My wifes '94 Blazer S10(4.3L V6 CPI motor, 4X4 auto trans) stopped running while I was driving it. After I got it to the shop I tested it for spark, fuel, pulse at the injector etc...

Everything seemed to be working fine. This car has the CPI or CFI? Central fuel injection system with one injector under the intake that has a built in regulator and six spider arms that go one to each cylinder.

I pulled the upper intake off to check the CPI injector.

I used a 'noid lite' that shows pulse at the electrical connector on the injector, and I have excellent spark.

Fuel pressure is steady at 38-40 PSI. Fuel is coming into the injector but not getting to any of the nozzles at the end of the spider arms.

I pulled the return line from the CPI injector and left the fuel inlet line connected but I have noi fuel comming through the injector and back out to the return side. Also as stated before no fuel is reaching the nozzle end on any of the six spider arms.

After removing one of the spider arms from the CPI injector I turned on the key and had fuel coming out of that hole where the arm used to be.

After doing some research on this CPI system I found the fuel pump pressure should be between 54-64 PSI. If that is the correct pressure for the '94 CPI fuel injection system then my problem could be a bad fuel pump.

From my understanding, the built in regulator on the CPI unit uses a spring diaphram to regulate a constant fuel pressure of 54-64 PSI regardless of engine load. I also understood that the nozzle on each one of the spider arms has a spring or a ball valve in the end that must have adequate fuel pressure or it will not spray into the combustion chamber.

My question(s) are if my fuel pressure is only a constant 40 PSI then will the CPI system work or does it require 54-64 PSI. I would like to verify the fuel pressure for this vehicle. I may be incorrect about the 54-64 PSI.

I think she needs a new fuel pump but Is it strange that my fuel pressure stays a constant 40 psi? Can it be because of the rubber in the tank between the pump and line is cracked or rotted.

Thanks in advance, I'm on to work now will check later.

My guess is that the low fuel pressure isn't causing your problem.  I would say that its the ECU.  Maybe you can borrow an ECU from a buddy, and swap it out to see if its causing the problem.  

Changed the fuel filter lately? I had a '89 Blazer that did that once. Took it to the shop and they checked the fuel filter and it was nasty...black and gummed up...they changed it out and it never did it again...

They told me that the filter just kept flowing until the filter could not pass enough fuel through and the engine stopped.....

had an old 4.3 like this except it would not start after running- it was the "spider" thingy  only costs like 600 for the part which fails again....heard of may people with this problem

OO your luckly I found your thread.

I've been pretty involved with these S-10 lately due to owning one.
I actually have 92 with the CPI in it.

Your 100% correct about the fuel pressure.

The poppet nozzles NEED at least 54-62psi to open, or it will not spray and kill the engine.

If you have gas coming out of the ports in the intake then you've also flooded the engine with gas or going to when the valve opens when you crank it over.
Make sure you change youe oil also after you change the pump.

Starting the car with the throttle to the floor with clear a flood condition FYI.

Heres a question for you, how many CPI injector have gone bad on you?
These gen1 vortecs (92-95) have an injector issue and they go bad alot, causing your engine to run like crap even though it could be fully tuned.

The easiest way to tell if your injector is leaking, the passanger side of the intake(when you have the upper intake off btw) will be clean with fuel. If the drivers side is clean with fuel, is the to and from fuel lines that go into the injector that can crack and leak.

Quoted: had an old 4.3 like this except it would not start after running- it was the "spider" thingy  only costs like 600 for the part which fails again....heard of may people with this problem

Hah, it costs 200 bucks on ebay or on other sites on the web.
You can replace it yourself in like 30min to 1hr.

DUPE..   www.ar15.com/forums/topic.html?b=1&f=5&t=241770

Wow someone's on it.

Quoted: had an old 4.3 like this except it would not start after running- it was the "spider" thingy  only costs like 600 for the part which fails again....heard of may people with this problem

It is very common on the Vortec engine..   Part is $375 at the dealer, or $245 at the dealer if you get a dealer discount  Plus If you replace the "hose kit" (2 fuel lines that generally go bad as well) it is another $40  The plenum gasket is another $9  

If you replace the hose kit you need a set of torx style allen wrenches (like the ones that come with leupold rings, but bigger..If they have a different name, sorry I dont know it) Because there is a PITA cap screw that is a SOB to get at with anything else.