Have bandaid but want fix - 39 flathead

[V8COOPMAN]

Originally Posted by 30-9

I am pretty sure your right adileo that gas tanks are vented but can't say with 100% certainty.

Translation........"It probably is, but maybe it ain't"?

DD

[30-9]

well is see a tube running up filler spout so I ass ume that is vent

Just trying to help as it seems only Vic came close to answering adileo inquiry

[flatjack9]

If it was a venting problem, I doubt that the electric pump would clear the problem.

[V8COOPMAN]

Originally Posted by oldskool

have you checked gas cap it should be vented

Originally Posted by 30-9

well is see a tube running up filler spout so I ass ume that is vent

Correct......that is a vent, which works as a vent only IF the gas cap is vented. DD

[30-9]

Ahh see I learned another new thing today thanks - and what is tell tail sign of a vented cap some type of hole in cap? Cause mine has none w the tube along side filler spout

[George/Maine]

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I run a electric pump only ,on my 39 and its been good for the past 4 years.
When I replaced the gas tank near the cap there was some tape and what I found was a 1/8 hole in the small tube, have a locking gas cap from Drakes works good.

[Kube]

Originally Posted by George/Maine

I run a electric pump only ,on my 39 and its been good for the past 4 years.
When I replaced the gas tank near the cap there was some tape and what I found was a 1/8 hole in the small tube, have a locking gas cap from Drakes works good.

That tube with the small hole was 1939 and perhaps some early 1940's as well. As it tended to leak, Ford changed the tube design... no more hole. They changed the cap as well by adding a hole.
Taping over that vent was exactly opposite of what should be... that vent was required for the tank to "breathe". Your Drake cap is vented so that hole is not necessary.

[SofaKing]

There must be vent to the gas tank, otherwise it is difficult to pump gas out of it. If you were able to pump gas out of it without a vent it would eventually collapse due to differential pressure. The cap is the most obvious place to put a vent because it is the highest point open to the tank, but it is not the only possibility in general , non-Ford, specific terms. I will defer to others regarding your Drake cap being vented. The small tube in the filler tube is to prevent splash-back during filling, it may also serve as a vent during normal operation. Checking for leaks , changing filters as previously mentioned seems to be sound advice. If it is not leaking gas at the connections and gaskets with the electric pump on, it seems unlikely, it is sucking air via the mech pump action. The symptoms you describe sound like what others are frequently attributing to vapor lock in threads here on the Barn. A faulty vacuum line to the distributor will not cause the fuel pressure loss you describe. The systems are unrelated and share no direct connection.

Regarding ethanol, and octane. Assuming you are still in the 6-7:1 range its doing nothing for you, but there is no harm. Ethanol has a higher octane rating than gasoline. Service stations receive their fuel by tanker truck, not pipeline. Fuel is sent via pipeline to tank farms. The tank farms have rigid testing and sampling standards for the fuel in the tanks, pipes and pumping equipment. Adding ethanol to a storage tank at a tank farm would introduce contamination problems they won't tolerate. Percentage of ethanol is regulated by the state but is unreliable. I have pumped gas that was a maximum 10% ethanol according to the pump, that tested at 14%. Good luck, please share your results.

[adileo]

Thanks all for your responses, I checked the glass filter to the electric pump and it appears to have rust/crud in it. I have to change this out every 3-4 weeks due to that build up,

Maybe my issue is that. Could it be the manual pump is not strong enough to pull trhough when dirt gets int the way? And turning the elec pump on for short burst, some how clears it out?

If new to this thread read my 1st post as the thread got somewhat side tracked.

[B-O-B]

So what is your problem. RUST & CRUD in the filter !!! PULL the gas tank & clean & seal it or replace it.

[Steves46]

Originally Posted by B-O-B

So what is your problem. RUST & CRUD in the filter !!! PULL the gas tank & clean & seal it or replace it.

I would also recommend replacing the gas line as well.