1968 Satellite, fuel tank pressurizes during every drive; blows out J-tube

[cudak888]

I know others have had this problem, and I think I've probably researched this more than Google can handle, but here goes. First off, a picture of my tank from a couple of months ago (when I put the proper lockring on the sender. Yes, I know the vents aren't supposed to be looped):

Here's the problem:

• On a full or just above 3/4 full (4" of air above the gas in the tank still results in the problem) tank, the pressure will periodically build up enough to cause the tank to relieve itself of fuel out the inverted J "candy cane" vent at the end of the tank.

Since then, I read the threads here and at Moparts that indicate that the Spectra repop tanks have their vent tubes inverted. And since this is a Spectra repop tank, I went under the car last week and swapped the vent tube positions inverted from the factory service manual.

Well, it's still pissing fuel out the J tube. Did it three times during a drive on Saturday, and again in the driveway. Mind you, it also has a brand-new non-vented cap.

So far, I've read the following:

1. If you fill the tank to the top at the station, and immediately park the car, it's going to puke fuel out the J-tube, so one should not fill it to the top. Since the tank is still pressurizing enough to blow fuel with the level 4" from the top if not lower, this sounds like denial-of-the-problem bull$hit to me. Especially since it does it while driving as well, not just after parking it following a fill-up (in fact, I haven't even had an occasion for this to happen yet).
2. Drill some 1/8" holes in the non-vented cap. This works to vent the fumes in the tank, but now you have fuel coming out of the 1/8" holes in the cap. So it's not a solution.
3. Don't drill the holes in the cap. Well, based on #2, duh.
4. Ethanol fuels have a higher RVP (Reid vapor pressure), and therefore expand/gas off more than old fuels. According to some documents I've pulled up, E10 fuel expands by 1 PSI more than conventional fuel. So this sounds like hokum too, unless someone can give me a better scientific explanation for it.
5. Later gas caps with vacuum vents only vent inwards to compensate for tank vacuum, not pressure, so this isn't a viable option either (and I don't think it fits).

At any rate, none of these solutions seem to answer the question of how to solve the problem - and I'm sick of driving the car only for it to blow fuel over the shock strut in the back and stink up the interior compartment with fumes until I can barely breath after a 30 minute run back from any car show.

The way I see it, the factory system simply fails to provide a tall enough vent location for the vapor to release.

I'd considered the Tanks Inc. alternative too, but I don't feel like blowing a crap-ton of money and regulating a whole lot of fuel injection baloney down to carb-friendly pressures. Furthermore, I don't even know how their tank vents; could have similar issues.

This said, before I go any further, I wanted to ask/bounce this off the forum:

1. Does anyone have a further solution other than the explanations above? Because this is all I could find. I've plumbed the vent lines to factory spec, and I've plumbed them to Spectra specifications, and neither work.
2. I have a huge suspicion that this venting system is a flawed design from factory - but I also suspect that the folks who drill holes in their cap might actually be on to something. The filler neck is, after all, the highest part of what I believe is a tank with a flawed venting system (unless you have a Charger with the side fill). If so, wouldn't it make perfect sense to modify the factory venting like this?

NOTE: In-tank lines are drawn to reflect the reverse Spectra tank plumbing.

Effectively, the filler neck would be modified to have a hose connection which would run on an external line (P-clipped to the inside framerail) all the way to the front of the tank, which would then feed up to a second vapor tube loop into the trunk. This would omit the J-tube and the need for the corresponding vent in the tank, which would be plugged off. And for the purposes of the actual car (as opposed to the sketch), I'd probably run it on the passenger's side, only because BOTH vents would be defeated if the car were leaning on its left side on a banked bit of road.

Thoughts?

-Kurt

 

[metaldad]

new tank, lines. factory 'correct' vent lines/ routing.
researching the internetz, wound up drilling a 1/16 hole. orientation to 'up', and marked.
problem has ended.
'68 coronet

 

[cudak888]

Did you read the entire thread?

I accept that the hole lets the vacuum out. I don't accept it as a safe or feasible fix.

