'89 V2500 randomly dies

[Girth]

The wife's Burb hates her. lol Well.... not just the Suburban, she has a knack for anything mechanical or electrical deciding she's not worthy.

1989, V2500, 350 TBI and TH400. Original-ish, at least powertrain wise. Wiring is a mess from the previous owners replacing the engine, and the years it obviously has on it, which is kinda where I'm leaning now.

Hasn't done it to me, or while I'm in the truck, but it intermittently just dies on her. No rhyme nor reason that I've found. Cool morning short drive, warm late afternoon, under load or idling along, going straight or in in a turn, it'll just shut off as she's driving now and then. Rolls to a stop. Puts it in park, sometimes it fires right back up, sometimes it takes a few tires, but it's made it home every time. Of course I get to ask questions and get the troubleshooting of simple stuff secondhand.

Fuel pump is new last fall, says she can hear it running. Aftermarket oil press and temp gauges below the dash, it's not hot and has oil pressure. Cap, rotor, coil, plugs and wires were new last year. Replaced the ICM for giggles, it died on her two days later. Pickup coil in distributor has resistance around 900ish ohms, seems ok? Had to pull the dash apart to see why I didn't have a SES light (I hate printed circuits, especially old ones), got that working...... it died again, no codes. Grounds to the computer checked good. Pulled all the fuses under the dash that might be associated, checked, reseated, no change.

I have a suspicion the ignition is just losing power intermittently. Of course because it's so intermittent, finding the fault is fun. Ignition switch maybe? Wiring is definitely suspect, which is gonna be my next look I think, figuring out what wires go where and tracing all that. Probably cleaning, wrapping, and properly securing all the engine harness while I'm at it. Old plastic loom is crumbling away to nothing anyways.

Is there another "normal" gotcha thing that will just shut the truck down, like you turned the key off, but allow it to restart?

 

[YakkoWarner]

I fought a problem with basically the same symptoms on my 1989 a couple years ago (mine is a 454 but I don't think that makes a real difference in this case). Random shutdowns as if the key had been turned off, no rhyme or reason.

I never found the actual smoking gun cause, but it went away (at least for now and hasn't done it in a year or so) after having the column taken apart to fix the common wobbly-tilt issue and they replaced the switch at the same time.

I had gone thru everything that I was capable of doing with no resolution. If the column is loose it might be allowing the linkages to move the switch actuator slightly and allow it to turn off for a fraction of a second, or the switch itself could be
wearing out - or both? The part that made it hardto troubleshoot (other than the randomness of it) was that the truck would not restart until I turned the key all the way off, and then back on. Just slipping into neutral and attempting restart would not work - had to go full key off. If I was going fast enough to keep the transmission pump pressure up and the engine turning, I could roll the key OFF completely and then back on and it would refire, but it required a full OFF which had me chasing computer phantoms for a long time unsuccessfully because I thought it was an ECU problem.

 

[idahovette]

How many keys are hanging off the column?

 

[Jawzjeep]

I had that issue on a different rig and the column connector was not staying connected.

Different rig had the connector at the distributor come loose when the engine twisted.

Good luck

 

[Girth]

How many keys are hanging off the column?

Just a couple. I considered that, since when I drive it, it's two keys and a little tag. Figured she might have her whole darn keyring on there. lol I asked though, and nope, she also just has two keys on a separate tag.

Tilt column isn't terribly loose, but does have a little wiggle to it. Suppose that could be a thing. Switch wiring is gonna be part of the circuits I gotta feel through anyways....... so maybe I'll just order a new switch and give it a try if I don't find any other culprits.

Distributor connections are secure, and the harness isn't tight.

Thanks guys, gives me a couple things to focus on at least. I was kinda dreading that ignition switch though, that dark hole up under the dash, where I can get one hand in but can't see anything. lol