1977 GMC RWD Truck Starting when warm issue

[awright580]

Hello all names Alex and I have an issue that's driving me nuts. I did see other similar posts to this but nothing dead on my issue. My truck will start when cold everyday no problem on the second try. After I drive it for even 15 minutes and turn it off, re-starting becomes very hard process. It will still crank like normal but I can tell the truck isnt going to start. A way to start it so far has been to spray star spray in the carb and that will do the trick. I have also noticed that the front side of the carb with the smaller flap is closed when I try to restart after it's warm. I am not very knowledgeable about vehicle's so excuse my lack of verbiage.  The current carb is a Rochester Quadra Jet and I have a different motor then original its a 307 out of a chevy van. Does anyone have any ideas what could be causing the issue?? Thanks!

[square81]

The small flap is the choke. Sounds like its staying closed and should be open once warmed up.

[awright580]

Even if I open that flap myself while someone else cranks will not make it start. Any other ideas?

[Chisholmcody]

What's your timing set at


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[Irish_Alley]

do you have a clear fuel filter on it? hows the fuel lines ran?

[msilveira]

Hi Alex, a "hot start" issue with a Quadrajet could be related to vapor lock (a common problem in California) or fuel leaking out of the plugs in the float bowls and leaking into the intake-- causing flooding.  If the motor smokes black exhaust once you get it started and you smell gas around the carb, that's a likely issue.

Another likely issue, if you have the in-cap coil HEI distributor, is that the ignition module or coil could be getting hot after running, causing a hot start condition.

As the other group members said, check the choke and ensure it is "open"-- the metal "flap" should be pointing up so you can look inside and see the primary carb venturies.  If it remains closed all the time, then the choke coil or wiring to the choke coil is bad.  You can check for those conditions with a 12v test light or a digital volt meter.

Good luck,

Matt

[awright580]

I have lines that I can't see throughthe fuel filter is clean inside the carb I just replaced not to long ago. The exhaust does stink when it starts and some smoke but the motor itself does not smoke at all. The choke is only open in the morning or at night when cilood starting. When I come back from a store after driving there the choke will be closed. I honestly have no idea what timing is set at, or even how to check something like that. I'm a YouTube mechanic is the best way to put it and learn form you guys on forums like these! I'm going to look into what type of distributor I have I appreciate all the suggestions

[Irish_Alley]

the choke should be closed when cold and open when warm

[awright580]

I understand what your saying. The choke is closed after I shut down the vehicle and try to restart if that means anything to you. The weird part is that it starts so easily when cold.