Thanks to mrfred (and 90zcrex) for all of the great info in this thread.

A few fairly simple questions:

1. What is the typical wire gauge of a fuel pump rewire kit? I'm thinking 12 or 10 gauge? Certainly no need for 8 gauge to feed your typical drop-in single pump, like a DW300, Aeromotive 340, or Treadstone 342, right?

2. For the rewire ground, do I just need to splice in a larger (10 gauge) ground wire to the existing thickest ground wire going to the fuel pump harness under the rear seat? My connector has a thicker (maybe 3mm with the insulation) white 12+ wire, a black wire in a matching thickness to the white wire, and two additional much slimmer black wires.

3. What kind of voltage increase under WOT is typically gained with rewiring the fuel pump high-voltage circuit with a rewire? Perhaps .6 to 1.0 volt?

 

Also, now that I've done this rewire (with the simplified 90zcrex method), I'm seeing only about 7.5 volts at idle and when closed throttle/in vacuum with than 8 inches of mercury, and upwards of 13.7 volts when it kicks over to the full voltage wiring, whether I'm at part-throttle and low boost, or at WOT and full boost.

These readings seem both too low and too high to me. Granted, I'm just using a $10 Harbor Freight multimeter to obtain these figures, but I did put a fresh 9-volt battery in it to ensure maximum accuracy, and this MM seems to register realistic, believable voltage readings when I use it to see resting battery voltage (12.7 to 12.8 on a healthy, strong battery) and voltage at the battery with the car idling/alternator charging (13.6 to 13.8).

 

13.7 sounds right if thats what your system is charging at while running. 7.5v seems a little low, I think when I tested mine that I was getting near 9v. If i have time tommorrow I will see if I can't check again for you.

 

Thanks for checking back in 90zcrex (assuming you're a former Honduh guy... I've owned many 2nd gen CRXs and EFs back in the day!)

Well actually, according to the exact same HF multimeter (same probe leads even), my car's voltage measured at the battery terminals with the car idling is 14.1 to 14.2. With the engine off, it is only 12.5 to 12.6 (it's a 4-year-old Odyssey PC680 that's on its last legs... it's been drained dead at least a couple dozen times).

Yeah, in this thread on highboostforum, jack_of_trades says 9 volts is what the low-voltage output is:

The factory power supply for the fuel pump is a two-stage system. At idle and low engine loads the voltage sent to the fuel pump is lower (roughly 9Vdc).

http://highboostforum.com/forum/show...-Capabilities?

I have no doubt the cheapo Harbor Freight multimeter is off maybe 5 to 8% in accuracy, but even being 8% off from 9 volts would still be around 8.3 volts...

 

It's funny you mention the harbor freight meter. I had a guy at work today who was checking voltage at a sensor and kept getting 10 volts where he needed 12. He went through checking everything and going crazy, my buddy walked over there to help him and he was using a harbor freight meter, Whipped out the Fluke meter and the harbor freight meter was reading close to 2 volts off of what it should.

 

Okay, that's a great "data point"... maybe I should try to borrow a decent multimeter and try testing again.

Regardless of how inaccurate my voltage readings may be, I found it interesting to see that on my car, the fuel pump circuit switches to the full-voltage mode way before the engine sees positive manifold pressure... I thought I'd read somewhere that it transitions right as the engine goes from vacuum to boost.

 

nice work!!! great info!

 

+1

 

I'm wondering if I have this fuel over-run problem. Unfortunately, I don't have a fuel pressure gauge. Stock 03 with an ETS 35R, HKS 272's, Walbro 255, Precision 1000cc. I bought it this way, and with a baffling problem of going lean, losing power, sounding like its running on a couple cylinders. Almost always at crusing speed on the freeway. Also, just after tip in at very light throttle. If I let off the gas, and then back on, it goes away. I don't drive it anywhere but local cause it sucks so bad.

Does anyone think this could be it?

 

mrfred.... just a heads up. i had my return line bust for whatever reason yesterday... no big deal nothign caught fire. but i did notice my pump kept running long after my car was off... i actually had to disconnect the battery to stop it. double checked against a customer car just to be certain and his turned off immediately... i have the easy dual voltage rewire mentioned in here and i think it may be the cause. i will find out soon enough. when i get my new line i will test it without the rewire and keep this updated. i also bought a new relay today just to ensure its not so weak that its causing it to stay on.

 

If it was stuck in full voltage mode, that would definitely put some stress on the return line rubber hose. Having the pump suck on after the motor turns off would suggest that the relay needed for the easy rewire toasted.

 

That was my thought... The line is stainless braided e85 fuel hose... Its only been on the car a few weeks... Idk what happen. The feed line is 12+ft long of the same stock so i'm worried now.

 

What brand hose was it? Presumably the stainless didn't fail, so just the rubber hose (or was it teflon?) developed a leak? Was the leak at a fitting connection?

 

Hmmmm, It's funny that you mention the pump staying on with the key off, I have had this happen a couple times as well. I unplugged the added fuel pump relay and plugged it back in and the pump stayed off.
Seems as though the ecu is sending just enough voltage on the relay to keep it latched, I'll see if I can get it do it and check voltage at the relay.

 

its from summit... can't recall if its summit or russel as i have ordered large amounts of both... it is a stainless braided line... and i do know for certain the line i bought was approved for e85 use.


there is no damage on the outside but it sure as hell gushes fuel... its the line from the bottom of my aem fpr to my oem metal line. and the hole is 6 inches from either fitting... boggles the mind i know...

as for the voltage at the relay... its the 3rd relay in a series after a damn resistor if i'm not mistaken... look back a few pages and you will see the wiring diagram.