66 SB hard to start when sitting for a month or so...any ideas why

[Wayne W.]

Re: 66 SB hard to start when sitting for a month or so...any ideas why

Almost any of these cars with open vented Holley's or Rochester's will hard start after months of sitting. I would say that is perfectly normal. The bowls are dry, whether you think they are or not. Prove it to yourself by pouring a little gas in the carb first before you do anything else. It will start right up, but will probably die in a few seconds, because the gas is not up yet. As soon as it gets there, it will run.

[William F.]

Re: 66 SB hard to start when sitting for a month or so...any ideas why

Let us know what happens AFTER you make sure fuel bowls are full AND checking to se if you're getting 12 V to coil with key in start position.

[Duke W.]

Re: 66 SB hard to start when sitting for a month or so...any ideas why

1. Pump the gas peddle about 10 times, Engage starter for about 15 seconds. If engine does not start which it won't,
2) Repeat step one
3) repeat step one. Engine will usually start to fire up but not enough for a full start
4) repeat step one. Engine will then start

You may actually be flooding the engine. Assuming that the choke valve fully closes and there is actual fuel coming out of the accelerator pump discharge nozzles when you pump the throttle, try the following procedure.

1. Pump the pedal to the floor two to three times.

2. WAIT AT LEAST ONE MINUTE before cranking the engine.

3. Crank engine five to six revolutions.

4. If it doesn't start, wait another minute, but don't pump the throttle again.

5. Repeat steps 3 and four above until the engine starts

The wait time after pumping the pedal will allow time for the fuel to vaporize sufficiently to form a combustible mixture, and when you first crank the engine with the choke valve fully closed more fuel should enter the engine.

If the above doesn't work, try extending the wait time to a couple of minutes or more.

As I stated previously, the problem is that the most volatile fuel components have evaporated while the car is sitting, and what's left will evaporate much more slowly, so you need to give it some time.

Because some of the fuel in the bowls has evaporated, there is room for more. If the above doesn't work, try this: Before pumping the pedal to set the choke and pump fuel into the venturis, crank the engine five to six revolutions. This will allow the fuel pump to add some fresh fuel, which will still have the higher volatility components, to the bowls. Then use the above procedure.

Because most vintage Corvettes have vented fuel tanks, the high volatility components can escape through the tank vents over time, especially in hot weather, and these highly volatile components are generally the highest octance components, so old fuel can be both hard to cold start and cause detonation.

Vintage cars should be driven enough to consume at least one tank of fuel per year.

Duke

[Monte M.]

Re: 66 SB hard to start when sitting for a month or so...any ideas why

I am jumping in this at the end, but I have a simple solution if it turns out to be right.
If it is a Holley, this will not apply as I describe it.
When you take a carb apart, on the bottom side of the main body there are a few areas that have been filled in with lead. It is a different color. These leak. A professional shop paints a coating of JB weld over them to prevent them from leaking.

Basically, what happens is the fuel from the bowl drains into the engine. There is typically a tiny bit in the accelerator pump, but that is it. Check for fuel, after you have already pumped it two or three times. If the bowls have drained, just pour gas in the tube that is about 3/8" round between the two front openings.

This had happened to two of my vehicles. I could not figure out why I had to crank it and crank it and crank it with it thinking about starting just once.

If you think this might be your problem, let me know and I will send you all the pictures you need to see it and fix it.

It only happens after sitting for a while. Weeks or months.

Best of luck.

[Duke W.]

Re: 66 SB hard to start when sitting for a month or so...any ideas why

All '66 Corvette engines have Holleys. What specific type of carburetor are you referring to?

Duke

[Monte M.]

Re: 66 SB hard to start when sitting for a month or so...any ideas why

Duke,

I do not have any good pictures, but I did throw one of a quadrajet in there because they are a lot easier to see. I am going to go out in the garage a little later and pull apart a Holley to see if I can find the lead plugs on it so we can all get a good look at it.

I learned this because my Jeep engine was having the same problem. Someone just happened to overhear us discussing the problem and explained the fix. He told me a number of the little tricks professional builders use to revive carberators that the average garage builder cannot get to run right.

He explained that sealing all lead plug is a must on all carberators more than five years old if they are going to be rebuilt. For ten years I have been pouring fuel in the little tube on the top front of the carb if I ever let the Jeep sit for more than a week or two.

I will try to find the plugs on the Holley and point them out a little later today. For now here are a few pictures to give you the general idea of what I am talking about.

I hope it helps a little.images.jpgIMG_0555.jpgMainBodyBottom.jpg

[John H.]

Re: 66 SB hard to start when sitting for a month or so...any ideas why

After the car has been sitting for a month or so I have to pump the gas peddle 20 to 30 times to get it to start. Runs fine once it is started. From then on starts right up hot or cold.

1) Carburetor bowls are not empty as I can see gas being squirted into the carb if I manually move the linkage back and forth (before I pump the gas peddle 20 to 30 times).

Ron -

Typical/predictable behavior if the car has sat for a month (fuel evaporation, even if only the "light ends"). Save the wear and tear on the starter and fill the primary float bowl before you try and start it. I use a plastic ketchup dispenser bottle whose nozzle fits nicely in the bowl vent tube - about 1/3 of a bottle will fill the bowl, and it'll start instantly. Holley 4-barrels don't have any "plugs" to leak like Q-Jets do.


