[elefantrider]

Am using the top octane already. I will check the distributor parts this weekend. This is amazing. Starts right away with 2 pumps after sitting for 2 months. Let it run for 2 min, turned off. Waited 20 min and it started on the key, no pump needed! Will try again tomorrow after getting it hotter.

What is interesting is that I can hear the fuel trickling back into the gas tank right after I shut the engine off. Not sure if that is the return line or what.

Not driving it much these days with good fuel well into the $4 here. For my needs, it is still better than having a big pickup.

[elefantrider]

Originally Posted by dmac

Your situation may be curable somehow, but sounds completely normal. You might get some improvement by doing as suggested- turn over a couple times before giving ANY gas when hot. I had vehicles that needed my foot fully on the gas, others just a little. Turning over before adding any more gas gives cooler air into motor, and if you did have any flooding, will clear that. The reason I don't think it is flooding in the usual sense of wet plugs, is because the engine will be so hot that any dripping fuel will likely just evaporate when it drips into the HOT HOT HOT intake manifold.

When you shut off the motor, at first the engine temp will be about the same as while running which is why it will restart quickly for a couple minutes after shutting down.. After a few minutes, your temp gauge will show a huge rise as all the hot metal heats up the now non-circulating coolant.

After using it all day yesterday in 80 degree weather, I think the above sums up what is happening. It will start easily when cold after one or two pumps. It will start "on the key" (no pump), for a period of up to about 5-10 min after being shut off when at full operating temp. After 10min, it will not start easy without turning it over before pumping a little to a lot. So I believe heat soak has something to do with it. Either I will learn to live with it and get friendly with my starter dealer, or I will experiment with insulating the fuel line and carb base next.

[RobbMc]

My guess is that you don't have a "vapor return" (VR) line coming off the pump. If so, changing to a pump with a VR will greatly improve things.

When you are using a mechanical pump without the VR, and you shut the engine off, pressure remains in the fuel line between the pump and the carb. The needle and seat don't seal perfectly, and if the engine is off for more than 15 minutes or so, enough fuel leaks into the bowl to flood the carb. If the engine sits several hours or overnight, the excess fuel evaporates and the engine is no longer flooded.

If you add a pump with VR and a VR line back to the tank, the pressure bleeds off as soon as you shut the engine off, so the engine is not flooded. The VR also helps prevent vapor lock on hot days.

To test this theory, get the engine up to normal operating temperature, shut the engine off, then quickly disconnect the fuel line between the pump and the carb (caution! The fuel will be under pressure!) to get rid of the pressure. Reconnect the fuel line, wait about 30 minutes, and try starting the engine. It should start without touching the gas pedal since the engine will still be warm but not flooded.

I had the same problem you are having with the 455 in my Olds 442. Adding a vapor return line completely solved the problem.

[elefantrider]

Makes perfect sense to me. But the car and pump have a return line stock. I don't think it is plugged because I can hear fuel or air bubbling back into the tank after I shut off the engine. Wouldn't that sound indicate a correcty operating return line?

[68 Firebird]

I have seen whee the rubber line for the return can collapse due to ethanol. i just dropped my tank on friday to replace rubber hose for filler neck and sending unit. Found rubber line's
that I installed 12 years ago for connecting sending lines to hard lines were collapsing internally. After I had sender on the work bench I tried to blow thru it from rubber line and
there was restriction. remove rubber line from original sender and was amazed how the
inner layers of rubber had swollen. Probably still passed gas but not as easily as it does now. Just an FYI!!!!

Gerry C.

[RobbMc]

Make sure the return line isn't plugged up. If the VR is working correctly, there shouldn't be any residual pressure in the fuel line between the pump and the carb right after you turn the engine off.

If the VR is working correctly, well, that blows my theory out of the water....

[elefantrider]

Could it be plugged up in the pump instead of just the line?

[72LuxuryLeMansLa.]

Originally Posted by elefantrider

What is the proper pump shot starting procedure for a stock '69 428 with a quadrajet?

Here's my problem:
Cold start is fine with one short pump (half to 3/4 pedal push).
Hot start less than 5 min after shutting off: starts fine on the key, no or little pump.

Hot start 5-30 min after shutting off: will not start unless I hold the pedal halfway or fully open and keep cranking, 5 seconds. I have tried all sorts of pump shots, is hit or miss.

What is wrong?

I don't know if you saw my thread the other day: http://forums.maxperformanceinc.com/...d.php?t=721097

My car was doing exactly what you describe. I always thought that the well plugs were leaking but as it turns out all I needed to do was make a new check ball seat. This completely took care of the problem.
I'm no carburetor expert and it took me all of four hours to change the accelerator pump, re-seat the check ball next to it, and wash the pound of sand out of the main well. Most guys can probably do this in less than half the time it took me.

