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91 S10 - Engine Wiring Harness Removal


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tb01
New User

Aug 7, 2015, 9:15 AM

Post #1 of 4 (6560 views)
91 S10 - Engine Wiring Harness Removal Sign In

  
Fri, Aug 7, 2015 - 12:08pm
--------------------------

1991 Chevrolet S10 Base Pickup
4.3L V6 4WD TBI AC 700R4-AT
241,328 mi - owned 12 yrs

This truck has electrical problems since I got it.

Initially, gauges and speedometer would die intermittently. A/C clutch died with gauges and performance seemed to shift into 'limp home' mode. Two years later, cruise control would not -hold-; few months after that it would no longer -set-.

Rebuilt alternator at a local machine shop, and replaced the battery two years ago. Alternator worked almost 45 miles, voltage dropped, charge indicator it-up, and alternator died. Bought (correct) new AC Delco online and installed. No problems and everything worked (except cruise) almost a year.

Intermittent gauges resurfaced about a year ago with loss of battery charging. Had to manually remove battery for charging after every (short!) trip. A few months ago the gauges started working, with alternator charging battery. ...Until one day it wouldn't crank or bulb test. Horn, brake lights, headlights and courtesy lights work, but instrument cluster is dead in all ignition switch positions.

I found all good when I pulled dash. Looking under hood (without poking) I found arcing from wiring harness across top of bellhousing (behind & below distributor). I disconnected the battery.

The truck had always leaked & burned oil, which only got worse over time. New oil lines to the remote filter housing and valve cover gasket (driver side) fixed oil leaks over a year ago. However, the firewall/ engine wiring harness had been oil-soaked where I saw the arcing. Plus, rural mice have a taste for vehicle wiring around here, as rumor goes.

I couldn't locate a replacement part resembling what I have, and decided to remove and repair the existing harness.

If anyone here has ever had to do this (complete removal) I would appreciate any tips. I'd really like to find a step-by-step procedure to completely remove the under-hood harness. I'll need to take it inside to inspect, clean and repair. With so many connections, ground straps, fusible links - I'm not sure where to start.

Let me know if you need more info. I thank you in advance for your time and assistance!

--Tom
tb01

Edited: Time stamp was indicating UTC instead of my local time zone (EDT)


(This post was edited by tb01 on Aug 7, 2015, 11:47 AM)


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Aug 7, 2015, 7:05 PM

Post #2 of 4 (6525 views)
Re: 91 S10 - Engine Wiring Harness Removal Sign In

Your not going to find a step by step procedure for removing the engine electrical harness on that. Removing the harness can be a nightmare and you could possibly create more problems than you fix. Especially on something that old. Taking one out is just going by your instinct on what needs to be unplugged or removed to get it out. If you really have no option but to remove it, take your time and label all the connectors. Most the time when the harness goes back together things tend to lay where they should go. Good luck with that one. Crazy





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


tb01
New User

Aug 7, 2015, 11:22 PM

Post #3 of 4 (6519 views)
Re: 91 S10 - Engine Wiring Harness Removal Sign In

Sat, Aug 8, 2015 - 02:17am

Thanks Discretesignals, for your reply. I considered your response might be what came back.

I agree -- it looks like a nightmare, particularly with everything covered in oil and road grime to the point I can't see anything. However, this is my only transportation. I've been able to drive it maybe six times in as many months -- apparently lucky to return home. I have a doctor appt coming up (and I'm running low on food). I don't want to reconnect the battery until I do something about exposed wiring.

Seeing the arcing/electrical fire indicated -one- location which -might- cause all of the strangeness. The corrugated plastic sleeve (loom?) is deteriorated and missing throughout the harness, except right around the power brake booster and (some) near the headlights. My original intent was to access the harness at that location and repair on the vehicle. However, I can't see what is holding it in place against the bellhousing.

My idea to remove the entire harness for inspection & repair was to hopefully (finally) solve all the electrical problems and go forward with a known-good wiring harness. Of course, I'd be cleaning, checking and repairing all the connectors as well. The (removal) task does seem ultimately difficult, especially without a proper work area.

Moving forward, it appears that freeing the harness for a foot or two either side of the bellhousing might provide enough slack that an on-vehicle repair could be performed, even if it might require removing the hood temporarily. Currently, without the air-cleaner housing, I can't see anything holding it between the engine and firewall to know where to begin.

I searched online for a hi-res photo of what the correct harness would look like, all laid out, hoping that seeing the connectors and fasteners/brackets would be a huge help. I found nothing appropriate.

Any other thoughts or ideas? I'm certainly open to any viable means to get this truck running again, asap. Thank you again for your reply, and I'll keep searching for that pic. I'll also update if anything significant happens.

I'll probably degrease that area the best I can in the afternoon, when my black rubber water hose is the hottest (laying in the sun). That should at least give me better visibility where I can see wires, and may help me find everything holding it in.

Thank you,
--Tom


tb01
New User

Aug 9, 2015, 12:15 AM

Post #4 of 4 (6429 views)
Re: 91 S10 - Engine Wiring Harness Removal Sign In

 
Sun, Aug 9, 2015 - 03:12am

The degreasing went exceptionally well, in that I now can see surfaces and colors on those wires, previously all black. I'll let it sit Monday (to dry out good) and hope to get back on it Tue or Wed.

--Tom






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