[Z06] fuel pressure dropping!!
Thread Starter
Racer
Joined: Mar 2007
Posts: 371
Likes: 0
From: smithtown ny
fuel pressure dropping!!
04 z 26,500 miles all stock. lately Its been having to crank over 4-5 times then it starts. when I turn the key too ruing!!n and pressurize the system plenty of fuel in the rail 60psi hot. I having that not checked pressure cold yet. so today this what the gauge shows 11:10am 60psi then immediately it drops to 50psi its now 12:53pm and I have 10psi. car runs strong pulls hard oil does not smell of fuel. so with that said it looks like a bad check valve in pump? all this work for a check valve!!! i'm thinking at cold startup pressure is nowhere near 60psi but i'm checking that next. what can I do so this don't happen again?
Drifting
Joined: Sep 2013
Posts: 1,943
Likes: 4
From: Lawrenceburg KY
Same problem with my 04, I guess it's a bad check valve somewhere but I haven't really investigated it yet - waiting until winter.
I cycle the key a few times for cold starts and it seems to help. Car runs perfectly once it's started.
I cycle the key a few times for cold starts and it seems to help. Car runs perfectly once it's started.
Thread Starter
Racer
Joined: Mar 2007
Posts: 371
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From: smithtown ny
I noticed this after I ran fuel low!! you would think 50psi would start the car!
Thread Starter
Racer
Joined: Mar 2007
Posts: 371
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From: smithtown ny
Ok alittle update.. woke up this morning and there was 20psi in the rail from last night . Even when the rail has no pressure in it I would cycle the key the pump will come on and I get 60psi at the rail. Car should start on first try? Maybe its not the check vavle? Coolant temp sensor?
Thread Starter
Racer
Joined: Mar 2007
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From: smithtown ny
Le Mans Master
Joined: Jun 2001
Posts: 7,331
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From: Admit Nothing, Deny Everything, Make Counter Accusations.
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Thread Starter
Racer
Joined: Mar 2007
Posts: 371
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From: smithtown ny
Le Mans Master
Joined: Jun 2001
Posts: 7,331
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From: Admit Nothing, Deny Everything, Make Counter Accusations.
50 PSI is enough to start the car. If your long crank times are related to the pressure drop, then as you said you might have a stuck/leaking injector, which could cause an overly rich condition. Try to cold crank it with the throttle to the floor (injectors will be off while cranking) and see if that helps.
FWIW, my car pumps up to 60 PSI when I turn the key on and it drops a little when the pump shuts off. I think that is normal. My car does hold pressure for a while, but I'll admit that I never felt the need to let it sit with a gauge on it for more than 15 minutes.
FWIW, my car pumps up to 60 PSI when I turn the key on and it drops a little when the pump shuts off. I think that is normal. My car does hold pressure for a while, but I'll admit that I never felt the need to let it sit with a gauge on it for more than 15 minutes.
Burning Brakes
Joined: Dec 2003
Posts: 1,243
Likes: 5
From: Loveland CO
should be enough to start the car. if you have a leaky injector or a bad check valve you would see other symptoms (rich exhaust and rough idle) or your fuel pressure would fall off instantly or very quickly (within a couple min.) sounds like your issue is elsewhere. My buddy had bad check valve and as soon as he shut it off it dropped to 10psi and bleed out within a few min (5-10)
S
S
Thread Starter
Racer
Joined: Mar 2007
Posts: 371
Likes: 0
From: smithtown ny
should be enough to start the car. if you have a leaky injector or a bad check valve you would see other symptoms (rich exhaust and rough idle) or your fuel pressure would fall off instantly or very quickly (within a couple min.) sounds like your issue is elsewhere. My buddy had bad check valve and as soon as he shut it off it dropped to 10psi and bleed out within a few min (5-10)
S
S
I was told the ethanol in the gas could have something to do with it.
Burning Brakes
Joined: Dec 2003
Posts: 1,243
Likes: 5
From: Loveland CO
defiantly put a gauge on it and check the pressure cold when you first start it. Turn the key to on (not start) for 3-4 seconds then try starting it. if it holds good for a while but not after then night you might have a slow drain back.. in that case a good "Prime" before start should be the easiest plan of action.. not a big deal and not work tearing things apart for it. ALOT of cars do this.
We have 10% Ethanol in our gas here in Colorado, no reason that will be a problem. E10 doesnt have enough to dry anything out like E85 (kills rubber not designed for Ethanol). might try some BG44K and a 1/2-3/4 tank of fresh fuel just to make sure its nice and clean. 04's dont have a filter that can be changed so no worries there.
S
We have 10% Ethanol in our gas here in Colorado, no reason that will be a problem. E10 doesnt have enough to dry anything out like E85 (kills rubber not designed for Ethanol). might try some BG44K and a 1/2-3/4 tank of fresh fuel just to make sure its nice and clean. 04's dont have a filter that can be changed so no worries there.
S
Thread Starter
Racer
Joined: Mar 2007
Posts: 371
Likes: 0
From: smithtown ny
defiantly put a gauge on it and check the pressure cold when you first start it. Turn the key to on (not start) for 3-4 seconds then try starting it. if it holds good for a while but not after then night you might have a slow drain back.. in that case a good "Prime" before start should be the easiest plan of action.. not a big deal and not work tearing things apart for it. ALOT of cars do this.
We have 10% Ethanol in our gas here in Colorado, no reason that will be a problem. E10 doesnt have enough to dry anything out like E85 (kills rubber not designed for Ethanol). might try some BG44K and a 1/2-3/4 tank of fresh fuel just to make sure its nice and clean. 04's dont have a filter that can be changed so no worries there.
S
We have 10% Ethanol in our gas here in Colorado, no reason that will be a problem. E10 doesnt have enough to dry anything out like E85 (kills rubber not designed for Ethanol). might try some BG44K and a 1/2-3/4 tank of fresh fuel just to make sure its nice and clean. 04's dont have a filter that can be changed so no worries there.
S
Thread Starter
Racer
Joined: Mar 2007
Posts: 371
Likes: 0
From: smithtown ny
if I don't start the car and just prime the system fuel pressure holds for 2 days. if I drive the car and put the gauge on it.. it hold s for 2 hrs. so what could be the problem? if I start the car in my garage it starts right up but once I drive it and leave it outside the next morning it cranks then starts!
Melting Slicks
Joined: Dec 2003
Posts: 2,334
Likes: 11
From: las vegas nv.
Likely no codes--there is a line that holds pressure to the injectors so it has pressure when first started--run some injector cleaner thru it--whatever its no biggy=maybe some bad fuel-