I recently purchased a 1989 full size blazer 5.7L 350, apparently a new fuel pump was installed and I can hear it engage when the key is turned on, however when i crank the engine it will not fire. if i pour fuel into the throttle body it will run. what do I need to do to see why there isnt any fuel coming out of the injectors?
thanks in advance for your help!!

 

Welcome. Have you checked the fuse?

 

Yes, fuse is good

 

disconnect One plug from the injector. Hook a test light up to it. Let someone crank the motor and see if the test light blinks. If it blinks Test the other plug and do the same test.

If you have a flashing Light this means the injectors might be bad. report back with the results. Make sure both plugs flash.

 

Often times, a typical incandescent test light will not react fast enough to show you an injector pulse. A low wattage test light or injector specific noid light is what you need to test for injector pulse. The injectors are both fed +12V from the ECM1 fuse and grounded by the ECU as required to supply fuel to the engine.

If you wanted to test the pressure, you will find that your throttle body will not have provisions as provided from GM for testing fuel pressure. A fuel pressure gauge with the appropriate adapters (kits for testing TBI fuel pressure are available and sometimes can be loaned from autoparts stores) can be placed inline on the main fuel feed line to make sure that the pressure is in the proper 9-11psi range for your application. Just because it has a pump that is making some kind of noise doesn't mean that it is doing what it is supposed to do.

 

Thank you both!! I ordered a set of noid lights and will see if I can pick up a fuel pressure tester. The truck is at my cottage and I am heading up there in a week, I will try these two suggestions and see how I make out.
Thanks again for the info!! I will let you both know how it goes

 

You have to make sure that the fuel pressure tester comes with the TBI adapter. It is an inline piece that must be added. It will look like the piece to the left of the gauge in this picture courtesy of Actron:


That is the Actron GM TBI Fuel Pressure Tester CP7817.

 

Ok, Thanks!! Would have got the wrong one...

 

Probably injectors, injector wiring, or bad ICM Module under distributor cap. When the ICM goes bad it either doesn't give spark or doesn't tell the ECM to pulse the injectors.

 

Sorry for the delay in getting back to you...I thought I would start with the fuel filter...glad I did!! Gas was bad!! The fuel pump stopped working all together....long story short I dropped the tank and the fuel pump was completely destroyed by the bad fuel. I have cleaned the tank, bought a new fuel pump, filter, injectors and relay...if that doesn't fix it then who knows!!