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I'd hit it
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Discussion Starter · #1 ·
what kind of fuel pressure should you be looking for on the radix on a 5.3 2000 silvy. I am having HUGE issues with misfiring, sputtering, vibration, and "lugging" at higher speeds and at ANY level of acceleration. I was telling Allen all this and I also complained that it seems to lose it's pull around 5800 or 5900 rather than 6K and a bad fuel pump sounds like a possibility. Running lean and losing power as the more air gets crammed in there with no fuel. I run anywhere between 36psi and 55psi...it's always moving around. Seems the average is about 40-45psi. Allen says 50 should be the norm. Onyx? Your psi? Anybody else? :think:
 

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It should be higher than that, and always be there, AFAIK. Even on a lame vortec 4.3 a couple of PSI of difference from correct will cause issues.
 

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I'd hit it
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Discussion Starter · #4 ·
blownchevy said:
Check your fuel pressure reg. When was the kit installed?


:bowtie:
3 months ago... I haven't ever had a chance to really see what it can do because of one issue to the next (broken driveshaft which caused a broken T-case). The really confusing part is that once I broke that shaft, replaced it and had a huge vibration...that turned out to be a bent output shaft on the T-case...fixed that then it still had this heavy vibration (always only at 65-80MPH under accelration) and that turned out to be a ruined T-Case yoke on the new shaft. Got new yoke, rebalanced...still had vibration. Then we got the sputtering. It threw a belt and we couldn't find any codes in the computer of misfires. Nothing. We then got a PO200 code, for the fuel injectors or system I believe, but not cylinder specific. THEN...just for shits and giggles while we were working on the sputtering issue I sent that shaft and yokes back out for a respin...it was unbalanced. I thought that was it...yeh...That had to be it and the computer just hickupped with the sputtering and firing off in the headers (loud crackling). We changed all the plugs. Took it out and....(sigh) yep, vibration, sputtering, lugging. See the issue, this was hidden behind the whole driveshaft accident. My real question about the fuel pressure is, it seems to me that it was this way all along (low pressure), shouldn't I have noticed it before? Well, nevertheless...we will attack the fuel system tomorrow for sure.
 

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blownchevy said:
I would replace the Fuel Pressure Regulator.....sounds like the culprit to me. :bowtie:

:word:

and i wish i could give you a psi reading but i dont have a gauge hooked up yet.

i'm still workin on my pay pal account.
 

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I'd hit it
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Discussion Starter · #7 ·
This all makes so much sense. The only prob with a fuel regulator is that the one there now is f-ing new. When we took the stock one out of the stock fuel rail the small gasket fell off in the fuel rail....so we ordered and installed a new regulator 3 months ago. SO this morning we are troubleshooting the pressure between the fuel regualtor and booster first...then pressure between booster and fuel pump. Hopefully it's just a defective regulator. We looked up on ShopKey and the stock regulator is supposed to keep psi between 52 to 60 psi.
 

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I'd hit it
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Discussion Starter · #9 ·
blownchevy said:
Key on, engine off should be 50-55 psi.
My digital gauge is 10 psi off for some reason. Key on engine off we have 55 psi. FUCK!!!!! :argh: :flame: Back to WTF!
 

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dewmanshu said:
My digital gauge is 10 psi off for some reason. Key on engine off we have 55 psi. FUCK!!!!! :argh: :flame: Back to WTF!

Stand by....could still be FPR. I would try to remove it and re-install it. Use Vasaline, LOTS and lube it up like a virgin!! Report back.
 

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I'd hit it
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Discussion Starter · #11 ·
blownchevy said:
Stand by....could still be FPR. I would try to remove it and re-install it. Use Vasaline, LOTS and lube it up like a virgin!! Report back.
I'll lube it up tomorrow, I am just too frustrated this evening. We used the test port on the fuel rail of the radix and it read dead 55psi. That's after the FPR, how could it still have something to do with it? The booster tested okay, the pump tested okay. :insane: :think:

I have the dash apart as well...my 4wd auto, 4wd hi, and 4wd lo indicator lights blink when push and never stops blinking. You can hear the motor engage the 4wd hi and lo when button is pressed, but no trouble codes. No trouble codes for anything. LOL :insane: The PCM replacemnt that ALLen sent me overnight was supposed to be here today so we could eliminate a faulty pcm...but UPS lost it. ugh. Hopefully tomorrow with some rest and we do plan to replace the FPR anyway we'll make some progress...especially if that pcm comes in as well. That would take alot of questions out it as well.

Lube it like I would a virgin...shit, that was 15 years ago when i had one of those, I wouldn't know what to do with one of those...I am sure I'd break it just like my truck. :D
 

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alot of times the FPR will get cocked even if it looks like it is flush... make sure that snap ring is in the slots and that the o-ring is binding in the groove... lots of vaseline... ohh yeah... feels good. :crazy:
 

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Discussion Starter · #13 ·
roger that...will pull it out, lube it, and stick it back in tomorrow, I've got other...err...experienced things to do tonight. :hump:
 

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I'd hit it
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Discussion Starter · #16 ·
blownchevy said:
You have a custom tune? Try the superchips and see if that helps. Not knocking Nelson at all, just trouble shooting. :think:
Yeh, ASllen has custom tuned twice...second tune was a bit more agressive. Allen sent me a new tune to eliminate it in our trouble shooting scenarios.

Superchips that came with radix only takes exhaust and FIPK in consideration. Since the order of the radix, I have bored the cylinders, larger pistons (onyl 20 thousandths), put a more agressive cam in, stage 3 heads, put headers and hi flow cats on, bigger stall, rebuilt tranny...so I really don't want to take that thing back to stock. But'll hopefully we'll see this morning soemtime if UPS ever comes through.
 

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I'd hit it
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Discussion Starter · #18 ·
blownchevy said:
update? :think:
Replaced PCM...problem didn't happen right away as usual, but once vehicle got warmed up (5 miles or so), same symptons.

I will admit, we didin't replace the FPR yet, it is on the way as well. That should be here tomorrow...will let you know about that then, but I just don't understand the computer not sending any codes. F-ing Crazy. I am so depressed and frustrated with this it is unbelievable. Could a valve spring (I have duals) be broken, and nothing happens until it gets warmed up? I don't know, just reaching for straws. Let you guys know on the FPR tomorrow. I have 55psi at the rail (after the FPR) so I don't know...ARGHGHGHGH. Any other ideas?
 

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I'd hit it
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Discussion Starter · #20 ·
blownchevy said:
so it is fine when it is cold?b :think: :think: :think:
oh I am lost...don't get me wrong, it doesn't run great cold...like any modded motor, needs to get a little warm first, but that sputtering and lugging doesn't happen until it's warmed up. :shrug:
 
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