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Blowing ECM "B" fuse

MTBLAZER89

MTBLAZER89

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Blowing ECM \"B\" fuse

Anybody know what systems we should start concentrating on in the "B" loop. This is for seventyK5 he is in the desert right now towing his 90 home. It died last night and won't start and now he is popping this fuse?? I am trying his cell to get more details, but any ideas?
 
Re: Blowing ECM \"B\" fuse

I know the fuel pump is on that fuse. When one of my pumps locked up it blew that fuse, replaced fuse, switched tanks, all was well. Ill place money on a dead fuel pump. One way to test the pump, run a wire from the test lead (red wire running from relays on firewall) to the positive post of the battery and see if the fuel pump moves the fuel. Mine made noise, doin this, just no fuel, it was simply locked up and makin a grinding type sound.
 
Re: Blowing ECM \"B\" fuse

K we'll check that first. /forums/images/graemlins/peace.gif
 
Re: Blowing ECM \"B\" fuse

Ditto on the fuel pump thing. My 88 was blowing the ECM fuse and come to find it was the fuel pump shorting the circuit..
 
Re: Blowing ECM \"B\" fuse

<font color="red"> its most def the pump, my buddy ahd that problem when he wire his up wrong, lol. blew like 3 fuses the dumbass he was. lol. </font>
 
Re: Blowing ECM \"B\" fuse

If it's the fuel pump, disconnecting the pump from the connector by the fuel tank would also prove or eliminate it as a problem, if there are other items on the same fuse that may cause problems. Disconnect pump, turn ignition on, if fuse pops again, it's not the pump.

Sounds like the one up in the engine bay is an easier bet. Can you TBI guys force the fuel pump to run via the ALDL?
 
Re: Blowing ECM \"B\" fuse

Check the relay and see if he can jumper it to make the pump run and the fuel filter to make sure it isnt clogged.
 
Re: Blowing ECM \"B\" fuse

I start the trouble shooting today. It was a long night. We had just went out to hangout at a bonfire when someone came out this "awesome" idea for some night wheeling. So off we went. Well I decided to turn off the road and see what the jimmy would do. So we are flyin over sand dunes (got some decent air a few times) and plowin over sage brush. Then we decided to turn around. I stopped went to put it in reverse and everything cut off. The truck died and all the lights went out. I tried to start it and nothing happened. So we got out ewiggled the connections and the lights came back on. We tried to crank it and it just shorted again. This happened 4 or 5 times. So we called some people got my lights working stood on my roof with my hella's in hand (good thing i didnt cut those wires shorter). Some friends made it out to us about 30 mins later and we hooke cables from his battery to my cables then we tried to crank it and it just kept turning over. So I checked the ECMB fuse b/c I had had this prob before. It was blown. So put it another one and It blew that one. One more samething. So Had to tow it home. Well how do you tow a 5000 lb piece of rolling mass up 3 sand dunes of over 50 degree angles and a mile stretch of sage brush the size of my truck. A 11,900 lb 99 dodge diesel. Man it was fun being towed at over 40 mph through the desert except I have no doors or top so I ate a lot of dust. But I will keep you all updated. We are going to replace the battery and test the pump today and change it if neccesary. Will also check the relay and then go from there. If any other ideas please let me know. /forums/images/graemlins/waytogo.gif
 
Re: Blowing ECM \"B\" fuse

It sounds like you have bad battery connections to me. Maybe the positive batt cable that runs to the starter is melted onto the exhaust or something.

Just figure out where the single point of failure is. I'd bet it's between the battery and the fuseblock, depending where you hooked up the ECM +12.

Andy
 
Re: Blowing ECM \"B\" fuse

Got a new battery, and it will crank now but blows the fuse. Got a new fuel pump and it starts and runs, but now the ecm b fuse randomly blows still. It's better, but still there. I'm posting this for seventyK5 to gewt some views before he goes back to work in the morning. /forums/images/graemlins/waytogo.gif
 
Re: Blowing ECM \"B\" fuse

What size is this fuse that keeps blowing? If you just turn the key to run w/o trying to start it does the fuse blow? What else is hooked up to this fuse B?

Andy
 
Re: Blowing ECM \"B\" fuse

Think it's like a 15 truck starts runs and drives, but will randomly die when the fuse blows /forums/images/graemlins/dunno.gif
 
Re: Blowing ECM \"B\" fuse

Its blown all the way up to a 30. And it blows as soon as I turn on the key. Thanks for posting Bryan.
 
Re: Blowing ECM \"B\" fuse

Try unhooking the fuel pump power from the pump itself, turn the ignition on, and see if the fuse blows...

I still think you've got a pinched wire somewhere unless there is something else hooked up to fuse B that we don't know about.

Andy
 
Re: Blowing ECM \"B\" fuse

Why it would it work fine after I changed the pump for about an hour. I am thinking it somewhere along the wiring to my pump but Icant find anything. Thanks for the info. Do you know of anything else that is run through this fuse?
 
Re: Blowing ECM \"B\" fuse

I know it's a PITA but unplug the fuel pump and turn the key on.

It would get better because you probably wiggled a wire around just enough when you replaced the pump/tank that it wasn't shorting out quite as solidly as before... Actually, are you using an in-tank pump?

andy
 
Re: Blowing ECM \"B\" fuse

Yes it is a intank fuel pump. I will have to wait to get off work in about 6 hours. Anything else you could think of pleasepost up. I will check everything I can tonight so I can post up tommorrow when I get back to work.
 
Re: Blowing ECM \"B\" fuse

I will look around and see if I can figure out what else might be on fuse B, but I suspect it's only the fuel pump power. It sounds to me like it's a short between fuse B and the fuel pump. If nothing else is on fuse B as I predict, there are few places this short can be. It could be internally shorted in the fuel pump relay, the fuel pump +12 supply (that comes from fuse B) wire to the relay is shorted, or the +12 wire going from the relay to the pump is shorted (and that could be in the tank, also).

If you remove the relay and it doesn't blow fuses anymore you've eliminated the problem being the wire from fuse B to the relay. It could still be the relay, or it could be the wiring from the relay to the pump.

Now what you want to do is unplug the pump and leave the relay out and check for a short to ground by measuring for continuity between ground (the frame) and the positive supply wire. So put your meter between the +12 wire that goes to the pump and the frame and see what you have for resistance. If you have anything between them you've got a short in the wire to the relay from the pump.

You could have also put in two bad pumps in a row but I doubt it.

Andy
 
Re: Blowing ECM \"B\" fuse

Thank you All this I will try tonight. If anything else comes to your head or anyone else reading this. Please post I deas and suggestions so I can check all this tonight. And thanks so much real squash.
-Shaun- /forums/images/graemlins/peace.gif
 
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