Going Crazy... ECM 1 fuse Blows!
 

Hi all,

I can't find my problem, and I'm going crazy. 1990 V2500, normally run perfect. :-)

On the road last week, and it died. get it home, check fuses... ECM 1 blown. replace..turn key to On position... blows again.

Before the blow, I can hear fuel pump relay click but no fuel pump prime. I changed the relay anyway.

I have traced wiring, everything seems OK. Did the process of elimination with sensors, unplug/plug in... still blows.

What am I missing?

HELP! :-) please Thank you!

Re: Going Crazy... ECM 1 fuse Blows!
 

Does the fuse blow with the fuel pump relay out? If not the next step would be to put the relay back in and unplug the fuel pump and see if the fuse blows. Good luck

Bob

Re: Going Crazy... ECM 1 fuse Blows!
 

I have traced every pink/blk wire I can find and as of this moment here is what is unplugged.

Injectors, Map, IAC, EGR solenoid, ESC, ECM, O2, Tranny, Fuel pump, relays, oil pressure sending unit, TPS, Coolant temp gauge, no radio, no dome lights, dash gauges completely unplugged, alternator, kickdown switch, and any pink/blk plug under dash.

I also removed distributor, and coil. check harness against firewall, all looks good.

Still blows fuse! Maybe, fuse panel?

Re: Going Crazy... ECM 1 fuse Blows!
 

My 91 K2500 did that couple years back and I had to replace the ECM

Re: Going Crazy... ECM 1 fuse Blows!
 

Use your VOM to find it. First set it to voltage and measure both contacts for the fues in question. The fuse must be out. One side has 12 volts the other side has nothing. Now set your VOM to ohms low setting if you can choose it. Like 200 ohms. Put one lead in the contact that had no voltage and the other lead to ground. There should be an infinite reading (digital VOMs use OL).

If yours is a short to ground, it will read low ohms like below 1 ohm. Leave the meter the way it set up and begin to wiggle every wire you find from the fuse holder to the other end of the wiring in question. If you find the spot causing the problem, the meter will change to a much higher reading.

Start by looking at locations where the wiring either passes through a hole in a panel or bends around a corner.