Electrical Issues... Need Help

[StevenAg03]

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.

[Sharpe]

Cold starts causing the fuel to gel a little and making it harder for the pump to work?

[DRAGOONRANCH]

Is the wire big enough to pull the amps as far as it's having to? Was the filter before or after the pump? How old is the pump?

[StevenAg03]

Cold starts causing the fuel to gel a little and making it harder for the pump to work?

maybe... but i dont think so. what temp does diesel gel at? also, i had it all through last winter so wouldnt the same problem have happened then too?

Is the wire big enough to pull the amps as far as it's having to? Was the filter before or after the pump? How old is the pump?

filter is after both pumps. the holley pump is near the fuel tank and stock pump and filter is on the side of the block. i havent had an issue with wire size for over a year (i think). i cant remember exactly when i installed it, but i think it was late 2007. I know it was pre-2008

[DRAGOONRANCH]

If it's that 'old', then the pump may just be going bad/wearing out. You would think it should last longer, but you may have just got a bad one. #2 starts to gel or cloud up around 20F IIRC, but if it is cold enough to just make it a little cloudy then that may have been enough to plug up the filter a bit and put some extra strain on the pump.

How long after the truck was started did it blow?

[eight]

It doesn't get cold enough here to affect this sorry excuse for diesel oil we get.

Pump probably going bad. Swap to a Carter, you can get them at a Cummins shop fairly cheaply.

[StevenAg03]

If it's that 'old', then the pump may just be going bad/wearing out. You would think it should last longer, but you may have just got a bad one. #2 starts to gel or cloud up around 20F IIRC, but if it is cold enough to just make it a little cloudy then that may have been enough to plug up the filter a bit and put some extra strain on the pump.

How long after the truck was started did it blow?

i dont think the pump is working too hard. i have the internal pressure setting dialed way back due to having dual pumps.

each time i would say within 1-2 minutes. also, fuse has blown since i replaced the filter last night.

It doesn't get cold enough here to affect this sorry excuse for diesel oil we get.

Pump probably going bad. Swap to a Carter, you can get them at a Cummins shop fairly cheaply.

i have a carter on the block.

[DRAGOONRANCH]

well, if there are no nicks in the wire and you are pretty sure you don't have trash in the tank that could be forking with the pump, then the pump is probably on it's way out.

[StevenAg03]

well, if there are no nicks in the wire and you are pretty sure you don't have trash in the tank that could be forking with the pump, then the pump is probably on it's way out.

hopefully your theory isnt right Ed... im kind of leaning in this direction...

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.

the only thing common between all situations is that it was cold enough for the grid heaters to be on. When at idle, you can watch the voltmeter drop as the heaters cycle on and off.

i plan to pull all the cables off the batteries and clean everything up this weekend. we shall see.

my temporary solution... 20A fuse...

[Doug Krebs]

have you checked the resistance of the wires?

[eight]

If you have a multimeter with inductive amps thing, see what the pump is actually pulling. If its 5A its probably a short somewhere. If its 14A it will do about what's happening to you. Then check what the specs are telling you.

Then chunk the holley pump. Keep your little warning light and fuel pressure gauge if you have one. If you're scared, keep a spare carter under the back seat.

[robertf03]

corroded terminals or crimps on the pump and wiring?

[StevenAg03]

corroded terminals or crimps on the pump and wiring?

i know there is corrosion at the battery terminals where the pump gets its main power from. i havent looked at the crimp on connectors at the pump.

[StevenAg03]

have you checked the resistance of the wires?

no not yet... its somewhat hard with a 15' span between the relay and the pump...

[StevenAg03]

If you have a multimeter with inductive amps thing, see what the pump is actually pulling. If its 5A its probably a short somewhere. If its 14A it will do about what's happening to you. Then check what the specs are telling you.

Can you expand on this?


Holley says the pump only draws 3A and recommends a 7.5A fuse. I dont think the pump is my problem here.

What guage wire should i have for ~15' run pulling 15 amps?