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Quadrajet Troubleshooting Help

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Oilbrnr

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So, my new to me '77 died Sunday about a half mile from home. Loaded up the kids, and headed out with my neighbor to scout out this next weekends camping trip near Bartlett Lake right near our homes. He is a Ford guy, and joked with me that he had his tow strap ready. Never thought I would have to take him up on it, especially so close to home. I've had the truck for one week, and have been driving it every day to-from work with zero issues. On our way to the lake it just died going down our dirt road. (about 3 miles of dirt/washboard to the pavement). I smelled gas, and upon looking under the hood, gas was pouring out of the carb onto the intake manifold. An obvious stuck float/valve. Now I'm never going to hear the end of this from him! I've never had this happen on a carb, that I'd not just worked on. Pretty odd.

Went to NAPA today and got a kit, and what I thought was the correct filter. Did the standard disassembly and cleaning in Lacquer Thinner. Put back on truck and it will run for about 5 seconds. The fuel line is kinked at the flair nut by the prior owner. I was careful not to kink it more, but IMHO I think if must be restricting the flow. Either that or the fuel filter. The one I got from NAPA today was wrong, too long, so the filter could be an issue as well.

Any other thoughts? Again it runs great for 4-5 seconds and then that is it. Crank it, and it will fire right back up for the same duration. I don't think it would do that if the float was stuck in the 'up' position. Is that hard line from the pump to the carb a GM only part, or do you think NAPA would have it? Or do I have to bend my own?

FWIW, do the plastic/bakelite floats ever go bad?
 
I have never seen a Q-Jet float go bad personally .

The internal filters one way restriction thingy is a joke and should be replaced with a inline filter down on the frame rail .

The hardline can be bent , but usually an unmolested can be found at a yard .

Doouble check and make sure no foreign dirt or grit gets in there stopping the need;es from dropping into the jets . My first Q-Jet on my 83 had sucked some charcoal bits from the evap can . Teardown by the lake sucks , but I learned that although rare , **** gets in there through vacuum lines .
 
brass huh?

They're pretty rare these days...

The phenolics have been the norm for decades now and rarely go bad...
 
I've seen phenolic and brass Q-jet floats sink.

Any debris in the carb can keep the truck from running. Q-jets are especially sensitive to debris.

The stock fuel filter is ridiculous IMO and an inline filter is a much better choice.

Where was gas pouring out from the carb? What fuel pump is on your truck? How did you get the wrong fuel filter to work at all? Are you sure you put it back together correctly? It sounds like everything got worse after you messed with it.
 
Bah, GM thought that filter was good enough to use for about 25 years, it's not that bad. It may not be that efficient, but if your system is in good shape, and the filter is, no reason it shouldn't work.

As much as I dislike carbs, I thought that was pretty ingenious of GM. People too lazy to change the filter, it simply bypasses. :)
 
38377k5 said:
Where was gas pouring out from the carb? What fuel pump is on your truck? How did you get the wrong fuel filter to work at all? Are you sure you put it back together correctly? It sounds like everything got worse after you messed with it.
Click to expand...

I didn't remove the air cleaner right away, nor did I continue to crank and it was a fair amount of gas coming out. I'm assuming it came out of the accelerator pump plunger hole. If it came out the vent, it would have gone down in the intake. Can't be sure without looking at it right now.

I re-used the old filter until I can get a new one today.

I'm pretty sure that I got it back together correctly, I've done a few Quads in my day, but the last time was about six years ago. There were two brass sleaves however, that I did question their location. I assumed they went on the main metering rods. The parts diagram with the kit did not show them, and the shop manual does not detail carb rebuilds. Did I put them in the wrong place?

I have the stock mechanical pump.
 
I've always had trouble puting the in-line fuel filter before the fuel pump, replaced a lot of pumps until I removed the filter. Maybe thats why GM did'nt ever do that.:rolleyes:
 
The more I think about it, I'm sure those brass sleeves should not be on the main metering rods. That is why it will run fine for a few seconds until the main jets starve for fuel. Arrg!

They have to go somewhere else, I think they might be for the idle circuit. Just seems strange that I'm not seeing them on any of the parts diagrams out there.
 
I suspect those are what GM called emulsion tubes (If I remember my Doug Roe book correctly) and they probably fell out of the air horn at some point, so when you pulled it, they were just laying there. They are just tapped into place, about midway of the airhorn, and they should feed from the secondary fuel wells...as I recall there are a fair number of holes the tubes will fit in on the air horn underside, but only one set (?) feed the discharge ports on the secondary side.
 
Well, they fit perfectly on the main metering rods so that gives an idea of the size.
 
Sounds about right, been a few years since I've had a Q-jet apart. I can't think of any more brass tubes that should be inside one. :)
 
Figured it out, they were the secondary feed tubes that go on the underside of the air horn. There are a total of four tubes, these were the larger of the four. Apparently they had fallen out and into the bowl at some point. I tapped them back in to the horn with a small wood mallet. They seem to be well secured, but I dunno. Not sure that they could have caused my stuck float the other day. Seems improbable.
 
dyeager535 said:
I suspect those are what GM called emulsion tubes (If I remember my Doug Roe book correctly) and they probably fell out of the air horn at some point, so when you pulled it, they were just laying there. They are just tapped into place, about midway of the airhorn, and they should feed from the secondary fuel wells...as I recall there are a fair number of holes the tubes will fit in on the air horn underside, but only one set (?) feed the discharge ports on the secondary side.
Click to expand...

That what they were. Finally found a picture online of the air horn. Tapped them back in with a small wood mallet. They *seem* to be secure, but I dunno.
 
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