Terrible fuel economy in my 6cyl Falcon.... tuning questions.... - Ford Muscle Forums : Ford Muscle Cars Tech Forum
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post #1 of 27 (permalink) Old 03-22-2007, 08:09 PM Thread Starter
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Terrible fuel economy in my 6cyl Falcon.... tuning questions....



So my '62 Falcon only gets 8mpg or so. I put in 8 gallons, drove it to work a few times (I work about 2 miles from home) and now its empty. Its so bad I think I have a hole in my gas tank.

I'm assuming that the carb must be running really rich. But the engine runs well and makes good power. And I don't think a carb running that rich would make such a drastic difference in fuel consumption.

Some more info on the engine... best I can tell its a 200. The carb is a Carter of some kind, a YF I think. The engine has a little bit of an exhaust leak at the manifold. I recently installed Duraspark II, the plugs are gapped at .040. The timing is set at the highest point on the marker. The plugs look good, more like its running lean than rich. I haven't done a compression test yet.

Anyhow, I'd appreciate some tuning tips. I'd like to get it running well soon and I'm sort of in a financial bind right now so theres no money for me to get a repair manual.
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post #2 of 27 (permalink) Old 03-22-2007, 08:39 PM
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Terrible fuel economy in my 6cyl Falcon.... tuning questions....

It may sound silly, but do you have a hole in your gas tank?

Or a leak of any kind?
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post #3 of 27 (permalink) Old 03-22-2007, 09:07 PM
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Terrible fuel economy in my 6cyl Falcon.... tuning questions....

Compression test and/or leak down sounds like the order of the day.
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post #4 of 27 (permalink) Old 03-22-2007, 09:07 PM
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Terrible fuel economy in my 6cyl Falcon.... tuning questions....

Compression test and/or leak down sounds like the order of the day.
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post #5 of 27 (permalink) Old 03-22-2007, 09:24 PM
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Terrible fuel economy in my 6cyl Falcon.... tuning questions....

Is your tail pipe really black and sooty? Otherwise you might have someone using your tank for their fuel. Real easy to steal gas from those old cars.
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post #6 of 27 (permalink) Old 03-22-2007, 11:06 PM
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Terrible fuel economy in my 6cyl Falcon.... tuning questions....

yeah.... Those 12-ish gallon tanks on a falcon are easy to take from...

If it is running good with lots of power how can you tune it up any more than that?

Onle last question, you said "it's timed to the highest point on the marker", what do you mean by this?


FE
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post #7 of 27 (permalink) Old 03-23-2007, 02:34 AM
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Terrible fuel economy in my 6cyl Falcon.... tuning questions....

Just what I was thinking Gary. It should be set at 6/8* BTDC, and the idle at about 550 Rpm with automatic.

Erick you can tell by looking at he freezeplugs on the side of the engine, what you have. The 144/170cid engines have 3. The 200cid has 5.

200cid was not available from Ford in 1962, of course somebody may have changed it.

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post #8 of 27 (permalink) Old 03-23-2007, 03:38 AM
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Terrible fuel economy in my 6cyl Falcon.... tuning questions....

You should be getting at least 18 MPG. No way an engine can use that much fuel, it would not be running it would be way too rich. Has to be a leak.

I know the mustang gas gaps... when they fit loose, everytime you step on the gas from a stop, gas sloshes straight out the tank.


Where is your tank filler pipe? Low and in the back? Loose cap? Worn cap gasket?


[ This Message was edited by: Mikes66 on 3/23/07 7:00pm ]
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post #9 of 27 (permalink) Old 03-23-2007, 07:27 AM
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Terrible fuel economy in my 6cyl Falcon.... tuning questions....

Fuel line and/or tank has pin holes rust. Stick your head under the car and smell around. I think someone is steeling your gas or you would see a puddle under the car

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post #10 of 27 (permalink) Old 03-23-2007, 07:40 AM
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Terrible fuel economy in my 6cyl Falcon.... tuning questions....

If it is really dark under there, use a match so you can see what your doing.....
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post #11 of 27 (permalink) Old 03-23-2007, 08:13 AM
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Terrible fuel economy in my 6cyl Falcon.... tuning questions....

I have built 5 inline 6's and never got less than 20mpg. On one I suddenly dropped to 11mpg. I thought someone was stealing gas. It turned out to be a pin hole leak in the fuel line from the pump to the carb. It only leaked with the engine running and sprayed down at the ground. As soon as the engine cut off it stopped so no puddle under the car. Run your hand along the fuel line with the engine running.

Other than that I would have to say someone is draining your tank. I can't think of any adjustments or combination that would drop your mileage that much. If it were that rich you would see a lot of black smoke coming out the tail pipe.
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post #12 of 27 (permalink) Old 03-23-2007, 08:16 AM Thread Starter
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Terrible fuel economy in my 6cyl Falcon.... tuning questions....

Quote:
On 2007-03-23 07:40, Mikes66 wrote:
If it is really dark under there, use a match so you can see what your doing.....
Nice try...

Have you seen my signature?

Anyhow, the fuel lines are very old. And the tank does have some places where the undercoating is peeling off, but the rust in these areas doesn't look like it would leak.

As for the condition of the filler tube and the filler neck, they are low and on the back. The gas cap sits right under the decklid, and theres a 60 deg. bent tube than connects to the tank with a peice of rubber hose as a coupler. The gas cap is probably in terribile condition. The cap fits tight on the filler neck, but I am sure the rubber seals are gone/deteriorated. It could just be evaporation? I haven't seen any sort of ventillation/check valve on the tank. Doesn't gas evaporate and expand when its in an enclosed tank without ventillation?

I can see 4 freeze plugs looking at the side of the motor. I guess theres another one back between the starter and the exhaust manifold, that would be 5 making it a 200. The distributor is next to #1 cylinder on this engine, the 250 has the distributor in the middle of the block, right?

I took the filler tube off the other day and looked down into the tank, the metal inside the tank that I could see looks to be clean and rust free. I'll probably take the sending unit out this weekend and examine it.

Its a distinct possibility that someone is stealing my gas. I might invest in a locking gas cap. I have one on my Jetta and it gets great mileage



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post #13 of 27 (permalink) Old 03-23-2007, 08:24 AM
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Terrible fuel economy in my 6cyl Falcon.... tuning questions....

The gas cap has a built in vent. You must get a real good vented gas cap. For some reason the $15.00 auto parts store vented gas caps don't work like they should.

You can tell, as when you try to open the tank, it re-pressurizes... That is a very bad thing.
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post #14 of 27 (permalink) Old 03-23-2007, 08:30 AM
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Terrible fuel economy in my 6cyl Falcon.... tuning questions....

The Falcon gas tanks and filler necks are designed to NOT slosh out the back on acceleration... I have one

You very likely have a poor neighbor who never needs to go to the gas station or you have a pinhole in the fuel lines or a cracked rubber hose somewhere.

Without 3 other carbs at the same time your Falcon cannot run good and still get 8 MPG.

FE
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post #15 of 27 (permalink) Old 03-23-2007, 09:20 AM
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Terrible fuel economy in my 6cyl Falcon.... tuning questions....

Maybe it's a joke. Next week they will add gas to you car then you'll think your getting WAY better MPG! Stu
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