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Old 01-13-2014, 05:01 PM   #1
Onlybackroads
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Default Dirty gas?

Hey everyone, I got my first Model A almost a year ago and it's finally on the road, probably first time since the 70's! I was driving the other day and started losing power and backfiring a bunch, I pulled over and cleaned out the sediment bowl and blew out the fuel line, and it ran better but not great (didn't do the carb since I was out on the road.) I ended up barely making it up the hill to my house, had to drive in the bike lane while traffic zoomed right past me but I finally backfired my way into the driveway. The current state of running was a tough idle, with skips, and would backfire any time I got the throttle halfway and above. I could only drive slowly with 1/4 throttle. Also, after I got home I noticed when I turned the car off and looked at the carb, it dripped a few drops of gas out of the intake.

I cleaned my carb, fuel line, and sediment bowl real well, and took it for a drive this morning. The car started right up and idled great, I drove for about a mile and it ran great with no backfires or trouble getting up to speed, and then it started doing the same thing again, rough idle at stoplights and only being able to drive at 1/4 throttle before backfiring.

The car was very dusty when we bought it in Visalia, CA, so I'm wondering if there's some residual dust/dirt particles in the tank that are fouling up my gas. When I cleaned the screens there weren't any significantly sized chunks, just a few tiny bits of junk.

Questions:
1. Does this sound like I just have a dirty gas tank?
2. Should I try my best to clean it out, or should I just continue driving the fuel through and constantly cleaning my lines until it goes away?
3. I smelled my oil and there's a faint hint of gasoline, which makes me think when somethings clogged and I give too much throttle, it floods the carb and engine and the unburnt fuel goes into my crankcase, does this sound possible?

Thanks in advance, from someone who is relatively new to mechanics and model a's, this same question may be answered before on here but I figured I'd just ask for answers tailored to my specific questions.
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Old 01-13-2014, 05:10 PM   #2
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Default Re: Dirty gas?

I would say condenser. Also check your point gap. 90% of "carb problems" are electric.

See you in Puyallup?
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Old 01-13-2014, 05:21 PM   #3
William Kelchner
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Smile Re: Dirty gas?

Experienced same problem. Run great for a while and then coughing through the carb, loss of power, idled nice but any throttle input was a no go. Creeped home riding the clutch, rollback, taking sweet to the car, etc.

How long has the gas been in your car. Could be a number of the usual culprits--dist condenser, coil, hung float, flooding like you mentioned, debris clogging filter. If you have a Zenith carb did you check the filter?

My problem was traced to a fuel line problem (too long). If your fuel line was replaced prior to all this trouble popping up just disconnect the line at the carb and check the distance between the end of the line and the ferrule, should be 1/8"

Good luck and keep us informed..
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Old 01-13-2014, 05:59 PM   #4
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Default Re: Dirty gas?

Check both ends of the line. It can "bottom out" on either end.
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Old 01-13-2014, 06:11 PM   #5
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Default Re: Dirty gas?

My Roadster had the same gas in it for a little over a year ( 10%ethanol ) was having similar problems , I drained the Tank and the Fuel was dark brown like weak coffee , refilled with fresh fuel and problem solved. may or may not be your problem .
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Old 01-13-2014, 06:12 PM   #6
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Default Re: Dirty gas?

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I did make sure when I replaced my line that the ends were the right length, I have cleaned everything out in the carb including the screen, the fuel i have in it is new within the last month. I just decided to take it for another drive after letting it sit for an hour to see what would happen, it started up just fine, idled good, and drove just fine without backfiring for about the same amount of time, then started over with all of the problems once again. It started when I was cruising down a long flat stretch, I was probably going around 30, but as soon as I got it up to there it just felt like it topped out and then jerked a little bit before I got the pedal to the floor, and when I did put the pedal to the floor it started to bog down so I let off and cruised at 30 for a bit. As soon as I stopped, the idle was off and then I started backfiring while accelerating through the gears. Any thoughts an this segment of my confusion?

Ray, what's going on in Puyallup? By the way, I am flying up to Portland on wednesday, and will be there till monday the 20th for the Portland Old-Time Gathering, we should meet up!
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Old 01-13-2014, 06:50 PM   #7
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Default Re: Dirty gas?

Backfiring through the carb usually indicates a lean fuel mixture. I would double check your fuel flow and also go over the timing again. You have a really great MAFCA chapter in Concord, Diablo A's, consider joining them. I'm sure one of those guys can help mentor you on this stuff, there is only so much that can be diagnosed on the net.
Good luck
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Old 01-13-2014, 07:17 PM   #8
William Kelchner
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Default Re: Dirty gas?

