LS1_Mann

Just bought a Z about a month ago and I'm having some issues with fuel pressure. I hooked up an auto zone loaner tool and taped it to my windshield. I get 30psi on prime and it drop really quickly, then when it starts I idle about 30 and under load drops to about 27ish. It idles and revs fine. And it drives fine to until about 4500rmp under WOT and then it feels like its not getting gas and I get codes p0131 and p0151.

The previous owner had a new gm pump put in about a year ago and I've got receipts for it, so I don't think its the pump. I changed the fuel filter last week and it didn't make a bit of difference in pressure. So the only thing left I can think of is the FPR. So I'm gonna do the trap door mod and pull the sending unit and change it and look for pin holes or anything else while I've got it out.

I've searched quite a while and I know that 98's have the old steel tank and a sending unit different from any other year with the regulator in a different place.

But anyway I'm trying to find a picture of what I'm looking at before I tear into it. I cant find one anywhere of the 98 housing with regulator. and wondering where I should get one from.

Thanks for your help guys.

Fry_

When the PO had the fuel pump replaced the sending unit and regulator would have been replaced with it that's the only way they sell factor replacement pump's. My T/A's pump started to die about 2 years after the PO replaced it so I guess new stock pumps are junk. get a racetronix 255.
http://www.ws6project.com/user_stor/...x-fuel-system/

LS1_Mann

Well that sucks. Thanks for the info. Do you know if anyone sells replacements that don't require re-wiring. All this car will see is probably bolts ons. I read somewhere that the stock pump is good for 500hp. I don't really want to upgrade if it doesn't need it.

Fry_

You could get just the racetronix pump and skip the hotwire kit.
http://www.ws6project.com/user_stor/...oducts_id=4033
It's cheaper than any stock pump you'll find. Also maybe the Corvette pump is good for 500hp but the f-body's is only good for 350-400hp I think.

My car had the trap door mod already done to it but the hole really should have been cut bigger to make it easier to get to the fuel line connections. Also be VERY careful on how deep you cut the fuel lines are within a inch of the floor pan and are made of plastic.
Google not only found me a picture.

but also a youtube video,
if you use the Racetronix pump just ignore every thing after he gets the pump and sending unit pulled and follow the Racetronix instructions.

LS1_Mann

thanks a ton man! This is definitely what ill be doing.

LS1_Mann

i tore it all apart yesterday and found out it was the regulator housing that was bad. its not a circle anymore its now an oval and the regulator wont seal. any idea how i could fix or replace it without buying a whole new sending unit.

Fry_

http://www.autozone.com/autozone/par...er=221962_0_0_

LS1_Mann

i actualy bought one of those last night and tired it. the part thats bad isnt the regulator itself but where it clips into. Thanks for the quick reply!

LS1_Mann

So I think I found a solution! (albeit maybe temporary) Lonnie's performance has supposedly come up with a replacement internal regulator for this issue that I will switching to soon. But this seemed to have fixed in the mean time.

So I read that when other people have this issue on their 98's they use a bigger o ring to seal the warped housing. So I tried this and clipped the FPR back in and I could still see a small gap at one end of the housing. So I squeezed the regulator and housing together really tight and it looked like it closed the gap. But as soon I would go it would separate again.

So I turned the nipple of the regulator parallel with the plastic line out of the housing and zip tied them together as tight as I could with a really thick zip tie while I squeezed it. The gap stayed shut. I hooked it all back up and it turned right over.

I used to have long hard starts and it was awesome just to turn the key and it fire right up. Also my car is ALOT faster now. Didn't realize how bad it was until it got its power back.

No more codes, No more sputtering over 4k! I'm super excited.

But even though its running right and I'm not getting the low voltage codes anymore, I checked my fuel pressure today its still only at about 44 PSI while its running and 42 under WOT.

Is the gauge maybe reading wrong since the car is running flawlessly and is starting good too?

Anyway thought I would share. Sorry for writing a book.

98blktrans

Hey ls1 Mann I know this is a very old thread but did you ever find that housing? I blew the o-rings out of mine and not sure how to get them back in. Searching for the housing.

curtisad

iTrader: (4)

What should the fuel pressure be at idle? I have a Walbro 255 pump and I believe that I'm at 60 PSI at idle. It's been awhile since I checked so I could be wrong...

FU_I_AM_UltraZ

iTrader: (20)

So ur regulator is that round thing on top of intake manifold on the fuel rail cross over pipe. The diafram inside could be coming apart or cracking. Was the receipt for pump or pump assembly? Bc you i know on the ltx cars you can replace pump in the assembly. Every lsx I've owned I have done the assembly bc if sending unit/float goes bad, I hate doing jobs twice and i never keep ltx cars long enough to worry about that kind of stuff (cheap n quick fixes bc I just flip them after fixing up n couple quick cheap bolt ons to attract buyers). Unless new pump assembly is bleeding out somewhere and fuel injectors n o-rings are good... I can't think of anything else but diaphragm in regulator.
good luck

FU_I_AM_UltraZ

iTrader: (20)

Lsx with stock fuel injectors etc... 58-60psi

G Atsma

I think it's supposed to be 58psi, but at 60 you should be OK.

ski7541

iTrader: (2)

can someone point out where the fuel pressure regulator is located on a 98 z28 I replaced what I thought was the regulator and it was the fuel dampener.. I have a bbk intake on it.Just need pictures of to where it is located. I'm getting a hard start , flooding when cold.but clears up after a couple minutes.

Laddimyr

If its the same as my 99, its in the fuel pump assembly in the tank.