C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Long start

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Old Nov 25, 2013 | 09:31 PM
  #1  
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Default Long start

Hello,hope some one can help.
94 vette was getting a long start
replaced the fuel pump, i was getting no
pressure on the old one. new one in cranked
right up.Took it home sat for a few, went to
start same thing long start but it does start.I think i
replaced the fuel pump relay. At least it is where i
think it is located,under the dash on driver side.( it is
on a block of 4 other relays ?).

Thanks for any help.
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Old Nov 25, 2013 | 09:33 PM
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What brand is the fuel pump? And do you know the flow rating?
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Old Nov 25, 2013 | 09:58 PM
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fuel pump is Airtex/Fuel Pump Maximum Free Flow Rate (gph): 60
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Old Nov 26, 2013 | 02:52 AM
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You should check the fuel pressure. Key on. Running. Key off.

Usually a long start is caused by the fuel pump relay not energizing. The oil pressure switch has to take over. It takes several seconds to build up enough oil pressure for it to turn on the fuel pump.
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Old Nov 29, 2013 | 12:31 PM
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Hey everyone.
I checked fuel pump pressure key on 20, car running 29. This is a new fuel pump.Key
off it drops to 0, i do think this is low right?
Thanks for any help.
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Old Nov 29, 2013 | 02:21 PM
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Check the fuel pressure regular (FPR). It and cause a long start if it is leaking fuel back into the manifold (from vacuum line) loading it up with fuel. It may also cause your loss in holding fuel pressure.

Pull off the vacuum line and see if it is wet. Turn key on and see if fuel comes out of FPR.
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Old Dec 1, 2013 | 06:59 PM
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No fuel in vac.line changed FPR, also fuel pump relay is working as is fuel pump working, i hear it come on.still low pressure 29 psi when running,turn off engine it drops to 0 within
seconds...
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Old Dec 3, 2013 | 10:12 PM
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You have a leak somewhere. After key on pressure should hold.

Could be bad ball check valve in new pump, fp regulator, pulse damper between pump and outlet tube in tank assembly......need to troubleshoot
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Old Dec 4, 2013 | 02:31 AM
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Originally Posted by yvette94
No fuel in vac.line changed FPR, also fuel pump relay is working as is fuel pump working, i hear it come on.still low pressure 29 psi when running,turn off engine it drops to 0 within
seconds...
Usually a rapid drop off in pressure at key off means one or more injectors are leaking. Sometimes the relief valve in the fuel pump will cause this.

I believe your fuel pressure should be around 40 PSI. It sure sounds like there is something wrong with it, either mechanically or it's the wrong model for your application.
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Old Dec 4, 2013 | 04:41 PM
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I think you need to pull the pump out and revisit your installation. There could be a broken hose or bad connection letting fuel out back into the tank. The pulse dampener might also be broken, cracked or blocked causing poor fuel flow. But if the pulser was only blocked, it probably would not cause fuel pressure to bleed off so fast. Sounds like you covered everything topside of the engine.

Time to go in the tank again.

Got faith in your fuel pressure gauge reading??
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Old Dec 4, 2013 | 05:31 PM
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If you re-installed pulsator instead on hose with clamps. trash pulsator and install hose with clamps
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