Fuel pressure/hard starting

[Andy Gargagliano]

What should the fuel pressure be on my 72 Monte with 350 mild street motor.A little back ground.It has stock fuel line from the tank to the fuel pump.Brand new Holly 80gph fuel pump.New summit 130gph fuel filter.3/8 braided fuel hose from pump to carb.Carb is freshly rebuilt 650 Holly with mec.secondaries and mec.choke which is in the open position.Fuel gauge is a summit 15 psi liquid filled.Fuel pressure fluctuates between 3to4 psi.Is this good?Also car is very hard to start after fully warmed up.Car starts imediatly when cold but after warmed up and sits for a while have to crank it and pump gas for 15 to 20 seconds before it starts again.Car cranks normal no starter kick back.car idels great and runs fantastic off the line and from a roll.Plenty of gas to the carb.Thats about all i can think of.Thanks for any help. Andy.

[CHAZBO1975]

Hi Peter

Fuel pressure seems a little low, stock, pump runs 5 to 8 lbs, but what you have is plenty to start and idle the engine. it starts cold so dont think you have drain back. I'm thinking heat problem. If you have a heat riser on the exhaust manifold that is stuck closed or are using the stock air cleaner and the thermac valve is stuck closed, either will cause the carb to get hot enought to boil off the gas in the carb when you shut it off.

[bigtankjones]

I run my fuel pressure at 7 psi for my 750 holley.I was told not to run the pressure any higher then 9psi. I am running the Holley blue electric fuel pump. Dont know off hand what it is rated for.

[Sam (Bones)]

6.5to 7 psi on a holley, do not trust that oil filled summit gauge!!!!

 

oil filled gauges seem to change with temp, my under the hood oil filled gauge reads 3-4 when engine is hot, my auto meter gauge mounted in my cowl hood reads 7 all the time

[Andy Gargagliano]

Sounds like my fuel pressure is ok.Now just have to figure out why the engine is hard to start when warmed up.I am running Hedman headers with a 2.5 inch exhaust,Edelbroc performer aluminum manifold and a chrome open element air filter.Engine temp stays at 160 degrees all day long and under hood temp dosent feel excesseve. thanks for any help. Andy.

[Mike 57]

Vacuum leak when warm?

[wallaby]

You say the choke is in the open position... do you need it when you start cold?

I'm wondering if maybe the carb is delivering plenty of fuel already. The engine doesn't want a rich mixture when it's warmed up and maybe the pumping of the pedal on your restarts is actually causing the problem.

Try your restarts without touching the gas pedal...or try with the pedal partly depressed... or with the pedal all the way down. (pick one) One of these methods might work for you. Try to avoid lifting off the pedal each time you let go of the key.

These old cars require a different procedure for cold VS warm starting. Rule of thumb: the hotter the engine, the less fuel it needs.

[Andy Gargagliano]

Choke is open during cold start but not that cold outside.I will check all my vacume connections and try the various gas pedal methods and see what happens.Thanks for all help.