Hotspotoutdoors

1996 S-10 Blazer
4.3L
186,605 miles

Original customer complaint: Runs OK at idle, not so good at normal throttle(missing/chugging), but better if you step it down.

Did the normal diagnostic procedure, and found the cam timing to be -14 deg.

Got it set to 0 deg., and ran great. Went for a test drive, all is good.

Customer pics up the vehicle, and has it for a day.

Now it won't start.

No Codes
Fuel pressure: 58-60 psi and holding
Injector pulse: yep
Spark: yep
Compression: 165 psi

Customer installed: cap,rotor, spark plugs Plugs are wet

Removed the two upstream O2 sensors to make sure the cat is not plugged: Nope

Check to see if the timing chain jumped(get #1 to TDC, and check the rotor alignment) good

The weird thing is when you crank it over like normal: nothing

When you just bump the ignition switch to crank, and not crank it over, it will try to start. Had it fire a couple times, but no start.


What in the heck is going on with this thing? What am I missing?

I am thinking that the Distributor is the cause.(Cam sensor)

Have any of you other techs run into this problem before?

Thanks

BBB

Do you have spark while cranking?

Yes, at the cylinders.

airjer,

Do you have any idea what this could be? I have about ran out of ideas on what to check next. It just doesn't make any sense to me why it won't start, or at least back fire while at a constant crank over.

I had a 97 for about 5 years and at some point or another just about every %$#@ sensor went out on it at one time or another. You did list two of the things Cap & rotor and fuel pump that I was going to suggest because yes they also went out on me. One other thing to check is the ignition switch it's self, that was yet another issue we had and had to replace. Glad it finally blow up and I got some cash for clunkers money out of it! Good luck!

You got me!

Nothing unusual with scan tool data?

The ignition thing seems weird but I cant figure out why it would react like that since the pink wire that basically powers everything appears to be powering everything.

I was told the resaon the ignition switch was bad, was because every time you turn on your igntion before the car starts it makes a test of all your sensors and other systems, and if one is bad, it can not complete the test. So it does not complete it and will not start the car. Once it was replaced, it started?

I worked on it for a while today.
Pulled the distributor/ checked for unusual wear/ nothing
Install the distributor back in.

This time I checked the compression on all the cylinders while watching the spark at the same time. The spark was hitting the same time the compression hit. It is not a timing issue. While having the plugs out, hooked up the injector harness to see if fuel was getting to every cylinder: yep.

Installed new AC Plugs( plugs that the customer put in had cracks in the porcelain around the poss. electrode on three of them).

Tried starting it: no go.

Removed the nuts in front of the cat, and separated it from the y-pipe. Spit/sputter/fired up and ran/checked the cam retard again/adjust to 0.

What the heck?

Slid the cat back together with the y-pipe to verify that was the problem. Still stays running with no back pressure. Tightened the cat nuts back up, started it up again.

I have no idea what I did, but it is still running with all the exhaust back in place.

Confused as all heck.

I will try it again after it sits overnight, and cools down.

Is there a sensor of some sort on the exhaust piece that you slid back? Maybe it got bumped and now is functioning again. That is a weird one... My son had one about the same year with the same problem. We found that the distributor was a couple teeth off but the computer seemed to be making up for it... most of the time... Thats a weird one... at first i though ignition switch but then you said that you had spark while cranking. Things that make ya go Hmmmmm!!! Take care and N Joy the Hunt././Jimbo

The only sensors on the exhaust are the O2 sensors(three before the cat). I had the front two O2 sensors out before to check to see if there was an excessive amount of back pressure in the exhaust, and it still wouldn't start with both the O2 sensors out.

There isn't anything unusual in the data readings on the scanner either.

Things that make you go Hmmmm, is right.

Did somebody stick a potato in the tailpipe?

That's funny, but no there was no restriction in the exhaust. I think that it was just coincidence that it started after separating the exhaust before the cat. I did put the exhaust back together while it was running, and still ran great. I will be trying it Monday morning to see if letting it sit over the weekend changed anything.

There easily could be a exhaust restiction that has nothing to do with the cat. (the proverbial potato in the tailpipe)

One of the dozen or so baffles could be loose inside of the muffler and getting in the way of the flow path. If its loose inside there it could be getting in the way and then rattling out of the way letting it run for a while. Kind of a pita to diagnose.

I used to work at a exhaust shop and I saw it several times where the spot welds holding the baffles in place break/rust out. We only saw that because we would get bored and cut them apart to see what it looked like on the inside. Pretty easy for something like that to go unoticed until the bugger stops running.

That is what we were thinking before we went home for the weekend. We figured that all the rattling from the impact wrench on the exhaust might have done something inside. I will be taking a closer look at the exhaust on Monday. The weird part is that I had both upstream O2 sensors out, and it still wouldn't start. The last plugged cat I had, it would run with the O2's out, unlike this one.

Another thing that tends to be a tough to diagnose problem with those trucks is the pcm. Its mounted on the passenger side fender and likes to have solder joints break off the circuit board.

When its running, tap it with your hand (firmly) and if the idle changes or it dies, bingo. Even with the scanner hooked up it all looks ok but it is really not.

That is one thing that I have not done yet, and will do that also. I haven't had too many bad ECM's in these, but will look at that possibility.

Curious... Is there an update for today? This has become quite intriguing...

Tried it this morning when I got to work. Guess what: No start. Tapped tested the ecm, and still a no go.

You got me what is going on with this. Doesn't make any sense with all the tests that have been done on it, and it won't start.

It sounds like it is flooding, correct?

Have you tried holding your foot to the floor (deflood) while cranking? How about the pedal just off idle while cranking?

Would it be possible for the IAC to be stuck in the closed position? The dodges are famous for this. They'll crank all day long, flood the cylinders, and never give the slightest hint of firing up until you barely crack the throttle or hold them wide open.

"It sounds like it is flooding, correct?"

That is what I thought when you said you had wet plugs.

One last thought. Over the years I have had a couple with weak spark that ended up being bad ignition modules. I don't know what kind of spark tester you have but it if you haven't already it may be worth checking the intensity of spark with an adjustable gap spark tester.

I tried opening the throttle, and it didn't make a difference. I do have an adjustable spark tester. Had it set to 20kv when I tested the spark.

The part that gets me, is when you tick it over, and not just keep cranking, it will try to start, but that is it. Try cranking over normal, and nothing.

I was thinking about the module and coil. Just thought that there was enough spark out of it.

Correct me if I'm wrong, but the way that I read it about the cam sensor in the distributor is that it doesn't even read it until at, or above 1,000 rpm. That is why you have to raise the rpm's when setting the cam retard. Is this correct?

[/quote]The part that gets me, is when you tick it over, and not just keep cranking, it will try to start, but that is it. Try cranking over normal, and nothing. [/quote]
Did you ever check the ignition switch it's self yet? It maybe wearing out, so when you turn it so far it turns over but when you go all the way it stops making contacted? Just because it turns over the starter does mean it is switching on the rest of the sensors if its wore out. My sons Blazer did the samething. I could spray a little WD-40 in it to make it work for awhile but it just went out all together in time.

I thought of that as well but he said he had spark while cranking?!

You said you checked and the dist is inserted correctly? It can be off and the computer makes up for it. That is what was wrong with my sons... WEIRD MAN, WEIRD!

Leech,

Did your sons have fuel pressure, spark, injector pulse while you were cranking it over?, or just when you would just tick it over?