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Thread: LT1 Fuel Pressure Question
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11-27-2015, 09:46 AM #1
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LT1 Fuel Pressure Question
Key on and pump primes. How long should it hold pressure? See video.
Chasing an off idle stumble. Car runs great other than that. Has good pressure when running. Car has a Racetronix 255lp pump and an adjustable Accel FPR. I think it's bleeding off too fast. What do you guys think? FPR or check valve in fuel pump??
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11-27-2015, 04:01 PM #2
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Could be the check valve in the pump, leaking injectors, leaking FPR or leaking lines. But the check valve should not have any effect once the engine is running. It's only there to hold the pressure when the pump is not running. If the pressure holds at 43.5psi minus vacuum at idle, it's not a fuel problem, per se.
The way it drops off is unusual.... appears to hit ~45psi, and as soon as the pump stops, drops instantaneously to 30psi. At least that's what the video appeared to show to my crappy eyesight. Never saw one do that before.SOLD - GONE TO A (VERY) GOOD HOME ! - 94 Formula A3+1: 381ci forged stroker - Callies Stealth, Oliver 5.85 billet rods, BME nitrous pistons / CNC LT4 heads / CC solid roller / TH400+GearVendors OD / 4.11 Strange 12-bolt / 300-shot N2O / Spohn Suspension / roll bar / MoTeC M48 Pro engine management system /a few other odds 'n ends.
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11-28-2015, 03:13 AM #3
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The check valve wouldn't have anything to do with how it runs after startup. I have the Granatelli 255 in my car (Walbro in a different box) and the internal valve doesn't hold after prime. Car runs fine though.
That instant drop to 30psi is weird. What's the pressure when idling?96Z M6, ERE-383 #60, AFR 210s, LE cam, 9", Procharger D1, ???whp
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11-28-2015, 10:40 AM #4
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Pressure is good idling. Car runs fine just has slight stumble off idle. Maybe I'll check TPS voltage at idle.
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