1988 K5 Blazer 5.7l TBI will not run - need help!

[themcguire]

I think I covered all the posts above with these tests:

Can you hear the pump run with key on, engine off? NO

Can you hear the pump run when the relay is jumped? NO

Can you hear the pump run when power is applied from battery to pump? Yes a few days ago, now NO ???????


So I bought a test light

On B2 there should be a 2 second on with key on even if you don't go to crank, as soon as you turn to crank it should again have power.

test light lights at B2 when turning on key that lasts for 2 seconds. On cranking I have power again.

Then if there is a crank signal to C9 when key is cranked the fuel pump trigger at A1 turns relay back on and looks for the signal again at B2.

test light lights when cranking to C9

Do you have power at Orange wire B1 and C16 Batt Power? Key off, key on, key Crank? Should be hot always.

test light lights at B1 and C16 under all 3 conditions.

Do you have power at Pink wire A6 Ignition, should be hot key on and key crank? Should be hot key on and key crank.

test light lights at A6 both conditions.

Also went back and tested C3. The test light lights with key on but does not light during cranking,

Note: With the engine connected via jumpers to a running car, the starting rotation rate during cranking is now very sluggish, but I sprayed a small shot of starter fluid and it started right up and ran until the started fluid was gone.


A reminder so scroll back not needed, I have replaced so far:

Spark Plugs and wires, ignition switch, Fuel Pump Assembly, Fuel Pump, Fuel Pump relay, Fuel Filter, Oil Pressure Switch, Battery, and the ECM.

Reminder: The engine ran when I put direct connection from battery directly to the fuel pump a few days ago.


Using Bypass wire on relay I have power at purple wire at fuel pump assembly.

Attached the test light to positive power and tested the ground wire at the fuel pump relay and at the bolt where the ground meets the frame. Test light lights up. So ground is good.

Again put 12 volt from battery to fuel pump. This is a brand new fuel pump. No WHIRRING this time. Could I have burned out the fuel pump with all this testing ?

Can the fuel pump be tested OFF the truck ? Put in a bucket of water and apply 12v ? will water hurt the pump ?

I am lost!