How to track down a short?

« **on:** July 10, 2009, 08:03:51 PM »

I need help with an electrical issue. My electric fuel pump just started blowing fuses. It is a Holley Red with maybe 15 hrs on it. I took it out and cleaned it all out, hooked it to a battery directly and it seemed to stick at first. Then after a couple taps it started again, every time. I reinstalled it and turned the key, it spun for about 10 seconds and it blew a 25A fuse. replaced the fuse (20A) and popped again. I tried aluminum foil around the fuse(ghetto, but I didnt have any more fuses) and it came right on but I felt the foil getting hot very quickly.

Is there any way to test the pump to see if it has an internal short? Is the 25A fuse too small?

Please help so I can get to the lake tomorrow. Thanks

« **Reply #1 on:** July 10, 2009, 09:02:57 PM »

Just my .02 but if the pump is only working when you ghetto it with foil, the pump has a internal short, and I would NOT use it. You would be asking for big trouble. Did you check the hot lead from the pump to the main power source

to make sure the wire doesnt have any cracks or anything

Does it take a little bit before the fuse blows, or does it blow right off the bat. Blows right off, then you have a short in your power source to the pump, if it takes a little bit then its your pump. Boy did I give you my .02 bass ackwards. Anyway dont use it if you have to mickey mouse it, would hate to see another flamer

« **Reply #2 on:** July 10, 2009, 10:43:02 PM »

Chaz, Is there any thing else running through that fuse ? Is the fuse right by the pump ? If I remember right those pumps should have less then 10A of current drain. If theres nothing else running through that fuse and the fuse is by the pump (to rule out a short on the wire between the fuse and the pump), then throw that pump away. The motor in it is bad. Dont run it like that (your ghetto foil fuse) or it will start melting wires.

« **Reply #3 on:** July 10, 2009, 10:47:18 PM »

Where is this thing grounded? If there are any loose connections, the resistance will eat up voltage and cause what you're seeing (if the volage drops the amperage goes up), my money is on a toasted pump, I would check the voltage at the pump with it running, if it is even .5 VDC less than battery voltage, you have an issue....If you have an old ammeter, just hook it up in series with the pump, it will give you an idea of the amps without spending $100 on a DVOM, backwoods, but effective

GT

« **Reply #4 on:** July 10, 2009, 10:55:58 PM »

Well I went and got a new one, plugged it in and popped the fuse.

The circuit runs off the key, all accessories I believe, and the fuse is under the bow. The ground to the pump runs maybe 4 feet to a main board and directly from there to the battery.

I read up and found that the pump only draws 2 amps so I knew there had to be a problem somewhere. I tried it with a 30A fuse and the pump unplugged. While watching the fuse I saw it bend and pop, maybe 3 seconds. I checked everything I could think of then on the last thing found the problem. This boat had an auto style cigarette lighter port installed at some point and it is the cause for the short. Unplugged it and all is good

I would never run a foil covered fuse

I know how quickly that would cause a fire, that is why I kept my finger on the foil to feel the temp while checking it.

« **Reply #5 on:** July 10, 2009, 11:11:21 PM »

Glad you found your problem Chaz. I had a feeling there was something else on that fuse. Didn't mean to insult you with the warning about the "foil fuse", but you wouldnt believe how many of those things I've pulled out of cars.

« **Reply #6 on:** July 10, 2009, 11:18:21 PM »

Hey Chaz, I would install a seperate relay to run the fuel pump which will alow you to fuse the pump all by itself......Glad you found the problem, have fun at the water

GT

The Chaz

How to track down a short?

76NORDIC

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