When firing up the Vette from sitting overnite, it takes four or five attempts and MUCH pumping of the carburetor to finally get the motor to "catch". After that, runs fine...will even RESTART on first 'hit' after a short, 5-10 minute shutdown.
Any LONGER than that and it is back to 4 or 5 attempts with MUCH pumping of the carburetor.
Is this considered "typical", or is there something I can do to alleviate all the carb pumping? It is a stock '79 L82 with the Rochester 4bbl carb.

 

When the car has been sitting over night, have you checked whether the choke fully closes after stepping and releasing the gas pedal once?
When trying to restart after 10 minutes, have you looked down the carburetor throat to see if gasoline is dripping?
When trying to restart after 10 minutes, do you step slightly on the pedal, maybe an 1/8 of full throttle and turn the key to start?

 

your fuel is dripping into the manifold .. flooding the engine and emptying the bowl. what kind of carb do you have?

 

Have a look down in the inlet manifold to see if fuel pooling inside .you might have to adjust your float level .Can you smell fuel in your engine oil .?My 69 used to be like yours pump ,pump crank pump pump crank ,running rough but once I sorted out the carbs now after a week I can go out and no pumping the gas ,just touch the accelerator she fires right up .Lars is the man on carbs so hopefully he will tune in

 

Here is starting procedure to give you a idea on how it should start.

 

Will check that as a last resort...I do NOT like working on carbs at my age.

Not that I can tell...no discoloration of any kind either.

After the car HAS sit for a good amount of time, and I turn the key, it ACTS and SOUNDS like it was GOING to start, but only for in instant, then just cranks and cranks until I pump the heck out of it, and THEN hold the acc pedal all the way down, and THEN it starts.

I can actually HEAR the choke plate snap shut when the motor is totally cold. And when it DOES start the fast idle cam is engaged, so I know the choke is doing its thing.

No on the first one.....yes on the second one, but does NOT start until a series of pumps on the GO pedal.

Sounds like that would be a definite fire hazard. It is a Rochester 4bbl carb, which came stock on a 79 Vette.

 

Maybe try a Napa Gold 3051 filter in the carb inlet. It has a check valve that keeps fuel from draining from carb

Also, your accelerator pump might not be working properly. You can try putting a few drops of motor oil down the pump shaft. It will help the seal work.

I had this problem and did the above along with proper timing and the problem totally disappeared.

VS

 

It sounds like you're not getting any gas. Take off the air cleaner when its been sitting over night and pump the throttle by hand. You should see gas squirting into the primary throttle body. It should be enough to get 3 squirt with 3 pumps, if you dont the fuel is either

1. draining back out the fuel inlet
2. draining though the fuel system into the intake
3. the carb is pourous and the fuel bowl is leaking and draining into the intake.
4. If its a quadrajet the old bowl plugs may be leaking

You can spray starter fluid into the carb when its cold, pump it once to set the choke and turn it over, it should fire right up and it would draw enough gas to fill the float bowl.
If this works then you can pull the carb and fill the float bowl and see if it seeps out the bottom with out any back pressure on the system. If it does, your carb needs the float bowl sealed, the plugs sealed or the section of the carb that houses it replaced. If it doesnt then you need to look at he check valve if the filter has one or the needle and seats.

I dont think its going to be a seating issue, maybe the check valve or the float bowl.

 

I had the same issue, until I had Lars build me a carb for my '68. Now the car can sit for weeks, and with one pump to set the choke and about 5 seconds of churning, she fires right up and hits the high idle. After running and warm, she starts with no pump and hint of gas needed. Might be worth talking to Lars and sending the carb out to him. Best money I ever spent on the car. Good luck, as these things can be frustrating.

 

Ok...sounds like a plan.......so excuse me for not being any smarter than a 5th grader, but WHO is this "Lars" and how do I go about getting in touch with him? And being as "late" in the season as it is getting, would this be a good idea to do it at this time? Vette sits outside under cover during the winter and other inclimate weather.

 

Here you go

Lars <v8fastcars@msn.com>

 

op says it only does it after sitting overnight, bet his accel pump could have an issue
Good carbs when all is right, went years without touching mine.

 

From my paper on the subject - these are the things that will cause the issue you describe:

Technical Explanation: My Car Is Hard to Start – My Carb Must be Leaking all the Fuel Overnight!

One of the most common complaints on a Q-Jet carb is that the car is hard to start after sitting overnight or for a few days: The engine must be cranked excessively and will finally start after pumping the gas pedal repeatedly. The common diagnosis is that “The carb well plugs are leaking – you need to epoxy the plugs.” Actually, there are several issues that can cause this symptom, and the plugs are seldom to blame – some of these things can be fixed, and others cannot, but there is no one single cause for this problem:

1. The most common cause of Q-Jet start problems, if it occurs after the car has been sitting overnight or longer, is that the fuel standing in the fuel line between the pump and the carb is draining back through the fuel pump checkvalve due to a slight leak in the pump's internal checkvalve. Since the Q-Jet's needle and seat is in the bottom of the float bowl, the fuel draining back through the fuel pump will actually siphon fuel out of the carb's float bowl. To fix this, you need to replace the pump, but not all new pumps have checkvalves that seal completely, thus the problem can persist. You can check for a leaky checkvalve in your fuel pump by running the engine for a minute and then shutting it off. Wait about 5 minutes and then loosen the fuel line at the carb. If the checkvalve is good, there will be fuel pressure at the carb when you disconnect, and gasoline will spray out forcefully when you loosen the fuel line. If gas does not spray out and you only get a slight dribble of fuel, your checkvalve is allowing drainback.

