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Old 03-16-2013, 01:29 PM
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Chugs and dies

Guys - I am working with a Chevy 350 in my '63 Avanti and the car was a 'barn find' I've been working on for several months.

I drained the old gas, as it'd been sitting for several years and besides shellac-like consistency which I would expect in really old gas, I didn't see any crud or particles.
Still, I know old gas tanks can harbor lots of junk and I've been changing my fuel filter every few weeks since getting it back on the road.

I've only got about 120 miles on it since replacing the tired old 305 that was in it with a 350 in good shape and a rebuilt TH350 tranny. (I hate automatics) Lately the car has begun dying on me and the frequency is getting shorter and shorter. Now I can't go down my street without it acting as though it's being fuel starved and quitting. I coast the the side, count to 100 and away I go for another 1/2 mile then it dies again.

Could this be my coil? It's an HEI system and I'd be willing to stick a VOM on the right contacts to test it, but I have no clue where to poke and am fully aware I could dispatch myself to the next life with a wrong poke.

Any ideas? I hate to start replacing things i think might be wrong. BTDT.

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Old 03-16-2013, 01:31 PM
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Here's what I see with the top off.
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Old 03-16-2013, 02:06 PM
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It might be the coil, but it sounds more to me, like you said, fuel starvation.....or even flooding. Have you had the carb apart?.......Is the choke opening all the way when its warmed up?
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Old 03-16-2013, 02:50 PM
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I bet you got an open element air cleaner and no heat to your intake!
Cold unheated air plus fuel doesn't stay a vapour in a cold intake.
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Old 03-16-2013, 02:50 PM
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I took the top off the carb yesterday and cleaned some gunk out, but not bad. Good squirt streams when I open the throttle.
Yes, the choke opens all the way on warm-up. :-(
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Old 03-16-2013, 03:33 PM
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Is there any way you can install a "T" fitting in the fuel line after the filter but before the carb, so that you can monitor the fuel pressure?
Could the filter sock in the tank be collapsing and stopping fuel flow?
Do you have an electric or mechanical fuel pump?
Its been my experience that when a coil or ignition module goes bad, it stays bad as if it were a blown fuse. No intermittent operation.
ssmonty

Last edited by ssmonty; 03-16-2013 at 03:46 PM.
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Old 03-16-2013, 04:15 PM
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I had a case where the fuel line rusted out just coming out of the tank and it was sucking air.....acted like that, run a bit then quit...Took a while to figure it out.
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Old 03-16-2013, 04:41 PM
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You can do a remote electric fuel psi gauge to the cabin with a sending unit.

The mechanical you can mount on the hood. A universal 52mm pod is $9 on *bay . It mounts to the hood with 3m double sided tape.

A mechanical you can line to the cabin and it will work, but it is a fire hazard.
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Old 03-16-2013, 04:57 PM
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Guys, thanks for the help!
I do have a mechanical pump and have found when the engine starts to chug, I flip it on but makes no difference. Engine still dies.

When I went thru the car, I replaced the fuel line from the tank all the way forward.

Thinking about trying a gravity fed bottle of gas right into the carb. If it still dies, it would at least rule out tank/line/filter crud.
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Old 03-16-2013, 05:18 PM
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"I had a case where the fuel line rusted out just coming out of the tank and it was sucking air.....acted like that, run a bit then quit...Took a while to figure it out." poncho62

I intended to mention something similar in my last post, but I type so slow that I forgot by the time I was "finished". Had a friend with a rubber hose from the tank to the hardline on the frame that was dry rotted and sucking in air. Had bubbles in the clear fuel filter before the carb, and you could just barely smell gas in the rear.
Just a thought. Is the tank vented? Seen something similar when there was no air getting into the tank to replace the fuel leaving(creating a vacuum in the tank). Might try driving a ways gently without the gas cap on?
Still you need to get a gauge on it to know for certain. A gravity feed bottle isn't going to have enough pressure IMO.
ssmonty

