Hello everyone, I just registered here in hopes of finding some information.
I have a 1995 Blazer with the Vortec 4.3. This thing is having some issues, I don't know its history, but here is what's up.

Engine cranks but will not fire, at least sounds like it will not fire, I have not checked for spark yet. Power to the coil is good.

Fuel pump was replaced and is audibly working, have not checked pressure yet.

It was recently serviced by a GM dealer that replaced the control module located on the coil. They also found a loose wire in the starter relay and repaired that.

Occasionally, it stalls during cranking as if it were firing out of sync or a mechanical problem in the starter/flexplate, but starter sounds normal usually.

Last time it was running, it ran at lower than normal RPM (500) and was having trouble shifting when warm. It died and has not started since.

Tried to connect a paperclip to the ADL, nothing. Hooked up a scanner, nothing. There is no communication at the diagnostic link.

Fuses all appear good condition, important ones verified working.

I was hoping to find someone willing to share a wiring diagram for the diagnostic link as well as the ECM wiring.

Someone has done something somewhere as there is residual stereo wiring and a relay box attached to the inside of the glove box that is not supposed to be there, evidently something from under dash though as it appears factory, just switched location.

Can anyone help me out here? Before I yank it all apart and put my bigblock in it?

I am actually thinking this has something to do with the crank sensor, it seems to be firing out of order at times, and I can faintly smell gas and the engine acts like it is flooded and then it is enough to stop it cranking dead in its tracks... what are the ohms readings supposed to be on that sensor?

 

Pull the plugs. I'm betting you'll find a cylinder or two full of fuel. This can be caused by a failed fuel pressure regulator. Have a look in the Tech Article (DIY) section for further information on the CPI FPR.

And your '95 could be any one of 3 different OBD setups. You likely have the OBD1.5 setup which requires a scan tool that explicitly calls out that it will work with '95 model year GM vehicles with an OBD2 plug.

 

Thanks for the reply. I have the innova 3140 scan tool, works quite nicely for the price.
I'll give it all a check, I have had issues with regulators before, quite regularly actually. It is all worth checking out, but I really feel it is something very simple. I'd really like to test the sensor first, just because I have a sneaking suspicion that it may be at least part of the problem. I know it most likely needs a tune-up, so I will definitely pull the plugs and check the wires, etc...

Thanks again for your help!

 

That scanner appears to be a nice one, but it does not state all 94-95 model GM vehicles are accessible. Nor does it state anything about the transition vehicles in the 94-95 time frame which were OBD1.5 (not quite fully OBD1 and not quite fully OBD2).

Your symptoms remind me of a FPR failure which is why I mentioned it. A simple fuel pressure test, paying attention to the leak down once you shut the pump off, will tell you if that is the cause.

 

I finally got around to looking at it today. I need to go to napa and get an adapter so my fuel pressure gauge will connect to it, but it had residual pressure after sitting for 3 days. I also added fuel manually to the intake and it didn't change anything at all, still won't fire and stops abruptly while cranking like it suddenly fired out of sync. I pulled one plug and it looked normal, but they need changed. It was also firing pretty good with the plug, except the spark was usually yellow rather than blue.

On a side note, twice I heard the ignition fire the charge straight out the passenger side exhaust. You could hear it as plain as day. Like it fired on the exhaust stroke.

 

Have you verified the distributor timing? If it is firing with the exhaust valve open, then there is likely a problem with the timing.

 

Actually when I pulled all the plugs they were so bad that I replaced them. It fired right up and ran great for about 45 seconds and then started bucking and died. Now it will not start again. I looked at the fpr and it was black with carbon just like the rest of the intake. I have not had enough time to verify fuel pressure. It should be about 35 psi, right? But the new plugs are slightly damp and smell like gas, just like they should be. I get a consistent spark from the coil to the cap as well as each plug getting spark, 175 psi compression.

 

Can't you still pull codes with a paperclip on the OBD1.5? I had a pinout of that specific connector on my desktop comp, but it died a while back.

 

IMHO, I would agree. Sounds like a timing issue. Maybe jumped timing, Ditributor 180 degrees out, plug wires in wrong order, maybe broken tooth on gear on bottom of distributor? Just throwing out ideas.

 

I just got the stuff to do a full tune-up on it, so tomorrow I will post back what I find out with that. I have to play catch up with the Snap-On man to get an adapter to fit my fuel pressure tester, it is a bit different and connects to my injector cleaner. The timing seems a bit erratic really, like it is jumping terminals in the cap or something. It is shameful the condition of the cap, rotor, wires and plugs on this thing. The electrodes on the plugs were burned off at a 45 degree angle and the gap was burned open to over .100!
There are tower pieces missing inside the cap and the rotor is all burned up as well. Some people just let things go until it needs everything to get it going again.