Ecm fuse blows while driving .

[Dave88chevy]

My 88 chevy c1500 4.3 keeps blowing the ecm ing fuse while driving down the road can sit and idle foever without a problem

 

[Knuckle Dragger]

Check the wires to the injectors where they go through the TB/air cleaner ring. They rub through the insulation and will short at random times as the engine vibrates/moves.

 

[Dave88chevy]

Thanks

 

[joep88cheyenne]

Does sound like a bare wire broken insulation issue for sure.. Check the wire looms near the firewall also as these may rub also.

 

[1989GMCSIERRA]

Pull/disconnect the battery and get two meters. Set them on continuity
Take one meter place the red lead on one side of the fuse prong. Take the black lead to a good ground
Do the same for the other fuse prong with the other meter.
Now start shaking squeezing moving the wiring.
Tap the ecm and the harness. The injector harness, the loom at different locations etc.
if you hear a beep coming out of the meter/s you have a short to ground in that area.

You can use one meter to check both prongs at the same time. You may need some stab in connectors with a bare connecting wire to check both prongs at once. You'll need a alligator clip or wind the bare wire around the tip of the probe. Once you get a beep then isolate each prong and check. Whichever prong beeps that's your ground.

When you're checking for ground have the battery disconnected.

To find which way the ground is going put the battery back in and place the meter on voltage D.C. and check for power at the prongs with the fuse removed. The prong that had the beep initially is either going to have power or not. If it has power the ground is towards the battery. If it doesn't it's towards the ecm.

It could be the ECM. That's what mine did. I started the truck and tapped the ecm. Truck shut off. Replaced ecm. Truck ran great.

You can also keep the truck running and poke the harness tap the ECM. The problem is you may inadvertently short or possibly bsckfeed power to another system if you see multiple bare wire with worn jackets