[Calibrator]

I've got a 1969 Qj on my engine that runs great. Cold starts aren't so good. Choke adjustment is exacltly like shop manual specification.

Here's some background information:

The wells aren't leaking. I've had the carb on a workbench overnight with fuel in it. It's still got the same fuel level when I check it the next day.

If I pump the accelerator once then hold 1/4 of the way down, crank 10-12 seconds in the morning it will start on that first crank, no stall after that. I don't like cranking that long.

If I crank 5 seconds, then turn the key off, pump the accel, then crank again, it will start right away, but stall. Then it will start right up.

If you let the car sit overnight, then look down the throat of the carb and pump the accelerator pump, the first one or two pumps are a little mediocre. The third is real strong. Why is that?

I've installed the GM heat shield under the carb thinking that my fuel might be evaporating from engine heat, but that doesn't seem to make a difference.

Is it possible my fuel is draining back out via the fuel filter?

Thanks!

[Calibrator]

I've got a 1969 Qj on my engine that runs great. Cold starts aren't so good. Choke adjustment is exacltly like shop manual specification.

Here's some background information:

The wells aren't leaking. I've had the carb on a workbench overnight with fuel in it. It's still got the same fuel level when I check it the next day.

If I pump the accelerator once then hold 1/4 of the way down, crank 10-12 seconds in the morning it will start on that first crank, no stall after that. I don't like cranking that long.

If I crank 5 seconds, then turn the key off, pump the accel, then crank again, it will start right away, but stall. Then it will start right up.

If you let the car sit overnight, then look down the throat of the carb and pump the accelerator pump, the first one or two pumps are a little mediocre. The third is real strong. Why is that?

I've installed the GM heat shield under the carb thinking that my fuel might be evaporating from engine heat, but that doesn't seem to make a difference.

Is it possible my fuel is draining back out via the fuel filter?

Thanks!

[wheelspin]

I had the same problem with the Q-jet on my 68 GP.

As you know, the tiny fuel bowl on these carbs is known for supply and evaporation problems. Having tried the heat shield also, I installed a Carter pusher fuel pump inline near the tank and wired it to a momentary pushbutton below the dash. A few seconds of priming now result in quick starts, after setting the choke and stroking the carb once.

Les

66 GTO Sport Coupe,455/trips,700r/2500stall,12bolt/3.08,1.79/13.01/104.5
68 GP daily driver and 2004 Route 66 Tour participant under restoration
--------------------------
Better lucky than good

[carbking]

Modern gasoline can have severe evaporation problems. Try the following method for a cold start.

(A) do not touch the gas petal
(B) crank engine 3 secondes
(C) push gas petal gently to the floor to engage choke, and fast idle circuit.
(D) pump gas petal 3 times (this may need to be changed later)
(E) remove foot from gas petal
(F) crank engine. It should start and jump to about 1800 RPM on the fast idle circuit.
(G) if it starts, and then stalls, you may need to adjust the choke, or the number of pumps.

On important concept to remember: vehicles with automatic chokes are designed to start WITH NO FOOT ON THE FOOTFEED! Placing one's foot on the footfeed during starting disables the fast idle circuit

Jon.

Good carburetion is fuelish hot air.

[Calibrator]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by carbking:
Modern gasoline can have severe evaporation problems. Try the following method for a cold start.

(A) do not touch the gas petal
(B) crank engine 3 secondes
(C) push gas petal gently to the floor to engage choke, and fast idle circuit.
(D) pump gas petal 3 times (this may need to be changed later)
(E) remove foot from gas petal
(F) crank engine. It should start and jump to about 1800 RPM on the fast idle circuit.
(G) if it starts, and then stalls, you may need to adjust the choke, or the number of pumps.


Jon.

Good carburetion is fuelish hot air.<HR></BLOCKQUOTE>

Could be something to the modern fuel angle. I always remembered Quadrajets as having great cold start and cold start driveability. Used to pump one time, then hold 1/4 of the way down and they would start just as soon as the starter engaged. If the fuels different though, I guess it's time for me to change my technique.

When this one does start, it goes right to about 1200 rpms, then over the course of about 15 seconds works its way up to 2,000 rpm. After 30 seconds I can put it in "D" and go without worrying about it stalling.

