Need advice on how to tackle an issue on my '86 305

[Ricko1966]

No apologies needed. I have parts never needed and not returned sitting around due to doing the same thing sometimes. Only reason I mentioned it.
Good news it’s not cobbled together, that helps. I was kinda assuming it was because in my limited experience it’s more common to pull a vacuum in the tank with a plugged vent. Maybe someone like @Ricko1966 has an explanation for the positive pressure?

Gasoline summer grade has a vapor pressure of 9psi winter blend 15psi. So if you have no vent and the fuel gets warm and starts to go from liquid to gaseous it can develop 9-15psi in the tank. Which is enough to blow the needle and seat open and create a flooding condition.

 

[goldpack]

You guys are legit heroes. Went home on for lunch, popped the gas cap off drove to Mcdonalds and back. Let the truck sit with the cap off while I ate, went back outside after about 15 minutes and the first start didnt catch but the second one did and she idled rough for about 5 seconds and then she was solid. I am now positive its a venting issue. Thank all of you so much, I wouldnt have thought of this probably for another week or so. Hell, I was pricing out 4 barrels and intake manifold cause I thought the little 2 barrel might have just taken a **** and figured "why not upgrade?" lol. Regardless, thank you!

just for asking,...your 1986 2 barrel 305 does not have a "choke" light?
my 1986 4 barrel 350 does have a choke light .

you did not mention if it is doing "anything" or working. other threads here talk about it,..and odd behavior, which I have found "enlightening".

(I just bought my square body,....trusting the 2018 O'Reilly's carb on there, with 1986 gmc automatic choke "thought" on a 40 year old antique,....makes me just wish it had a manual choke handle,...as just less crap to fail from an electrical short/ lack of use...and with the old school handle I would hope I could feel it open / close "properly".)

other thoughts: sediments and varnish packing what you got,.... ...and how are your relays ?...any correlation in tempature / humidity. help to open the hood and vent some heat ?

 

[Grit dog]

just for asking,...your 1986 2 barrel 305 does not have a "choke" light?
my 1986 4 barrel 350 does have a choke light .

you did not mention if it is doing "anything" or working. other threads here talk about it,..and odd behavior, which I have found "enlightening".

(I just bought my square body,....trusting the 2018 O'Reilly's carb on there, with 1986 gmc automatic choke "thought" on a 40 year old antique,....makes me just wish it had a manual choke handle,...as just less crap to fail from an electrical short/ lack of use...and with the old school handle I would hope I could feel it open / close "properly".)

other thoughts: sediments and varnish packing what you got,.... ...and how are your relays ?...any correlation in tempature / humidity. help to open the hood and vent some heat ?

Wonder if my 86 (originally a 350) has a choke light? For no other reason than it would be cool to get it working.

 

[goldpack]

Wonder if my 86 (originally a 350) has a choke light? For no other reason than it would be cool to get it working.

its or orange "choke" light at 5 o'clock position in the left side gauge under the odometer 10'ths
(hopefully yours is working just fine,...and it just stays unlit as its got nothing to report).

 

[hack_man]

I'm still trying to figure out what would trigger the CHECK ENGINE light in my '83 K10.
I think you could remove the engine and the light would stay off.

 

[Ricko1966]

I'm still trying to figure out what would trigger the CHECK ENGINE light in my '83 K10.
I think you could remove the engine and the light would stay off.

Lots of things can trip the check engine l8ght. Short terminals A and B together at the ALDL count the flashes on the check engine light. Example 1 long flash 2 quick flashes would be a code 12. You should have a code 12 but check for others report what you find.

 

[Trucksareforwork]

its or orange "choke" light at 5 o'clock position in the left side gauge under the odometer 10'ths
(hopefully yours is working just fine,...and it just stays unlit as its got nothing to report).

Pretty sure the choke light on my ‘85 means low oil pressure. Makes perfect sense.

 

[Ricko1966]

Pretty sure the choke light on my ‘85 means low oil pressure. Makes perfect sense.

Might be a byproduct but not the real intention,the choke power is routed through an oil pressure switch so the choke only has power when you have oil pressure.

 

[Turbo4whl]

Wonder if my 86 (originally a 350) has a choke light? For no other reason than it would be cool to get it working.

Choke light wiring is super simple, starting in 1981:

You must be registered for see images attach

When there is no oil pressure, switch is open. Key on current through the light and grounds through the choke, not enough amps to effect the choke. Start engine, now choke light has 2 positive connections, light goes out.

GM added the light because people thought electric choke, no need to set the choke. Light reminds driver you still need to push the accelerator pedal one time to reset the choke on cold start.

 

[Grit dog]

Choke light wiring is super simple, starting in 1981:

You must be registered for see images attach

When there is no oil pressure, switch is open. Key on current through the light and grounds through the choke, not enough amps to effect the choke. Start engine, now choke light has 2 positive connections, light goes out.

GM added the light because people thought electric choke, no need to set the choke. Light reminds driver you still need to push the accelerator pedal one time to reset the choke on cold start.

Your knowledge amazes me!

 

[Grit dog]

I know the ch

its or orange "choke" light at 5 o'clock position in the left side gauge under the odometer 10'ths
(hopefully yours is working just fine,...and it just stays unlit as its got nothing to report)

I know the electric choke works fine on the Eddy carbs. Both trucks.
Never seen a choke light on either and I’m sure I’ve cranked them without setting g the choke when needed but generally just set the choke anytime engine is cold.

 

[hack_man]

Wonder if my 86 (originally a 350) has a choke light? For no other reason than it would be cool to get it working.

It is very cool looking, kind of "Lost in Space" retro,
Danger Will Robinson!