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Old 08-24-2011, 02:39 PM   #1
The Big Green
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ECM-B fuse blowing, please help!

Took it to a shop a couple months ago and they said after 2hrs labor it was a bad ground. It blew again and it's parked. 2 months later I need to fix this badly. Truck is a '95 GMC with a 305 auto, vin shows 4.3 manual and it has a blazer tank and I put a used fuel pump from a '94 350. Both engines are TBI. I need help!
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Old 08-24-2011, 06:21 PM   #2
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Never saw a fuse blow caused by a bad ground

Never since getting into the repair business in the mid 70's and getting an electrical degree have I ever known a bad ground to burn a fuse.

Intermittent contact always, short from the power side to ground obviously.

What I can tell you is you have to have a schematic. Without that, your dead in the water.

Try a Haynes manual or if nothing else, a library.
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Old 08-24-2011, 07:59 PM   #3
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Re: ECM-B fuse blowing, please help!

The shop that thought they fixed it had 3 printouts in the seat when I got the truck back. Oh, and what's your opinion on using a OEM fuel pump because others can be notorious for blowing fuses? How about an inline fuel pump and an aftermarket fuel regulator to run the correct pressure? If nothing else one could do that.
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Old 08-24-2011, 08:59 PM   #4
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Re: ECM-B fuse blowing, please help!

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Originally Posted by The Big Green View Post
How about an inline fuel pump and an aftermarket fuel regulator to run the correct pressure?

First, I'm with speedy...... No way a bad ground will blow a fuse.

I feel for ya......They done the same thing as my local dealer did with my non working speedo, Played around for 2 hrs, Replaced the cluster AND installed a used ECU so they said. 600 bux and 12 miles later it quit working again, Took me less than a hour and no money to fix the problem they couldn't with all their fancy pants equipment and schooling.....


Believe me, Go with a new OEM in-tank pump..... I had nothing but problems with in-line frame mounted pumps, They rattle like crazy and won't suck the fuel from the bottom of the tank well (would stop pumping at 1/4 tank). They also run hotter being out in the open, My last new in-line quit 13 miles after installing. I replaced the entire fuel system front to rear with factory 94 parts 2 yrs ago and haven't had a problem since.


If you still have fuse issues with a new OEM pump follow speedy's suggestion and find a diagram, Start tracing wires for that circuit until you find the short.......
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Old 08-25-2011, 10:25 AM   #5
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Re: ECM-B fuse blowing, please help!

not 100% sure of what fuse you meen is it the one in the pic?


the fuse in the pic is for your fuel injectors it feeds the injectors 12v power constantly all the computer dose is ground them out,,, ive seen the wires (pic 2) get pinched between the breather ring and short out
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Old 08-25-2011, 10:39 AM   #6
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Re: ECM-B fuse blowing, please help!

Its a fuse block under the hood and it's mini fuses, a 20 and it's labeled on the cap as ECM-B. It'll blow and cause my fuel pump to not work. It's a 1995 gmc Serria.
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Old 08-25-2011, 10:43 AM   #7
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Re: ECM-B fuse blowing, please help!

sorry man i aint got nothin that new to look off of hmmm
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Old 08-25-2011, 10:50 AM   #8
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Re: ECM-B fuse blowing, please help!

Hard to see but it's in the mini fuses top left, left of the horn fuse. That's ECM-B.
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Old 08-25-2011, 10:51 AM   #9
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Re: ECM-B fuse blowing, please help!


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Old 08-25-2011, 11:39 AM   #10
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Re: ECM-B fuse blowing, please help!

take a test light hook it to the positive side of the batt and probe both sides of the fuse dose it light?
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Old 08-25-2011, 11:57 AM   #11
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Re: ECM-B fuse blowing, please help!

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take a test light hook it to the positive side of the batt and probe both sides of the fuse dose it light?
What will this tell me? I know that the fuse blows but varies by just turning the key or maybe 100yrs or 2.
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Old 08-25-2011, 12:22 PM   #12
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Re: ECM-B fuse blowing, please help!

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What will this tell me?
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In theory, the test light should not illuminate because there is no ground in the circuit, due to the other side of the light being connected to a positive source. Now if a wire were shorted to ground, then the light should illuminate.

In other words:
No light = good....no short
Light = bad....short somewhere and you gotta find it

You might wanna check the owner's manual though. There's probably more stuff connected to this fuse other than the fuel pump. Chevy likes to connect 3 or 4 things to one fuse for some odd reason.
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Old 08-25-2011, 12:25 PM   #13
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Re: ECM-B fuse blowing, please help!

Ok went to start it today and it's firing on 1-2 cylinders and won't run. Now this?! Had it traded tomorrow but I think I'll get more enjoyment watching it burn to earth in which it came from!
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Old 08-25-2011, 12:38 PM   #14
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Re: ECM-B fuse blowing, please help!

i work at a Chevy dealership and I see this all the time on TBIs. Its either the fuel injector wires rubbed threw on the breather or a bad fuel pump.. Its probably a bad pump.....
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Old 08-25-2011, 02:01 PM   #15
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Re: ECM-B fuse blowing, please help!

Quote:
Originally Posted by Dark Knight View Post
In theory, the test light should not illuminate because there is no ground in the circuit, due to the other side of the light being connected to a positive source. Now if a wire were shorted to ground, then the light should illuminate.

In other words:
No light = good....no short
Light = bad....short somewhere and you gotta find it

You might wanna check the owner's manual though. There's probably more stuff connected to this fuse other than the fuel pump. Chevy likes to connect 3 or 4 things to one fuse for some odd reason.
well said
.... i went lookin for the 94 service manual cant find it right now .... dose the light illuminate ... is it as brite as crossing the batt?
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