97 S10 4.3L No start no spark

So, let me preface this with the statement that my son is apparently a moron.

Vehicle is a 97 S10, 4.3L V6, 5 speed manual.

Issue may be related to one or both of these incidents.

Incident #1. While shoveling, I ask son who just got his license a few weeks ago, but has been around cars and ATVs and working on them with me for some time now and should know better to move the S10 so we can shovel that part of the driveway. While I continue shoveling, I hear him trying to start it by only turning the key like 1-2 seconds at a time, then turning it off. It pops and burbles the first few times he does this, but he does not crank it long enough, give it a little gas, or anything he should do to actually make it start like a normal person would. This goes on for maybe 5-6 tries or more and now I hear it just cranking not firing at all so I walk over and ask him what the heck he is doing. He recalls an earlier ATV incident where he had done the opposite and cranked the thing for like 30 seconds solid and I had told him you cant do that the starter will get hot, something must be wrong, etc. So apparently in his mind there is no in between 2 seconds and 30 seconds but whatever. Now the S10 at that point wouldn't start, wasnt firing at all, etc. so I just left it since it was dark and a weeknight etc. Few days later Saturday rolls around and I go to look into it and the truck fires right up. I did scan the codes and it had a P0108 Map sensor high voltage, but it cleared and the truck started right up. So, I figure that the kid probably just flooded it when he cranked it so many times without it starting and in the couple of days the plugs had dried out so now it started fine. Truck then starts and runs fine for the next few weeks.

Flash forward to incident #2 a few days ago. Son is driving truck to give his friend a ride home. IQ in car drops by a factor of 2 since theres 2 kids in the car. Despite having numerous discussions since I obviously have a lot of "fun" cars that there is absolutely no reason to beat on the "daily driver" cars since a) noone is going to be impressed by squeeling the tires on a 97 rusty S10, and b) none of these cars hes driving are HIS, and c) we need these cars for people to get to school and work he proceeds to beat on the S10. Story as best as I could drag out of him is he launched it fairly hard from a stop sign (despite the fact that its winter and roads are wet, etc. so noone is really going to be impressed with a rusty S10 spinning the tires in the snow/slush/water lol) . Then to quote him "the RPMS shot way up, then I forgot to shift sorta and they dropped way down and the truck was then barely running really rough and it wouldn't go anywhere so I shut it off". From that point on it wouldn't start. He says it kinda popped/burbled like before like it wanted to start the first few times, but now nothing it just cranks and cranks. So, I'm guessing he spun the tires, bounced it off the rev limiter, then killed it or whatever. I dragged it home and looked at it a bit and it indeed cranks and cranks but no indication that it is firing at all. I pulled the same P0108 code. I also pulled the plugs and they were soaked in gas, so I figured great, maybe he just overrevved it then killed it then screwed it up restarting it and flooded it again. So, I put a fresh set of plugs in it and replaced the MAP sensor for the heck of it, even though I believe it should start and run fine with the MAP sensor unplugged or dead even since the truck has a MAF sensor as well. From what I understand the MAP is only used to check the EGR and a few other ancillary things, maybe set timing advance. Anyways after new plugs truck still doesn't start, and it seems like its getting no spark per the old school pull the coil wire off and hold it near the coil. Another thing that sticks out at me as fairly screwy is that I had my scan tool hooked up and if I have it hooked up then start cranking it keeps going dead then restarting while I crank, and when I can read the live data while cranking I see a lot of zeros like RPMS stays at 0 while cranking. I am not sure if that is just how the port works like it shuts off when I go from on to start with the key, or if this is some sort of indicator of an ECU problem. I did compression test one cylinder thinking maybe he broke the timing chain and it seemed to have good compression. Currently it has no codes, seems to be getting fuel because the plugs get wet with gas, but no spark. I'm thinking if a sensor was bad or something computer controlled was stopping it from sparking that it would a) throw a code, and b) it wouldn't be adding the fuel, it would be cutting both if it was doing it "on purpose"

So, I'm leaning towards maybe he jumped the chain a few teeth, or maybe his incident #2 is just coincidence and the same problem from when it would start is back and maybe its a flaky ECU, dead or intermittant ignition component like the coil or there is what looks to be a little ignition module thing right next to the coil, or there still is what looks like a distributor on it.

Anyone familiar with the 4.6L let me know if anyone has any ideas.

spun the distributor? bad rpm pickup?

Im going to start going through the ignition system - distributor, coil, ignition module, etc. this weekend I found a good site on how to test it all out and narrow it down hopefully. I'm still hoping he didn't break something mechanical by overrevving it. I would think the rev limiter would prevent that, and he only got like 50 feet from the stop sign lol so it seems to me its unlikely he would have broke the motor...

http://easyautodiagnostics.com/gm_mi...re_tests_1.php

This actually looks like a pretty decent site in general.

the preload on the hydraulic rollers in those motors acts like a mechanical rev limiter...same with the 350 etc....just another trick gm engineers used to keep people from destroying their motor.

the 4.3 is robust enough that I cant imagine he broke something big. You say it had good compression on all cylinder? probably not a valve problem then. Ive never seen a MAP stop a car from running, but may cause shitty running conditions.

Spun distro or maybe he stripped the gear on the distro and its not actually doing anything? Pull the cap off and see if it even rotates.

if it has compression in the proper cylinder at the proper time the chain is not jumped and a leak down test would show no bent vallve train items,my guess is it has a crank sensor/cam sensor type issue jmo

Yeah I didn't think to compression test it as I did the plugs, I only did one cylinder quick afterwards. I will check the distributor this weekend, what is this "spun" distributor you guys mentioned do they commonly get damaged somehow so they jumped or no longer spin or something?

the distributor spins around and the timing becomes way off to the point it doesn't start the engine....the computer will try and adjust it and wont be able to get it right.... based on the poor performance after he peeled out ...the chugging/barely running no power.... thats the way an engine runs when it becomes severely retarded

iirc the distributor housing is plastic but the gear is metal...the bushings can seize like anything or the hold down for the distributor may have come loose enough to let the high rpms spin it around

It absolutely needs the map sensor, it won't do much of anything w/o it. The MAF can be unplugged and it will revert to speed density and run ok on the map sensor. If you get up against a wall, I can scan it during cranking to see if it's picking up a tach signal and check the cranking timing. This sounds like classic cam sensor issues in an ls1 car. If something happens to the cam sensor where it's looking for a matched signal to compare crank angle the timing of injection a ign will be all dicked up. But the crank sensor, if it fails you get no spark, no fuel, and no tach wiggle when cranking.


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Pull the cap off the distributor and see if it is green as hell inside there-incredibly common for a 4.3L Also get yourself a spark tester, they are cheap as hell and just hook it up to the coil wire to see if the coil is giving spark as it is also a common fail point. If you have spark out of the coil, hook the spark tester up to the end of a plug wire to see if you have spark out of the cap.

Ran though the tests of the ignition system today. Found no spark off plug wires, no spark off coil, coil had power and seemed ok resistance wise. Didn't seem like it was being triggered. Checked the trigger from the PCM to the little ignition module next to the coil and that seemed ok so I replaced that little module and sure enough that was it. Not sure how overevving it would kill or fry that little thing, maybe it was just coincidence that it happened while the kid was screwing around.