87 Chevy Pickup 350 EFI "Blown ECM Fuse"

Hi everyone, I'm new to the site. I came across it when trying to figure out why my 87 chevy pickup 350 EFI,,,refuses to start. A member named Pode had
the same exact problem I was having. Here's what he said: This motor normally starts with out a hitch. When I tried to start the truck I got nothing, nada, zilch. I checked over the fuses under the dash and found only one that was blown. It is labled "ECM B". When I replace the 10 Amp fuse it instantly pops. I can't recall hearing the fuel pump priming either. I did get the engine to fire by pouring a little gas down the throttle body, but immediatly dies. So at this point I know I am not getting fuel. So what else could possibly be blown and or shorted out at this point?
In response to that, a member "Elliot" responded:
ECM-B is the computer's battery output to the fuel pump. Sounds like you blew the computer. Pull out the computer and replace the fuse. If it doesn't blow, measure the voltage on the socket (same as the orange wire to the fuel pump relay. If the voltage is low, measure the resistance from the ECMB fuse to ground (not sure which side). If it isn't shorted to ground you probably isolated the problem to the computer. If that's the case you may have damaged the computer's PROMs too (hope not) - but just in case, a J-yard replacement w/ chips seems the way to go (AZ has them w/o chips). If it is still shorted w/o the computer, pull the fuel pump relay, and do it again. If it's still shorted (blowing fuses) try pulling the Electronic Spark Module (ESM (a flat black box in the middle of the fire wall with an hand full of wires to it)). Elliott
Looks like Elliot knew what he was talking about from Pode's response:
I followed Elliotts instructions and he was right. First I did test the ESC, and the fuel pump relay. All were good. I then pulled the power on the fuel pump and the ECM-B fuse would still blow when I replaced it. Last but not least, I disconnected the Computer and BAM, no blown fuse. I picked up a new ECM, move the PROMs and the damn thing fired up like it use to. Thanx to you and the board members I save a a.s load of money.
Man!!! Wish I had Pode's luck. I've done the same thing to my truck, good news is that by process of elimation, I too found that it was the ecm,,,,, when I disconnected it, the fuse didn't blow. So, fuse blowing problem fixed,, ,,,,,,The bad news is, I purchased a new ecm, switched the PROMS and the truck STILL won't start!!!! Now what??? ANY advice or suggestions, welcome! Thanks, Rick
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

There is still a chance that the fuel pump is going bad and the extra draw from it shorted out ECM output and caused its failure. Those pumps have a fairly high failure rate if you are one to run them low on fuel a lot. ----------------- TheSnoMan.com
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
SnoMan wrote:

Hmm ok, we'll have to check on that then. Also, since replacing the ECM, when cranking, the check engine light comes on, blinks off once and then comes back on and stays on?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

A code is being set in ECM. Have you tried to read it! ----------------- TheSnoMan.com
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.