Wheelspin,

Did you observe the first pump or two being rather anemic with your 68? I guess having it start right away with the pusher pump proves the choke was set right!

[wheelspin]

Call,

On my 68 below, there is no visible pump shot after a couple days of sitting as all the fuel has evaporated. In your case, maybe it took a couple of strokes to lubricate the pump seal.

Les

66 GTO Sport Coupe,455/trips,700r/2500stall,12bolt/3.08,1.79/13.01/104.5
68 GP daily driver and 2004 Route 66 Tour participant under restoration
--------------------------
Better lucky than good

[Kenth]

8 out of 10 carb problems are ignition related, the ninth is a clueless mechanic and in the tenth case it really is the carb.

[Calibrator]

You are right about 8/10 of all carb problems being located in the distributor.

This one is definately carb. My Holley doesn't have that problem, but the Qj is much more responsive and gets 3 mpg better than my 600 CFM vacuum secondary Holley!!!

[PMDRACER]

The next time the car sits overnight, go out and pull the air cleaner. Look down the carb while taking the throttle full stroke. Are you get an accelerator pump shot? Where does the choke door end up - all the way closed, or closed except for a tiny air gap. You should have a small gap. Had a prob with my new motor that it wouldn't cold start unless I had my foot in it because the choke door was completely shut. If that's the prob, there's a screw on the backside of the arm moved by the vacuum dashpot. Adjust the screw until you get the air gap.

No pump shot is an obvious starting problem.

Cranking voltage is easy too. Pull a spark plug wire and stick a screwdriver into it. Hold on to the screwdriver while you crank the engine. You'll know if you have good spark or not.

TIGER EFI - Electronic Fuel Injection for the Traditional Pontiac Engine. [email protected]

The point to life isn't necessarilly the decimal.

[Calibrator]

PMD racer,

The choke closes all the way.

If I let the car sit overnight, remove the aircleaner and look down the carb, the first two pumps are not as strong as the third pump. Not sure why. If I pump three times, it still takes a lot of cranking.

The ignition is in mint condition. The engine has always had this problem. I've replaced all of the primary and secondary ignition components a couple of times.

[PMDRACER]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR> PMD racer,

The choke closes all the way.
<HR></BLOCKQUOTE>

When you are cranking, the door should be open just slightly. No air, no fire.

TIGER EFI - Electronic Fuel Injection for the Traditional Pontiac Engine. [email protected]

The point to life isn't necessarilly the decimal.

[Kenth]

The choke valve opens approximate .0290" when engine starts, some even have a delay choke valve opening system to give the engine rich enough mixture to run on.
Check if choke/sec air valve control works, otherwise choke valve remains closed until engine gets warm creating a too rich mixture and hard starting.
Not to mention erratic WOT sec opening.

[Calibrator]

Well, I added the THICK GM base gasket on top of the heat shield. Now it starts with 6 seconds of crank after sitting two days!!!

[JPJ]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Calibrator:
Well, I added the THICK GM base gasket on top of the heat shield. Now it starts with 6 seconds of crank after sitting two days!!! <HR></BLOCKQUOTE>


Do you have the P/N for the thick gasket? Where did you get it -- did you have to go to a dealer or do any other local shops stock it?

[Calibrator]

JPJ,

Don't have a part number. It's actually just one of the thick base gaskets from a later model rebuild kit I had laying around.

Felpro makes one. Go to any good local auto parts store (Kosins, Van Born Auto, Larry's Auto Parts) and ask for a Felpro carb base gasket with the buttons in the bolt holes for a Qj. They come in open and four hole styles. The open was much cheaper.

[jimrws6]

Ok, I'll play stupid. What is the thick gasket doing to solve this problem?

[goathead68]

I'm guessing that it's working as a heat insulator. You can achieve the same effect, and maybe get a little better performance, if you use a carb spacer.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Changing the face of Earth, 21 tons at a time.

[Calibrator]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by jimrws6:
Ok, I'll play stupid. What is the thick gasket doing to solve this problem?<HR></BLOCKQUOTE>

My theory is that it was getting so hot that most of the fuel in the bowl would evaporate. All I know is, it's started in under 5 seconds 4 mornings in a row now. Up till I installed that gasket I had 2 years of cranking for 10+ seconds!