Engine dies under load.

[Kerzy]

Hello, the truck starts but only when you prime it with gas down the carb,it will idle nicely but when you hit the gas or try to drive it dies right away, you can hear what sounds like lots of air then if you let off the gas it will come back and idle, so I bought a carb kit from Mikes carb parts and rebuild the factory Rochester single barrel, that did not help, same exact problem. New points, new plugs all with in spec, timed properly, the fuel pump works fine but it sounds like the carb is starving for fuel? I had an old farmer come over to see if he could help, he took apart the carb I just rebuilt and said everything looks good. I’m at a loss. Any info is greatly appreciated. Thanks!

1965 GMC 910
230

[FetchMeAPepsi]

Sucking air maybe? There's a filter under the passenger side cab that can have the seal rot out if it's not changed in years. My guess would be that, or the fuel pump is wearing out and not pumping enough or holding pressure. You did change the float needle, right?

[Kerzy]

I ordered a new fuel pump, gasket and push rod, I’ll give that a try.
Where is this filter under the cab you’re talking about?

[Funky61]

Hello Kerzy, if you have the fuel filter it will look like this:

[Kerzy]

Ok, nope nothing like that on my unit. I just have a small inline fuel filter that I just replaced. Hopefully the new fuel pump solves the issue.

[Kerzy]

Originally Posted by FetchMeAPepsi

Sucking air maybe? There's a filter under the passenger side cab that can have the seal rot out if it's not changed in years. My guess would be that, or the fuel pump is wearing out and not pumping enough or holding pressure. You did change the float needle, right?

Yes, brand new float needle. Pretty much everything is new inside the carb. Float, springs, gasket, check !Bork!!Bork!!Bork!!Bork!!Bork!, accelerator pump etc.

[AZKen]

1. Why did you say the fuel pump works fine?
2. Any vacuum leaks, hoses, fittings, hard lines. Check the rubber lines carefully. Difficult to find a leak by just looking.
3. What exact motor? and what timing setting do you have?
4. Is vacuum advance working? Hose hooked up?
5. It does sounds like the carb bowl is empty. Recheck float level dimension and float drop dimension.
6. Choke working? Not stuck?
7. Let us know what new fuel pump does, but you can check the one you have now. Do you know how? If it works OK or the new pump does not fix it, that's OK. It narrows it down to few other areas.

[FetchMeAPepsi]

Yeah, my guess is the fuel pump. Ken has some good questions too. When you change the fuel pump, fuel will pour out of the line so be prepared for that. You also may need to prime the pump to get it to pull right.

On Cecilia I have to get a funnel tied to the fuel line in a position above the gas tank and pour gas down the line until it goes back to the tank almost completely. It's a pain to prime.

Hopefully yours won't lose too much and it'll prime itself easily. Good luck!

[65GMCKV4000]

I had a partially plugged fuel tank suction line that caused the same thing on mine. Now first thing I make sure of on all these old rigs is a clean tank and unrestricted suction line. Also replace rubber lines. Saves me a lot of time and parts.

[Kerzy]

I’m running it off of a Jerry can and Hose for now till I can clean the factory tank and lines.