Installed 255, now high fuel pressure

[david-b]

Hey all.
I'm working on finishing up my turbo kit and I just installed a Walrbo 255 fuel pump this morning. I have a 12:1 FMU also. Now when I first turboed, the fuel pressure was fine. I didn't boost but just running the gauge was reading perfect as before I turboed. Now with the 255 in, the pressure is off the chart reading ~90psi+. I thought maybe my gauge was bad or a wire got knocked out so I drove around a little and I ended up blowing off a return fuel line and leaked fuel all over the ground. Car ran great , but obviously not right.

Now I searched and came up with the fact that on a 95, I don't need a SMFU or a FPR since the stocker is built into the rail, and yes it's still connected. I read somewhere about taking off a pressure thing on the rail or something?? Not sure what that was. But it seems like most people with this issue, the threads are never resolved or it was something stupid like they had the return lines hooked up the wrong way on the FMU. They're on right for sure.

PLEASE HELP as I needed this car done 2 weeks ago now. Thanks

 

[talon187]

you need an adjustable regualtor a 255 over runs the stocker if you had a 190 you would be ok but 255 is a diffrent story doesnt matter what year your car is

 

[iluvmy4g63]

255 pumps are strong pumps. any thing over a 190 you need a fpr. map performace has full kits that would help your problem.

 

[david-b]

Are you serious! Son of a bi***. I specifically didn't want to redo the whole f-in fuel and now it looks like it. Was going to get a 190 originally and everyone said oh get a 255. So now I have to waste even more money. Now that means I have to cut out that damn built in fpr right? If so... anyone want a 255? I'll trade for a 190.

 

[LD25Delta9]

you don't need to pull th stock FPR. just add you new one after it and you'll be fine. kinda works like a piggy back system. most people put them in the engine bay anyways.

 

[talon187]

relax first off what are your golas with the car? second the stock fpr just unbolts and you get a new fitting to take its place and then it goes to the fpr its money yes but its well worth it trust me ive got all this on my car ive got ss line from the tank to the reg and to the filter

 

[97 4G63]

relax first off what are your golas with the car? second the stock fpr just unbolts and you get a new fitting to take its place and then it goes to the fpr its money yes but its well worth it trust me ive got all this on my car ive got ss line from the tank to the reg and to the filter

He has a n/t so his fpr might be different than ours..

 

[ivan300]

4g63 guys plese dont post in the 420a forum if yore not sure.

the 255 + 12:1 fmu is a standard setup there shouldn't be any issues unless maybe your stock fpr is shot. or more likely you installed the fmu wrong.

 

[totaleclipse_05]

Ivan is right, 255 pump on a 420a car is perfectly fine and will NOT overrun the stock FPR. Please stop spreading misinformation guys.

OP, do you have your FMU hooked up correctly? Since you have a 95, you have the FMU in the engine bay?

 

[TalonESIT]

It's either something is wrong with your FPR like ivan was stating or check your FMU connections... an aftermarket FPR is not necessary with your current setup. Do you have any other ratio disks?


The stock 2g n/t fpr does not unbolt like the 4g63, they are held in by a split ring.

"Now I searched and came up with the fact that on a 95, I don't need a SMFU or a FPR since the stocker is built into the rail, and yes it's still connected. I read somewhere about taking off a pressure thing on the rail or something??


Ok I read your original post and I just want to clarify that an SFMU and FPR are two completely different components. An FMU will raise your fuel pressure with respect to your boost (using different ratio disks); an SFMU will do the same thing, but has the added benefit of a nipple to adjust your fuel pressure at which point you would be required to disable the stock FPR. You don't "need" an SFMU, but it is a better unit than the FMU (and is not the same as your FPR), but it is more expensive. You have probably read often here that this route of fuel management is more of a "bandaid" for your fuel system then actually controlling your fuel for proper tuning...

You don't need an aftermarket FPR, but in the event that you change your fuel setup and get an aftermarket FPR (1:1) then you can go ahead and disable the stock FPR (I'm not sure if this is still done since I haven't messed with my stock FPR for quite a while). Did your remove the vacuum line going to the nipple of your stock FPR?

Here is the appropriate setup for all the years of the FPR system:

http://www.dsmtuners.com/forums/newbie-forum/266516-fmu-configuration.html


I also noticed in your profile that you have a SAFC installed, are you still using?

 

[david-b]

Thanks guys for all the responses.

The FMU IS hooked up correctly, just as shown in the diagram. I have the fuel filter going to the feed (replaced with SS line a couple months back) and then the 12:1 FMU is in the return. Pretty easy there.

Yes, the FMU is installed in the engine bay since the 95 rail has the FPR built in.

As for goals, this is pretty much it. Just wanted to turbo it and keep it as is probably until she dies. I have no plans on upgrading her to a larger setup at any point right now. Just wanted the tun the t3/4 at 7.25psi.

I am still using the SAFC, although all the settings are zeroed out. I even tried dropping the idle which made no changes to the FP.

And I know the differences between a FPR and a SFMU... sorry for the confusion. Just mentioned that I thought I didn't need neither with the simple setup that I'm running.

Thanks guys.

EDIT: And no I didn't remove the vacuum from the stock FPR. Heard you're not supposed to.

 

[david-b]

Alright just got back from working on the car... Found a problem...

The wires going to the fuel pressure gauge were pulled out UNDER THE DASH! That's weird because I wasn't even in the drivers seat until after I installed the 255, so not sure how this all happened.

Anyways I got it hooked up as a temp and it was reading ~60psi at idle... but also while driving around the block. I never got out of vacuum, and only about 15% MAX on throttle. It never moved. I'm going to rewire the gauge tomorrow and see what happens. Shouldn't the FP go up, or was it because I never got out of vacuum that it never rose. The FMU raises 12psi per 1lb of boost, but if I never hit boost, it won't move right?

Oh, and I have a WB coming in one of these days. This will be attempt #3 at a WB. Plain and simple, god doesn't want me to own a wideband.