-Kurt

 

[metaldad]

jah, i did.
your interpetation may work. a drilled hole in a cap is ez, and ez to 'return as found'

 

[cudak888]

jah, i did.
your interpetation may work. a drilled hole in a cap is ez, and ez to 'return as found'

Thanks.

Easy, perhaps. It's also easy to ignore fuel spilling out the back of the car on acceleration when you can't see it or smell it, than it is to ignore it in the driveway.

-Kurt

 

[metaldad]

Thanks.

Easy, perhaps. It's also easy to ignore fuel spilling out the back of the car on acceleration when you can't see it or smell it, than it is to ignore it in the driveway.

-Kurt

if, and IF it is pouring out my drilled hole, my son needs his eyeballs checked because he was following me after i did the deed.
and there is no puddle underneath when parked. up hill downhill, left shoulder, right shoulder.
all the above was present using a non drilled cap.

 

[cudak888]

if, and IF it is pouring out my drilled hole, my son needs his eyeballs checked because he was following me after i did the deed.
and there is no puddle underneath when parked. up hill downhill, left shoulder, right shoulder.
all the above was present using a non drilled cap.

Interesting. Any particular section of the cap drilled, or dead center?

 

[metaldad]

cap goes on, (at least the slant(?)) i bought, up or down. doesnt matter. i chose one spot, that when 'closed', is 'up'. hole is placed so it's up, and cap marked as such. (horror, a sharpie mark)
please let me know, if your vent system works. i think it will. however, i'm not futzing with the filler neck.
this problem of leakage, seemed to be common in late 60's gm's. or at least in the searches i found.
searches here, seemed inconclusive.
if someone else has other ideas, that works, please don't flame me, enlighten me.

 

[metaldad]

and, nice car collection, btw.

 

[Yatzee]

I know others have had this problem, and I think I've probably researched this more than Google can handle, but here goes. First off, a picture of my tank from a couple of months ago (when I put the proper lockring on the sender. Yes, I know the vents aren't supposed to be looped):

Here's the problem:

• On a full or just above 3/4 full (4" of air above the gas in the tank still results in the problem) tank, the pressure will periodically build up enough to cause the tank to relieve itself of fuel out the inverted J "candy cane" vent at the end of the tank.

Since then, I read the threads here and at Moparts that indicate that the Spectra repop tanks have their vent tubes inverted. And since this is a Spectra repop tank, I went under the car last week and swapped the vent tube positions inverted from the factory service manual.

Well, it's still pissing fuel out the J tube. Did it three times during a drive on Saturday, and again in the driveway. Mind you, it also has a brand-new non-vented cap.

So far, I've read the following:

1. If you fill the tank to the top at the station, and immediately park the car, it's going to puke fuel out the J-tube, so one should not fill it to the top. Since the tank is still pressurizing enough to blow fuel with the level 4" from the top if not lower, this sounds like denial-of-the-problem bull$hit to me. Especially since it does it while driving as well, not just after parking it following a fill-up (in fact, I haven't even had an occasion for this to happen yet).
2. Drill some 1/8" holes in the non-vented cap. This works to vent the fumes in the tank, but now you have fuel coming out of the 1/8" holes in the cap. So it's not a solution.
3. Don't drill the holes in the cap. Well, based on #2, duh.
4. Ethanol fuels have a higher RVP (Reid vapor pressure), and therefore expand/gas off more than old fuels. According to some documents I've pulled up, E10 fuel expands by 1 PSI more than conventional fuel. So this sounds like hokum too, unless someone can give me a better scientific explanation for it.
5. Later gas caps with vacuum vents only vent inwards to compensate for tank vacuum, not pressure, so this isn't a viable option either (and I don't think it fits).

At any rate, none of these solutions seem to answer the question of how to solve the problem - and I'm sick of driving the car only for it to blow fuel over the shock strut in the back and stink up the interior compartment with fumes until I can barely breath after a 30 minute run back from any car show.

The way I see it, the factory system simply fails to provide a tall enough vent location for the vapor to release.

I'd considered the Tanks Inc. alternative too, but I don't feel like blowing a crap-ton of money and regulating a whole lot of fuel injection baloney down to carb-friendly pressures. Furthermore, I don't even know how their tank vents; could have similar issues.

