Gmp440

[GMP440]

Having hard starting problems when engine is cold. The car is an 87' Pontiac Firebird with 305 v8 and 4 barrel Rochester carb. When trying to start the car in the morning you have to crank and crank. However, when the car has been run it starts and runs very easily. The carb is getting accelerator pump shot. The choke is in good order. The plate closes and only has a 1/8" opening. Plugs, wires, distributer cap, rotor is in good condition. Coil is new. I checked fuel pressure when cranking. The fuel pressure fluctuates from 5 to 8 psi. Now, it uses both a mechanical fuel pump actuated by the camshaft and an electrical supply pump located in the tank. If I am getting fuel pump pressure then I believe that the supply pump is operating. I used an OTC Monitor scan tool to pull codes. No trouble codes appeared. Can someone on the board assist me with this problem. Thanks.

[clean_birdie]

one thing i have noticed with a carb in winter and cold situations is that alot of the time the butterfly valve sticks... same problem in the old rodchester m4's one trick is the remove the air cleaner cover and stick a screwdriver to prop the butterfly valve open and then start the car... just make sure to remove the screwdriver afterwords less you wish to have debris in your engine which is never good... i had an old gm that had a bad death that way.

[tacoma man.]

the butterfly valve will just about do it everytime, may need a little carb cleaner.

[GMP440]

Originally Posted by clean_birdie

one thing i have noticed with a carb in winter and cold situations is that alot of the time the butterfly valve sticks... same problem in the old rodchester m4's one trick is the remove the air cleaner cover and stick a screwdriver to prop the butterfly valve open and then start the car... just make sure to remove the screwdriver afterwords less you wish to have debris in your engine which is never good... i had an old gm that had a bad death that way.

Thanks for the tip. The choke works fine. Nothing is binding or sticking.
You have to pump the accelerator about 8 to 10 times, then it will fire off. I still need to check to see what kind of pressure I am getting out of the in-tank supply pump. I get good pump shot coming out of the primary jets. Is it possible the enrichment part of the carb is not working?

[Philo]

The only spec I have on fuel pressure is for older 305 engines, but they hit the range of 5-9 lbs. They did not say if it was cranking or running pressure, but it looks like you are good since yours was cranking pressure.

When the engine is cold, have you checked for the accelerator fuel shot before cranking the first time? The reason I ask - I think if the fuel bowls are empty there will still be fuel in the accelerator bowl, but it will take a few pumps to supply enough fuel to start the engine.

Another check would be to not hit the throttle at all when cranking the first time, except to set the choke, and see if it will start after cranking for a while (say 30 seconds). Don't overheat the starter.

I was thinking the fuel in the line is draining back to the tank when sitting for a while, or there is a small leak in the fuel line that empties it out (smell of fuel around the car)? Of course, the next step would be to pull the top of the carb when the engine has been sitting overnight to see how much fuel is in the bowls (this is some work, but is what I would probably check if I was looking for the problem).

Good luck, and please let us know the fix.

[PurpleJesus]

I have a 79 with a 71 YC 455 & and Edelbroc Carb... I've put an electric choke on it (yeah, I'm lazy) It seems when the air temperture gets really cold, the Choke spring closes too tightly. So I have to lean the choke in the Winter and Richen it in the Springtime.
Hope this helps...

(esp... if you have an electric choke, after the key's been on for a while, the ceramic part heats up, and volla, if finally let's it breath)

[PurpleJesus]

Oh one more thing... My ride would suck the choke closed sometimes... (I pull about 17 or so inches of vacuum at idle) I'd look at it, it'd be fine, but when it was cranking over it'd pull it shut...