i've installed a gmc speed density tune port fuel injection system on my factory 350hp 327. car runs great and fires right up when cold. problem is when it gets hot, i have to spin it over alot to get it too start. i've done a pressure leak down test and it falls pretty quickly, like 10 lbs in 30 to 40 seconds. this is with the fuel lines pinched off. i have soom 30lb lt-1 injectors (or what ever stock is) i was going to try but i'm not sure. the car has original 305 injectors in it (19lbs) and runs alittle rich at idle. let it idle for 45 mins last week and now i have a miss. new adj fuel pressure regulator, and msd coil. i have driven the car like this for 3 years and ready to fix it as it's imbarrassing to start hot in front of people. thanks, airtime

 

LT1 stock injectors are 24lbs.

Your fuel pressure dies off quickly? Could be a number of things.
1) leaky injectors, but since you said it falls 10lbs in 30 seconds, that is really bad for injectors, I would start else where first.
2) bad fuel pressure regulator, might be the cause of the gas not holding pressure, but still that would have to have a very broken diaphram.
3) fuel pump. The pump might be going bad not allowing the lines to stay pressurized.

Start looking in those areas first.

 

when i pinched the fuel lines off, that eliminated the electric fuel pump since it's in the rear of the car next to the fuel tank. the adj fuel regulator is new, but that doesn't mean it cain't be bad. since those are the original 305 injectors, i was leaning towards them. especially since i have a fouled spark plug now from letting it idle for 40 mins. plus, when it does crank, it blows black smoke out the exhuast. do you think putting in the larger 24lb lt-i injectors would be too much fuel for the car? thanks for the reply, gerald

 

19 to 24 probably won't do much, at least nothing more than it is now. It is worth a shot in my book. The fouled plug is probably causing the miss, from running rich.

 

Where are you pinching the fuel line off at?

 

I am having very similar problems... you ever get that fixed?

 

sounds like a regulator problem to me.

 

You think it could be the FPR? Not holding pressure in the line and having to give the motor a few revs to get it to not sound like it has misfires? On the initial startup of course. Wanting to stall? But then after about 30 minutes of drive (City) the car runs perfect?

 

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