Hey everyone, I have a 94 Jimmy with the 4.3 vortec, and been chasing a problem that has me a bit stumped. Think I've got it narrowed down, but since I don't have a cash cannon, (or I'd just buy all new parts for what could be wrong) I'm trying to figure out exact problem. I am experienced in auto work, have pretty much every tool needed, or access to them, so "advanced"suggestions are possible. This is going to be a tad long, so bear with me, lol

A few days ago, after first start of the day, I started getting missing, popping, etc while accelerating on highway, pulled off to get coffee and glance at it, and it restarted fine, idled fine, etc. Yeah I know it sounds like a fuel issue, but wait, keep reading.

I then left the store, and it got worse, resulting in a total stall about 500 yards up the road. No restart. Got towed home, and boom. Restarted, idled normal, etc. Went on test drive, did it again, got my butt back home immediately, and it died as I pulled into neighborhood, ended up stalling down street from house, so I walked home, ate lunch, came back, boom, restarted fine. Got to my driveway and went to work on diag. Of course my first thought was fuel system. During the shutdown on side of road I used starting fluid, it would kinda start, then die immediately, couldn't get a good run off ether, you know like how you can get an engine to run off it, it would fire, but kinda sputter and die. Anyways, I hooked up a fuel pressure gauge and all seemed well. I also checked the fuel spider,etc for issues, no leaks. One thing I did notice was a quick bleed down from 55-60 psi to about 15 if pump not running, always started fine, and I'm pretty sure it's not the root issue, as I'll explain in a bit, however it may become one so this will be addressed later. Anyways, I then started hunting around, eventually found my distributor hold down was loose, I'll go into that in a bit too. I retimed motor (more on this in a bit as well) it started, ran fine, went for a test run, ran up and down highway, some city traffic, etc, even did a few full throttle pulls from 20mph getting off and on interstate, all in all logged about 30 or so miles, no issues, gauges normal, nothing out of ordinary. Declared victory, went on with my day. The next day, I started up fine, idled about 5 mins, then drove a mile, parked, got coffee. Restarted fine, idled a minute or so while I reset radio station because I killed battery when on side of road the day before trying to restart, then it just shut off as cleanly as if you turned it off. No restart, and I killed battery again. Since I was closer to home, on a hunch, I lugged battery home, charged it an hour, then got a ride back, about 90 mins total. Boom, instant restart, ran fine, as soon as it started I hauled butt home, no issues, parked it. This is where I'm at now.

​​​​​When I installed the fuel pressure gauge to test, I made it semi permanent, I actually drilled a hole in my hood and set it up, so I could watch it as I drove. It seemed to be just fine the whole time, even with the last stall. As I said, I've pretty much eliminated the fuel system as the culprit, unless a vortec wizard or such says otherwise.

I then went back and looked at distributor again, I replaced cap, rotor, plugs, coil, and wires about 4 months ago. All Standard Ign Blue Streak series, except plugs, can't remember what they are but not cheapies or super platinum, middle of road copper core if I remember. I also had to retime engine then, had to pull dist because last owner broke a cap screw off, and it was a pain, I'll get into that in a sec. The cap had what I think was a lot of black crap in it for being 4 months old, this may help with diagnosing. It also seemed to me to have excessive end play, however after seeing a few videos, it doesn't look as bad as I thought. I'm guessing about .100 to .125, etc could be wrong, no dial indicator handy so I'm guessing.As I said, it will start and idle fine, just not right after a stall, shutdown. But in the 3 times it has died, after an hour or so, it will restart just fine.

I did have issues timing motor, seems the timing marks are off, when I time at zero with the marks it seems to be too much advanced, have yet to find actual TDC, so I then retard timing till sounded normal, it worked for the few months since I did it the first time. It also seemed to jump around sometimes on my first retime, the second seems steady.


​​​​​​So that how far I got. My thoughts are:

Distributor or Ign module inside bad - replace 3 mo old Std Ign Blue Streak dist cap and rotor bad - replace Engine coolant sensor bad, not the temp gauge sensor, but the ECM coolant sensor - replace 3 month old Std Ign Blue Streak coil bad - replace
CRank sensor bad - replace
Less likely like I said, fuel pump starting to go bad. I'm doubting this as fuel pressure during start and no start exactly same.


