350 small block

[boloboss]

What's up Chevy family????
My 84 Chevy C10 has a 350 small block with a Edelbrock carburetor. It used to crank right up when I turned the ignition and now I'm having to tap the gas a few times before it start and sometimes more than that. But then once it gets going I can turn the truck off, turn the ignition and it starts right up and it will continue to start up consistently.. But then I'll let truck sit for a while, and the same scenario happens again Why am I having this problem?

 

[Chris64]

Electric choke, electronic choke or manual choke? I don't know much about how to fix it but I bet this will be a factor in diagnosing it.

Electric choke is supposed to squirt gas in there when the ignition is turned on I think. Maybe that's not working.

I was going to get an Edelbrock AVS2 with electric choke so I'm interested in hearing what others think the problem might be.

 

[Grit dog]

Accelerator pump. Easy to replace. 1 pump cold starts again.

 

[boloboss]

What and where is the accelerator pump? @Grit dog

 

[75gmck25]

For a carbureted engine, it sounds like it works as designed.

- on a cold engine the choke closes a flap in the carburetor to reduce (or choke) air flow and make the mixture richer. As the engine warms up, the choke slowly opens to allow more air, and finally opens completely.
Older engines used a choke with a thermostatic flap controlled by hot air, which eventually transitioned to using one controlled by electric power. A few chokes are also cable controlled, but they are not common on a squarebody.

- when you pump the accelerator pedal, the accelerator pump in the carburetor squirts additional fuel into the carburetor. This provides more fuel to get a cold engine to fire, or to provide more fuel when you quickly accelerate. The pump has a rubber seal in a small cylinder, which can tear, stick in the bore, or otherwise wear or malfunction.

Chokes are easy to adjust, and an accelerator pump is relatively easy adjust or replace (carburetor top has to come off to replace it).

 

[fast 99]

Above + linkage has adjustments. Accelerator pump is in the front right corner. To check operation, engine off, open choke plate, look down venturis and open throttle. Should produce a reasonably strong squirt of fuel.

Ethanol fuel is not your friend.

 

[85K304SPD]

I think that all Edelbrock carburetors have this problem. they don't hold the gas in the bowl, overnight. It must evaporate or something. I am not sure if this happens with other types of carburetors. I usually have to crank it for a few seconds, then pump it about 10 times, then repeat a couple of times, until it starts. I have heard about people putting a back-flow preventing valve in the fuel line.
I am curious what others have to say about this.

 

[Grit dog]

I now have 2 Edelbrocks and neither of which did I buy, install or adjust. I’d guess both are just running however they’re set out of the box.
The only “hard start” I get is warm engine, both act the same, at least 50% of the time, have to crank a couple seconds to get it to start. Whether no throttle, cracked throttle or even a pumping the throttle 1-2x first.
Not a carb expert. Sure they could be a bit better but they work 90% flawless imo.

 

[Grit dog]

What and where is the accelerator pump? @Grit dog

What they said above. And do a little googling on replacing and adjusting. Not too difficult to replace. But test first like said above. Open the throttle and pump it a couple times. If you don’t see a good primer squirt of gas come out the acc pump is likely the issue.

 

[fast 99]

All carbs with an open bowl vent, fuel will evaporate with time. Overnight no, a week or 2 yes. Ethanol and higher temperatures it will be more problematic.

I haven't installed an Edelbrock carb recently but in the past most needed jetting and adjusting of some sort. They are generic, not specific to any application.

OP needs to do basic testing and inspection. Items like fuel pressure, volume, vacuum leaks, ignition advances and timing. Baseline items first them move on to the hard start.

 

[boloboss]

Do you guys think advancing the timing would help because I did advance it from 4° just a little

 

[fast 99]

Do you guys think advancing the timing would help because I did advance it from 4° just a little

Do the advances work?

 

[75gmck25]

Most stock smog-era SBC’s will handle up to 12 degrees base timing without any pinging issue. They really have low compression.

Have you measured your base timing and base plus centrifugal/mechanical (at about 3k rpm), with vacuum advance disconnected and plugged?

A stock distributor should add 18-20 degrees mechanical advance as rpm goes up, but someone may have swapped springs and weights to change how quickly it rises. A general guideline is to not exceed 30-36 degrees total (base plus mechanical) for example - 12 degrees base plus 18 mechanical.

Vacuum advance will add another 18-20 degrees at light throttle cruise. This improves gas mileage a lot, so you want it working,

 

[rich weyand]

Nobody mentioned the fact that the choke on an Edelbrock (and many other carbs) will stay in the 'warm engine' position (choke plate open) when the engine is turned off. I always needed one accelerator push to the floor for a first-key-on start. That takes the choke off the 'warm engine' position and gives one shot of fuel from the accelerator pump. Turning the key at that point - with a gear-driven starter - would kick over in the first couple cranks.

 

[75gmck25]

That’s a really good tip, and one I forgot about since I do it all the time without thinking.

If you don’t move the pedal to the floor at least once and then release it again, the choke linkage is resting on the stop and the choke stays in the warm (lean) position. As already explained in the last post, that same up/down throttle motion puts an initial shot of fuel into the manifold, which gives the engine something to ignite.