83 K10 Survivor, Part 2

[Wwes]

Kind of hit a couple potholes lately.
After sitting for a month, the old truck wouldn't start. After a couple minutes of cranking I just said "forget it".
A month after that, I went out and it started right up!

Last week it wouldn't start again. The next day started right up.

Took it for a short drive. Ran good, but did have a loping (searching idle). Pulled into driveway and it dies. Won't start. Luckily I'm at home.

Next day, go out and it starts up, then dies immediately. Ran battery down cranking.

Yesterday, go out, charge battery, it starts right up but has a real bad searching idle. Like it goes down, hits' the anti-stall, which doesn't catch it. Won't start again.

Going to test the IAC, TPS, and EGR. All the wires and vacuum lines look good.

[Wwes]

Turns out the problem was the IAC. I unhooked it and it started up and runs great. The idle is a little elevated but it's smooth and consistent.

[daddyjeep]

I had some IAC issues with my TBI 350 swap in my Jeep. I had to go through the re-calibration procedure and it worked fine after that.

[Wwes]

Long time, no update.

From last August I spoke of a searching idle that just didn't seem to fix itself. The IAC unhooked and it ran fine until it didn't.

Late October, I drove the old truck into town. Stopped at two stores and then a tire store to have a trailer tire fixed. Guy walks up to me and asks about truck, wants to see engine, asks to hear it run. SURE! Won't start. Battery ran down cranking. Towed home.

Charged up battery, turned key and it started right up.

I was seriously about to JUNK this thing.

I pulled the engine wire harness, went through the entire thing wire by wire, replaced every end that was even questionable.

Here's a picture of (from left to right), Delco coil wire new, original coil wire pack, and eBay coil wire. You can see there is a drastic difference between the eBay junk and the Delco coil wire.

Continued...

[Wwes]

I used the heat melted solder wires which seemed to work well. And then I continuity tested every wire. All looked good so I reinstalled, restabbed the distributor, and crank.

Did it start? No.

Figured out the injectors still weren't firing. Replaced ignition module and it started up, ran about 30 seconds, then died and then no injectors pulsing again. Tried using my backup ECM no change.

Let me fast forward a bit here - it's running great again. Any guesses as to what the issue ended up being? It's simple to fix, but complicated to determine.

[Hart_Rod]

Bad ground?

[Wwes]

Originally Posted by Hart_Rod

Bad ground?

No, I checked all those religiously. Good guess though.

It was a bad connection inside the bulkhead connector on the fuse box.
Two power wires go to the computer, fused and constant. The constant had 12.5V, and the fused had 11.3V. The computer wouldn't have enough power to ground the injectors. Occasionally the voltage would match and it would run fine, and when the voltage fluctuated it was running rough.

I cleaned it out well, bent the pin, and applied some di-electric grease, and the voltage went to 12.5 on both circuits. That's when I got the start, and it's been running fine since.

[focusedontheprize]

Congratulations on chasing down the issue. I am finding from each of these old trucks I buy the electrical work is always terrible. People cut in, splice, and unfortunately do not finish it the right way, which create electrical ghosts down the road.

The truck is looking great, what's next on the hit list?

[Hart_Rod]

Originally Posted by Wwes

No, I checked all those religiously. Good guess though.

It was a bad connection inside the bulkhead connector on the fuse box.
Two power wires go to the computer, fused and constant. The constant had 12.5V, and the fused had 11.3V. The computer wouldn't have enough power to ground the injectors. Occasionally the voltage would match and it would run fine, and when the voltage fluctuated it was running rough.

I cleaned it out well, bent the pin, and applied some di-electric grease, and the voltage went to 12.5 on both circuits. That's when I got the start, and it's been running fine since.

Glad you figured it out. Good engineering is a must, but a little luck always help.