Just like to add, I just drove from Colorado to VA in January to help some family out, 1800 miles, no issues, and if I was at home I'd probably just park it and deal with it slowly, as I have other cars I can use, etc, but since I'm not I have to fix this, and without a cash cannon. Of course, I just bought new tires for it when I got here too, so the reserve cash I had for problems is gone, as I figured I needed tires bad and I do have work here I can do, but lol, without this car I'm stuck at family house . Yay me.

If anyone had had similar issues with a pre 96 4.3 vortec please let me know what you think. From what I can tell the pre 96 ones were more of a pain because of the OBD1 thing, also if any of y'all know a good scanner for this that reads live engine data, let me know, I know the paperclip trick, and only code I get is 32, egr, but it's always done that since I got it about a year ago, and I cleaned,and reinstalled with new screened gasket a few months ago too, checked again this breakdown and it looks fine, and the MIL is intermittent for it.
Anyways, hope you read this far.

 

Managed to recreate situation. I started it, idled a few mins, drove to store, then parked in a spot by store I could walk away from without worry, idled about 10 mins, then shutdown. No restart. Waited 10 mins, started back up. I then idled another ten mins, and shutdown again, this time took 20 mins for restart, hauled *** home after that. During the downtime I sniffed around for fuel, even opened throttle plate, no strong smell, I also smelled exhaust on restart and it smelled fine. Starting to think it's the coolant sensor or distributor modules, both times it was fully warmed up for about 10 mins before shutdown.

 

These comments are only some first thoughts so I hope someone else can suggest some other ideas.

• Does the 94 have a fuel return system that is not working? Could the fuel cap or tank not be sealing correctly?
• I am suspicious that the fuel pump is on its way out. Does it matter if the tank is full or empty? But this is hard one to diagnose.
• Are you confident that the timing chain is not slipping a bit or on the verge of skipping a tooth? (To suggest this is a measure of my grasping for straws! LOL)
• On this forum, some of the most consistent advice I've seen is to always use GM rotors and caps on our distributors.

 

Ok ideas are good. Since I recreated the problem consistently I can try these. Since I posted this I've been able to make the car die pretty much like clockwork so I can try some, I'm pretty sure fuel system good, I've got a pressure gauge mounted semi permanent so I've been watching it, and it stays steady at stall, and an immediate restart attempt with starting fluid doesn't really get it going. It'll pop and try to start, but every engine I've ever used it on I can get it to run fairly good off spraying in the intake, but hey, this could be the oddball. The fuel return/sealing idea might be it, I'm going to recreate problem later and when it dies, crack the gas cap open and vent tank and see if it restarts. It pretty much idled about 10 minutes or so, then shuts down clean like you turn the key off, with no warning,untill it dies it runs fine, except the initial breakdown, and when it restarted the first time it was stuttering and such when you drove it, but it idled fine. This whole time I've had roughly a half tank of gas, so that's probably no help.

Yeah I've been working my way thru this entire forum and seen the posts about using AC Delco ignition stuff, pretty sure the cap I got is ok, as it does restarts just fine after about 15mins, and looks ok, as well as never had an issue in the 4 or so months I've had the blue streak cap on, looked around and it appears an AC Delco can't really be gotten locally, only online, and as this is my only car, I can't really sit for a week not working. I'm going to keep it in mind though.
Haven't checked for timing chain slack yet, was on my list for today when it warms up a bit, this another thing I kinda eliminated as I went, as car runs just fine when it does start, and the whole "runs 15 mins fine, dies, restarts after 15 mins" with no popping, missing, etc kinda eliminated a persistent mechanical problem. I was quick to make sure the base mechanical system was good, as if something major was wrong then I'm junking car, and going home to get another. Being 1800 miles from home restricts what I can do because I don't have access to a shop or another vehicle here, and the place my family lives kind of keeps me from being able to do a full teardown, or basically anything I can't pack up and put away quickly, some of the local kids think they funny, know what I mean? Already caught one looking at my tools etc when I ran inside real quick, he didn't know about the cameras lol. Anyways thanks for your input, I'm going to try a few different things when it warms up today, and try and get this thing going.

 

So looking like it was distributor. Got distracted by the fuel system. Both the module and bushings appeared shot when I finally got a hold of a new unit. Finished swap an hour ago, and mystery noises gone, as well as noise I thought was just 200k engine noise. If I don't update further, assume this was the solution. And hey, hopefully with my long-winded post, someone else chasing this down will be able to pinpoint the issue.

 

Congrats and thanks for the update. These updates are super useful to people searching the forum. I know I have benefited from this!