1G Just blew my 30amp in-line fuel pump fuse!

[1cleangsx]

Hey guys! My cars currently spending the night on the side of the road till morning. I was out ripping/tuning when this happened…

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I’m assuming it shorted out on something after that last 2nd gear pull, has this ever happened to any of you guys? Tomorrow morning I’m gonna cut out the FUBAR’d fuse holder and splice in this little guy..

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Hopefully I can get the car home tomorrow and find out what caused it to short out

 

[curt-s]

I guess it did it's job? Albeit poorly.
I would personally consider that a failure of its slow blow mechanism. 30A is a lot of current even for a fuel pump. Perhaps that's a shit happens moment, or a really cheap fuse from those countries that produce really cheap products.

 

[1cleangsx]

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I’ve had this fuse/re wire set up in the car since 2014? Maybe it worked it’s way loose or something I don’t know, I’m confident she’ll fire right up when I replace it in the morning, assuming my cars still there

 

[We're on Boost]

has this ever happened to any of you guys?

Yah! It seems your intank pumps (couple of DW 300's) need about 15 amps each, or more, to run at high pressure. So if you run both pumps through 1 circuit, it's probably going to exceed 30 amps at times.
I see some different numbers for DW 300 current requirement, but I'd plan on the higher numbers for your circuit.
I agree though that the fuse holder shouldn't have melted like that.

The higher numbers are in a fuel pump test done by AMS in 2011 and posted in Evom in July of 2011: https://www.evolutionm.net/forums/a...werks-dw300-walbro-255lph-fuel-pump-test.html

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The lower numbers I see on the Deatschwerks tech data sheet for the DW 300:

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Now the real reason your fuse blew is because mine blew a few weeks ago and yours just, I don't know, thought maybe it should too.
But no, mine blew because my "rewire" wire was stupidly laying across the exposed part of the steering column where it goes into the rack, and that turns haha. So dah it wore a little tiny hole through the wire insulation and shorted out there. And I found out that flat bed response, at least with Hagerty coverage, is super slow here where I live. But it quit only about a block from home, so I took the nose off the car and walked home with it, to get it out of the way for the cable to pull it up onto the truck. Ha!

Anyway, my circuit with a 30 amp fuse in it only has to run one little Walbro 255 intank.
The second pump which is an external inline Walbro 255 has its own circuit.

 

[Vegas Smith]

I’ve never had dual fuel pumps, cause I’m not a loser, jk, but can you do dual feed/relays with them?

 

[1cleangsx]

I’ve got dual relays, I guess my next question would be which size fuse should I run? 250? Lol maybe 35 or 40 should work, and I’ll certainly check the wire for a possible short thank you guys!

 

[curt-s]

Would have helped had I looked at the mod list and seen the double pumper.
Are you not running dual power feeds, one for each relay?

 

[1cleangsx]

I’m running the dual power feed/relay that the hanger came with, quick update, i spliced in the new in line fuse and she fired right up, but after 5 minutes or so of idling that fuse/wire is getting hot, I might go get a 35amp fuse to try and hopefully make it back to the house without it melting, so I’m pretty sure I don’t have a short or it would’ve right off the bat correct?

 

[curt-s]

A short can present itself also only when vibrations caused by the moving of the vehicle, as the wire comes into contact intermittently with a grounded surface.
If you insulated the wire enough with grommets and such as it passed through/around metal surfaces, you probably don't have a short. A 35A or 40A should get you home, as long as you don't exceed the amperage of the wiring, including any of the wires on the fuel pump hanger itself.
This is one of the things that some forget, you could do a FP rewire to 8Ga but if you're attaching it to 12 or 14Ga wire at the fuel pump harness, you've necked down that part anyway.

 

[1cleangsx]

So I just got the car home after splicing in the new in line 30amp from oreillys, but the wire/fuse are HOT. The existing fuel pump 10gauge wire is aluminum and the new in line is copper, I don’t know if that’s the issue, I did what I could on the side of the road but I’m hesitant to continue driving the car with the janky connection I currently have

 

[Stapl3]

2 relays is a bad idea. If 1 relay goes bad, you won't know until you're WOT and missing half the fuel you need up top. There are relays out there with 2 outputs...

IDK why everyone rewires their pumps with small gauge wire and small fuses and small relays. It's the same cost to go big. When I rewire my pumps I treat it like I'm wiring up an amplifier in the trunk. I run 2-gauge (I think) wire from the battery, I even cut apart the 450 to delete Walbro's wires and step up to 8-gauge. There's no benefit to using the 1" x 1" Radioshack relay, it's so small. It's just commonplace in this community because someone figured it out in the 90s and put it on vfaq. This relay I used is 80amp, it's beyond overkill, but works perfect. I think it's intended for a mobile home with a secondary battery. Relays are very simple so pick your poison and don't be afraid to go too large as there's no drawback I can think of. And they're dirt cheap too, this one was 15 bucks.

 

[Vegas Smith]

If the wire is hot then you're probably using too small of a wire. You might consider going to 8awg if it's going all the way to the front of the car.

