What is next on trouble shooting fuel injectors?

possible causes for code P0300
you've already change coil and plug....

P0300 could be bad #3 plug or coil... switch those also and see if code change..

if it persist try the next thing..

I would try trading fuel injector 4 to 5 and putting 5 into 4 and see which code you get.....

• Faulty spark plug (s)
• Faulty ignition coil (s)
• Clogged or faulty fuel injector (s)
• Intake air leak
• Fuel injectors harness is open or shorted
• Fuel Injectors circuit poor electrical connection
• Ignition coils harness is open or shorted
• Ignition coils circuit poor electrical connection
• Insufficient cylinders compression
• Incorrect fuel pressure

code P0305 is simmilar....

• Faulty spark plug 5
• Clogged or faulty fuel injector 5
• Faulty ignition coil 5
• Fuel injector 5 harness is open or shorted
• Fuel injector 5 circuit poor electrical connection
• Ignition coil 5 harness is open or shorted
• Ignition coil 5 circuit poor electrical connection
• Insufficient cylinder 5 compression
• Incorrect fuel pressure
• Intake air leak

Is there a tach place on the distributor cap? If so, use a test light on that terminal, engine cranking, see if the lite pulses? A pink wire should carry voltage to coil or distributor cap. It goes got with the key on? Use a test lite and check for voltage. A couple of possibilities, check the ignition module and pickup coil in distributor. Does the distributor rotor turn when you crank it? With gm bypass ignition, it's the ignition module that controls spark during cranking rpms, not the computer.
There is an oil pressure switch in the fuel pump circuit, so once you crank it enough to bring up oil pressure and that switch closes, the fuel pump will run even w/o a rpm signal, but, for other components, the rpm signal is important.
The ignition module gets signal from pickup coil, engine cranking, then ignition module sends rpm signal to computer on purple wire with white tracer. If no signal, the computer won't ground the fuel injectors, among other issues.

Sounds like it could be the ignition module in the distributor. You have a throttle body instead of a carb. The injectors get a ground signal from the engine computer when they are supposed to open. The ignition module takes a signal from the pickup coil in the bottom of the distributor and decides when to fire the plugs and also the injectors.
If the injectors and the coil has power, it could be the module or the pickup coil.

Hi sugriva 108,

I saw your comment on one of my other posts;
http://www.fixya.com/cars/t12417950-93_s10_2_8_just_shut_off_woulnt_start?eventid=21761548

yes, if you have battery power at the injector, but when you check for "pulse" from the computer on the ground side of the injector and the test light does not blink, the most common problem is a failed distributor module.
The pick-up coil in the distributor can cause the same symptom. It is the pickup coil that the injector and spark control signals originate from it is connected directly to the distributor module. The module is what sends the signal to the ecm for fuel control and timing advance and also pulses the ignition coil. Some people call the distributor module the "ignition control module". However, it affects fuel as well as ignition, which is why I refer to it as simply the "distributor module".

If the module is bad, you can replace only the distributor module. If the pickup coil is bad, you will either have to disassemble the entire distributor to replace the coil (the hard way) or you can simply buy a remanufactured distributor. It is less expensive to replace only the coil, but the coils usually go bad as a result of worn distributor bushings and it is usually more trouble than it is worth by the time you get everything right.

If you have lots of time to work with me and do some electrical testing, I can help you determine if it is the module or the coil. However, if you just want to get your vehicle running as fast as possible, the easiest and quickest way is to go ahead and get a remanufactured distributor and be done with it. They are not real expensive. AutoZone lists the distributor for your vehicle for under $100 (click link below)
http://www.autozone.com/autozone/parts/Cardone-Reman-Distributor/1993-Chevrolet-S10-P-U-2WD/_/N-izmhuZ93xku?itemIdentifier=765107_0_0_

check the fuel line pressure on the injector rail ,here you will find a valve that looks like a tyre valve and take the cap off and connect a pressure gauge to this and see what you get should be around 55lbs

I saw what you replaced, didn't see any testing? Any applicable trouble codes? Use a gage and check proper fuel pressure, TBI--9--13 psi. As an example, 5 psi fuel pressure makes a nice looking injector spray pattern, but, 5 psi won't start and run a v8. My opinion.
Could be other issues.

Can be clogged althoug its rare to see all clogged up. The computer sends a signal for each injector to open so the computer can be bad. That is the only two choices there are if fuel delivery to the injectors are there. Did you check the ignition coil and ignition module as well? These two items control the spark to the plugs for ignition

I have a 90 chevy k1500 350 tbi with same problem! I have traced problem to... after turning on key fuel pump kicks on when u crank it over injectors shoot gas and truck starts! After few seconds injectors stop spraying and truck dies! This can happen many times over and over! Eventually sometimes truck stays running and all is great! I changed ignition module, oil pressure sending unit (which i was told controls gas after vehicle is running) fuel filter, computer, fuel pump relay, I am at a loss now! Hope this helps and hope someone can help me!

Check possibly the ignition module and/or the pick up coil

Most likely it is the ignition module or the crank pickup.