Hey guys I’m new here I just picked up an 89 full size blazer which sat for about 6 years. I switched out the fuel pump and fuel pump relay on it and got it running it was running great but when I when I went to get emissions done on it it died on me about half mile from my house due to a blown ecm b fuse. Now every time I turn the engine over the fuse blows. I’ve checked all the orange wires going and coming from the fuse box and haven’t notice any breaks or exposed wire. I thought it might have been the oil pressure sensor throwing it off so I changed that as well but it’s still doing the same thing. Would a bad ECM cause this? Fuel pump going out already? Bad ground? Any advice would be helpful. Thanks!

 

Which motor do you have?

George

 

Just the 350 tbi

 

We need to isolate each load on that fuse circuit until we find what's blowing the fuse but I can't find a set of electrical schematics for this truck. Do you have schematics for your truck. If not, Don can you help out?

George

 

I was able to find this schematic it is from an 87 c10 but I believe it’s the same on the blazers minus the fuel module which is for selecting your fuel tank in the trucks(I may be mistaken). I’ve replaced most of the things in the circuit (relay, fuel pump, and oil pressure switch) which is why I’m leaning toward possibly a bad ecm or a short somewhere in one of the wires although i guess it’s possible I got faulty parts on any of the replacements

 

Does this only happen when you are cranking the starter or does it also happen just from turning the ignition on to the run position?

I dont think that this is the ECM.

Do you know what else is fed by the ECM B fuse besides what is shown in your diagram?

Try this for starters. Remove the fuel pump relay and engage the starter. It wont run but I want to see if the fuel pump circuit is causing this,

George

 

Ok I’ll try that once the weather clears up and see what happens. If not I’ll probably just start going down the line disconnecting things until I figure it out. I’ll keep you posted though.

 

Thats the way to go about it. I suggested the fuel pump relay because you just worked on the circuit and the relay is easy to pull. Once you find the circuit then disconnect the load. If that doesn't do it then its the wire or connector.

George