Karl

[elefantrider]

Didn't see that. Thanks. Might as well try that too.

BTW, I took looked down the carb and didn't see any amount of fuel dribbling after I shut it off HOT.
Going to go back out there and check again now that 20 min have passed.

[elefantrider]

Was thinking about picking up one of these devices:

http://www.ebay.com/itm/190599343707

[dmac]

Do you have an electric choke? Electric choke will close after 12 volts is off for a while even if the engine is still hot.

[Ben M.]

If it makes you feel any better, I've got the exact same situation going on with a 100% bone stock '74 455 and quadrajet. After about 5-10m of sitting it won't refire right away unless it cranks a while (4-5 revolutions easy) and maybe gets a shot from the throttle while cranking. It still has a good pump shot and the return lines aren't plugged. The only difference is this one has an EGR intake (EGR disabled) and runs at 215 in the cylinder head because of the 195 thermostat. Plugs and spark are all great, timing dead on.

I'm going to change the thermostat, timing chain, and water pump because it's an 82k mile original car, but I am presuming this is something we just have to live with because of old cars and lesser quality gas. Strangely enough my 2GV cars never have this issue (they just can't start cold to save their lives).

[elefantrider]

Not sure it is a Q-jet carb issue. If it was, I would think one of the carb experts would have chimed in by now.

Choke is stock, whatever came in '69.

Came real close to draining the battery the other day. This is frustrating enough to make you think about a modern engine swap! My Rochester 2bbl engine does not have this problem either.

[mzbk2l]

Not a Pontiac, but the 330 in my '67 Olds used to be very bad about that... shut if off hot and restart it within 5 minutes, it fired before a complete revolution. Go into a fast food restaurant for lunch and come out 20 minutes later and it would take 30 seconds of cranking to get it to fire.

When I had the heads off recently to replace the valve guides, I filled the exhaust crossovers. While there's still a little more cranking after a hot soak, I can usually just hold the throttle open all the way and it only has to crank for 2-3 seconds to start. (I just have to be careful to take my foot off the pedal as soon as it starts to catch so I don't race the engine on startup.)

I'm not recommending filling the exhaust crossover just to deal with that issue, but it does lend credence to the theory of excess heat in the carb contributing to the issue. Perhaps your spacer idea will give similar results to my filled heads.

[Kenth]

FLOODING

THERE ARE THREE COMMON REASONS FOR FLOODING
A. The engine is started and fuel flows over the top of the carburetor, or pours into the intake manifold. This condition is generally a result of either dirt between the needle and seat, or a stuck float. A light tap on the fuel inlet fitting will sometimes cure this condition.
B. The engine is shut off and the fuel drips down the barrel(s) of the carburetor. This condition can be caused by the fuel line being located too close to a heat source such as a radiator hose or exhaust manifold. This causes the fuel in the line to expand and be forced past the needle and seat causing flooding. Also, fuel can boil inside the carburetor as the result of improper or missing gaskets or spacers between the carburetor and the intake manifold. A heat riser that is stuck in the closed position will cause excessive heat under the carburetor and boil the fuel causing flooding and hard starting when the engine is hot.
C. When there is excessive fuel pressure. Excessive fuel pump pressure can be caused by a detective or worn out fuel pump. This condition will cause flooding. Refer to manufacturers specifications for correct fuel pressures.


Also, the Owners Manual says to hold the loud pedal halfway to the floor at hot starting conditions. NO pumping!

[68 Firebird]

I had similar issue when using thin gasket only under my Q-jet.

Found that using a thin black gasket then the purple 1/4" gasket
from Cliff helped to isolate the heat from intake from the carb.


This has worked well since last summer and car seems crisper driving around.

When I checked the carb was much cooler to the touch after a long drive and
less issue with a hot restart. Usually just touch the key and she fires instantly
for up to about 45 from a drive.

Good Luck

Gerry

[elefantrider]

Thanks, I assume the 1/4 gasket you are referring to is a 4 hole, phenolic material, which takes a regular gasket on both sides. Not looking for purple but I will buy it if it helps.

I have seen the large aluminum plate heat shields also.

[goatwgn]

Originally Posted by elefantrider

Thanks, I assume the 1/4 gasket you are referring to is a 4 hole, phenolic material, which takes a regular gasket on both sides. Not looking for purple but I will buy it if it helps.

I have seen the large aluminum plate heat shields also.

That is actually a very thick gasket with bushings in the bolt holes that they used on smog era cars with a q-jet. I used a 1/2 wooden spacer on mine when I encountered a similar problem , and the problem went away. The thick gasket should accomplish the same thing.

[pugslyx234]

I too have a thick gasket under my quad and i hav had no start up problems.

[elefantrider]

thanks fellas, will try it & see if it helps.