Hard Start

[Xxyyzz]

So I am new to carbs and I'm not sure if this is a carb problem, or a problem with my particular car/engine.

 

After the car has been sitting for at least an hour it starts right up. But if I run into a store real quick and come back out it just keeps turning over. Eventually it will catch, but only after it starts cranking real slow. I'm scared the battery will die one of these times.

 

Thanks,

Mark

[TrunkMatt]

Common Chevy problem, and carbureted engine problem in general. It actually happens to a few of us, especially if it is above 90 degrees, and you live in a dry climate. It is due to a form of Vapor Lock... and is made worse these days by the damn Ethanol blended fuels with a lower evap point... this new gas evaps about 5% lower than non-ethanol fuel.

 

Here is what is happening (as best explained to me when I had this issue).

 

The carb and fuel line is heated by the engine while driving. When you turn off your car, off the coolant stops cycling and the engine actually increases in temperature a bit, and the fuel line and float chamber heats up more to the point where the fuel begins boiling away / gassifying. This causes the fuel in the line or the carb to vaporize... and now you have vaporlock, as there is no liquid to pump.

 

For some of us it happens while idling at a stop light for more than a few minutes. Did to me in Boise. It gets worse as you get higher above sea-level.

 

FIXES:

Try getting some heat shielding on the carb and the fuel line to make sure it stays cool... For fuel lines int eh od day, the old-timers used to buy about 20 wooden clothespins and clip them to the fuel lines to shield & insulate it from engine heat. It actually works. Now you can buy the aluminum wrap.

 

If the fuel line runs near the block / headers etc - you'll want to move it at least 1/2 to 1 inch away and insulate it. Most gasoline can boil / gassify at 100°F... so it is important that the lines stay cool.

 

For the carb heat shields there are a variety - and you are probably missing yours. It should be installed standard these days - but most rebuilders don't know about it (mine was missing). http://www.jegs.com/i/Holley/510/108-70/10002/-1?parentProductId=743655

 

http://www.google.com/products/catalog?q...ved=0CEcQ8wIwAA

 

Also, some cars don't have a fuel vapor return line to the tank (I need to add one). This amplifies the issue as the vapor can't escape to the tank and draw up more fuel as it leaves.

 

 

The true fix seems to be doing all 3 things: Heat Shield / Spacer on the Carb, Insulating the fuel line, Installing a fuel vapor return line. People that have those three things done seem to never get v-lock.

 

In the meantime you can add some fuel stabilizer (drygas) or carb cleaner like SeaFoam to a tank, that lowers the evaporation point. Read up on ones that have a low RVP (Reid Vapor Pressure) taht means they have to be heated higher to evap.

 

If you can't get it started, you can always also dump some cold water right on the fuel line and it'll chill it just enough degrees (about 10 or so) for the fuel to liquify again... I had to do that when i vapor-locked while idling at a stop light.

 

Keep your foot pressed to the floor (don't pump - just keep it full on) while starting in these situations.

 

 

ULTRA CHEAP SOLUTIONS:

The cheapest solution is to do what my dad called the "Chevy Hangout"... which is a bunch of guys that own Chevys sitting around talking for 30 minutes while their engines and fuel systems cool enough to start.

 

Sometimes it is nice to find a place to grab a beer or a soda... and think about how great our cars are, despite the issues. Should take 30 minutes :-)

 

 

[Xxyyzz]

thank you for the very intuitive response. Ill start with the easy stuff and try some heat wrap... i found something perfect:

 

http://www.heatshieldproducts.com/productdetail/heat-shield-sleeves/fuel-line-heat-shield/102/43

 

After that ill do the carb shield and if the problem still persists ill do the return line.

 

Thanks again for the diagnosis and fixes.

-Mark

 

Are my lines 3/4" or 1/2"?

 

http://www.lickscycles.com/catalog/product_info.php?products_id=1846

[72MC]

One thing I do AFTER the car has been warmed up. If I make a quick or extended stop somewhere, I will NOT pump the gas before starting. I will hit the gas after the starter has engaged. Mine has fired up right away using this technique. If I pump the gas before I attempt to start the car, then I have an issue of extended starter use before it will fire. Since doing this routine, I only pump my gas before starting the car on the first start up of the day.

 

Now, this may be a situation that works for me since I run an electric fuel pump. I also have a carb spacer and my fuel line is well away from my engine and headers until it reaches the intake manifold area. - Dave

[TrunkMatt]

This stuff should work too.. and may be easier:

http://www.amazon.com/Heatshield-Thermaflect-Tape-10-Roll/dp/B002UPLBDS

 

Today I went all out to fix my problems once and for all. Bought a new Edelbrock carb with heat shield and bought braided heat shielded fuel line and reran the line from the pump to the new carb.

 

 

[Xxyyzz]

fuel line sleeves shud be here by friday... im perusing aummit for a carb shield and today i installed a starter shield. I know that the starter shiled has notihng to do with my problem, but i figured IF i do get vaporlock, it will help me out in the cranking department (and only 15$ shipped)

 

-Mark

[72 LS5]

Does it crank real slowly after being driven around and shut off for a short period (electrical issue)? Or cranks normally and won't fire (fuel issue)?

 

Mine used to crank slowly if I shut it off for just a few minutes and it was not carb related. It was all starter/battery/cables issue.

 

For me, the reason it wouldn't start if I ran into a store real quick was because the starter was cooking next to the headers. But if I waited 1+ hour, it would crank quick enough to start.

 

I would first get the battery tested to see how many cca's you are putting out. Should be over 700. Next, run the thickest battery cables possible like 1 or 0 gage. Get a starter heat shield - the one with asbestos sandwiched between two pieces of metal. I even got the remote solenoid kit (Summit sells it), but that will require some rewiring and having a solenoid on your inner fender.

 

OR, a high torque gear reduction starter can solve almost any hot-start electrical issue.

 

Good Luck!

[Xxyyzz]

at first it cranks fine, but after a while it slows down. I'm thinking its fuel related... only time will tell

[72-CLASSIC_RIDE]

This may not be related but was a problem for me when hot starting engine. When cold, would crank over just fine. But, once engine had warmed to normal operating temp and I turned engine off and then tried to restart, engine would crank very slowly like battery was low. Thing is, battery never drained and engine would finally catch and start. I even had a starter heat shield in place. Finally decided to swap out starter with a delco rebuilt. It was a heavy duty BB starter and never had another issue. Starter was worn enough internally to cause enough voltage drop when warm to make it hard to start. Had I not made the change out, not sure eventually it would not catch while warm and not start.

Just a thought for future consideration if what you have done does not fix problem.

 

Best of kuck,

 

Doug

[Xxyyzz]

i dont think its related, but its def good to know for future reference and i do appreciate the info.