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No power to fuel pump???

Old 09-15-2014, 09:57 PM
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Angry No power to fuel pump???

Okay, have a 1993 Blazer Sport 4X4 with the 5.7L. Drove it home running fine and shut it off and then the next day it wouldn't start. Plenty of fuel in the tank, strong spark to the plugs but it just spins. On the first few items I checked, I found no pressure at the injectors in the top of the FI unit. Pulled the cover under the hood on the passenger side firewall and there was no power to the fuel pump fuse (gray wires). Checked the fuel pump relay beside it and there is constant 12V power on the orange wire as there should be. However, in the "Start" or "Run" position, no power shows on the black/white wire to the fuel pump or the red wire to the prime circuit. Also never shows any power off the gray wire which should be to the pump fuse if I traced the diagram correctly. All the fuses under the drivers side of the dash by the brake release are fine but I only found one full size fuse marked for the Eng/ECM although the book wiring chart references two 20A mini fuses under the hood also for the ECM1 & ECM2 circuits. I supposedly have a PCM but it shows it should be where my anti-lock brake controller sits on the driver's side inner wheel well. I can also find no pink power wire anywhere that is supposed to power the PCM in any of the visible harnesses to follow and try and locate the actual module.

Any ideas about:

(1) where to find the PCM so I can verify power (although the idiot lights work which should mean it's powered up),

(2) where the mini ECM1 & ECM2 fuses referenced in the wiring diagrams can be found under the hood, or maybe elsewhere,

(3) or any ideas on another possible area to check such as ignition switch?, neutral safety switch?, or something that controls the power to the fuel circuit (ECM maybe) that I haven't found in the pages of wiring diagrams?

Thanks in advance for ANY ideas or personal experiences that may help me get this thing fired back up!!!
Old 09-15-2014, 10:04 PM
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Check the oil level. Just had same problem with 1987 K5 with 5.7. Oil was low, there is a low level sensor of some kind that blocks signal to fuel pump.
Old 09-15-2014, 10:13 PM
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Fresh oil change a month ago and never got a light but I'll go pull the stick. Maybe that sensor could be the problem???? Thanks for the tip!!!
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