Alright, so I'm trying to figure this out now over the last day on what could be wrong with my 94' S10 Blazer with the 4.3 Vortec motor. I bought it about a year ago for $500.00 and got it running after figuring out the idiot before me just never changed the oil and it plugged the oil pump up which he thought it was bad and it was running strong for seven months now with no engine oil burning or anything of the sort.

About 6 months ago I replaced the fuel pump with screen, The fuel pressure regulator as it show signs in the plenum of washing out on the passenger side. Than also have done a tune up at that time of plugs, wires, cap & rotor. I had similar issues going on back than as I do now. So I put a fuel pressure gauge on and got 58 psi. It than dropped back to 56 after 15min and if it sits over night it will go down to 32psi. So I had a lifetime warranty on the fuel pump and have a access door made and yanked out my fuel pump and exchanged it for a new one as it should read 60psi when key'd over and my fuel pump did the same thing last time and when I replaced it, it solved all the problems. It than read 60psi when I key'd over, but did not fix my issue of not starting and did leak down over a period of time.

So than I went and checked spark, had good spark coming out of the main module and also out of the cap. I also had autozone check my ignition module under the cap and rotor and it passed, than failed. So I replaced it and it didn't do the trick. So I took that fricken thing back as it was 45.00 and not needed. I also have a engine code of engine knock sensor eiether below voltage or above and didn't think this was causing it not to start as the engine code had been on and I just thought it was a o2 sensor orig. for the last month. My engine had no knock at all by any means as that sounds pretty nasty and def. would hear that, so I'm sure the sensor just failed from age.

I had problems for two days before it did not start, first it wasnt much, than it slowly progressed to worse. It would run and drive smooth, than would sound like its missing, than it would clear up and drive great again. I couldnt figure it out as all wires looked good and was moving at the time, so couldn't rip it apart. Well than two days ago when on my way home from work, it took a turn for the worse and started missing and bogging down to the point I could barely push the gas or it would do nothing. When I slammed the gas down, it wouldnt move or bring it up to speed, a light foot and it would keep limping along. Than it clunked out and after ten minutes of sitting and upset along with calling someone to come get me. It started again and limped along again for maybe 3-4 miles and has not started again. It sounded like I was not getting enough gas, or not enough spark at that time. So this is where It all sits now.

So my question is. I want to figure out how to diagnosis whats leaking and if its a fuel problem or is something else? I was thinking of tossing some starting fluid into the air intake and see if kicks over at all. Than if it does, I know its a fuel issue. But than how do I know if the assembly is bad or if its the regulator, or the nut kit? I know I replaced the regulator with that fuel pump not long ago and can't believe it would go bad. Otherwise the spider assembly could be plugged up? Would I be able to free it up at all somehow or am I stuck on replacing it? Whats the route to go on discovering all this.........

Thank you for all your comments and I appreciate it all as I'm pretty frustrated.

 

When you replaced the fuel pressure regulator, did you remove the CPI spider or move it in any way? If so, you may still have a leak inside the plenum. The internal fuel lines do not like to be disturbed. I always factor their replacement into the cost of messing with any in-engine fuel system components on the CPI engines.

Another problem with the CPI engines is the connector to the electronic injector. These have been known to loose contact causing an intermittent injector activation which can lead to a no-start or stalling situation.

As with both fuel system configurations using pressure actuated poppet nozzles (CPI & the newer SCFI) the poppet nozzles can gunk up and cause problems. GM has a TSB on this issue that states to clean the nozzles using their fuel system cleaning process (run the engine off of a bottle attached directly to the fuel feed line at the intake) and if that doesn't work, replace the fuel spider.

Just some ideas. Good luck!

 

No I didn't disturb or move the assembly at all as I was warned when going into the plenum that I should not move it in anyway as it becomes fragile over time. So i didn't move it and replaced the regulator with it all in the upper intake as it was only two screws to take off and replaced easily. The nutkit looked good at the time as it was not washed out at all. I never cleaned the whole plenum up as I didn't want to disturb anything or bump the injector lines. The passanger side looked like it was starting to get a little bit of gum on it, but was still cleaner than the rest of the system, but I'm sure that is still due to the old one washing it out not long ago.

So how do you run a bottle straight from the engine? I know that the fuel pump is what pumps it into the injectors and also requires a good amount of pressure to activate the injector? Anywhere where info was on this? I will have to do a google search on it after Im done posting here.

I appreciate your time and help in this!

Also will have to check out that connector on there. I know when I removed the top sensor. Can't remember which sensor that is, but allows me to look down into the plenum.

Thanks
Conrad

 

Hes talking about the wire plug that connects to the top of the injector. You changed your FPR on the spider, but there is also a wire plug that goes to the injector. Its got a rubber insert that holds it tight to the injector. Well rubber and gas dont mix, and it erodes easily once it gets gas on it making the connector flop around on the injector top and lose electrical connection. You cant buy the rubber, but at NAPA you can get the plug assembly for 15 bucks, just cut off the old plug, and solder on the new one and heatshrink the connections, you wont be able to get the new one through the plenum, so cut the wires off at the old plug so you have some legnth to work with. It has blue and red wires coming off it, and you will need to pull the upper plenum off to get at it. Napa wont be able to find this part for a 90s blazer, but ask the napa guy for the injector harness for a 95 half ton with the V6 and its the same part. My blazer had this same sort of problem, and this was the fix. Once you unhook it look up into the plug. There will be 2 tiny wires that straddle each of the 2 prongs on the injector, these should be perfectly PARALLELL to one another, one side of mine had a crooked wire in it making a crappy connection

Try wiggling the blue and red wires where they come out of the right front of the plenum and see if it makes your problem happen when the engine is on. Just below and to the right of the throttlebody. If this connector is junked, you will make your problem happen while its idling and you jiggles that wire around some.

 

Well I sprayed some starter fluid in the intake and it kicked right over, it did not stay running at all. So i know its gotta deal with the fuel injecters as I stated above I have a brand new fuel pump and its getting 60psi to the rail at the gauge. Time to pull the plenum and check wiring and what not... I'm just afraid if that spider assembly some how got plugged, I don't know how I can get it unplugged or what not. I will look over the wiring and everything right now within the half hour


Conrad

 

Thank you everyone for your help. The issue ended up being that I had a old brittle wire connector plug on my spider assembly. I messed with it and the truck fired right up. So I'm replacing it today and truck ran great after that.

Thanks again!
Conrad

 

This may solve my problem as well. I tried using RTV liquid gasket on the connector after seeing the rubber was melted, and that may not have fixed the issue.. probly gonna have to buy a new one, but now at least i know what else could be ailing my beast and how to fix her. thanks for your helpful posts!!

 

Chucks, i woudlnt try to tighten that injector connector with RTV, cause RTV is an insulator not a conductor, and could very well make the problem worse by blocking the current you want to pass on to the injector. The replacement harness is available for no more than 15 bucks, just cut the blue and red wires (not at the same time) and solder on the new harness. If you really want to not spend the 15 bucks, then use 5minute EPOXY resin to glue it in place.

The easy way to see if you need this harness is this:
With the engine running, wiggle and tug on the blue/red wires that come out the plenum to the bottom right of your EGR valve. If you get a poor run condition or stall, then you need that connector replaced.

Cut the wires on the INSIDE of the plenum, and pull them back through the gromet (you will never get that gromet out) then push your new wires through from the inside, put it all back together, and do the soldering and heat shring on the OUTSIDE of the plenum. The replacement harness is plenty long enough to do this. I had this problem on my 93 and the 15 dollar harness was my final fix and had her top running now.