If this is the case, you can first install a checkvalve inlet filter, part number 3052 from NAPA (for the “long” filter, or 3051 for the “short” filter) and see if that cures the problem. If not, you can remove the clip from your needle so that it will drop down into the seat after engine shutdown to seal off the seat from the siphon action.


2. If this does not cure it, you may have a leaky float bowl well plug (either on the primary or secondary side). Before doing any well plug repairs, I strongly recommend that you verify this problem first: If you remove the carb from the engine and set it up on some tall sockets on your workbench, you can fill the float bowl with fuel and easily see if the well plugs are dripping. Leaky well plugs will be readily and immediately visible. It is seldom that a post-’70 Q-Jet will leak from the well plugs. To fix leaky primary well plugs, drill and tap the well plug area for #10-32 screws. Install 10-32 x ¼” Flat Head Socket Cap Screws coated with JBWeld epoxy into the threaded holes – this is the only permanent repair to the leaky plugs. If the leak is on the secondary side, you can install the thick secondary well gasket that is provided in almost all NAPA/Echlin rebuild kits.

3. Many Q-Jets came from the factory with porous castings, resulting in fuel leaks right through the exterior and internal walls of the carb. If this is the case, you need to replace the carb. I have seen many of these, and you can often find the problem by, again, setting the carb up on your workbench, filling the bowl, and observing where the drips are coming from.

4. A bad accel pump will cause hard starting (since no fuel will discharge when giving it the “pump” as described in step 1), and bad accel pumps are extremely common with today’s ethanol-additive fuels. After the engine has been running, shut it off, look down the carb, and flick the throttle lever slightly. Verify that you have an immediate pump shot in both primary venturies. The accel pump will often lock up in the pump bore due to the ethanol in the fuel, resulting in an inoperable accel pump – the lever and pump rod will go up and down, but the rubber “cup” can be seized in the pump bore. This will make the car very difficult to cold-start, but can produce satisfactory performance once the engine has started.

5. Verify correct operation and setting of the choke. An inoperable choke will make the car very difficult to start. See the Choke Setup section of this paper.

6. Operator error. Many new musclecar owners are not familiar with the correct operation of carbureted engines, and believe that the engine should cold-start without touching the gas pedal. A carbureted engine requires a fuel shot from the accelerator pump in order to start cold, so the gas pedal must be pumped a few times in order to “set” the choke and to squirt fuel into the intake manifold. Be sure you are using the correct cold-start technique of pumping the gas pedal two to four times before cranking the engine on a cold start.

7. Finally, there is the issue of modern fuel. If you have stopped the drain-back and siphon problem and have verified that you have no leaks, you likely have a problem with the high vapor pressure of modern fuels in the Q-Jet's vented float bowl. The fuel currently available has significantly higher vapor pressure than the fuels that these carbs were designed for. Since the Q-Jet float bowls are vented, the modern fuels will evaporate out the vent tube, dropping the float bowl level just enough so that the accel pump well will not fill with fuel (the Q-Jet accel pump does not get its fuel from the bottom of the float bowl: the bowl must be nearly full for the pump to function). If you have ethanol-additives and high vapor pressure fuel in your area, causing evaporation loss out the carb’s vent, there is no fix to the problem.

 

My 81 has this same issue so I will start with Lars #1 and see how it goes. Would it also explain a gas smell after driving and putting back in the garage? I have looked all over and cant find a gas leak but it seems to be from the carb or near it.

 

Lars,good read. I to have the QJ fuel drain-back problem. It seems the Napa-#3051&52 is paper element only,no check valve or gasket. Can the proper filt be ordered in a kit? Will the one-way valve hinder the fuel flow @ higher RPM on my 78' mostly stk L-82? Can the pressure valve sprg inside be modified. Changing out the f/pump would be my last resort. Hdal

 

That's not correct. NAPA part numbers 3051 and 3052 are the part numbers for the NAPA Gold filters (i.e. Wix) with checkvalve:






The checkvalve does not impede high rpm fuel flow, but if you have a very weak pump (putting out less than 3psi), you can see fuel starvation under load.

Lars

 

Wow,I got skunked,the Napa-3052 one I bght did not have the rubber check valve. I'm pissed! Back to the store,20 miles away! I hoping the f/pump is good for 3-4 psi's,it has been replaced once yrs ago.Thanx for your input. Hdal

 

Or or the procedure I follow after converting to my Sniper:
1) Lean in and slide the key into the ignition
2) Turn the key and let it crank for about 1 second and it starts
3) Walk away while it warms itself up.

Cold or hot.

Just sayin.

 

Thanks Lars I put in the WIX33052 filter from Oreillys for 5 bux and it really helped with cold starting. When cold I give it a small throttle to set the choke and high idle and it starts in a few seconds. Still working on adjusting the choke and high idle.

 

Good job!
Lars