ECM 1 fuse blowing 1987 chevy

[Yellowcat]

Have a 1987 chevy tbi 350 which was blowing the  ECM 1 fuse soon as I turned ignition key on. It done it a few times but now I driving it for a week an nout blowing fues.  What components are running on this one ECM 1 fuse? I need to trace all these wires going out from the ECM 1 fuse?

[Yellowcat]

photo of fuse box

[VileZambonie]

Does it have an AIR pump? EGR Solenoid or EGR Vacuum Regulator? Not enough info on you truck but see the attached.

[Yellowcat]

It has smog air pump if that what you mean. I just got stranded on the road again today. As soon as I turn key on it blows ECM 1 fuse please help tell me which items are going to this fuse.

[bd]

In order to help you, we need your help.

Remove the air cleaner and snap pictures of the engine from either side and front then snap a full-frame picture of the Vehicle Emission Control Information (VECI) label affixed to the radiator support or air cleaner housing.  Post the pics.  This will show us the emission control configuration and many of the electrical appliances powered through the ECM I (ECM Ignition) fuse.

GM routinely color codes ignition power feed (I+) wiring pink with black tracer (PNK/BLK).  All of the wires protected by the ECM I fuse are color-coded PNK/BLK, designated on wiring diagrams as circuit 439 (CKT 439).  However, not all PNK/BLK wires are protected by the ECM I fuse.  Some PNK/BLK wires are protected by other fuses and carry different circuit numbers.  In other words, all ECM I wires are PNK/BLK, but not all PNK/BLK wires are ECM I wires.  This will become important as you troubleshoot.

[Yellowcat]

The photos

[Yellowcat]

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[Yellowcat]

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[Yellowcat]

The harness here has constant 12v but the green and white wire will not get any power when you turn key on to power fuel pump or relay . Tried to jump fuel pump from fuel pump relay wire and do not hear fuel pump. Forgot to mention it is not blowing any fuse under dash for some reason

[Yellowcat]

Constant 12 v on orange wire I forgot to menton

[Yellowcat]

which wires to jump to test fuel pump to make sure i did right?  someone told me might be a fusible link somewhere on this model to keep power going to fuel pump relay harness?

[bd]

The items labeled with yellow text, along with the ECM, are powered by the ECM I fuse via PNK/BLK circuit 439.

To test the components for shorts, switch the ignition OFF, unplug the EGR solenoid, EAC valve, and ESC module (yellow labels), and lay the connectors to the side.  Connect an ohmmeter between the two pins of the EGR solenoid and then the two pins of the EAC valve.  Both should measure greater than 10 ohms.  If either measures less than 10 ohms, the component is faulty.  Checking the ESC module is slightly more challenging.  Use the ESC harness connector to determine which two ESC module pins connect to the PNK/BLK wire and the brown (BRN) wire.  Connect the ohmmeter between those two module pins (should be terminals "B" and "D" according to the factory diagram).  As before, if the measurement is less than 10 ohms, the module is faulty (don't be alarmed if the ESC module measures considerably greater than 10 ohms).

If all of your resistance measurements were 10 ohms or greater, reconnect the wiring harness to the three components.  Trace the harness while carefully looking for any place where the harness comes into contact with bare metal or turns a corner around a sharp metal edge.  Inspect for chafing or pinching of the harness or any of its wires.

The fuel pump circuit is powered by the ECM B (constant battery power) fuse via orange (ORG) circuit 440.  The ECM supplies 12 volts to control the fuel pump relay via dark green & white (DK GRN/WHT) circuit 465.  The black & white (BLK/WHT) relay wire is the relay ground.  When the ignition is switched ON, the relay will energize the in-tank fuel pump via the tan & white (TAN/WHT) circuit 120 for up to two seconds before shutting off automatically if the engine does not start and run.  The fuel pump should continue to run as long as the engine is cranking to start.  The fuel pump relay connector has a 3" long RED/WHT pigtail with a brown connector.  Jump the short RED/WHT pigtail to battery positive (B+) to bypass the relay and power the fuel pump directly for testing purposes only.

[Yellowcat]

The ESC module tested out with a fluke meter only staying on OL. The wires  you had said was different colors here on B and D. Why is the Fluke meter staying only on OL when I touch the two pins B&D is it supposed to do this?

[Yellowcat]

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[Yellowcat]

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