My neighbor had this blazer and has given me all his receipts for everything he has had done. The garage said that it has a short in the injector unit. It won't start most of the time and when it does it runs like crap. The fuel pump was checked and has enough and holds pressure. When I removed the top half of the plenum there is gas laying in the intake by the fuel lines (maybe a 1/4 cup). I don't think this is normal and checked the lines with a very bad rub from one of the injector lines on one of the lines. It is on the line that does not have the pressure relief valve (return?) I also did a continuity check on the fuel unit which is OK and have an ohm restance of 1.8. Are there any checks I can do to this unit? Could the fuel leak be the issue? I have bought a Haynes manual but it has no checks for the fuel injector unit. Anything I need to know when I reassemble the manifold?

it sounds like you are going to need to replace both fuel inlet and return lines in the plenum, also called a nut kit. since you already have the upper intake off, have someone look under the hood for leaks while you turn the key to the on position, which pressurizes the fuel system. another way to check would be to put a fuel pressure guage on the shrader valve and look for pressure to bleed off quickly. Also, check to see if the fuel pressure regulator on the side of the CPI unit is leaking as these go bad frequently. If you took it appart, you pretty much know how to put it back together. Just don't over tighten the bolts use a new upper intake gasket.

On the short did they say what or how it was shorting?
Check the wiring from the intake plug in to the top of the injector unit.
I have found some bad and loose/burned where they plug onto injector unit.
MT

An Update***
On the garage receipt it has:
Check engine stalling and running rough.
Perform tests with scanner.
Engine running very rich due to coolant temperatue too low. MAP sensor voltage is too high and oxygen sensor voltage fixed at 0.5 volts. Voltage for the injector and rpm are erratic from the computer. (replaced both sensors and computer, engine still has CFI unit that is shorting and causing stall condition).
Is it possible that this is all caused by a fuel leak inside the plenum? If the engine was running rich because it was pulling in gas vapor instead of air, would that account for the other issues? Maybe there is no short just a fuel leak. Anybody see this before or a CFI that is shorting out?
I did do a continuity check on the wires that go through the plenum wall .... OK

Do you have the part numbers for the nut kit? I tried to find it on GMdirect but couldn't.

With the upper cover off I would jumper the fuel pump and look for fuel leaks.
The Nut kit/pressure and return lines and the fuel pressure regulator on the injector body are the places to look for leaks.
As far as the short I am not sure.
But I have never saw one short out.
If it is shorting they are fused and should pop fuse.
To see if the injector is working disable engine spark at coil or dist and crank engine and see if the poppet valves on the end of plastic lines to the cylinder are squirting fuel.
But be careful with the little plastic lines when old and brittle they will break.

You can order the nut kit at any auto parts store that handles HELP products...the big red display with everything from exhaust manifold studs to door hinge bushings. The Nut Kit fuel line kit is part #55163.

Any updates on this? I have a '93 with similar problems.

My neighbor had this blazer and has given me all his receipts for everything he has had done. The garage said that it has a short in the injector unit. It won't start most of the time and when it does it runs like crap. The fuel pump was checked and has enough and holds pressure. When I removed the top half of the plenum there is gas laying in the intake by the fuel lines (maybe a 1/4 cup). I don't think this is normal and checked the lines with a very bad rub from one of the injector lines on one of the lines. It is on the line that does not have the pressure relief valve (return?) I also did a continuity check on the fuel unit which is OK and have an ohm restance of 1.8. Are there any checks I can do to this unit? Could the fuel leak be the issue? I have bought a Haynes manual but it has no checks for the fuel injector unit. Anything I need to know when I reassemble the manifold?

Hey, Have you looked in the "how to" section of this forum there is a 92-95 CFI section:

http://www.automotiveforums.com/vbulletin/showthread.php?t=462726

There is a lot of good info about this particular subject. Somewhere I remember reading something about an Injection Doctor web site which supplies regulators and injector mechanisms, couldn't find it in a brief look see. You may be able to google it or find the link in the post.

Good luck,

Sparky

Any updates on this? I have a '93 with similar problems.

Welcome to AF
If you have a problem on yours it is better to start a new tread/post and give us all info on what it is doing and not doing.
MT

Got 'er done, I posted symptoms and what I've done so far. Sure hope we can get this thing going, I have a high maintenance sweetheart that's needing something (or so she thinks!)