I (we) feel your pain BACKROADS This happened to me on at least four occasions to the point I lost all confidence in the car and finally quit driving it.. Conversely, knowing your chances of making it back home is 50/50at best is part of the A driving experience (at least for some of us).

When we thought we had the problem fixed we would let the car idle in the garage for 30 to 40 minutes purring like a kitten and it would just die.

I know one thing for sure---- trying to make it back to your driveway is full of "come on baby you can do its" and when your destination is in sight the relief of knowing you can summon neighbor support to help push that last half-mile....
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Old 01-13-2014, 07:23 PM   #9
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Default Re: Dirty gas?

If my fuel flow was too lean, why would it be flooding at the same time?
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Old 01-13-2014, 07:36 PM   #10
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Default Re: Dirty gas?

When it is acting up have you stopped and checked to make sure you have
a good strong spark from the coil?

Bob
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Old 01-13-2014, 07:57 PM   #11
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Default Re: Dirty gas?

Try this thread from a few days ago. Similar symptoms discussed here:

http://www.fordbarn.com/forum/showthread.php?t=128291
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Old 01-13-2014, 08:08 PM   #12
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Default Re: Dirty gas?

Quote:
Originally Posted by Onlybackroads View Post
If my fuel flow was too lean, why would it be flooding at the same time?
Maybe some crud stuck the float valve open?
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Old 01-13-2014, 11:17 PM   #13
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Default Re: Dirty gas?

I am sort of a newbie, but when it starts to lose power, pull over and open up the gas cap. The vent in it may be plugged, not allowing proper flow. Leave it loose and try driving it under heavy throttle. If it is the vent, you may even hear a "whoosh" when you open the cap. Good luck
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Old 01-13-2014, 11:23 PM   #14
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Default Re: Dirty gas?

Radiator cap on the gas tank?
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Old 01-13-2014, 11:44 PM   #15
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Default Re: Dirty gas?

I made sure the vents were open on my cap. One thing, my coil wire going into the dist. cap is pretty loose, I'll try tightening that up tomorrow, maybe zip tie it on there so it's on good and tight. A local "model a guru" told me he thinks it's dirt in my tank, said it should run good at first since the sediment had a chance to settle, then when I drive it, the dirt eventually fouls up again. I don't know if dirt/dust in my tank could really make such a difference, should I keep that as a possibility? I don't see any large particles in my tank, it's fairly clean but it did sit for a very long time before I got it, and there was dust on just about every part under the hood so there's definitely a chance it could have floated into the tank.
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Old 01-14-2014, 12:41 AM   #16
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Default Re: Dirty gas?

If you don't have the small stand up filter in the tank valve I would install one. I use them on my clean tanks just for added protection in case dirt gets in the tank. Some neighbor jerks put dirt and leaves in my mowers and Cub Cadet tanks about 12 years ago.
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Old 01-14-2014, 12:56 AM   #17
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Default Re: Dirty gas?

One thing that has not been mentioned so far, is that it might be a heating issue. This could affect the coil as well as the valves. I had the later issue many years ago on a '29 with B carb, and nothing helped until I heavily dosed it with STP thru the carb and then threw the rest of the can into the oil. Multiple valves had been sticking at operating temp, but were free and fine at cold temps. Go figure !!!
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Old 01-14-2014, 04:40 AM   #18
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Default Re: Dirty gas?

Put in a dirty leg.

http://www.fordgarage.com/pages/kellyshutoff.htm

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Old 01-14-2014, 05:40 AM   #19
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Default Re: Dirty gas?

If you want to do a quick diagnosis.

Simply hook up a timing light to your coil lead and hang the light inside where you can see it while driving.

When it coughs and backfires, you see instantly whether it is spark or other.

Your symptoms are identical to what I had.

Pulled the carb apart 4 times,

It turned out to be an overcharging generator burning the points blue and probably overtaxing the condenser, but I was sure it was fuel.

When it played up, the light flickered wildly.

Wasted a lot of time chasing a non-existent fuel problem.
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Old 01-14-2014, 06:45 AM   #20
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Default Re: Dirty gas?

Quote:
Originally Posted by pooch View Post
If you want to do a quick diagnosis.

Simply hook up a timing light to your coil lead and hang the light inside where you can see it while driving.

When it coughs and backfires, you see instantly whether it is spark or other.

Your symptoms are identical to what I had.

Pulled the carb apart 4 times,

It turned out to be an overcharging generator burning the points blue and probably overtaxing the condenser, but I was sure it was fuel.

When it played up, the light flickered wildly.

Wasted a lot of time chasing a non-existent fuel problem.
Most fuel problems are electrical.
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