PrimeBottle.jpg

[Monte M.]

Re: 66 SB hard to start when sitting for a month or so...any ideas why

Ron,

What typically happens is the accelerator pump itself will hold a small amount of fuel. When I had the problem with my Jeep, if I took the air cleaner off before trying anything, I could manually move the throttle and look down into the carburetor and see fuel being shot down into the engine.

This would work for the first two or three times I hit the throttle. Anything after that and the accelerator pump had run dry and the fuel would dry up.

So, if you want to give it a try, hit the accelerator a bunch of times before doing anything else. then go look down the carb and see if you are still getting fuel as you pump it now.

If you see the accelerator pump running a little dry, do what we suggested by filling the bowls with a bottle. This will prevent you from having to turn the engine over and over trying to suck fuel from the tank all the way through the lines, fill up the bowl, fill up the accelerator pump, and finally jumping out of the jets in the motor to start it. It is a lot easier on the starter and the battery.

Best of luck and let us know what happens.

Monte

[Clem Z.]

Re: 66 SB hard to start when sitting for a month or so...any ideas why

if you want to get away from having to fill the float bowls just install a electric in line fuel pump as it will fill the bowl for you when you turn on the ignition.

[Monte M.]

Re: 66 SB hard to start when sitting for a month or so...any ideas why

If it is excessive fuel evaporation, I would have the tendency to think there is a fuel seepage somewhere when the vehicle is sitting. If you can find the seepage, you will no longer have a problem at all.

Now, the Jeep I have mentioned a number of times, sits three or four months all the time. No seepage or evaporation at all. I do like a little delay in it before it starts and have the engine turn over a few times before it lights off, to get oil back into the bearings before to keep them lubed before the engine does fire off.

You cannot win. If it fires off too fast after sitting a while, there is no oil in the bearing journals and you can cause quite a bit of damage if you are not careful. I have a kill switch in it anyway. For start-up and anti-theft.

Monte

[Ralph P.]

Re: 66 SB hard to start when sitting for a month or so...any ideas why

I have the same issue with fuel evaporation . But, after 12-15 seconds at least the oil pressure is starting to come up... I always thought most of the engine wear happened on cold start up because of lack of oil for these few seconds. So, isn't this really a good thing? ( discounting the starter & battery wear)

[Timothy B.]

Re: 66 SB hard to start when sitting for a month or so...any ideas why

Oil flow in a cold engine can always contribute to engine problems but engine bearings are never completely dry after just sitting.

The bigger problem is the dilution of the oil by the unburnt mixture (blowby) which can reduce the lubrication qualities of the oil. After the engine oil warms to operating temperature the oil will boil off any dilution from blowby, that's why engines that are not properly run to operating temperature need the oil changed more often.

[Clem Z.]

Re: 66 SB hard to start when sitting for a month or so...any ideas why

Oil flow in a cold engine can always contribute to engine problems but engine bearings are never completely dry after just sitting.

The bigger problem is the dilution of the oil by the unburnt mixture (blowby) which can reduce the lubrication qualities of the oil. After the engine oil warms to operating temperature the oil will boil off any dilution from blowby, that's why engines that are not properly run to operating temperature need the oil changed more often.

my fuel injection cars start so fast you hardly have time to release the key back. you are better off to get full oil pressure to the bearing a quick as possible.

[Michael J.]

Re: 66 SB hard to start when sitting for a month or so...any ideas why

You may actually be flooding the engine. Assuming that the choke valve fully closes and there is actual fuel coming out of the accelerator pump discharge nozzles when you pump the throttle, try the following procedure.

1. Pump the pedal to the floor two to three times.

2. WAIT AT LEAST ONE MINUTE before cranking the engine.

3. Crank engine five to six revolutions.

4. If it doesn't start, wait another minute, but don't pump the throttle again.

5. Repeat steps 3 and four above until the engine starts

The wait time after pumping the pedal will allow time for the fuel to vaporize sufficiently to form a combustible mixture, and when you first crank the engine with the choke valve fully closed more fuel should enter the engine.

If the above doesn't work, try extending the wait time to a couple of minutes or more.

As I stated previously, the problem is that the most volatile fuel components have evaporated while the car is sitting, and what's left will evaporate much more slowly, so you need to give it some time.

Because some of the fuel in the bowls has evaporated, there is room for more. If the above doesn't work, try this: Before pumping the pedal to set the choke and pump fuel into the venturis, crank the engine five to six revolutions. This will allow the fuel pump to add some fresh fuel, which will still have the higher volatility components, to the bowls. Then use the above procedure.

Because most vintage Corvettes have vented fuel tanks, the high volatility components can escape through the tank vents over time, especially in hot weather, and these highly volatile components are generally the highest octance components, so old fuel can be both hard to cold start and cause detonation.

Vintage cars should be driven enough to consume at least one tank of fuel per year.

Duke

Duke, would this procedure also work with a '67 tri-power Holley setup on an L71?

[Duke W.]

Re: 66 SB hard to start when sitting for a month or so...any ideas why

It's worth trying on any carbureted engine that is hard to cold start after sitting for a week or more. It's generally worked for me.

Duke