Last edited by ssmonty; 03-16-2013 at 05:28 PM.
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Old 03-16-2013, 06:00 PM
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Cut the fuel line near the carb to temporarily install something like these
ZEX Nitrous Tee Fittings NS6685 - SummitRacing.com
Summit Racing® Analog Mechanical Gauges SUM-G3122 - SummitRacing.com
Not too expensive IMO.
ssmonty
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Old 03-16-2013, 06:06 PM
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It certainly does sound like it could be fuel starvation and as was already mentioned about the fuel tank creating a vacuum, due to ether a vented cap that is plugged or if the tank was built with a vent, that is could be plugged. The obvious simple test there is to loosen or take the cap off and if need be cover the filler over with something and have a small hole in it and then drive to see how it responds.

Not that flushing the line from the tank to the engine will show up a pin hole in the fuel tank outlet if you can't see onto the top of the tank, but carefully pressuring the tank up slightly with compressed air while the line is off before the pump and another section of line connected to route into a pail, then shoot in some air { a simple smooth wood block large enough to cover the fuel filler and a hole drilled in the center for the air gun to press into } and you should be able to get a decent volume of fuel to flush through the line and if not, that would be telling. One has to be careful doing that as after all a fuel tank could be distorted with much pressure building inside a tank. Although unlikely it is possible something has damaged or kinked your new fuel line, even a twist/kink put into it near the fuel tank before it was reinstalled and with time it would soften and collapse on itself causing a bad restriction that fuel pump vacuum would easily collapse.

Had you checked your engine oil level just in case the diaphragm of the mechanical fuel pump is failing and trying to fill your crank case with fuel ?
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Old 03-16-2013, 07:34 PM
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I remember once having a 51 Stude die after a short while and found the filler cap wasn't venting. Big woosh when I took it off. drilled a pin hole in the cap and that fixed it.

This Avanti tank has a rubber hose to 'nowhere' for venting - pulling in air as the fuel goes out. I replaced the old hard hose when I was checking things out there, before all this started.

Can't hurt to run the car without the filler cap, in the garage. Will try it.
My carb is an Edelbrock 1407 (4V) and I could put a pressure gauge at the inlet. Also wouldn't hurt.

Thanks so much!
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Old 03-16-2013, 09:30 PM
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Ok so it is a vented style and so using that suggestion of air applied into the tank would just blow air out of the vent pipe if its not restricting so that test will confirm your vent is working properly. If you can access the vent line, you could clamp it flat to do the fuel flush from the tank forward. I've also had an issue where I performed that and had fuel come out before the fuel pump and yet had the unit starving for fuel when under load { large gasoline truck } and finally out of frustration decided to blow back through the line from the engine after pulling the cap off the tank and whatever it was that was partially blocking the line must have dislodged ... never did know what was stuck in the line to be honest.

I don't know if I caught that right before or not but I would be tempted to hook up a known good electric fuel pump that is pressure regulated directly to the carb and rig up a small gas container strapped securely under the hood and go for a test drive.

By any chance would it be possible that a piece of rubber hose for instance could have come off from inside the fuel line after your inline filter and now be partially plugging the fuel inlet or jambed into the carb body before the float valve. Typically if something is holding the float valve open then it may starve for fuel under load but then flood the carb when at idle. I've also had it where a float needle isn't sliding freely in its bore and isn't opening up far enough but usually that's a problem off the start in using a carb that hasn't been run for a long time and not after driving it the distance you have so far.
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Old 03-16-2013, 11:17 PM
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Whatever it is, it has become 'chronic'. :-) Getting worse. Now my car will fire right up but run only a minute before choking to a halt. I'm going to try shooting that blast of compressed air into the line. If there is a blockage of some kind I'm hopeful it'll dislodge.

Of course, I'll have that knowledge and every time I drive the car, wonder if that dingleberry will find it's way back into my line!
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