If you remove the upper plenum and see this:


copper color pass. side ------------ carbon black driver side

Then your FPR needs replacement. Dorman Products Part number: #55162
http://www.oreillyauto.comprice $45 w/ tax

Edit:
For the vacuum issue you might want to check your vacuum ball (mounted on the hood drivers side. I have found several with cracks. Just my 2 cents on the subject.

 

When I took my upper plenum off it looked worse than that. Very clean on left side and huge carbon deposits on right side.I decided to leave the FPR/spider injector alone since there were NO gas puddles anywhere. But the connector wireto the injector was loose in the socket. The connector and small harness was $95.00 at dealer. I don't know if the connector was the problem because I changed the cap, rotor, wires and plugs at the same time and the miss was gone. That was at around 200K. I now have over 350K with the original FPR/spider injector. Runs fine. Garage wanted $700 to change it, but would not guarantee that that was the problem. Ahh OK!Two or three owners have had it changed in the last couple of months on here and it wasn't the problem. It's a lot of $$ to shell out and not be sure if it will be the fix. The spider injectoralone is about $300 new on ebay and $450+ at the GM dealer (not including the nut kit).

 

[&o]

I've said it before and I'll say it again (broken record here I come), you cannot just blindly ignore the spider assembly!!!! There are simple checks that can (and should) be done, but please do not continue to give bad advice and say that such a wide spread & known problem really is nothing to even consider just because your wonder truck hasn't had an issue. That is just ignorant.

There, I'm done.

 

Ok. Ill make sure once im home from college to get it all checked out. What are the simple checks i can do so that i know its working properly? Is taking the upper plenum off the only way to check? Im sure it is i just wanna make sure before i rip it down in the near future...

thanks for all your help

 

Read my previous post in this thread. If you check the fuel pressure and notice that it drops over time after key off, then you have a leak somewhere in the system. It could be in the fuel pump check valve, it could be an internal leak in the FPR just bypassing to the return line, it could be an injector leaking, could be a faulty FPR leaking into the intake, or it could be a faulty o-ring somewhere in the system.

Once you have verified that there is a leak in the system with a gauge, you would then remove the upper plenum (CPI motors) and pressurize the system. What you'll be looking for is wet areas around the FPR or under the CPI spider itself. Pull out each of the poppet nozzles from their bores in the lower intake manifold and check to see if any of them are weeping. If they are, then a new CPI unit would be in order as I do not believe that the main injector is serviceable. If it is just the FPR, that can be replaced independent of the CPI unit, but if you remove the internal fuel lines (nut kit), you should replace them. While you're in there, check the electrical connection to the CPI unit as Blasir states just to verify that it is making good contact.

 

The Spider Injector Assembly is repairable.
Areas they leak:

Spider lines (3 per side) O rings go bad (fixable) Lines crack (GM part)
FPR goes bad (Fixable)
Fuel Supply lines go bad (Fixable)
Single Injector goes bad (Fixable)

All these can be fixed for LESS then replacing with a $300 and up unit.
Info supplied by a GM Mechanic via GM dealership (off the record that is). They stated that this is mainly what they do over replacing it with a new unit. Its up to the shop manager on how they bill it out. So if anyone has an old spiderinjector unit laying around, they can be rebuilt as long as the main housing is not broken.

 

Here is my advice. If someone tells you that your problem is the spider injector, just ask them if you have to pay for it if that does not fix the problem? That is all you have to ask. I did and they said that they would NOT guarantee that that was the problem. DAH! I was going to shell out $700 for someone to guess? There is NO doubt in my mind that when I went to pick up the truck I would have heard the old "well you also needed the harness and we did a tune up afterward." That is when I decided to look inside there myself and I did not see gasoline puddlesall over the place. Yes, the LEFT side is clean and the RIGHT side was black withcarbon deposits. The exact same as every picture that I see on this forum when people take the upper plenums off. My feeling is, let's start with the cheap crap FIRST. Get inside your plenum as aLAST resort. Don't start there. If your spider injector is NOT broken, you can easily break it by trying to remove the injectors or the FPR. The injector lines are some sort of polyvinyl that looked very fragile from the heat that they are subject to over the years. Injectors are justa plastic material that you could easily snap the clips off.

One other thing that I noticed when I removed my upper plenum was that there was carbonON the plenum gasket which I assume ment that the gasket itself was leaking. Just replacing the plenum gaskets may have an impact on helping the Vortecs to run better.That is only a $12.00 part.

And I do not believe that I have a wonder truck. I believe that the reason I have survived over 350K miles is because "if it ain't broke, don't fix it!"

Use 40 weight oil year round.
Keep your air cleaner clean.
Change your spark plugs often.
Keep your wires away from the heat of the manifolds.

My last 88 Blazer 4.3L went 325K miles. This 95is no wonder truck.

 

Before you start to pop your intake manifold off, check you rotor cap to make sure that isnt easy visible scratches that could cause you fire to arch. While the cap is off, look at your rotor button to see if there is any carbon build up. This happens due to have the cap on to tight.

 

When you do your cap/rotor I found a nice rotor that was a surprise. Its got a life-time warranty,after viewing the rotor next to the OEM one. No wonder they state this.

Its made be "BWD Select" (Engine Management Technology TM)part number D236
MFG info BWD Automotive 37-18 Northern BLVD. Long Island City, NY 11101

It was worth the extra cost to have the warranty. And its made way better then the OEM.

 

Ok I just have to come in on the spider injector thing. I am new to the forum but for the past 13 years I have been supplementing my income buying vehicles with problems, fixing them and reselling. I have found a niche with blazers, jimmys and 4x4 s10s because once they run good the value returns very nicely, and with the 4.3 9 out of 10 times when the engine idles very rough and start running so bad it becomes un drivable it is the spider injector. The owners at some point have enough and bail out. I will buy very cheap, go to a junkyard and get the whole manifold for about $60 to $80. Not all injectors fail and if you seen enough of them you can tell just by looking in the plenum if they are good or not. Now I have said 9 out of 10 times and I just took a break and got my records, since the first of the year I have bought 36 4.3’s and 27 of them I replaced the manifold and resold. When I say the spider injector was bad that I am including the nut kit, the FPR and the popets as well. All but 2 of the 27 had gas puddles inside the manifold and the last one I made a postabout ita few days ago was the worse. The guy who owned it got advise like I have heard in this thread to "not mess with the spider". He did not, so when he reached the end of his rope I got the Jimmy for less than I give for a set of used tires and it had new tires. It also had over 2 gal of gas in the block! The engine had stopped turning over and when I pulled the plugs gas shot out of each cylinder (always wear eye protection). There had also been a fire inside the plenum that must have fortunately smothered it’s self out. I am not sure yet if the engine will survive but if it does not the jimmy is in such good shape I could put a new engine in it and still make a profit. But since this guy was not going "mess with the spider" and had exhusted all other options it was worthless to him, Any way my point is if you smell gas check in the plenum… Or keep trying to find what else it could be and when you give up let me know and I will make you offer (the yards here still have plenty of 4.3 with good injectors) and I will come take the problem off your hands.