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How to track down a short?

2296 Views 14 Replies 9 Participants Last post by  jetboatperformance
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
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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
The pump is junk, throw it in the lake and go get a mech. pump, carter, holley, what ever flips your trigger and put it on there and go have fun for several years without any more bull shi--.
Yeah,I would do that but I can not remember if I put the fuel pump cam back in on the last rebuild :(
Chaz, I don't kow your motor but check out the Clay Smith fuel pumps. I decided not to go elctrict and these work great. You will need a regulator.
its probably not a short, but rather your pump is drawing way to much current to make it run. (which is why runs when jumped directly to battery with no fuse) if it ran fine before you touched it, then it sounds like you need to take it apart again and see if you maybe did something wrong when putting it back together.

another thing is that your pump should be run off of relay system. fuel pumps require enough current as it is, and running all the way to the front on a switch or running it through the ignition switch is not smart. there is a substantial voltage drop from just the extremely long wiring, not to mention the possibility of causing a fire if something were to actually short. This can also cause dirty power at times depending on connections, feedback voltage, cross voltage, large voltage drops caused by...turning on the radio, or hitting a wake hard enough to jolt a connection. these are all things people dont even think twice about, and something you may never notice when running, but all are reasons for a relay.

I've never had any bad luck with electric pumps, but i have heard many many people that don't like them and have had them give out. i personally think it has to do with the way its wired up and how much clean power its getting.

AP
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After many electric pumps, I deceided to go back to mechanical. Just much simpler to install and no wiring to go bad.
Well I went and got a new one, plugged it in and popped the fuse.

I read up and found that the pump only draws 2 amps so I knew there had to be a problem somewhere. 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:D

As far a running a relay, I am a little confused as my weakest point on my boat is the electrical. Does that mean you run a wire from the fuel pump directly to the battery with a on/off switch somewhere in the middle? If so I assume this switch has a "relay" to the front which controls the current flow?

Assuming again this is correct, is there an inline fuse to protect the fuel pump?
God i hate wiring problems, I once pulled the whole wiring harness thinking a wire was touching something, turns out one of the wires was touch the Metal bracket that holds the gauge in. :)coffee
... auto style cigarette lighter port installed at some point and it is the cause for the short. Unplugged it and all is good:D

As far a running a relay, I am a little confused as my weakest point on my boat is the electrical. Does that mean you run a wire from the fuel pump directly to the battery with a on/off switch somewhere in the middle? If so I assume this switch has a "relay" to the front which controls the current flow?

Assuming again this is correct, is there an inline fuse to protect the fuel pump?
I can't tell you how many mid 80's/early 90's Camaro's I fixed with INOP door locks, clock, cigarette lighter, power trunk release, console box light... because of a penny a child stuck in the cigarette lighter...

A standard ignition switch should be more than capable of handling a electric fuel pump on your type of boat with no relay's.

Most boats don't have a fuse for "just" the electric fuel pump, but that doesn't mean it should be unprotected.
Get yourself a fuel pump relay kit like the one from Painless Performance Wiring and be done with it....

googleisthemaster:)




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

I read up and found that the pump only draws 2 amps so I knew there had to be a problem somewhere. 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:D

As far a running a relay, I am a little confused as my weakest point on my boat is the electrical. Does that mean you run a wire from the fuel pump directly to the battery with a on/off switch somewhere in the middle? If so I assume this switch has a "relay" to the front which controls the current flow?

Assuming again this is correct, is there an inline fuse to protect the fuel pump?

thats exactly what a relay is. its a device that controls a high load circuit...or even a low load circuit that you want completely isolated from all other circuits, and is switched on and off by the "control" portion which is a coil winding that creates a magnetic field and closes the "switch" portion of the relay to allow current flow of the high load circuit. it takes almost nothing to activate the relay, which will turn on the high load fuel pump circuit at the back of the boat. now if you want, you can run the "control" circuit to the ignition switch, or to a separate switch, or even to a separate switch that gets it power from the ignition switch. lots of options, and all of which would have made it much easier to diagnose your current problem.

in your case the pump would have not done anything, but the fuse that provides power to the front of the boat would have been blown. or you saw the pump doesn't turn on, so you check the relay and find you have no control power. no matter what, you immediately isolate your problem to the front.

On my personal boat the fuel pump, ignition box, ems (i have fuel injection) are all controlled with relays, it isolates everything, and breaks up the entire harness into sections. its easier to fix, more efficient and much safer. everything should have a fuse too control and load.

AP
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I can't tell you how many mid 80's/early 90's Camaro's I fixed with INOP door locks, clock, cigarette lighter, power trunk release, console box light... because of a penny a child stuck in the cigarette lighter...

A standard ignition switch should be more than capable of handling a electric fuel pump on your type of boat with no relay's.

Most boats don't have a fuse for "just" the electric fuel pump, but that doesn't mean it should be unprotected.

I could not DISAGREE more with this statement.

AP
I could not DISAGREE more with this statement.

AP
He said the fuel pump draw's 2 amps, I'd like to hear your opinion on why a relay is recomended.
The reason a relay is recommended is to reduce the voltage drop caused by the ~20-40 feet of wire used to connect to the pump. 20-40 FEET of wire??? Yes, from the battery to the motor mounted junction box, box back over to gunnel, along gunnel to switch, switch back along gunnel to pump. A suprising amount of wire. Also, most guys use too small wire further aggravating the issue.

Additionally, the guys that make the pumps recommend use a relay and keep the connection to the battery as short as possible.
Chaz I think I found some shorts :D

Just kiddin Bud call me if I can help Tom
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