Here's a good one to test the combined wisdom of the group:

The vehicle in question is a 1996 4wd 4.3l CSEFI Blazer.

My son has been having performance problems for the last few months.

It started in late summer last year. It would lose power & surge during acceleration & the fuel economy is pretty bad. It is only an intermittent problem as at times it would do OK.

We did the standard plug, wires, rotor. It didn't really help much. We even changed the fuel filter. It was definitely shot. You could hear the filter element rattling inside the metal can. Just to be on the safe side we put some fuel cleaner in it in case it was clogging the injectors.

Then several months ago it wouldn't start at all (crank but no start). At that time I checked spark with an inductive tester & also with a spark tester that you plug into the plug wire. Both showed I was getting spark. I wasn't sure if it was adequate spark, though, so I took the ignition module to Autozone & had them test it. It was questionable so I got a new one. It didn't help.

I then got a new distributor pick up module & installed it & it then started up & ran quite a bit better...for a while. After a few weeks it went back to acting up again but, at least, it started up every time.

Then in December it wouldn't start again. I checked for spark again, did a compression check & all cylinders showed good. I could smell gas when we cranked it so I was fairly sure I was getting good fuel.

Since we had just had a really wet snow I guessed it might be a moisture problem but I had no idea where so we left it sit for a day or two & it started up & ran the same as before...kind of crappy but at least it ran.

Then last Wednesday after a few raininy days it wouldn't start again. I did a quick check of the rotor, wires, several connectors, etc but couldn't find anything obvious. I got a can of electrical connector dryer & sprayed it on all the connectors I could easily get to having to do with the ignition system but it didn' do any good. Out of desperation I even put in a new ignition coil but to no avail.

When we were putting the dist. cap back on, the front screw hole in the ditributor broke out (the distributir base is frickin' plastic!). I figure there was at least one screw holding it on so I took a chance that it would be OK.

After a couple if days it started right up again, though.

Then that afternoon as he was driving down the highway he said it started bogging down then back fired a couple of times & died.

It hasn't started since.

THIS TIME:

- I took off the cap & found the rotor contact was busted off. I figured that the cap may have jumped since it only had one screw holding it down & damaged the rotor. I got a new rotor & used a slightly oversized screw to hold down the front of the cap. It still wouldn't run.

- I thought that the cap may have been damaged by the rotor flying apart so I got a new cap even though the old one looked OK. When I went to install it I noticed cracks in the rear screw hole on the distributor & as soon as I went to screw it in, it broke out, too.

- I then went & bought a new distributor. I marked the old one before I pulled it & marked the new one based on the old one. I put it back in exactly as I took the old one out. Still wouldn't run.

- I then pulled the plugs & rotated the engine to line up the timing marks & the rotor pointed at the mark on the distributor base exactly as it should have so I'm positive I've got the distributor in correctly.

- I rechecked the spark with the inductive tester, AGAIN, & had power to the plugs.

- I bought a fuel pressure tester & when the key is turned on I get 60psi & when the engine cranks I get 65psi.

- I pulled the injector connector & ohmed the injector coils & got between 11.5 to 12.2 ohms on each one. I used a test light at the connector & every plug had power to it (flashed intermittently).

- I pulled the ignition module again & had it tested & it was fine.

- The guy at autozone recommended checking the crank position sensor. I pulled off the connector & with the key on I had 11.49v on the upper terminal. My Haynes manual says that to do a quick & dirty check on the sensor you can check between the other two pins on the sensor itself & it should read between 800-1200ohms. On doing that I had an open so I checked between every combination of pins in there just in case I had the wrong 2 pins & always had an open. I bought a new crank sensor, installed it &...NOTHING. It still won't start.

- I thought MAYBE when the engine backfired it may have screwed up the timing so I rechecked the compression. I had anywhere between 150 - 165psi on all cylinders except #3. I didn't check that one since the plug is so difficult to get out but the rest were good so I had no reason to suspect that one either.

- All the plugs I pulled were damp with gas but not fouled completely so I cleaned them off, checked the gaps & put them back in.

- It still won't run. I doesn't even try to run.

TO RECAP:

New ignition module
New rotor, distributor, cap
New wires
New coil
3 new spark plugs (I broke them pulling them the first time)
Good gas pressure
I assume the injectors are working based on the above checks & smelling gas when I crank it
Checked distributor timing
Good compression
New crank position sensor

Any suggestions on where to go next before I take it to the dealer to have them, hopefully, diagnose it?

This truck is killing me! It's too bad he's too broke to buy a different one.

Any help on this would be GREATLY APPRECIATED!

 

Not to long a go there was a post about the crank position sensor gap causing a no start condition. I think the gap was to great in that instance. Look for that post. I'll look and reply again if I can find it.

 

Lets verify.. you HAVE spark, right? Pull the coil wire off the cap, stick a plug in it and verify hot blue spark.

About 3 times a rev.

That post Chevy33 referenced:
https://blazerforum.com/forum/engine...o-start-68126/
That's on the ylw and ppl wires

 

I didn't verify the spark at the plug this time but all of the other times I did & yes it was a small blue spark. I did check it with an inductive tester (the light thing you wrap around the plug wire) and I had voltage/current at the plug.

I'll try the coil wire directly tomorrow.

I kind of doubt that it's the gap on the crank sensor since it had been working & it's the same mounting surface but it's definitely something to check out.

Thanks!

Anything else while I'm in there AGAIN?