[JJake]

My 1979 TA 400 starts hard after sitting overnight seems that there is no gas in the carb. Cranks for about 20-30 seconds before firing then runs and idles fine. Starts OK after initial start-up for the day and will start right back up after initial start. I've heard about well plugs, could this cause the carb to empty overnight? How is it fixed?

[Z Code 400]

Jjake,

My 1975 Q-Jet did this on a regular basis. I was convinced it was leaking from the various plugs in the Q-Jet so I sealed them with epoxy. No difference.

I recently swapped in a 1977 Buick main body (with APT) and it still did the same thing. So, I lifted the carb off the manifold (hot) and left it connected to the fuel line (with a section of rubber hose) and watched it.

No leaks....nothing.

I came out the next morning and the carb was empty with no trace of fuel anywhere.

It doesn't do it in the wintertime, so I think its either the high ambient temps are just vaporizing the fuel from the bowls, or Dad thinks it could be a bad fuel pump.

I'm still not sure...Robert

P.S. Cliff's book is something everyone should have...

[PONTIAC DUDE]

Try replacing the carb fuel filter with a bleed back valve filter in it like the newer Q-jets have.

[Z Code 400]

That's an interesting idea, Dude....I didn't think of that one. I always removed the 'flapper' since I suspected it inhibited flow.

Any input, Cliff???...Robert

[Schurkey]

Try it with the flapper/check valve installed. If that makes a difference, I'd be suspicious of the check valve(s) in the fuel pump. If they leaked (slightly) you could easily siphon fuel back to the level of the fuel in the tank overnight--yet the pump would probably still pump at 99.44% of normal capacity.

[TheMonkey]

i recently went through this several weeks ago. carb is a newly rebuilt edelbrock. it was an issue of no gas in the fuel line. it would do a tiny cough, then had to let the pump send up fresh fuel while cranking. this was after every overnight setting, but wouldn't do it if i parked the car the night before when motor was cool. then... next morning it would be fine. only when i parked the car with hot motor.

turned out it needed a simple tune up. set dwell, timing, and new points. it fixed it, and i have not had the problem again.

i suspect that the motor was running too hot and burning off the fuel after parking a hot motor. some folks suggested a phelonic spacer to get the carb away from the heat.

[shotgun]

I suspect it is our wonderful new fuel.
Had the same issue after swapping to a open air filter.
Got to the point,would let the pump run for 30 seconds,pump the gas a couple times then it would start.
Put the stock housing back on and it got better.Still would pump etc. but much better.
Added a snorkle to the rad supprt and got even better.
I do notice it is much worse with customers cars with open elements and/or open shakers.
I am guessing our new fuel with added metanol is just floating away.
Is raw fuel evaporating off good for the enviroment?!
Hmmmmm

[lust4speed]

I would think that if the fuel pump check valves were working correctly, then even if the carb went totally dry overnight, it would still fire up no more than about 8-10 seconds. If the fuel is draining out of the line back in to the tank, then the pump would have to replace the fuel in the line before filling the carb. Adding to the problem is that the marginal check valves would probably also cut the actual flow during cranking. Once the engine fired off, the leak-back in the pump wouldn't be noticable.

[Z Code 400]

Mick,

I think you hit the nail on the head. That is what I suspect in my case...Robert

[Bumper]

Or you may have a windowed needle/seat in the float bowl on your qjet. It will allow the fuel to drain back to a certain extent and if you have the exhaust crossover open, it would evaporate what is left in the carb. Just an idea.

[performerrpm]

mine did that same thing before , it urned out to be my fuel pump bleeding off and a new pump cured it

[Z Code 400]

Bumper,

I made sure I used the 'non-windowed' needle and seat just to be sure...Robert

[matt1970pon]

my car does the same thing.Its mostly stock,1968 400 q-jet,stock manifold with exhuast crossover not blocked off.I started having problems with it when I put the new Carter fuel pump on it.The gauge reads 5 to 6 lbs when the engine is running.Do you all know if these Carter pumps are any good.I just assumed with the carter name it was good.I don't mean to jump on your thread just this seems to be a more fequent problem then I thought.Should I order a stock pump for PY and get rid of the carter one?My carb was rebuilt about 5 months ago by Paul Spotts and he epoxied everything that needed to be so I know the carb isn't the problem.New tune up.Dead on with timing,Pertronix.The only aftermarket parts on my engine are the headers,pertronix and fuel pump.

[Pontirag]

I was just going to say what performerrpm said. check your fuel pump. Ipso facto check oil level, viscocity and the smell of gasoline in the oil. Cosider your fuel milage. usually if there is water in the fuel over winter the water settles to the bottom and freezes at night. When you start up first thing you pump diaphagm is pumping ice and the diaphagm tears. or the valves get tweeked.

It could then be draining/syphoning off fuel from both the carb and the tank. check for leaks through out the entire system. Look for any kind of staining. see if it happens more or less witht the tank full, half full or empty.

Also check your fuel tank pickup and screen. I am currently rectifying problems related to the pick-up line and filter sock that could only have occured during the cars initial manufacture. Coincidently just prior to a strike at that plant. this alone would have caused fuel starvation .

Also there was enourmous amounts of varnish and debris in the tank that all but clogged the pick-up screen/filter sock. It is a slimy sticky dirty mess that i am trying to clean out as i write this.

Also an incorrect gas cap may cause a vacuum on the system that is relieved slowly by sucking fuel back out of the system into the tank.

I've also seen F body's that have had fuel lines kinked and crushed by improperly locating a jack on it.

these fuel systems are old. they have had a considerable veriety of fuels, types and grades in them. Many mechanics have worked on them some knowingly some not. The car was never intended to be servicable this long. nor were many of its components. you cannot speculate on any component in the system enless you personally have serviced it and determined its suitability for continued use. Start at the gas cap and work your way forward. replace hoses filters and clamps. clean and inspect the tank and sender unit. inspect the lines to the pump. Inspect the pump. Is it the right one for your application. Is it compatable with your polution controls/devices. If not are they deactivated. Correctly?. its a days work, two days if you have to clean your tank out.

If your car sat for an extended period befor the problem occured look for symptoms of bad gas. If you run bad gas through your system or mixed with fresh gas it will still do a number on all but the most competently serviced fuel system. Run bad gas through and you also risk stuck and possibly bent valves.

[JJake]

Thanks guys. I'll check for the new style fuel filter valve, fuel in the oil, and if that doesn't fix the problem replace the fuel pump.

[Bumper]

Originally Posted by Z Code 400

Bumper,

I made sure I used the 'non-windowed' needle and seat just to be sure...Robert

Z, I had the windowed seat and didn't have a problem until I unblocked the exhaust crossover. The heat must have taken care of whatever gas was left under the holes/windows in the float bowl.

[Z Code 400]

Bumper,

That's quite possible. My crossover on the 350 is currently open, but I am blocking it on the upcoming camshaft swap. There isn't any need for that much heat under the carburetor out here in California...Robert

[Bumper]

Also, I would like to apologize to Robert for acting immature on some of my posts.
Cheers

[Z Code 400]

Bumper,

Thanks, Man...but no need to apologize. Its cool. I'm very opinionated on some topics and I know that can stir things up a lot.

I'm really going to start looking into this now that there has been such an exchange of ideas on the topic. We always threw the little 'flappers' in the Q-Jet filters away because we felt like it was a restriction.

The check valves in the pump are starting to make more and more sense to me. My pump is probably stock. The odometer just rolled up 58,000 earlier this week...Robert