ecm/ing fuse blowing

one morning when i got to work i noticed the truck was runnin kinda rough so i gave it a little throttle thinkin that it was loaded up but when i did the truck died. when i tried to start the truck agian it just cranked forever. so i check the spark plug wires thinking one had come lose since i just change them , they were all good then i checked the fuse box and the ecm/ing fuse had blown so i changed it. now was i try to start the truck the fuse keeps blowin, even a 30 amp. it only does it when i turn the key to start. any other postion it doesnt blow, someone please help.

In order to try and help you we need to know what year, model & engine you have.

1988 5.7 liter tbi,

IIRC, the fuel pump can cause this fuse to blow. Under the black cover on the firewall, pull the fuel pump fuse and relay. Then see if the ECM fuse blows while trying to start the truck. Note that the truck will not start but at least you will know if the fuel pump is causing the ECM fuse to blow.

I have a wiring diagram at home and can look at it later tonight.

//2000CAYukon

nope that didnt work, i have a wiring diagram, but im not to familiar reading them,

also before the fuse problem the oil presure gage would not read after the truck was warmed up, i just looked at a wiring diagram and saw that it is conected to the ecm, im goin to check it out and see if it has a melted wire for short in it,

also before the fuse problem the oil presure gage would not read after the truck was warmed up, i just looked at a wiring diagram and saw that it is conected to the ecm, im goin to check it out and see if it has a melted wire for short in it,

I will take a look at the wiring diagram tonight. Do not use a higher amp fuse in your testing since it can allow more current than the circuit is designed for.

//2000CAYukon

I have the 90 Factory Manuals. The ECM/ING provides power to:

TCC
Air Diverter
ESC
EGR
ECM/Ignition (goes to ignition switch and ignition coil)
Rear Wheel Antilock Brake Switch

ESC is the square sensor on pass side of the intake. Same for EGR solenoid. Try unpluging both of them. Also unplug RWAL controller.

//2000CAYukon

I have an '88 C/K manual and I'll try to add to what the "yukon" said.

The ECM/IGN fuse gets it's power FROM the ignition switch in either the START or RUN position. Are you sure the fuse is not blowing with the switch in the RUN position also?

FROM the fuse (which is were your problem is) it powers the following:

1. ECM
2. AIR DIVERTER SWITCH
3. EGR
4. ESC
5. EVRV (Not sure what that is)
6. STOP/TCC SWITCH (stop light switch) It's out of here that the Rear Wheel Anti-Lock and TCC is powered.

Try disconnecting as many of these items as you can and hopefully all of them.

If the fuse holds then start reconnecting one at a time starting with the ECM.

If the fuse does not hold with all this stuff disconnected then you've probably got a chaffed wire shorting to ground.

Let us know what you find............Steve

i figured it out, i changed clusters a few months ago, found one in a junkyard that was in pretty good shape, i just replaced it with the old one and now the fuse does not blow, thanx for all your help. also to answer your question, the fuse was only blowing in the START position, not the RUN position,

Wow!! The gauge cluster. Who would of thought of that? Good job and thanks for posting back............Steve