rewire fuel pump?

[tektic]

Is fuel pump voltage an issue for Galants like it is for dsms? I am about a point high from my target AFR above 1400hz and playing with the maf comp doesn't change it.

I'm using an Evo 8 pump and stock everywhere else in fuel system.

 

[iceman69510]

Sure. Not identical, but a similar execution of the design. I have the battery in my trunk, so rewire was a no-brainer in that case.

 

[tektic]

So voltage is an issue then. I guess ill get on that.

 

[gvr4ever]

I measured way back in the day. I forget the exact reading of the voltage drop, but it does exist. .3 volts, .4 maybe.

 

[Coltsfan]

I would put yourself a step ahead of the game by just putting in a Saturn or 3.4L Camaro alternator. I put one in mine last week when the Mitsubishi unit quit, and 14.5v at idle with everything on is nice. Besides, check a log, the original alternators don't do squat above 5000 rpm anyway.
Been rocking one in my Colt for the last couple years with great results.

 

[GSTwithPSI]

^ Are the GM units bolt up?

Why do you say the stock alt doesn't do anything above 5k? Is there a known issue with the regulator or something?

If that's true, it would explain something I've been seeing in my logs. At cruise, I have a ~14.1v consistently. However, at WOT the voltage progressively drops up to redline. I would expect a few tenths of a volt, but at redline I'm dropping all the way down to 13.3v in some logs, which seems low to me. I'm not currently seeing any impact on performance, but I'm guessing this situation isn't optimal.

My current alternator has less than 5k miles on it. It's a factory reman Mitsu unit. I've also gone through the trouble of running a copper 8 gauge wire grounding the case terminal to a clean point on the block. Also, I have another piece of the same 8 gauge wire running directly from the charging post on the alt to the main battery fuse block, which meets the 4 gauge wire running to the battery in the trunk. This is in addition to the factory wiring, which is also hooked up to the charging post as it should be.

As a tertiary precaution, I'm also running the stock lower heat shield on my exhaust manifold to provide whatever heat shielding to the alt that I can.

After all the extra wiring , I see EXACTLY the same voltages at redline, which leads me to believe the alt just isn't putting out. I'm looking for a better alt. I'd love the buy the Denso unit G linked to in the other alt thread, but if there's a lower cost alternative that works just as well, the DSMer in me is open to suggestions.

Edit: Here's the other alt thread I was referencing: click

Also, as to not turn this into another alt thread, yes, there is a voltage drop in the VR-4 just as there is the DSM. The wiring configuration for the fuel pump is nearly identical. A rewire is a good idea and the wiring is fairly easy to do. The part that sucks is running a heavier gauge wire from the engine bay to the trunk area. Unless your batt is relocated to the trunk, in which case, it's really simple. If you need help with the wiring, let me know. There is plenty of info about how to do it, but I can spell it out quickly and easily if you want.

 

[thomcasey]

You have to grind away a bit of the block (Saturn alternator is not as wide for mounting) and round out the front case where the alternator mounts to allow adjustment/movement. Or, go with the Jay Racing Alt. relocation kit. It is easy to wire in, there are several write-ups on it. I ran one on my colt. If I didn't have this brand new alternator, I would run one on 1025.

 

[marvinmadman]

Is there a write up somewhere?

 

[thomcasey]

Here is the install write-up, but picks are broke:
Saturn Alt swap write-up

Here are some good pics.
Saturn Alt Pics

Just note, once you modify the Saturn Alternator, you may void it's warranty.

edit:
Another note, the Saturn alternator install does NOT preclude the need for a fuel-pump rewire. The voltage drop is due to the miles of too-small wire for the fuel pump power, not the alternator output.

 

[prove_it]

Doesn't the alternator stop charging at WOT so more power can be made? (less parastic draw)

 

[thomcasey]

The ECU will cut power for the "excite" wire to the alternator to effectively shut it off, but there are some folks that run a self exciting alternator so this will not work (My Saturn I had on my Colt was a normal alternator, until one day it became self-aware and stayed on all the time, draining the battery. Had to cut the excite wire.) The parasitic draw isn't really the issue. The issue is the power wires from the factory are too small for full power to the FP at high demand levels. The rewire takes that out of the equation, but does not affect the ECU telling the alternator to GTFO with all that charging volts.

 

[donniekak]

Quoting prove_it:
Doesn't the alternator stop charging at WOT so more power can be made? (less parastic draw)



The ecu has no control over the alternator in the 1g dsm and galant vr4.

 

[iceman69510]

That's correct. Only two wires. Later models (2g) with the 4-wire alternator connection have this.

 

[Coltsfan]

13.3 is impressive at redline! I've seen peoples logs showing as low as 10 volts at redline. I was usually lucky to see 13.3 at cruise with nothing turned on, and voltage below 12 at redline. A pump rewire can't hurt, but having 14.5 volts to start with is a big help too.

 

[donniekak]

I modified my fan wiring to be controlled by the fps, and egr, Ecu outputs. They're shut off over 5500 rpm or 70% tps. My afr's went from 11's wot at 30+ psi, to high 9's from the extra pump voltage. This is with a walbro 450 and 3582htz.

 

[prove_it]

That's why it's nice to have a fuel pressure gauge or way to log it. As Boost increases so does fuel pressure (1:1) and if voltage drops then the pump really struggles. This becomes a big issue with E85 since not only do you need more fuel, but it's a thicker fuel so pump has to really work hard.

There really is no reason to re-wire the fuel pump. 20+yr old wiring isn't really up to the task of a huge pump. Also it's best to re-wire through the pump housing and not just to the external post. Lots of resistance can happen there. Just make sure the wiring isolation is fuel compatible.

 

[tektic]

Finally got around to doing this...
Did I just connect the wrong wire?!

By the way this is a noob question... Posted in the right section. I allready searched for an answer and didn't find galant specific info. I should have looked up the connector pin out in the manual but I'm being lazy. .... F-it. Ill turn on my computer now and look it up.

edit: Looks pretty wrong to me now.

If I'm reading this right i was supposed to cut the Black with white stripe wire right?

 

[kumfasa]

Check this out.

This should answer most of your questions.

 

[CutlassJim]

Quoting tektic:
Finally got around to doing this...
Did I just connect the wrong wire?!

By the way this is a noob question... Posted in the right section. I allready searched for an answer and didn't find galant specific info. I should have looked up the connector pin out in the manual but I'm being lazy. .... F-it. Ill turn on my computer now and look it up.

edit: Looks pretty wrong to me now.

If I'm reading this right i was supposed to cut the Black with white stripe wire right?




Two issues I see right off the bat.

1. The wiring looks a little small. I'm an overkill type of guy but I run at least 10 gauge to a bigger than stock fuel pump. \

2. Everyone always forgets the ground wire. You need the same size wire on the ground coming out of the pump. DC voltage is circular so the whole loop needs to be free flowing or you still have a current restriction.

The way you did it is also how I first did it way back in the day but now I like to run that larger size wire right into the tank through the pump. Even with a stock alt and a Walbro 255 I noticed that factory connector getting burnt up from the extra current flowing through it. Brett(GSTwithPSI or whatever) had a nice elegant way of enlarging the feedthroughs on the pump housing.

 

[tektic]

Outside frame the wire is 10awg to a 30a fuse at the battery. I didn't think the last 16" of 16awg would be a significant voltage drop. What is the stock wiring 18awg?

I will add an additional ground wire that is a good call.

Just to double check pin one is power (black white stripe) three (black) is ground?