How a carbureted engine should start and run cold

SirRobyn0 said:

I completely agree with your statement. I just had a 67 Satelite in the shop that another shop setup the aftermarket Holley Carburetor. Customers complaint was the exhaust smell. It was burn your eyes bad. So I went though and rejetted it, adjusted and set it up all properly. Another thing is I think guys still try to read plugs to know where they are at. As you know back in the day we looked for light tan to medium tan and being a good burn, but gas has changed and a normal running carb will result in almost a white plug with maybe a few spots of very light tan. Regardless gasoline has changed and and reading plugs just isn't as reliable as it use to be.

That and there are a LOT fewer of us that even know how to properly work on and tune a carburetor.

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Yeah, I chuckle at a stop light when a rich running vehicle is nearby. After being around this stuff for a while you know what rich, lean or correct running engines smell like. Most are rich.

I have tried 87 regular, 91 e free and AV gas. Of course, they run better on AV gas but it is not a realistic choice. Best option is e free. That is what my SB have in them. Hurts to fill both tanks.

fast 99 said:

Yeah, I chuckle at a stop light when a rich running vehicle is nearby. After being around this stuff for a while you know what rich, lean or correct running engines smell like. Most are rich.

I have tried 87 regular, 91 e free and AV gas. Of course, they run better on AV gas but it is not a realistic choice. Best option is e free. That is what my SB have in them. Hurts to fill both tanks.

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I hear ya "hurts to fill both tanks". But when I sat down and did the math it made no sense for me to purchase a commuter car. I'd spend all my fuel savings on the commuter, Figuring purchase price for a beater, insurance and repair. Plus a commuter CAR would not fit my lifestyle well.

So I keep driving the square, but still the fuel bill is noticeable and fresh in my mind. Last night I filled both tanks in the square $175, filled 4, 5 gallon gas cans for the farm $99, and one 5 gallon diesel can to tide us over until I can get some off road diesel for the tractors and other farm equipment $30 Total $304.00 I should probably post that in the gas prices thread to.....

SirRobyn0 said:

I hear ya "hurts to fill both tanks". But when I sat down and did the math it made no sense for me to purchase a commuter car. I'd spend all my fuel savings on the commuter, Figuring purchase price for a beater, insurance and repair. Plus a commuter CAR would not fit my lifestyle well.

So I keep driving the square, but still the fuel bill is noticeable and fresh in my mind. Last night I filled both tanks in the square $175, filled 4, 5 gallon gas cans for the farm $99, and one 5 gallon diesel can to tide us over until I can get some off road diesel for the tractors and other farm equipment $30 Total $304.00 I should probably post that in the gas prices thread to.....

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I tell customers to keep the vehicle they have as long as it is dependable. Yes, new vehicles are more fuel efficient but won't make up the difference. Back when diesel options on 6.5's were about 2k it took 100k miles to pay for that option on fuel millage alone. [Between the broken cranks and heads popping off the head bolts it never did.]

A friend was giving me a little grief just today about my trucks. Said I should get a newer one. My reply, no chance as he was changing the coil on a 2018 Ford F150 with 19k miles.

fast 99 said:

I tell customers to keep the vehicle they have as long as it is dependable. Yes, new vehicles are more fuel efficient but won't make up the difference. Back when diesel options on 6.5's were about 2k it took 100k miles to pay for that option on fuel millage alone. [Between the broken cranks and heads popping off the head bolts it never did.]

A friend was giving me a little grief just today about my trucks. Said I should get a newer one. My reply, no chance as he was changing the coil on a 2018 Ford F150 with 19k miles.

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Agree.

Something else to consider on hot restart problems is the fuel return line on the fuel pump.

Picture this: you’re sweating your ass off in the truck. It’s a typical 90* day in central indiana, with the humidity to match. The engine is hot, so is the fuel pump. You shut the truck off and let it sit for a half hour or so. The fuel pump is already hot, the fuel in the pump begins to boil, raising fuel pressure high enough to force the needle open, flooding the engine. Bingo! Difficult hot restart.

What to do?

GM was smart enough to solve this problem. They used a fuel pump with a 3rd fitting. It’s purpose is to A, provide a metered fuel leak back to the tank. The metered leak constantly circulates fuel thru the pump, helping to keep it and the pump cool. The other benefit is the metered leak provides a vent to bleed off the pressure from boiling fuel. Instead of pushing the needle off the seat and flooding the engine, the pressure bleeds off back into the tank.

The 3 line pumps typically are capable of higher fuel pressure. That’s designed into the pump to compensate for the metered leak. Which brings me to the problem.

Most people don’t understand the 3 line fuel pump and fuel return system. How many times have you seen a engine with that 3 lined capped off? If the pump is designed to run about 5 psi with the fuel return functional, what do you think will happen with the return line capped off? That 5psi pump is now providing much more pressure. The engine might run ok, but it’s not going to be happy when you shut it off. Now the already overpressurize fuel has no place to go but into the engine.

If the truck was originally equipped with A/C, it almost certainly had a fuel pump with a return line setup. If the line is capped, or a 2 line pump was installed, install the correct pump and make the return line functional again.

Another contributing factor that unfortunately we have zero control over is the fuel available today. People with carbureted vehicle make up a very tiny percentage of fuel use today. The additives that were common in gas 30 years ago to prevent fuel evaporation has long ago been phased out. Cars/trucks today have closed systems, fuel can’t evaporate out of the fuel tank, so those additives are a unneeded expense. That makes the fuel return system even more important on old iron. Todays fuel can cause problem these trucks didn’t have new.

I just took this, this morning. Of course I realize there are colder places, and if cold enough can cause starting problems. But I wanted a decent video with a little better lighting than the previous ones and this was a good cold morning and the truck has sat some. We currently have about a foot of snow and the ground and haven't had highs above freezing since the middle of last week. and most of the lows have been upper teens. This morning it was 20F. I didn't drive the truck for 3 days, and this is how a carbureted vehicle should start in those conditions.

I don't actually drive the truck because I needed to get the windshield cleared off, but I do put it in gear to prove it won't stall and you could pull away right away.

I have the original quadrajet 4bbl on my '78 with a 350, and 1-2 pump max is all it ever needs to crank up no matter how long it has been sitting. Once cranked, it will then idle at ~1500-1600 rpm until it heats up, then the idle will drop to ~900- 1,000rpm.

ulm4lyf said:

I have the original quadrajet 4bbl on my '78 with a 350, and 1-2 pump max is all it ever needs to crank up no matter how long it has been sitting. Once cranked, it will then idle at ~1500-1600 rpm until it heats up, then the idle will drop to ~900- 1,000rpm.

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I'd say your idle is a little high, but isn't it great to drive an old truck that starts just that easy!