'59 Plymouth Forum

got my gas tank in last night, didn't leave the shop till midnight. but car is still no go. i put 5 gallons of gas to start it off with, (had to remove air from the line, electric pump was just getting air, started it (no leaks finally, yaeh!) ran it for 5-10 minutes and then drove across the street to the gas station, which ain't the best place in town at midnight , popped the fuel cap (which is new, oreilly's part) and it like to have shot off, it let out a big bpfff as the positive pressure released. i was like okay, and proceeded with putting a few gallons more fuel to verify everything funtioning, and so far, leak free. went to start it, no go. hmmm so i popped the hood, and i could see the fuel filter (which is clear) was dry, whipped out my pocket knife and removed the line, and release of pressure there also. w/ line off turned the key on, but the fuel pump was just sucking air. so given my earlier experience, i ran across the street (about the same time hoolagons where coming out of the woodwork ) to my shop and grabbed my little cheap hand vaccumn pump. sucked the air back up to the filter, turned the key on, let the pump run for a sec, and she fired up. drove her back to the shop and parked her. popped the cap back off, no pressure. checked it at lunch (3:30pm) today and some pressure is built up in the tank again.
maybe running the vehicle stationary let exhaust heat build up and expand the vapor which then made its way to the pump which then cobbled up the works.

my ten million dollar question is, do the factory caps vent both ways? mine only allows air in, has diaphram and will not let vapor out. has any of ya'll had this particular problem?

i also notice that my gas tanks were of different designs, same basic setup and shape but diffenately different critters. i'm glad i had john send me a filler tube also, mine was way different. mine was soldered on, and yall kept talking about an o-ring, which did not make sense to me, but seeing this other tank, i can see what yall r talking about. the original one, had to be soldered. sending units were also different. the way the sheetmetal was stamped, was different. has anyone heard or know if there is any difference between plants that would explain this, or is this possible a different mopar tank or aftermarket unit?--j

Jeremy, the gas cap should be positively vented. Are you sure that it was pressure built up, or vacuum? I would definitely use a different cap regardless. There were several varieties of the '57-'59 fuel tanks, but I have never determined what the reason for this, possibly a different supplier for different assembly plants? ---John

Jeremy and John,

Been their - done that!

I had my gas tank restored by a local company using the "RenU" process. http://www.renugastank.com

It cost about $400 but it has a lifetime warranty.
The tank leaked after the restoration at the sending unit seal because I was using an after-market non-vented cap. The company drilled a small hole through the cap and gasket to resolve the problem. They also dropped the tank again and re-sealed the sending unit at no-charge since they did not discover the non-vented cap originally. I have since found an original vented cap.

I hope this solves all your gremlins (it is close to Halloween ya know)!

Curt in MD

I've experienced too much VACUUM being created in the tank (due to using a non-vented cap), but never as much PRESSURE as you describe.
Sounds like you have an electric fuel pump AND the original mechanical pump. Could one of them be installed backwards? This would explain how the fuel bowl emptied itself........My brother has a Sunbeam Alpine, and turned out the fuel pump lever was installed over the drive cam instead of under it.........
The factory fuel caps in 1959 were vented "both ways"..there was no concern for air pollution and vapor release back then, and air could move freely in and out of the tank. The tank's vent tube was there so a person could fill the tank without getting backsplash ("burp").
I am glad I don't live in YOUR part of town..sounds scary!

P.S. Drill a 1/8" hole thru your O"Reilly gas cap NOW...the tank needs to be vented!

vented both ways, i kinda figured that was probably the case. i removed the cap - before it done damage. (but thanx for the tip anyways roger- i new that kinda pressure couldn't be good!) the cap i have has a valve that will let air in, but not vapor out, i guess so because of some dang epa crap. i dissassembled one today, gutted the valve out, and replaced it with some crank case breather filter material. looks like it was made that way. i think this one should do the trick, will put it on tomorrow (too dang tired today).
just one working fuel pump, the mechanical is disconnected, bought the car with this setup. was still working, and u know what they say, if it ain't broke, don't fix it. so it's still on there, not bad for a 20 year old (or so) universal pump.
i took the car out for a spin friday, had the fuel cap removed, and the car ran perfect, but stopping was a WHOLE 'nother matter. brakes work great when they want to, but every so often, with out warning, the pedal will go to the floor, no braking action sowhatsoever. replaced the m/c 2 times (little or no change). no external leaks. my only other option is the proportioning valve, i know, '59s ain't got em, i have a coubled together braking system out of an 89 diplomat. worked good when i left for cali, something must have deterioated in the couple years she was sitting. anyways, back to my story: car was doing fair, i was taking her easy, i pulled back into the parking lot at work after lunch, carefully checking the brakes 2-3 times as i pulled in to make sure they would work, as i went to pull into the appropiate stall, the pedal went to the floor ! i pumped them brakes like it was a goin' outta style, but no help. well the curb stopped me, kinda. both tires hopped it and were dangling over it, the curb was up to my driver's door. talk about embarrassing , i got my boss to pull my off, since a was sitting on the frame. midway though batmobile stopped moving, both of our tires were smoking (he has a later model ford 1/2 ton). we shut her down, i got out and notice my left wheel was turned sharply, i looked and the other one was still straight! one tie rod later, and a little work, i got the car down and eventually back to my shop which it is currently awaiting brake repair and re-alignment.
it was kind of an expensive, time consuming lunch, but i love being behind that big 'ol wheel! (and i don't regret taking her out, my horrific incedent even being considered) i got several compliments even after/during the curb jumping incident. not so much on condition, but that it is a cool looking car in general. had one guy pull up beside me at a drive thru just say he liked it, and that it reminded him of his dad.
--jeremy

Ah thrills of owning an old car that can only be experienced. I could write a book on all the unintended adventures I've gone on due to things like ruptured wheels cylinders, broken axle clips and grenading spider gears. As long as the car survives (and the organics encased inside), these minor setbacks lead us to new plans ("Since I've got it apart anyway"). Lets face it, some of us can only be happy when a car is complete, if we have another one (or twelve) that isn't.