 

[We're on Boost]

I’m running the dual power feed/relay that the hanger came with

I'm still unclear about this circuit. It sounds like you have 2 relays, but still only 1 fuse supplies both of them?
I picture your circuit like this:

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If that's what it is, then the part that is a single 10ga wire with a 30 amp fuse in it is not good and should be done bigger. That would be the "minimum" fix. You could go beyond that like Stapl3 suggested.

Also, are you sure that the existing fuel pump wire is aluminum? Copper wire that is tinned looks a lot like aluminum. I'd be surprised if it was aluminum. Mixing copper and aluminum wire is something that was tried in home building several years ago, there were problems that didn't show up right away, and my understanding is that the problems were sort of "solved" and there are ways to do it now that last, I guess. But one of the products I ran into when I looked in to that subject a few years ago is called "Penetrox A" which is an anti-seize that is loaded with zinc dust rather than aluminum or copper or graphite or moly or ....
Read the label on this thing:

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Kind of a whole can of worms by itself, hope that is not part of it with your car. If you want to read about this particular mess, I can give you a link to a Quora discussion about it. To make it worse, Penetrox A is not recommended for use on wire with rubber or polyethylene insulation. They make "Penetrox A-13" for that!

 

[1cleangsx]

With my battery in the trunk I could just ditch that old wire in the front and run 2 10 gauge wires/fuses to the pumps considering the pumps are 2 feet away from the power source.

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This drawing is correct on what I currently have going on.

 

[1cleangsx]

Except the 10gauge wire is connected to the positive end of the 2gauge wire in the engine bay along with the mpi fuse box

 

[We're on Boost]

With my battery in the trunk I could just ditch that old wire in the front and run 2 10 gauge wires/fuses to the pumps considering the pumps are 2 feet away from the power source.

That would be pretty easy and it would work. And you could keep using your existing 2 relays that way.

It would be good to know if the DW300's have an anti-backflow valve built into their outlets. Then you could sort of know what kind of behavior to expect from the car if one of the circuits quits working while you are driving. I put a question in to Deatschwerks asking if there is an anti-backflow valve there using their "contact us" thing. Do you already know if there is?

In the long term I suppose it is safer to have an "all-or-nothing" type of circuit for the pumps that are in parallel with each other.

 

[We're on Boost]

You want each pump to have its own fuse anyway. Because then if one pump shorts or seizes, it only needs to pull enough current to blow its own fuse. That could be a 25 amp fuse probably.

If you have just one fuse, it has to be big enough to run both pumps, maybe a 50 amp fuse. Then if one pump shorts or seizes, it would in some situations have to pull most of that 50 amps all by itself to blow the fuse. I don't think that is very safe.

So I don't think you want to have just one huge fuse running both pumps.

 

[1cleangsx]

I’m not sure if it has an anti backflow valve, but I think the 2 wire/fuse route is the one I’m gonna take. I really appreciate everyone’s input thanks guys.

 

[Vegas Smith]

I’m not sure if it has an anti backflow valve, but I think the 2 wire/fuse route is the one I’m gonna take. I really appreciate everyone’s input thanks guys.

If you're battery is relocated then theoretically you should only need 10awg wire but sometimes crimps/solder connections aren't good which ups the resistance in the wire. Hard to believe that your little baby turbo is causing the fuel pumps to work hard

 

[1cleangsx]

I know right , it’s not like it’s connecting rod snapping power

 

[1cleangsx]

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[1cleangsx]

Nice little idle vid I made with the new muffler right before the fuse blew

 

[Vegas Smith]

I know right , it’s not like it’s connecting rod snapping power

Whoa, too far.

 

[We're on Boost]

I did get an email back from Mark at Deatschwerks on my question "does the DW300 in-tank pump have an anti-backflow valve (check valve) built in on the outlet". He says yes it does.
So what will happen if one pump quits is, you might not even notice any difference until fairly high boost levels. Because on the pump that quits, the anti-backflow valve will slam shut, which will keep flow from the other pump going to the engine, and not going back into the tank through the non-running pump.

I was kind of hoping that there would be no anti-backflow valve in them. Then if one pump quits, you'd have probably almost no fuel pressure, maybe enough to limp home, but not enough to make any of that harmful power haha! In that scenario you could still have an anti-backflow valve. One of their 10AN check valves, in the line that goes up to the engine bay.

But no, I guess, unless they offer "no check valve" as an option or mod to the DW300.

There is this effect called the "regulation slope" or "droop" effect, where the regulator output pressure will go up or down a little bit when there is a radical change in the amount of fuel flowing through it. Don't know if it would be noticeable!
The Fuelab 515 regulator for example has a Regulation Slope of 3 psi per GPM of fuel going through the regulator. Your pumps are about 1.5 GPM each. So if one pump quits, that should change fuel pressure by 4.5 psi if it's like at idle where all the fuel is going through the regulator. Something less than 4.5 psi under power. Maybe if you had a fuel pressure gauge right on the dashboard you'd see it! Wow, isn't it great how complicated these fricking cars can get?

Your car sounds real nice BTW!

 

[1cleangsx]

Thanks man! I’ve actually decided to do a 8gauge single 40 amp set up, so again if the fuse blows the motor dies instead instead of limping on 1 fuel pump.