rewireing fuel pump, why?

[Perez]

I read the tutorial on how to rewire the fuel pump and thought it was done very well.
It didn't say why one would do that so I'm wondering why is that done?
I started out looking at it because I'm having a problem with my acceleration.
When I'm taking off it's great up to 20mph and then it just hangs and the turbo just keeps winding up, but not much acceleration going on.
Then I get up to 30mph and it goes right away to 60mph and then hangs again.
If I take my foot off the gas for a bit the turbo goes down and I start to accelerate again.
So there you have it as to how I got to the fuel pump rewire.

Oh, and incase you're wondering no I haven't figured out what the problem is yet.
I'm also considering new injectors because I did add some injector cleaner and that helps alot, but didn't really resolve the problem.
I'm not looking to race this car as when I bought it the thing had been hacked like crazy.
So I'm just trying to bring it back to life.
Any suggestions are welcome and thank you.

 

[dsm10sec]

The reason to rewire the fuel pump is because Mitsubishi only used 18 gauge wire for the fuel pump. Often people get 10 volts or lower to the pump, when you rewire with 10 gauge you get the full 13-14 volts.

 

[Perez]

That was a great answer to my question.
So with the increased voltage the pump performs better and is able to deliver more accurate amout of fuel?

 

[Stanford]

People do it because the stock wiring is small and as always bigger is better. Seriously though, at higher Rpms the voltage to the pump drops off. This can cause a leaning out condition which is not good. When you rewire it to the battery it is steady voltage. As for your problem it may just be your turbo running out of steam at higher RPM's. If you have a 2g the Stock T25 can't hold boost past around 5k. It's been a over a year since I have driven my old Gst with the T25 so it may hold to 5500 but either way you get my point. Thats where the lack of power is coming from. If you have a 1g with a 14B, well then you may have a problem. Because the 14B isn't a bad turbo at all and can hold boost fairly well, unless you are trying to run 20Lbs.

 

[95gstnotwalkin]

i dont know but to me it sounds like your clutch is slipping.. im assuming that those mph are the high rpms of first and second gear.. when your making power at the top of the gear, the clutch will start to slip until you go and shift for the next one..

As for the fuel pump, the stock wires are very small and carry a very high resistance. Ive seen up to 20 extra horses run off the stock pump with just the rewire.. im not sayin youll get 20 horses, im sayin the stock pump can flow for 20 more horses..
matt

 

[Defiant]

http://vfaq.com/mods/pump-relay.html

First line:

"Rewiring the fuel pump with a larger gauge wire can help the stock pump (or any aftermarket pump) maintain higher fuel pressure/volume throughout its' entire operating range, as the stock wire is pretty small. "

 

[Perez]

Now if that had been the how too that I had read I would have never asked the question.

For my issue with the acceleration.
I'm hitting 20mph with the turbo way up according to the stock gauge, RPM's on the other hand are around 2 to 3k and that's it they don't go up.
It's not like I could wrap out the engine the RPM's simply don't go up and no acceleration.
Now if I let off the gas a bit and the turbo shows a decrease then my RPM's start to climb a little and I do start to accelerate.

I get the same thing when I'm going about 80mph and I step on it, car lurches for a second like it's going to take off and then the turbo cranks up and the car starts to stall out and run in a very jerky manner. The second I take my foot off the gas a little and the turbo goes down I start to accelerate again.

 

[dsm10sec]

Check the coil and check the plugs/wires. Another thing, the stock boost gauge doesn't even read boost it guesses it. Buy a real boost gauge.

 

[NewB2dsm]

I am making 338awhp on race gas and using a walbro 190 pump with stock wireing. Im really just to lazy to rewire it. So the stock wireing may be limiting but, not as much as everyone thinks?

 

[Chrisjones500]

I am not in agreeance with the rewiring part but your car has other issues. Most likely knock is taking your timing away and hence no real power noticed during acceleration. I would check that before you look at a problem that really not that big of a problem. Get a logger if you don't have one. Fill out your profile.

 

[trebornash]

the same thing when I'm going about 80mph and I step on it, car lurches for a second like it's going to take off and then the turbo cranks up and the car starts to stall out and run in a very jerky manner. The second I take my foot off the gas a little and the turbo goes down I start to accelerate again.

What causes this to happen?Wires?