This said, before I go any further, I wanted to ask/bounce this off the forum:

1. Does anyone have a further solution other than the explanations above? Because this is all I could find. I've plumbed the vent lines to factory spec, and I've plumbed them to Spectra specifications, and neither work.
2. I have a huge suspicion that this venting system is a flawed design from factory - but I also suspect that the folks who drill holes in their cap might actually be on to something. The filler neck is, after all, the highest part of what I believe is a tank with a flawed venting system (unless you have a Charger with the side fill). If so, wouldn't it make perfect sense to modify the factory venting like this?

NOTE: In-tank lines are drawn to reflect the reverse Spectra tank plumbing.

Effectively, the filler neck would be modified to have a hose connection which would run on an external line (P-clipped to the inside framerail) all the way to the front of the tank, which would then feed up to a second vapor tube loop into the trunk. This would omit the J-tube and the need for the corresponding vent in the tank, which would be plugged off. And for the purposes of the actual car (as opposed to the sketch), I'd probably run it on the passenger's side, only because BOTH vents would be defeated if the car were leaning on its left side on a banked bit of road.

Thoughts?

-Kurt

 

[cudak888]

Yatzee, the forum ate your post.

-Kurt

 

[Yatzee]

Did you ever fill one of those plastic jerry cans with fuel for your lawn mower and leave it outside only to find the sides had bulged out and it spewed fuel vapor at you when you opened it? There's the problem you have but in your case, your filler is low so it's worse as gas sloshes backwards on acceleration or when the cars slanted upwards. All the air pressure in the tank is in front of the fuel ( front and top of the tank )pushing pushing liquid fuel towards the filler. You will notice that most tank vents are at the front/top of the tank.Your looped solution should work rather than drilling the cap providing there is enough volume in the loop for the volume of gas vapors produced at peak. I prefer exterior venting with one way check valves to prevent fumes in the car but these must be used with one way gas caps to alleviate a vacuum build up in the tank as the fuel cools and shrinks in volume. I have seen these types of vents exit in the wheel tubs at the very top. You can actually buy them. If exiting lower in the tubs, you need to make a fairly long and looped steel vent tube in the trunk ( up under the rear package tray, or wherever to do the same thing as a sink trap does - allow condensed fuel to drain back to the tank. 3/8 line is best because if the vent is to small droplets of condensing fuel will have vapor pressure behind them and force them outside the vehicle. By the way, there are check valves ( mounted vertically ) that are specifically for this purpose. Check out Speedway Motors. I have actually seen a pickup truck that had a tank vent hidden inside the rear-most stake pocket. Neat idea. If you do install your looped vent, don't scrimp on the tube diameter for convenience - bigger is better. Another big plus is divorcing the tank from the trunk floor with a thick insulating pad and pay attention to how close your exhaust runs beside the tank. Cool fuel stays liquid, and lets face it, the tank is fairly close to the ground where it's cool unless your on hot pavement.

 

[cudak888]

Did you ever fill one of those plastic jerry cans with fuel for your lawn mower and leave it outside only to find the sides had bulged out and it spewed fuel vapor at you when you opened it? There's the problem you have but in your case, your filler is low so it's worse as gas sloshes backwards on acceleration or when the cars slanted upwards. All the air pressure in the tank is in front of the fuel ( front and top of the tank )pushing pushing liquid fuel towards the filler. You will notice that most tank vents are at the front/top of the tank.Your looped solution should work rather than drilling the cap providing there is enough volume in the loop for the volume of gas vapors produced at peak. I prefer exterior venting with one way check valves to prevent fumes in the car but these must be used with one way gas caps to alleviate a vacuum build up in the tank as the fuel cools and shrinks in volume. I have seen these types of vents exit in the wheel tubs at the very top. You can actually buy them. If exiting lower in the tubs, you need to make a fairly long and looped steel vent tube in the trunk ( up under the rear package tray, or wherever to do the same thing as a sink trap does - allow condensed fuel to drain back to the tank. 3/8 line is best because if the vent is to small droplets of condensing fuel will have vapor pressure behind them and force them outside the vehicle. By the way, there are check valves ( mounted vertically ) that are specifically for this purpose. Check out Speedway Motors. I have actually seen a pickup truck that had a tank vent hidden inside the rear-most stake pocket. Neat idea. If you do install your looped vent, don't scrimp on the tube diameter for convenience - bigger is better. Another big plus is divorcing the tank from the trunk floor with a thick insulating pad and pay attention to how close your exhaust runs beside the tank. Cool fuel stays liquid, and lets face it, the tank is fairly close to the ground where it's cool unless your on hot pavement.

