Ksths2

iTrader: (1)

I've run this car for 2 years with this exact setup so its tried and true but a new issue happned Friday night & i'm wanting suggestions to make sure i cover all the bases before i make another N20 pass.

I ran a 10.49 @ 129.97 on the normal 150hp shot in my C5 & worked great.

I made another pass right after that, bottles up to temp, everything good, Launched good, 1st & 2nd gear good, 3rd about 5000 it surged 3 times & had this bad vibration at the same time. (like not running on all 8 cyl type vibration) I of course lifted right away & it kept running fine.

I got back to the pits, and cleaned it out a few times running great, no vibrations at all. I didnt' know what happend so i stopped for the night till i can do a leak down on it/pull the plugs. But even yesterday when i unloaded it ran great idle'd awesome, good oil pressure etc.
Both bottles were still almost full so i know it wasn't out of N20.

Any suggestions?

I was thinking if all looks good on the leak down that maybe solenoid related?

Neal@NitrousOutlet

Could be a lot of things but should be able to get on track since everything has been running kosher for a while.

Are you running a nitrous filter?? Could be clogged up or if you dont have one it could be something getting into the solenoid.

Maybe check to make sure your grounds are still good and solid. After 2 years you might have a connect loose or oxidized.

Check the solenoids for trash.

Was the bottle(s) recently filled? Could possibly be a bad bottle fill.

Ksths2

iTrader: (1)

Neal, thats the first thing i thought of as well was crap clogged the solenoid, no actually i'm not running a filter on the car, I have a big filter on my fill station & i've been lucky so far.
I'll check the noids out & see what i find.

Yes i just filled them the night before & weighed them both w/ a digital scale.

I'm going to do a leak down on the cylinders tonight to see what it says. Any idea on the vibration though? that has me more scared than anything...... The LS1 (stock bottom end) has 50k on it with 3 years of on/off drag racing & probably has 75+ N20 passes on it. Any idea what percentage would be acceptable on this engine?

Ksths2

iTrader: (1)

Update, I weighed both bottles & they were identical 22.8lbs, I checked both noids & they looked good, no debris. The rubber plunger had an odd non circular indent so I replaced it.
Im trying to figure out a way to rotate the crank so I can do the leak down but on a Vette the during track its right in the way......any suggestions
I fired it up tonight & it seemed good no blow by out of the oil fill. So I'm stumped on the surging & vibration.....

Ksths2

iTrader: (1)

No one?

ATVracr

iTrader: (5)

Do compression test.
If they all pump good, load up fresh bottle make another hit. (1/8th make sure everything is good)

Leakdown dont tell you much. IMO.

Ksths2

iTrader: (1)

Wow I always thought the leak down was the best diagnostic tool, i've got both & the compression tester would be waaayy easier.

One thing i found weird was the fuel pressure, its a C5 vette so it has the fuel filter/regulator built together & i replaced it 2 years ago worth of racing when i swapped to the Lingenfelter high-flow fuel pump as well & its always been at 58-60lbs of FP but last night at idle it had 35ish, not sure if it changed back to 60 as the rpms increased cuz the gauge is on the rails & i couldn't see it.
Whats the chances the filter/regulator is going bad or the fuel pump? That would definently explain the surging

Neal@NitrousOutlet

have you pulled the plugs out of the car to see if the straps are good?

Ksths2

iTrader: (1)

I'm going to do all that tonight, i was trying to get all the leak down tools rounded up so i could do it all at once, warm it up, remove plugs, leak down etc but still fighting a way to turn the engine over....... damn corvettes anyway

ATVracr

iTrader: (5)

35= not good

Ksths2

iTrader: (1)

100% agree with the fuel pressure at 35lbs, I've got $46 regulator/filter on order local auto store should be here tonight & i'll try swapping it first & see what happens.

I called Lingenfelter (Jeff) said its most likely not the pump, easy for him to say but i hope he's right lol

Ryan@Lingenfelter

Usually when a fuel pump goes bad it completely stops working, not just down on pressure. Not saying it's impossible, but very unlikely to be the pump.

Ryan

Ksths2

iTrader: (1)

Update, I had my wife turn the key on while I watched the gauge on the drivers side fuel rail & it hit about 28lbs and never changed when she fired it up other than a small drop then right back to 30 max..... I had her rev it up but out never went above 30...... So I tore everything apart & put a new filter/regulator in tonight & to my surprise it went in easy. But I had her cycle the key a few times, fired it up, revved it & it never went above 30lbs...
So, I'm thinking maybe gauge or fuel pump?
Answer me this, would an LS engine even run right on 30lbs? Cuz this thing acts normal, revs good and all that......?

Fastdriver1992

iTrader: (1)

have u driven the car under a load? free reving in the driveway might not bring up any symptoms, friend of mine running a C5 Forced Induction had a pump start to go bad very slowly, kept going lean up top, added more fuel to the tune, kept getting leaner and leaner

Ksths2

iTrader: (1)

no i haven't drove it other than off the trailer, I'm pulling all the plugs tonight & doing a compression test on them, if all looks good i'll take it go and stomp on it on my personal drag strip otherwise known as the highway lol
I've got a FAST air/fuel logger in the car so i'll keep an eye on the a/f ratios

Ksths2

iTrader: (1)

Ryan or anyone else i'm open for suggestions?

It really is that simple though right, I mean if the pressure is 35lbs & it needs to be 58ish & i've replace the filter/regulator combo its either the pump or the gauge right?
I've got aftermarket fuel rails w/ braided line between them, no factory stuff & its a straight shot from filter to rails.... sorry i'm just trying to think this through.

Jason Haines @ LPE

An LS engine will run at 30 psi fuel pressure but the ECM/PCM will be at the maximum positiive LT and ST fuel trims trying to add fuel and you will probably still be lean.

If you have any concern about the gauge, get another one and recheck before you do anything more. If the system can't make 54-60 psi on key up/engine off then something is very wrong. It could be very low voltage to the pump (resistance somewhere/bad connection). It could be a cut seal or loose fitting in one of the transfer lines or other lines inside the module/tank. Or it could be a bad regulator or pump. You already say you changed the regulator so that probably crosses that off the list. As Ryan stated the pumps rarely work a little bit. They usually work or they don't. And if you have enough fuel flow to run the engine at all then you should have more than enough to make 54-60 psi at key on/engine off.

If the gauge is correct I would start looking for fuel line leaks/fitting leaks/o-rings etc. in the fuel system. If it isn't leaking out on the floor then it is probably doing so inside the tanks.

If you can read/view diagnostic data, once the engine warms up/goes closed loop it should be at maximum fuel trims at that pressure. If it isn't then the gauge is probably wrong.

What year car is this? Is the regulator at the rail (return style rail) or is the regulator in the fuel filter (short return out of the tank, to the filter and back)?

[Added later] - I noticed your sig indicates the vehicle is a 2002. If that is the case the fuel pressure regulator is in the filter. I just want to make sure you didn't replace the fuel pulsation damper that is at the rail thinking that was the regulator (it has happened before).

dnkynrbk

iTrader: (34)

I bet its the pump. Hows the plugs look. Have you ran it in motor yet since this happened?

Jason Haines @ LPE

If you really only have 30 psi of fuel pressure do NOT run this car under load, even without the nitrous, until you figure out what is wrong.

Ksths2

iTrader: (1)

Update! - I rented a fuel pressure tester from O O Oreillys and it was the &%$@!) gauge the whole time...... either way i'm happy thats all it was.

FYI, plugs look good - time to hit it again Friday night & see how it goes

Thanks for the help guys I really appreciate it!!!!!