Fuel injectors not getting power (1990 GMC Jimmy 4.3L)

My guess is either the injector is not opening enough, or the fuel pressure is low.

Spray some starting fluid, (ether), directly into the throttle body. Does it start with that?

If you have checked the fuel pressure with a gauge and it is below spec, the pump is inside the gas tank so the tank would need to be dropped.
You would need to check the fuel filter and also make sure the pump is getting power before replacing the pump.

You'll need to make sure you have spark to the plugs, then try spraying starting fluid into the throttle body to substitute for fuel.
If it will start on starting fluid, you would need to check fuel pressure with a gauge, and check the injectors for power and ground pulse.

What is the fuel pressure? these trucks need a certain amount of pressure to start, if low just 3psi it will not start, if you are sure the pump is good then you may bad spider injector. check fuel pressure first and also try spraying starting fluid into throttle body and see if truck starts. the pump needs 60 -66 psi to start the truck.

The pump is powered by the relay. The relay is grounded by the computer. It gets a ground signal for the first 3 seconds, then only if the computer sees oil pressure or RPM to know the engine is running.
You should be able to ground the relay and run the pump for several minutes. After 30 seconds you should be at max pressure.
Normal pressure is 15psi for a truck that has throttle body injectors such as a mid 80s model, and 65psi for trucks that have port fuel injection like yours.
You may have the wrong pump.

Unfortunetly....these spider injectors and fuel pumps can have very similar symptoms when failing. What I do know is I work on this motor more than any other motor in my shop. Very common with fuel problems...and I can comfortably tell you that they updated the injector kits on these car for a reason. The original model is junk. I have done these on just about every one of my cutomers vehicles over 150,000 miles. However, I am not going to tell you that is your problem....but it sounds fuel related. Did/does your vehicle skip? Leaking injectors will usually cause a skip due to shortage of fuel to that cylinder. I also have a computer that allows me to monitor the firing of each cylinder, and do an injector kill test. This is what I would do first. Unfortunetly, sounds like you can't so start with this: Clean your throttle body. The pintle that the IAC motor pushes in and out goes into a small port. Spray that port out with carb clean. Get a fine wire brush and get that throttle body clean and shinny. That pintle can easily stick on existing carbon in that port...new part or not. Check for vacuum leaking with carb clean...spray it around the intake and vacuum hoses...see if any particular spot changes how it runs when you spray it. Do you have a vacuum gauge? what is manifold vacuum? Since you are in the intake...make sure your puddled fuel is not due to pulling the main lines off the the injector assembly. After intake is off. hook fuel lines and harnes back up to injector assembly. key up (no start) vehicle...this pressurizes fuel system. look for leaking. The fuel pressure regulator is built on to the side of that assembly....its the round diaphragm with the tube coming out of it. If it leaks fuel out...that may be your problem. And you can replace that without doing the whole injector kit...fairly cheap. If not fixed....what is your fuel pressure. You need to have 60-64 PSI at key up. Try the carbon build up and intake test first...both quick, easy, and cheap. If this is not your issues...its sounds fuel related....just want to confirm that you don have a misfire/skip. That could change diagnosis quite a bit. Keep me posted....more than happy to help. By the way....I own all GM's too...lol...haven't learned my lesson yet

You jimmy has no throttle body, the injectors are in the intake manifold in front of the intake ports. To have them activate, you need 62 to 65 PSI at the shredder valve. Anything different will not activate the injectors and DO NOT TRY TO START THE ENGINE BY PORING GAS THROUGH THE THROTTLE BODY. It's been know for the gas to catch fire and burn up the poppet valves, (fuel injectors) which will result in a $1,500 Spider injector replacement. If you do not have the proper fuel pressure, chances are the fuel pump will need to be replaced. When replacing the fuel pump, replace the wire harness from the fuel pump to the frame, it's only $12.00 and will keep the gremlins away. Good luck and keep me posted, the other thing too that would cause the injectors not to fire is a bad ignition modulator with is located under the rotor in the distributor. Keep me posted, be glad to help you get your jimmy running again soon.

need alot more info....is this multiport fuel injection or does it have the two injectors in throttle body......... is the check engine light on has any one pulled codes.. while engine is at an idle.. look in throttle body and look at the fuel being injected... they should be clean looking fans...they have problems with those injectors... if you see one that is dripping and appears to be dumping in to much fuel in intake check injector and injector orings....also where the wires to the injectors exit the round spacer the wires have known to be pinched grounding the injector causing excessive fuel flow let me know

It sounds like you need a tune up, Spark plugs and wire and cap and rotor, fuel filter and clean the EGR Valve. I'ld say the EGR valve is dirty with carbon which is common in the 95 JIMMY"S and BLAZER"S which also means the throttle body needs to be sprayed down with throttle body cleaner, not carb cleaner since it's to corrosive to the gasket on the throttle body. Keep me posted, be glad to answer any questions you may have and good luck friend.