1990 GMC K1500 350TBI Blows Injector Fuse

threefiveleven

Original poster
Member
Jan 12, 2018
34
28409
My old faithful Beach Truck has been... unfaithful to me lately. I still love it though and want to work things out!

For about a year it has died randomly. It'll sputter as if it lost fuel pressure briefly, then smooth out. It might die completely and then start again within minutes and run fine for a week. I have thus far used this time to reflect on life's many mysteries alongside the road, or to take a few extra minutes getting back to the road from the sand. Really need it to just run right though, yanno?

Recently it finally blew an injector fuse. Great! Now I know it's a short to ground somewhere. Easy enough, right? Nope. I cannot find a short anywhere. It's an old truck that was rednecked up pretty bad when I got it, but I cleaned up all the wiring when I put a motor in it years ago. There is no wire or wiring harness obviously damaged under the hood or under the dash. Wherever it is shorting, it must be doing so inside a wiring harness.

I have two wishes:

1) That one of you will magically just know exactly where it's shorting out and I can go fix it.

2) Barring hope of the magic above, if one of you has a wiring diagram of said truck I will just rewire everything on that fuse circuit and be done with it, and head back out to the beach for a swim, and perhaps an evening lying in the bed of it in a big pile of blankets and pillows under the stars with my lady. Seagulls will serenade, the sunset will glow effervescently, and many joyous cuddles will ensue. Probably a late night skinny dip as well. Depends on the mood, yanno?

Please help make my dreams come true. Songs will be sung in your honor until your Grandchildren have turned to dust. You are my heroes.

20200130_171437.jpg
 

mrrsm

Lifetime VIP Donor
Supporting Donor
Member
Oct 22, 2015
7,639
Tampa Bay Area
Tell you what... if this Truck was MINE.... I would want my Own, Two Volume Set Of GM OEM "Paper" Service Manuals... Like THESE and at a VERY Reasonable Price, Too:


s-l1600a.jpgs-l1600.jpg

Or... Start by getting your Hands on THIS Item ...BEFORE you get your Hands DIRTY:

https://www.ebay.com/itm/3607708862...=0&customid=link&campid=&toolid=20001&mkevt=1

K1500SERVICEMANUALONCD.jpg

While following the GM OEM Factory Flow Chart Diagnostics inside of that Digital CD Manual... also check over the Engine Harnessing for any signs of Rodent Predation from their Incessant "Need To Gnaw" endlessly and wear down their ever-growing Incisors.

You could also have a possible Dead Short inside one of those Injector Pods of the TBI Unit.


Watch Jimmy from “1Road” for his Entertaining and Edifying Re-Build of his TBI Unit:


This stuff is just about as close to being “Old School” in the GM Motor World of Fuel Injected Engine Repair as it gets… So Look Up a Decent Wiring Schematic for your Vehicle and Trace out the TBI Circuit with a DMM and Lighted Probe for Continuity (KO-KO).

THEN EXAMINE EVERYTHING UNDER THE HOOD WITH A BRIGHT FLASHLIGHT FOR HIDDEN RUBS AND CONTACTS that are Very Hard To See on a 32 Year Old Engine Wire Harness that may be Keeping Its Secrets.... :>)
 
Last edited:
  • Like
Reactions: threefiveleven

threefiveleven

Original poster
Member
Jan 12, 2018
34
28409
Start by getting your Hands on THIS Item ...BEFORE you get your Hands DIRTY:

https://www.ebay.com/itm/3607708862...=0&customid=link&campid=&toolid=20001&mkevt=1

View attachment 104336

While following the GM OEM Factory Flow Chart Diagnostics inside of that Digital CD Manual... also check over the Engine Harnessing for any signs of Rodent Predation from their Incessant "Need To Gnaw" endlessly and wear down their ever-growing Incisors.

You could also have a possible Dead Short inside one of those Injector Pods of the TBI Unit.


Watch Jimmy from “1Road” for his Entertaining and Edifying Re-Build of his TBI Unit:


This stuff is just about as close to being “Old School” in the GM Motor World of Fuel Injected Engine Repair as it gets… So Look Up a Decent Wiring Schematic for your Vehicle and Trace out the TBI Circuit with a DMM and Lighted Probe for Continuity (KOKO).

THEN EXAMINE EVERYTHING UNDER THE HOOD WITH A BRIGHT FLASHLIGHT FOR HIDDEN RUBS AND CONTACTS that are Very Hard To See on a 32 Year Old Engine Wire Harness that may be Keeping Its Secrets.... :>)
Thanks, I won't be able to watch that long video until later this eve but are you saying that the injector itself can have an intermittent short? I can put a new fuse in it and drive it a while before it blows again. So whatever is shorting is doing so very intermittently and inconsistently.
 

mrrsm

Lifetime VIP Donor
Supporting Donor
Member
Oct 22, 2015
7,639
Tampa Bay Area
Yes... The Throttle Body Injection Fuel Injector (TBI) "Pods" are nothing more than Sophisticated Electrical Solenoids that get Pulsed to Open Spring Loaded Spray Nozzles that allow Liquid Fuel into the Intake Plenum where the Fuel can get Atomized and Mixed with enough Ambient, Naturally Aspirated AIR to achieve the Right Fuel-Air Ratio. But if there is any Excessive Electrical Resistance inside those Coil Windings ...They can HEAT Up and Begin to Fail.

Like most Solenoids... These consist of Densely Wound, Sealed Fine Wire Copper Coils designed to work to actuate the Fuel Pintles after being Rapidly Triggered to create Brief Electromagnetic Fields and to operate in an EXTREMELY HOSTILE Environment... but NOT necessarily be able to Perform PERFECTLY after over Three Decades of Repetitive Activation.

Those Manuals will have some Basic Electrical Diagnostic Tests that you can perform on the TB I Pods using a DMM and get a Baseline for whether or not they can still do the job. Always check Amazon, eBay and ANY Genuine GM Parts On Line Distributors for the ACDelco or Delphi OEM 1990 Circa TBI Parts and Kits required. In some cases, perhaps some Dude has the Entire New Rig your need to replace the Old One on your Motor... for a LOT less than Buying OEM Parts & Pieces and then having to Re-Build your Original TBI Unit. :>)
 
  • Like
Reactions: threefiveleven

littleblazer

Member
Jul 6, 2014
9,265
I pinched an injector wire on the air cleaner housing... Was tricky to find but that was it. Same thing. Very intermittent. Easy enough to check too.
 

Forum Statistics

Threads
23,271
Posts
637,476
Members
18,472
Latest member
MissCrutcher

Members Online

No members online now.