Hard Starting 350
 

I’m looking for any thoughts or opinions. 1971 original 350 with Quadrajet 4 barrel and aluminum intake. HEI ignition. Engine timed and curved within the last 12 months / 1,000 miles. My problem is hard starting after sitting. If it’s only a day or two lots of throttle pumping will bring it to life. Sitting longer contributes to taking more effort to start. Once started and warm it runs well.

I’ve checked the carb and I’m not sure if I’m getting fuel at the venturis. When I pump the throttle linkage by hand I don’t see fuel spray. Should I? There is a sound as the plunger on top of the carb is depressed by the cam during throttle but it could be air as much as liquid by ear.

Obviously written by someone with virtually no carb experience and appreciate any comments!
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Re: Hard Starting 350
 

Should have fuel visible.
That sound is a collapsed plunger.
It’s not seating in the bore and the sound is air escaping.

Could be you need to check float level or the plunger itself.
A low float level lets air in under the plunger.

And I forgot to mention a stuck check ball can cause low fuel level in the pump chamber.

Re: Hard Starting 350
 

Today's ethanol gas doesn't help. If mine sits for a week I know it will take a couple of crank cycles before it will start.

Good luck, Rg

Thanks Geezer. Now onward to You Tube for some education on how to check the things you mention.
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Re: Hard Starting 350
 

Moved thread to E&D for more eyeballs.

Fwiw here’s GMs engine starting instructions for a 72.

Re: Hard Starting 350
 

Instead of YouTube you should buy some info.
Some wannabe carb guys on YouTube tune with a big hammer and cold chisel.
One like this.
Cliff Ruggles sells them.




https://cliffshighperformance.com/pr...category/books

Re: Hard Starting 350
 

Do you have a pic of your carb from several sides.

I’ll post some later today.
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Re: Hard Starting 350
 

Seeing your location it's probably cold outside, without a manual choke it's gonna be a hard start. Mine usually has trouble with anything lower than freezing, never use ethanol, i use premium since most stations have it. I also switched to a redtop battery, it helped a lot on cold mornings. My previous truck had a headbolt heater, it worked wonders, debating using one on this truck. Hope this helped.

Cheers,
Nathan

Hey Nathan. No choke on this carb, just the factory manual throttle I use to set high idle for warm up after starting. It’s not cold here, 40* +. I’ve owned the Jimmy since late 2016 and it normally starts right up after a couple of crank cycles regardless of ambient temperatures. The hard-start problem has gotten gradually worse over the past several weeks. I spent 10 minutes cranking and pumping the gas yesterday before posting looking for help.
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Re: Hard Starting 350
 

Q-jets are a bit famous for leaking back since the inlet is on the bottom of the carb vs the top like a Holley.

I forget what it's called but there's a filter with a check valve that helps fix the problem.

My friend had this problem so bad he went with a electric fuel pump. Even after a few attempts at repairs. His was a DD, and would leak back in as little as a hour.

Re: Hard Starting 350
 

If I recall the quad has two fuel filters one line filter you may see gas running through and the other is an internal where the fuel line goes into the carb, they're both a cheap easy replacement I would recommend replacing both. then check your vacuum lines for cracks and leaks, had that issue once. If good go to points, plugs, condenser old school tune-up, may be starting to foul. Missed the HEI, nvrmind on the last item.

Cheers,
Nathan

I’m listening and considering all the responses. I failed to mention the last time it was started was about a week ago. It wouldn’t start so I replaced the inlet fuel filter. I didn’t know there was a second one until now. In any event it started and ran almost immediately. I let it warm then turned it off. It started immediately and continued to whenever I tried over the following few hours. That leads up to yesterday when I posted about my problem.

I’m attaching pictures as previously requested.
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Update: with the help of a 1- second spray of starting fluid Ingot it started, running and warm. It starts right up after sitting an hour or so. I’ve ordered the Quadrajet manual and am preparing to learn all about what I’m experiencing. Thanks for all the input.
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Re: Hard Starting 350
 

See the plug on the front of the filter housing? Those can leak and let the gas in the bowl out. There are also two similar plugs under the bowl that can leak. GM issued a "fix" for the bowl plugs that involved a rubber piece that goes under the pair of plugs. Now usually included in rebuild kits. Not considered an effective fix.
The common fix involves JBWeld or similar. But the JBWeld stuff often breaks down after a couple of years of constant gas exposure.

Re: Hard Starting 350
 

All my Chevys start hard after they sit for a week. If they sit one day it's no problem. After they sit for a week I don't even pump the gas until the oil pressure gauge comes up. Once it has oil pressure it usually has fuel pressure and a couple pumps will get it going. I hate to wear out my accelerator pump by pumping it when there is no gas in there.

I got tired of the slow starting and started squirting some gas in the carb to make it fire right up. Then I spun a crank bearing and I blamed the cold dry starts. The engine was starting immediately before it had oil pressure. Now I don't mind waiting for the oil pressure to come up before they start.