory connectors are crimped with no solder. Lots of hate here for heat-shrink butt connectors, but that's what a dealer technician would do, and you'd never know the difference.

If you want to keep your truck pristine, by all means hunt down the correct metripacks. Take the time to solder if you want. If you really want to get "perfect wiring", there's a Facebook group for "race car wiring" where they get into arguments over using the correct factory wire. I couldn't stand the pettiness and had to leave the group. It was pretty obvious there were a couple guys running "European Motorsports" shops where they specialized in making "perfect" wiring harnesses to integrate upgrades into Audis and BMWs that were indistinguishable from stock. They were charging five figures and taking weeks to do wiring jobs. That's not "race car wiring".

After about twenty races of quick fixes and hastily added equipment, this is what race car wiring typically looks like. Yes, this is horrible and I want to rewire it, but cleaning it up to "good enough" standards would take me a week, and the car lives two hundred miles away. I'm going to tackle the wiring as I can, and I won't hesitate to use heat-shrink butt connectors because they're never the point of failure.

You must be registered for see images attach

If your truck is a truck to be used and abused, I wouldn't hesitate to use heat-shrink butt connectors and use the time I saved to fix something else.

Now, open crimp connectors? Those are garbage. They loosen up and collect corrosion.

You're right, millivolts not amps,...... The strongest connection is a soldered one with heat shrink over it. But I've used butt connectors, heat shrink butt connectors, and the "presoldered" butt connectors that one heats up with a gun or flame with success. In the end the soldered with heat shrink is the best in my experience. Actually a gen-u-ine certified John Deere tech showed me how. He also showed me how to make battery terminal ends out of copper pipe--makes for a very strong terminal.

 

[Erik the Awful]

He also showed me how to make battery terminal ends out of copper pipe--makes for a very strong terminal.

I've also used 1/2" aluminum fuel tubing.

 

[Schurkey]

soldered with heat shrink is the best in my experience. Actually a gen-u-ine certified John Deere tech showed me how.

Take a look in a Genuine GM service manual. Wire-splicing guidelines are given substantial treatment in the "front of the book"; including shielded-wire splicing. Not only do you have to splice the conductor, but also the shield wires.

He also showed me how to make battery terminal ends out of copper pipe--makes for a very strong terminal.

Copper tubing, not pipe. And, yes, I've done that. (but not for a long time. I gave up and bought an assortment of copper lugs/ Pre-formed time-savers.)

Good-quality crimping tools make a verifiable difference, too.