spectacle

Backstory and details on my initial install can be found here

Cliffs: I installed the Walbro 400 (gas model) with a seemingly shoddy rewire to the battery and within a day burned up the relay. I had everything rewired by a reputable shop, but I've run into the same problem again.

Deja vu:



I've lucked out TWICE now with this stupid thing, both good and bad. The bad is obvious. But, the good on both failures is attributed to when they happened. On the first go around, the relay died right after I got tuned and wouldn't let the car start. This time around, I went to my friends shop to troubleshoot a completely unrelated problem (those little motorcycle batteries suck at starting this car) and he spotted the relay on its last legs. Judging from the looks of it, I was pretty close to this one giving up on me too. You could imagine what would have happened if it would have died in the middle of a pull...and no, I didn't have any telltale signs of weird AFR or anything out of the ordinary to check it beforehand. I plain got lucky.

So we got to work on tearing everything down and fixing this thing. First thing he asked me is "jesus how much current does this pump pull?" Here's a chart I found on Radium's site from their fuel pump comparison (click the picture to read the article, it's worth a read):



I'm running a base pressure of ~ 53psi (you really need an adjustable fuel pressure regulator if you want to run stock base pressure with this pump and stock lines) with 15 psi on 93oct which puts me right around a max of 16.5 amps power draw. Not sure on my first relay, but I know this second one was at least 30amp rated so I wasn't exceeding its power handling. That leaves the problem somewhere in the wiring. We yanked the cover off and disconnected everything.

This is the wire going to the top of the stock connector on the top of the housing:



In my first thread, I stated I wasn't sure how far the last rewiring job went into the fuel pump assembly. I surmised that they repinned the connector with the 10ga wire, but we now know that is not the case. The wire and pin going into the stock connector looks to be about 14g a (stock wire). I asked my friend to just use the stock pin with the 10ga going directly into it, but that is not possible. You need a specialty 10ga pin made to fit the stock weatherpack connector in order to do that (which we didn't have available). So we did the best we could with what we had.



Connection after soldering, before heat shrink:



Finished product:



My old relay had a Pico style connector (click the pic for details):



The problem with this connector style is it isn't a snug fit on the relay. My friend thinks its possible the connector was loose enough to cause extra resistance at that juncture on the relay and the subsequent heat generated is what started melting the connectors' plastic housing. As a matter of fact, if you click the link to Summit and read the second review, that guy had the same problem. Might be a design flaw with this connector style when the current draw goes up.

We switched to a higher quality Bosch relay with direct terminal access:



The connections are all super snug on the relay now. The car ran fine on the way home and I haven't driven it since. My S is a weekend toy and the only reason I drove it that day (during the week) was because my daily was in the shop. It will be a while before I get some decent miles on the new wiring to see if I run into this problem again. If I do, we'll add a second relay to this one to spread out the power draw across two and see if that helps. At this point, I don't feel like the change in wire gauge through the fuel pump assembly/connector is the problem. If you're running this pump or the e85 version, and a Pico connector relay, I highly suggest you keep an eye on your relay(s). You might not be as lucky as me!

s2k manic

that sucks check out my relay install on my 340 I actually opened the pin up and installed the 10 gauge wire into it and resoldered it also I used gold plated spade terminal's on the relay soldered on the wires with shrink tube over them for insulators so far so good I also have an areomotive fpr hope you get it sorted

99SH

What's the PN on the relay? Make sure the Amperage rating is for continuous and not peak current. You shouldn't have any issue whatsoever if properly derated.

Redline S2K

Make sure your ground wire is larger too.

riceball777

There will still be a problem since you soldiered the 10 power wire in to the stock pump tiny 16 or 18 gauge wire. When you really need to do is drill into the top of the fuel pump housing and run the 10-12 gauge power wire from the really straight into the pump. The must be Teflon wire be cause fuel will not travel up the internals of Teflon wire.

Or.

Just buy science of speeds new kit that actually give you a correct plug that has 12 gauge wire connected to it that plugs into the top of your stock fuel pump housing


My brothers s2000runs the aueromotive 340 pump which draws less power than a walbro 400. He has it wired the same way as you. The 10 gauge power wire from the relay soldered to the top of the pump housing useing a few inches of the stock 16 gauge wire. His relays would melt just like yours after about 10,000 miles or so and he would change relays. We drilled into his pump housing and wire the pump directly to the relay and he has never has a problem since.

The way your doing it by useing a few inches of the stock power wire is only acceptable with a walbro 255. A 340 pump or a walbro 400 pump will burn up the relays with time with the current way you have it setup. I know because my brother and I have go through this issue enough time for the past several years.

waleed786

I have a Walbro 400 E85 and never had any issues. I'm running 12g wires with a 30amp direct terminal relay. And I'm still using a few inches of the OEM walbro wiring on the pump side (not sure if its a thicker gauge than the gas 400).

I did notice one time that the wires and relay were getting really hot, but that was due to a loose connection somewhere else in the line. Never had any problems after that, and its been a few months.

I'm thinking it was just your relay that was causing the issues...but I would do the above anyway, as riceball pointed out, as a precaution

Sent from my HTC One using Tapatalk

AFK-S2K

The Walbro 400 comes with a 14ga wire, wich i believe is enough to supply it (from pump to relay). I have depinned an OEM bulk head wich has 18ga wire from the factory. Using a drafters compass (has two very stiff pointed needles on the ends) I opened up the factory pins and replaced the 18ga wire with 14ga, utilizing the factory plugs (inside the tank and outside). I havent tested this yet as I am still building the car but again I believe it to be more than enough. I am also using an upgraded relay that is used on FAL fans i believe, you can get it from d3 performance engineering. Hope this helps.

spectacle

Here's the relay I was using.


I'm assuming "40/30a" on the front refers to peak/continous rating.


My friend noticed the ground wire going into the pump housing connector was 12ga. That was fixed as well.


I've thought about this and decided I won't go this route. I'm sure it works, but I don't want to play around with the housing anymore than I have to.


Was your brother setup using a Pico relay like I was?


We believe this to be the issue. The Pico connector was loose when we took everything apart. It's the only thing that I can think of to explain why I had zero problems for over a year, but then this happens. I barely drive the car, but every now and then I did check on the relay. I think the last time I checked it I probably wiggled it loose.

ScienceofSpeed

Please consider this kit - it will solve your problems:
http://scienceofspeed.com/products/e...ump_power_kit/

1SlowSi

I use this bad boy right here with all 10awg wiring and two aem 320 pumps without issue.