Probably a stupid carb question... but I don't know the answer.

[joeydurango]

My truck is in one piece again, so I took it for a test drive the other day. No problems, everything ran great! Fast forward to tonight, I convinced my wife to take a little cruise to the store with me. Of course, after we come out of the store, the truck fired right up, ran for 15 seconds, sputtered, and died. You should have seen the look on her face.

Anyway, I turned it over again but it acted like it was flooded, so I popped the hood, and flooded is an understatement. There was fuel pooling in the intake manifold bolt head areas, and most of the lower half of the carb was wet. Fuel line/fuel filter area was completely dry. Somehow or another the carb just puked up a bunch of gas and it seeped out between the air cleaner spacer and the top of the carb. I mopped it up with a rag, let it sit for a bit, and started it up and got back home. Checked it again after shutting it off and it was nice and dry - in other words, completely normal.

What happened here? I'm not super-experienced with carbed vehicles, but I've never seen that on the three that I've owned over the years. Does that happen sometimes normally? Makes me nervous, would hate to have it happen again on a hotter engine and start a fire. QJet 4-barrel on a 350. I've never seen any sign of fuel seepage on this carb before, it appears to function very well, until tonight. Thanks! Gonna go purchase a fire extinguisher now.

[hamjet]

Sounds like the needle seat to the float didn't seal and gas kept entering the bowl till the pump pressure ran down.

[hugger6933]

I concur be sure to check you oil level and make sure you don't have gas in the crankcase. That could happen with a stuck N/S.
Sometimes they stick from varnish other times trash get stuck in there holding them open

[joeydurango]

Ah, bummer. Okay, I'll check for gas in the oil.

I've checked a few basic things on the carb - the accelerator pump works well, I've changed the filter, the secondary throttle plates move freely. It looks pretty clean down in there. Opinions: Is this possibly just an isolated incident, not to worry about, or does this mean I should tear the whole thing off the engine and do a rebuild on the carb? Never done it before but it looks... doable, if time consuming.

[special-K]

I'd crank some Sea Foam into the carb (pull coil wire first), let it sit an hour, and start it up for a while. Could save you a rebuild. I think it's ethanol causing moisture to accumulate. That's moisture, not water, crappy murky sludgy liquid yuck. I had a rebuilt carb fountain up after I had dealt with the truck's ethanol related issues before putting the carb on. I was very thorough with flushing the tank, but did not remove it. I did a series of purge with air/flush a couple fresh gallons/purge/flush... The truck had been running fine and with the buyer an hur and a half out I started it up, ran a few minutes, got all fluttery, and stalled. I look under the open hood and it's the fountain of gas! It seemed like gas was coming out everywhere. I did the Sea Foam trick and when the guy showed up I fired it up and pulled it on his trailer without a sputter.

[Coley]

Yeah, I've seen that happen from time to time.
One thing I've heard is to take the handle of a screw driver and 'gently' tap it on the side of the carb where the accelerator pump is to loosen/free it up.
Do this when the truck is off then retry.
Keep us posted if it continues...
All Good
Coley

[joeydurango]

If we're talking about rebuild or SeaFoam (or maybe rebuild then SeaFoam for the heck of it), here's one more piece of info to add: I've adjusted the carb with a vacuum gauge, and didn't need to bottom out the mixture screws in either direction. But I know this truck has been at sea level for at least a decade. I live at 6500' and routinely drive up to 8-10,000' - how would I know if I needed different metering rods? Up until the other night, it drove pretty well. If I knew that things needed to change on the carb for proper setup anyway, I'd probably just tear it down.

[gvw5400]

My $2 cents worth. I live at 9052' and when I drive my 71 to work (15.7 miles), the elevation changes from 9052' down to 7460' up to 9467' ending at 8890'.
The truck runs fine and contrary to popular belief you don't have to rejet and change metering rods every 1000' elevation change. This is with the dreaded eddy performer/AFB
600 cfm. I loved the Qjet for many years BUT the crappy ethanol gas + a nytrofil plastic float made me want a different carb. All the Best, Dirk

[joeydurango]

Update: Yep, gas in the oil. I wonder if it was all from that one overflow or if it's done it before, less badly, so that it didn't quite stall out. It certainly has been difficult to start when hot sometimes, now I wonder if it was just filling up with gas after shutdown. Do I need to flush the old oil - as in drain, fill, run, drain and fill again? Or can I just do an oil change? (Hope so, seems like a waste of money and oil otherwise!)

I'll be changing the fuel pump, the oil, and having the carb rebuilt. Was going to rebuild it myself but I decided to contact Lars Grimsrud on a whim, since he's here in Colorado and a recognized Q-Jet genius. Turns out he does rebuild carbs for people on the side, and for much less than a lot of the bigger rebuild houses! Couldn't pass it up. One thing he mentioned that made a lot of sense: 44 years ago he would have leaned the jetting on a Qjet at 6500', but modern gas makes it so that now he enriches the jetting on sea level carbs and leaves stock jetting in carbs at altitude. Explains why I was able to tune the thing halfway decently! I checked my new plugs and they look good - a nice, even tan coat.

So close to having this thing pretty thoroughly gone through. I would sure like to drive it more than the 10 miles I cruise testing each system I get into...