My '71 Mustang has a vent check valve at the center top, and the filler neck has a crude piece of U-channel steel soldered into it's much-higher-exiting fill neck which serves as the vapor escape. Ditto for all Ford products at least up to 1979, as a '79 Lincoln is the newest Ford I've had to drop a tank on. Believe me, the superiority of a center-mounted vent hasn't escaped my observation. But the low filler on the B's still presents a problem not on the Fords.

That said, the factory loop works its way through the trunk, but exits into the framerail without any check valve. Frankly, I think I'd stuff a charcoal canister at the end rather than a check valve, if only so I don't have to run the tube back vertical (and there aren't many vertical places to put the check valve outside the car, only in the trunk).

That said, you have brought to mind something I had been wondering about - whether the factory 1/4" piping would have enough volume to accommodate the gases, and thus allow me just to buy a second factory tube from a forum member and call it done. But from the track record of the tank and your 3/8" recommendation, I have a feeling that some custom lines are in order.

I'm just a bit worried now, as this means I'd have to bend my own 3/8" tube. I don't mind doing it around the tank, but when I try to make a tidy, tight bend, I always kink the damn tube.

-Kurt

P.S.: I'm in Miami. There's no such thing as cool pavement around here.

 

[Yatzee]

My '71 Mustang has a vent check valve at the center top, and the filler neck has a crude piece of U-channel steel soldered into it's much-higher-exiting fill neck which serves as the vapor escape. Ditto for all Ford products at least up to 1979, as a '79 Lincoln is the newest Ford I've had to drop a tank on. Believe me, the superiority of a center-mounted vent hasn't escaped my observation. But the low filler on the B's still presents a problem not on the Fords.

That said, the factory loop works its way through the trunk, but exits into the framerail without any check valve. Frankly, I think I'd stuff a charcoal canister at the end rather than a check valve, if only so I don't have to run the tube back vertical (and there aren't many vertical places to put the check valve outside the car, only in the trunk).

That said, you have brought to mind something I had been wondering about - whether the factory 1/4" piping would have enough volume to accommodate the gases, and thus allow me just to buy a second factory tube from a forum member and call it done. But from the track record of the tank and your 3/8" recommendation, I have a feeling that some custom lines are in order.

I'm just a bit worried now, as this means I'd have to bend my own 3/8" tube. I don't mind doing it around the tank, but when I try to make a tidy, tight bend, I always kink the damn tube.

-Kurt

P.S.: I'm in Miami. There's no such thing as cool pavement around here.

You can go to a local car parts shop and purchase "cupra-nickle" brake line in 1/4, 5/16 or 3/8 . This is copper/nickle tube that's very easy to bend especially if you wrap it around a round object like a large socket secured in a vice. Joining will be done with the appropriate size rubber hose and clamps made for fuel and I prefer the high pressure style clamps with a band and small bolts. I have formed 5/16 line to as fine as a 1/2 inch radius by wrapping it around a socket and 3/8 line to a 3/4 radius. Just buy a short piece and practice a nice smooth bend using the method above and I think you'll be pleasantly surprised. The check valves I mentioned earlier are used because they only open at a certain small pressure otherwise they remain closed and don't vent. I'm sure that you are aware that you can make multiple loops to accomodate the volume of expanded fuel vapors and I have see double and triple vent loops in conceled areas. One installation I saw was loops within loops ( sorta like the old style electric stove burners except long and oblong ) and I bet if it were unwound there would be about 10 feet or more. It was tucked up under the package tray.

