Ok, I'm officially frustrated. I"m out of ideas how to get this fixed. Here's the problem:
Engine was replaced with a GM crate engine. So any mechanical failure from that area can be ruled out. Engine starts, runs for a short while then stalls, plenty of black smoke coming from the exhaust, raw fuel is found in the intake and EGR.
IAC, TPS, Fuel Filter replaced. Same thing. EGR, cleaned, one valve was stuck, same thing. Floods and stalls. Fuel pressure regulator, tested diapraghm, holds the vacuum, no fluid leaking from that side. Applied pressure to the regulator through air compressor, regulator opens. Disconnected battery to reset PCM, same thing runs for a while, floods, stalls. Checked all spark plug wires for proper resistance, they check out, Spark plugs, new. 95 has no MAF, so that one can be ruled out. Don't have a code scanner handy, on my Buick i can jump terminals to get the codes displayed on the dash, doesn't work on 95 Montes, only has two wires in the ALDL connector. Fuel injectors under pressure won't drip.
I have checked the internet, and a lot of folks seemed to have had that problem , but nobody really posted the fix.
That's why I don't like fuel ignition, too much crap to go wrong. Love my Pontiac 400 for it. Anybody with an idea out there what could cause this?

 

Sorry 2 read about your frustrating problem. Do you have a friend that you can borrow a scanner to check for codes ? Your (Thread) post is now on the World Wide Web & I hope that one of our expert techs reads your thread & posts a solution...Good Luck 4-Sure

 

I would never believe that 100%, any company builds 1000's of something, there is bound to be one that's not right (hence warranties). But odds are in your favor, the engine is probably not it.

You are getting un-ignited gas through the intake. I believe you have 1 of 2 situations (possibly a combo) going on:
- You are not getting proper spark
- A situation is existing that the PCM is telling the engine to dump more fuel then it should

Now, I mentioned a "combo" situation, the PCM in these cars has a "limp home" mode. If this is like the '94/'95 3100 powered Grand Ams I used to spend a lot of time with, when the car detects a mis-fire, the PCM will increase the Injector Pulse Width (how long the injector sprays fuel). I don't believe those mid-90's 3100s could determine which cylinder was miss-ing, so the was to compensate for the miss by throwing more fuel at all cylinders to help get you home.

First order of business, take your ICM off (sits under the coils), drive it to the parts store. They should be able to bench test this (have them run the bench test about 2-3 times). This controls the ignition system in the car. If it failed, this could be as simple as some or all cylinders are NOT firing. Another way to at least test if you are getting spark is a test light that goes inline with the plug wire. DO NOT remove the plug wire and try to start or run the car with it disconnected. Because this is a computer controlled system, trying to do that method to see the arcing could damage the electronics.

Next, if the ICM test good, I would consider inspecting the coils. Now, I've been lucky if I ever think it's the coils, I can borrow them from one of my other cars to test. It's rare I see a coil die (it's more common to see the ICM fail). Also, in the rare times I've seen a coil die, I won't use an autopart's store coil again. They have issues lasting the long haul, I trust factory original off a salvage car more.

Keep in mind, your coils on your '95 3100 are the same coils GM has used on the '94-'2004 (maybe longer), 3100/3400 and 3800 Naturally Aspirated engines (the SuperCharged 3800 coils are a tad different, but will work on a non-supercharged car, all my cars have a set of them). Also, the ICM is the same from the '94-'04 3100 and 3400 (3800 ICMs don't fit).

This is also my typical statement about plugs, if you have BOSCH plugs, get rid of them. I've had too many bad-out-of-box or fail in 6 months. AC Delco or NGK are the best plugs to run in these engines.

Sorry for the long post, but I hope it give you some direction to move forward.

 

coils and icm checked out. the plugs are ac delco.

 

OK, so the ICM and plugs check out. Do you know if all cylinders are getting spark? I know stores sell test lights that can be plugged in line with the plug wires, this would be a good safe way to check for spark (and should pose no risk to the electronics).

Do you know if it has any check engine codes? I know you mentioned trying to jump to terminals to flash out the code (I believe GM did away with that technique long ago). You will probably need to borrow a scan tool. Finding out if there are any codes in memory may be the quick way to getting your answer.

Something is either telling the PCM to dump more fuel in then it should OR something is causing the cylinder to not ignite at the right time.

As I am typing this, I just had an offer the wall thought (but don't have the time to search for the answer). Do you know that the firing order is correct? FYI - some people assume the numbers GM stamped on the coils are correct firing positions, don't assume that. If perhaps the firing order is wrong, this might explain everything.

Just grasping at straws in hopes to find an answer man.

 

spark plug wires are hooked up correctly. triple checked it. i ordered a scan tool, but it will take weeks to arrive.

 

so after numermous attempts trying to scan for errors with no luck i went with the kiss method, and in a desperate attempt tried the craziest idea and pulled the fuel injectors again and replaced the o-rings with newer and thicker ones, and it runs! so nothing but a few tiny rubber pieces causing this situation. crazy.

 

Nice!! Glad it turned out to be something so simple (and cheap). Just stinks it took so long to figure out.

 

I'm not saying this is what happened, but it sounds to me like the injector wiring was out of sequence so some cylinders were receiving fuel at the wrong time. Worn/Leaky o rings will not cause an engine to flood. Glad to hear you resolved the problem though.