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I have a ’02 s10 2.2 The truck will start run for 30 sec and then blow the 20a ecm fuse. That fuse is for continuous ecm power as well as power to the fuel pump though a relay. The truck ran fine until I had a battery issue, the battery had broken inside and did not have a good enough conection to start the truck or even for the lights to come on. I have since replace the battery and the engine cranks fine. When I was tying to figure out what the problem was, checking battery terminals, engine ground, etc, the relays were clicking on and off from lack of power. Would a fuel pump fail because of this and draw 20+ amps? Truck runs fine for 30+ secs, no miss or hesitation. How would I test this my multimeter only goes up to 10a?
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I think the ECM would be on the ‘control’ side of the fuel pump relay, not driving the pump directly so I’d think the fuel pump would have a separate fuse – I would check a wiring diagram to make sure. If the relay had a shorted coil, that would do it.
Does the fuse blow even with the ignition just on for 30 seconds? If that’s the case maybe you can disconnect the outputs and plug things in one at a time to see if you can narrow it down like that.
If that doesn’t work, I would check using a clamp-on style ammeter probe, clamp it around each output wire at the ECM and see who’s drawing all that power. As far as testing a 20A circuit with a 10A meter, I know those clamp probes step-down the readings so you can actually test up to 80A. If you don’t have access to one of those then you would have to put the probes of your meter in series with each circuit, but like you said, I’d be concerned about running 20A though a 10A meter – make sure it’s one that is fused.
I found the problem. I put a 20a resettable fuse inline with some alligator clips, jumped from the Battery Positive on the fuse block to the load side of the relay with the relay out so the fuel pump would run continuosly. I put a new fuse in the ecm slot and started the truck, the resettable fuse trips out every 30 sec or so and kills the truck. ecm fuse does not blow. even with the key off I can jump the relay and the the reset fuse trips. Its drawing a ton of power because the jump wire rated for 30a get hot. I have never seen a pump fail like this so It had me stumped for a while. I have since pulled the pump and confirmed this. I am almost positive it is the fuel pump as there is no curent draw with the pump unplugged so no short anywhere besides the pump. I thought filter may be plugged but truck runs fine with no other symptoms. I checked the wiring diagrams before anything else if it wasn’t for that I would never have found the fuel pump is fuesed through the ecm fuse.
Well done and thanks for posting the fix. In fact you did exactly what I was going to suggest which was start unplugging things on the circuit till the fuse stopped blowing. Once again well done and thanks for using the ETCG forum.
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