OUTTA GAS!!! Vapor lock fix for today's fuel

[ThomasVader]

Greetings Square body gods!! My dad picked up a 74 Sierra 2500 4x4 when I was about 17, I'm now 54. Over the years it was always reliable. Until.... it runs out of fuel with full tanks!

I live in Arizona. Heat is the issue for corn fuel

I've replaced both sending Units, tank selector solenoid, all existing fuel line and gone through several mechanical and electric pumps, rerouted the lines away from heat and still starves for fuel, especially during the summer. During the "winter" not so bad. A buddy gave me a 3 nipple fuel filter to return vapor and boiled fuel but my sending units only have 2

Has anyone else experienced this?

Winter restarting isn't an issue, acceleration is.... fuel isn't making it to the carb before boiling. Will the 3 nipple filter help? Can I use it?

Thank you all for you time and wisdom

 

[Bextreme04]

The solution would have been to put a three connection pump and a three outlet sending unit in the tanks when you changed all those parts. Having the excess fuel return to the tank permanently solves the problem unless you are dumping a ton of heat in to the line from the exhaust.

 

[ThomasVader]

That'll fix it? Nuff said. Can't thank you enough. These 2 parts are under $100

 

[Ricko1966]

If it starves for fuel in the winter,I don't think vapor is your problem. When's the last time you checked float level and trash in the float bowl. I do agree that a 3 port pump and a return line is a vastly superior system. Here's something to consider. Did you put an electric pump back by the tank in your electric pump installs. I'm asking because boiling points change based on pressure. Liquid under vacuum boils at a lower temp,liquid under pressure boils a higher temp. If you installed an electric pump at the front of the truck that can contribute to vapor lock by creating a vacuum. Back by the tank it should eliminate vapor lock becausebit puts pressure on the fuel increasing boiling point.Keep the run to the tank short and the pump below fuel level. Is your tank vented correctly that can contribute to fuel starvation and vapor lock.

 

[PrairieDrifter]

Cold winter air is more dense and requires more fuel for a "normal" burn. I had to go to bigger primary jets for the winter.

Afr gauge is a game changer.

 

[fast 99]

Cold winter air is more dense and requires more fuel for a "normal" burn. I had to go to bigger primary jets for the winter.

Afr gauge is a game changer.

Agree about increased density ask any pilot. However, must have been very close to begin with. Imagine general public having to bring a vehicle in every fall for snow tires and re-jet?

 

[PrairieDrifter]

Agree about increased density ask any pilot. However, must have been very close to begin with. Imagine general public having to bring a vehicle in every fall for snow tires and re-jet?

Oh yeah super close, only went up a couple sizes, could maybe go one bigger but I'm trying to find a good in between size for this time of year.

Jets? They can't even keep their oil changedEverybody has gone soft these days. We've gotten too comfortable.

 

[fast 99]

Oh yeah super close, only went up a couple sizes, could maybe go one bigger but I'm trying to find a good in between size for this time of year.

Jets? They can't even keep their oil changedEverybody has gone soft these days. We've gotten too comfortable.

That engine must be very sensitive.

On hot days especially I did notice when truck got filled with ethanol fuel instead of e free it idled a little rough. My brother borrowed the truck. He didn't know I used e free. Guess that $150 fill up scared him.

Agree, can't imagine the public today having to get a tune up once a year. Didn't cost $4-600+ either.

 

[PrairieDrifter]

That engine must be very sensitive.

On hot days especially I did notice when truck got filled with ethanol fuel instead of e free it idled a little rough. My brother borrowed the truck. He didn't know I used e free. Guess that $150 fill up scared him.

Agree, can't imagine the public today having to get a tune up once a year. Didn't cost $4-600+ either.

I think the carb is sensitive. The engine is tired but runs good lol. It's a Holley 670. The only place I was having an issue was off cruise acceleration, well the main problem is too small of primaries so it's cruising lean then to speed up the throttle blades open more and there's a moment of extra lean, sometimes can be felt.

Was just a hair lean in summer so I expected it.

To be fair the reman Quadrajets that I've had have all run really lean, I am at about 10-11 for initial timing though.

 

[fast 99]

To be fair the reman Quadrajets that I've had have all run really lean

Reman carbs are junk, nearly all of them. Q-jet is the best all round carb for a stock GM. Know some disagree with that but is usually because they don't understand how they work. Do agree they can be more time consuming to repair or jet on than Holly.

Apparently there are custom rebuilders that do a good job on Q-jets. Might chack that out.

 

[PrairieDrifter]

Reman carbs are junk, nearly all of them. Q-jet is the best all round carb for a stock GM. Know some disagree with that but is usually because they don't understand how they work. Do agree they can be more time consuming to repair or jet on than Holly.

Apparently there are custom rebuilders that do a good job on Q-jets. Might chack that out.

I went for the Holley for ease of repair and tuning, and parts availability. Stupid simple. Took me 10 minutes to do the jets for the first time. 4 bolts and a hose.

With the Afr and the Holley I understand how carbs work wayyyy more. Lots of die hard Holley guys on youtube, lots of info out there. Makes me feel more confident diving into my Quadrajets myself. I'm a visual learner so being able to match the numbers and theories to hardware in front of me was a game changer for understanding carbs.

So many tuning parts available.

I am a fan of Quadrajets for sure, I just needed to get the daily going and didn't have time to learn on the Quadrajet.

I like how the Holley runs, real snappy and I finally have an accelerator pump after how many years lol. Fires up good in the morning and the cold.

 

[JBswth]

Oh yeah super close, only went up a couple sizes, could maybe go one bigger but I'm trying to find a good in between size for this time of year.

Jets? They can't even keep their oil changedEverybody has gone soft these days. We've gotten too comfortable.

And they can't even tighten a loose fan belt.