Fuel issue

[rbagley]

Background:
So I bought this '72 a month back and everything seemed fine. I drove it 50 miles or so to get home and took it out a few times after that without incident. The PO had sprayed the engine with some type of degreaser and didn't get it all off, so I was leaving a cloud of smoke behind/all around me once the engine would get up to temperature. To remedy this, I started cleaning up the degreaser, which led to me wanting to finish the job the PO had started. I tried various products and it eventually escalated to oven cleaner. I was trying to keep it off of sensitive parts, but I'm not sure how well I did at that. Truck has an original 350 with q-jet carb, stock intake, and 4 speed.

Problem:
The day after oven cleaner I couldn't get the truck to run. It would fire if I primed it with a few pumps of gas but would die once that ran out. While the truck is off, I can pump the gas a few times, turn the key, and it fires right up. The more times I pump the gas the longer it will run, but pumping the gas pedal does nothing once it's started. It still just dies once it uses up what I pumped in there before starting it. It will run anywhere from about 1 second to maybe 3.

Troubleshooting:
I pulled the carb filter and it was full of junk. I replaced the filter but still couldn't get it to run. I pulled the carb and did a basic rebuild, and that didn't fix it either. I pulled the air horn and the bowl has plenty of fuel sitting in it, but it just won't go into the engine once it's running. It seems to me that the oven cleaner has to be at fault, but I can't seem to make any headway.

Any thoughts?

Here are some pictures to keep people engaged.

[geezer#99]

I see you have a manual choke set up.
Do you use it for starting?

[bigmac73]

maybe the oven cleaner ate up a gasket??Also pull out the fuel sending unit and remove the sock filter on the pick up tube, you said the filter and carb where full of crap

[rbagley]

I see you have a manual choke set up.
Do you use it for starting?

When it's cold out I do. I tried with and without and it doesn't make a difference.

maybe the oven cleaner ate up a gasket??Also pull out the fuel sending unit and remove the sock filter on the pick up tube, you said the filter and carb where full of crap

The gaskets on the carb got replaced when I did the rebuild, and the old ones looked okay. Pulling the sock is on my list of things to do, but I feel like having a bowl full of gas indicates that I'm getting fuel up to the carb. My problem seems to be in getting the fuel out of the bowl.

Thanks for the ideas, guys! Anyone else?

[bluek5]

I bought a 72 that had been sitting for years. I was having issues with plugged filters. I even had to pull the sending unit out of the tank and clean it out to get home one time. I ended up removing the tank and cleaning it out. I could not believe all the gunk that came out of it.
Paul

[davepl]

If it starts and dies when cold that's usually the choke pulloff. I would imagine even manual choke carbs still have it. On my 1970 that pulloff solenoid valve is made of plastic, and has a rubber line.

If you have a little hand vacuum pump (insert joke here) you could test it to see if it still will pull and hold its rod that pulls back the choke.

I mention this because perhaps oven cleaner eats plastic.

Just FYI, on a Q-Jet if the filter gets plugged the fuel pressure will push the filter back on its spring and let fuel in "at any cost", including dirty and debris. So it'll run with the filter clogged until more dirt gets in and eventually gets to an important location.

[kenn]

Don't forget the vac hoses the cleaner might have eaten those.

[GASoline71]

If there was junk in the filter, I'd assume there is maybe more junk in the filter now. Junk in the tank, and rusty fuel lines can do that.

Gary

[Oldtruckfanatic]

If the bowl has fuel in it and is staying full but the truck only runs after you pump the gas there is something going on with the air bleeds or main jets. Usually if the filter or pickup is plugged up the engine will run until theres nothing in the bowl. It runs when you pump it because the accelerator pump sprays the fuel right Into the throttle bore and doesnt rely on air going by a bleed hole to draw the fuel in. I know it sucks but the only real way to fix that is to diasassemble the carb and clear out all the air bleeds and fuel passages with carb cleaner and compressed air. Sometimes if youre lucky you can pull off the air cleaner and pull out the adjustment screws and the metering rods and spray carb cleaner in the bleed holes etc. and then compressed air without taking everything apart but its usually a temporary fix. Id try that first if it were me just because its simple. If theres trash in the main jets or fuel passages it will likely take more work. Also if water gets into any of those passages the carb wont draw fuel either.

[rbagley]

Originally Posted by Oldtruckfanatic

If the bowl has fuel in it and is staying full but the truck only runs after you pump the gas there is something going on with the air bleeds or main jets. Usually if the filter or pickup is plugged up the engine will run until theres nothing in the bowl. It runs when you pump it because the accelerator pump sprays the fuel right Into the throttle bore and doesnt rely on air going by a bleed hole to draw the fuel in. I know it sucks but the only real way to fix that is to diasassemble the carb and clear out all the air bleeds and fuel passages with carb cleaner and compressed air. Sometimes if youre lucky you can pull off the air cleaner and pull out the adjustment screws and the metering rods and spray carb cleaner in the bleed holes etc. and then compressed air without taking everything apart but its usually a temporary fix. Id try that first if it were me just because its simple. If theres trash in the main jets or fuel passages it will likely take more work. Also if water gets into any of those passages the carb wont draw fuel either.

Winner winner chicken dinner! I took it all back apart and gave it 110 lbs of air through all the passages. It didn't seem dirty at all when I was in there before, but a blast into the jets sent a cloud of crud into the air. I slapped it all back together and it roared to life (hole in muffler).

[davepl]

Originally Posted by davepl

On a Q-Jet if the filter gets plugged the fuel pressure will push the filter back on its spring and let fuel in "at any cost", including dirty and debris. So it'll run with the filter clogged until more dirt gets in and eventually gets to an important location.

Hey, where's my chicken dinner? I even described how it happened :-)

[Oldtruckfanatic]

Glad you got it running again. Davepl probably nailed how it got plugged up but I have to say I cant remember when the last time I took a Q-jet apart that still had the filter inside the housing was. I always find them empty and a cheap inline right on top of the manifold waiting for the right time to dump fuel on a hot manifold and burn the car down.

[rbagley]

Originally Posted by davepl

Hey, where's my chicken dinner? I even described how it happened :-)

The judges felt like your correct answer was combined with the choke pull off answer, so that worked against you in this particular case. But your hand pump innuendo certainly gets you an honorable mention. Thanks to everyone who gave input. It's nice to have a group of knowledgeable people available when I need it.

[Fitz]

Originally Posted by rbagley

The judges felt like your correct answer was combined with the choke pull off answer, so that worked against you in this particular case. But your hand pump innuendo certainly gets you an honorable mention. Thanks to everyone who gave input. It's nice to have a group of knowledgeable people available when I need it.

Never give a judges job to a weasel!