 

[sephion]

I have the same problem with my laser. It accelerates better under partial throttle than it does full throttle. If I try to accelerate at wide open throttle it accelerates for a couple thousand rpm then as soon as the factory boost gauge gets almost to 14 it cuts out and the car shakes. It does it no matter what gear I'm in and it doesn't matter if the car is cold or if it has been driven a while and is up to operating temp. just as long as the factory guage shows about 10-12psi, but as soon as i let off the throttle a little and the boost level goes down it accelerates fine. The vehicle is completely stock. The previous owner had the turbo replaced with a remanufactured one, but still the same size turbo that would come with it, and after looking around when i heard an exhaust leak from under the hood I saw that an exhaust manifold stud was left out by cylinder number 4. Could this have anything to do with it? What could that cause? I bought a boost guage and i'm going to install it soon, and i'm going to replace the plugs and wires too, and i plan on doing a compression test and leak down test too. Any help would be much appreciated. Thanks

 

[ken inn]

fuel pumps dont just die, they gradually lose pressure. also, after i did my rewire, i noticed pressure came up about 2 psi static.

 

[DSMvroom]

could it be a boost leak?

One of the clamp slid off of a coupler on my upper intercooler pipe and even though the coupler stayed where it should be, if i pressed hard on the gas as soon as a high amount of boost was attained, the rpms just sat and the car went no faster.

 

[FORMONTOYA]

fuel pumps dont just die, they gradually lose pressure. also, after i did my rewire, i noticed pressure came up about 2 psi static.

i would have to disagree with this statement as i bought my 98 gs-t in nov 97...had the car about 2 1/2-3 years and the fuel pump did just that...no warning/no issues with how the car ran. got the car home one night everything fine...woke up the next morning and nothing...did all the checks and found out the pump was not working, had power...warrenty (sp?) to replace the pump and it has run great ever since.


jim

 

[laxdudeee]

this post jumps around more than any I have ever read. To try and answer your question, I would do a boost leak test. Also what does it feel like when you are accelerating? Does anything pop and misfire or does everything sound fine just not go anywhere? It is possible for your FP to be junk but I would look elsewhere for the time being then maybe get a walb 190 for safe measures. Get a logger it is one of the best things that I have purchaced. (www.dsmloggers.com)

 

[draneusmc]

Everybody here has great input. I agree with doing a compression check, leak down, replacing schedule maintenance parts ,but the problem that you are describing could be alot of things but I think you might be losing boost or just not building boost so the car goes into a saftey mode and doesn't let you go any higher in RPMS. Part Throttle or closed loop runs great because your not building a lot of boost under those conditions. Although open loop or wide open throttle is going into saftey mode because something obviously isn't right. Just putting another perspective out there. Make sure to keep us all updated with your progress. Just my .02 cents

 

[Perez]

Let me start by saying thank you to all of you.

First when I purchased the car it had 100K miles on it.
Part of the deal was that the engine would be rebuilt.
It went to a local Dealership and the engine was rebuild.
They did a so, so job as the day I got it back I also had to take it back and get a module replaced as the car had a very tough time starting.
All, in all not to bad a deal. Since I got the car for $2300 with carbon fiber hood and custom wheels.

Had it about 4 months and had all the belts redone and filters.
I've been keeping up on my regular oil changes.
Replaced the spark plugs and wires. NOTE: when the plugs were changed the showed to be burning very lean.
So typical up keep has been done.

This weekend I'll be re-wiring the fuel pump just because from the articles I've read it just makes good sense.

The reason that I'm thinking it might be the injectors is because I have added Techron(sp?) and another time Sea Foam and did see a nice improvement. Just not what I know it should be. I have had someone offer to sell me some 98 450 injectors for $36 shipped which doesn't sound to bad. It would be a very cheep way for me to go and know that the injectors are sound and that part of the equation could be eliminated.

I'm thinking of taking it to a shop to have them put it on the dyno and have the thing checked out that way.

The suggestions here have just been great, especially the guys that gave some type of reasoning behind their suggestions. I'll keep you guys posted on my progress.

Let me restate the problem just incase it triggers anything for you guys.
1) Start to accelerate and up to 20mph it’s like a jackrabbit suddenly at that point is stops accelerating. I can hear the turbo all wound up and I let off on the gas the turbo starts slowing down and I start to accelerate again.
2) I hit 60mph and the process starts all over again.
3) I let off it starts to accelerate again and I’m up to 80mph and I’m fine.
4) If I step on it at that speed it will start to run sluggishly and the turbo is all wound up. I let off and bang it’s moving again.
5) If I’m in normal traffic and I stomp on it the turbo winds up very quickly and suddenly it’s stalling again. The instant that I stomp on it the car lurches forward but then just hangs. Doesn’t go any faster or slower just stays at the same speed.

Well there you have it.

Thanks