I am in desperate need of some help. On three of the past four mornings and once in the evening when leaving work, the 15A fuse that supplies power to my auxiliary fuel pump (Holley Blue) has blown. I have the pump powered through a relay with the signal wire coming from the factory lift pump. The fuse is connected between the battery and the relay.

I have replaced the relay thinking that it might be faulty. I inspected the wires that are in the engine compartment and see no wear indications. I replaced the fuel filter thinking it might have been clogged causing the pump to work harder thus pulling more power.

I wonder if its temperature related. The fuse blew Monday morning, Tuesday morning, and this morning as well as yesterday evening when I left work. Seems the only thing in common these days is the weather. Its not real cold, maybe mid 40s, but it is cold enough for the grid heaters to cycle. The only reason I even consider this is because I do get feedback from the grid heater cycles through my subs in the mornings. I don’t think it is a wiring problem since it has only blown within minutes of startup.

There is some corrosion on the battery terminals which I will clean off tonight. I only want to replace the pump as a last result…

I am no electrical expert, so I come to you for help.

 

i would get an inline fuse and wire the pump out of the powerbox and see if that fuse blows and go from there

 

I would check your battery and wire size to the pump. When it's cold the pump will have a harder time moving the fuel and the battery has less power. It could be the voltage is droping to the pump. Say the pump draws 14 amps, converting it to watts is 12 volts X 14 amps=168 watts. Then voltage drops to 10 volts , 168 watts/10volts =16.8 amps. The wire sizing may be marginal, too thin of wire will increase the resistance to the pump. Being intermittent and only during cold leads me to believe it's one of the two.

 

i like your thought process. I think i used 12 gauge wire... i would think its capable. i also need to clean the terminals so there is clean power.

 

Get a cheap inductive amp gauge , test .
Bigger wire is always better .

 

can you expand on this? i have no clue what your talking about... i left all that inductive crap back in college physics...

 

Cheap gauge , test - see if there is too much amp draw , find the problem and fix / replace only whats needed .
Larger wire , lots of sources out there to figure what size wire to run how many amps / how many feet .
You do not need collage physics for this kind of work , if you took collage physics , you would not have to ask .
Sorry when I get what seems like a bad aptitude , I respond the that way . If I got the wrong impression from your reply , then sorry again .

 

its cool... didnt have an atitude. i really didnt know what an inductive amp meter was...

i did take college physics, but seeing how i am a mechanical engineer, i hate electronics. ill look for one of those gauges...

 

An "inductive amp clamp" can get at Home Depot. It's a clamp that when wraped around a wire can measure the amps running thru it. It looks like a big pliers but doesn't clamp on the wire it clamps around the wire. Just make sure it can measure DC. They aren't very expensive, my guess is $100 but I have not priced them for a long time. It may seem expensive but it would help troubleshooting, good luck.

 

They come in high or low amp draws , low-for stuff like what you are working on .
High for like starters .
Just touch to to wire in question , turn on circuit , gauge reads what it the load is pulling .
I would say at a parts house , about $30 .
These are what I have .


http://buy1.snapon.com/catalog/item....re&dir=catalog

 

so the website says it runs at 3 amps. how accurate is this? if it is over, is that a good sign that the pump is going south? if its under, does that mean the pump is definatly not the culprit?

 

The website says 3 amps for the pump and your blowing a 15 amp fuse...wow . I don't know what kind of pump it is. A piston pump will work harder if it is deadheading (like an air compressor). A centrifugal pump ( like a vacuum cleaner) will draw less amps when deadheading and will draw higher amps if moving more flow than designed.

 

this is exactly why i doubt its the pump...



website says rotor/vane design...

 

dont doubt that it could be the pump. it just means that the 3amp spec is for a good pump operating normally. so is 3amps a no load value. is it pumping water, gas, diesel, oil. i know in tx its not very cold out. but the viscosity of diesel is much more than gasoline. with the added viscosity the pump must work harder. best way to verify you problem cheaply is to overlay the fused power circuit to pump. if it still blows you know the pump is bad so either protect circuit to 20amps for another test or replace pump.

 

It may not be the pump [ but it seems like it ] , if the spec is 3 amps & your blowing a 15 amp fuse , there is definitely a problem with that circuit / pump .
The amp tester ' at ' the pump will eliminate everything else .