Fuel pressure when cranking
05-31-2009, 11:20 AM
#1
Fuel pressure when cranking
I searched but wasn't able to find an answer, what should fuel pressure psi be when cranking the engine? Key on engine off its right about 40, when I crank it dips to the upper 30's to maybe 35psi. When running its at 42-44psi. The car has has cold start issues since my swap and I'm trying to narrow it down, just wondering if this is normal or not. Also if I hear the relay prime with the key on engine off, is it safe to assume the relay and connections are fine?
05-31-2009, 05:24 PM
#2
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Car: 86 vette
Engine: 383
Transmission: 700R4
Axle/Gears: 3.07
Re: Fuel pressure when cranking
I searched but wasn't able to find an answer, what should fuel pressure psi be when cranking the engine? Key on engine off its right about 40, when I crank it dips to the upper 30's to maybe 35psi. When running its at 42-44psi. The car has has cold start issues since my swap and I'm trying to narrow it down, just wondering if this is normal or not. Also if I hear the relay prime with the key on engine off, is it safe to assume the relay and connections are fine?
Key on engine crank = low battery volts (mine drops to 9 volts during crank some times), low fuel pressure.
Key on engine run = high volts (14.2) and high vacuum, so 44 psi would be fine.
Try disconnecting the vacuum line from the AFPR when running, to see the total change, 7 psi is typical.
Cold start issues are going to be fuel (pulse width) and spark advance related.
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