 

[wild bill]

I know others have had this problem, and I think I've probably researched this more than Google can handle, but here goes. First off, a picture of my tank from a couple of months ago (when I put the proper lockring on the sender. Yes, I know the vents aren't supposed to be looped):

Here's the problem:

• On a full or just above 3/4 full (4" of air above the gas in the tank still results in the problem) tank, the pressure will periodically build up enough to cause the tank to relieve itself of fuel out the inverted J "candy cane" vent at the end of the tank.

Since then, I read the threads here and at Moparts that indicate that the Spectra repop tanks have their vent tubes inverted. And since this is a Spectra repop tank, I went under the car last week and swapped the vent tube positions inverted from the factory service manual.

Well, it's still pissing fuel out the J tube. Did it three times during a drive on Saturday, and again in the driveway. Mind you, it also has a brand-new non-vented cap.

So far, I've read the following:

1. If you fill the tank to the top at the station, and immediately park the car, it's going to puke fuel out the J-tube, so one should not fill it to the top. Since the tank is still pressurizing enough to blow fuel with the level 4" from the top if not lower, this sounds like denial-of-the-problem bull$hit to me. Especially since it does it while driving as well, not just after parking it following a fill-up (in fact, I haven't even had an occasion for this to happen yet).
2. Drill some 1/8" holes in the non-vented cap. This works to vent the fumes in the tank, but now you have fuel coming out of the 1/8" holes in the cap. So it's not a solution.
3. Don't drill the holes in the cap. Well, based on #2, duh.
4. Ethanol fuels have a higher RVP (Reid vapor pressure), and therefore expand/gas off more than old fuels. According to some documents I've pulled up, E10 fuel expands by 1 PSI more than conventional fuel. So this sounds like hokum too, unless someone can give me a better scientific explanation for it.
5. Later gas caps with vacuum vents only vent inwards to compensate for tank vacuum, not pressure, so this isn't a viable option either (and I don't think it fits).

At any rate, none of these solutions seem to answer the question of how to solve the problem - and I'm sick of driving the car only for it to blow fuel over the shock strut in the back and stink up the interior compartment with fumes until I can barely breath after a 30 minute run back from any car show.

The way I see it, the factory system simply fails to provide a tall enough vent location for the vapor to release.

I'd considered the Tanks Inc. alternative too, but I don't feel like blowing a crap-ton of money and regulating a whole lot of fuel injection baloney down to carb-friendly pressures. Furthermore, I don't even know how their tank vents; could have similar issues.

This said, before I go any further, I wanted to ask/bounce this off the forum:

1. Does anyone have a further solution other than the explanations above? Because this is all I could find. I've plumbed the vent lines to factory spec, and I've plumbed them to Spectra specifications, and neither work.
2. I have a huge suspicion that this venting system is a flawed design from factory - but I also suspect that the folks who drill holes in their cap might actually be on to something. The filler neck is, after all, the highest part of what I believe is a tank with a flawed venting system (unless you have a Charger with the side fill). If so, wouldn't it make perfect sense to modify the factory venting like this?

NOTE: In-tank lines are drawn to reflect the reverse Spectra tank plumbing.

Effectively, the filler neck would be modified to have a hose connection which would run on an external line (P-clipped to the inside framerail) all the way to the front of the tank, which would then feed up to a second vapor tube loop into the trunk. This would omit the J-tube and the need for the corresponding vent in the tank, which would be plugged off. And for the purposes of the actual car (as opposed to the sketch), I'd probably run it on the passenger's side, only because BOTH vents would be defeated if the car were leaning on its left side on a banked bit of road.

Thoughts?

-Kurt[/QUOKurt I have done a number of restorations on older cars. GM (preemtive boo!) and now a 69 RR. On each of these I have used a breather (can get at auto zone) attached to a rubber gasline hose and then attached that to ne of the multiple nipples on the rear gas tank. I make sure to coil the hose and loop and try to get he breather as high up as i can. This works pretty well. on my cutlass (70) i ran this hose all the way to the front of the case, and then attached the breather. the problem as i see it is you have pressure build up and the problem can only be solved by relieving it. anyway that is how i do it. Its not the way the factory did thiings but it works andis simple to install and monitor. Good Luck, Will Bill

 

[Dennis H]

Sorry if I missed anything here, but I fucked with this for years before a solution was found. The vent tube routing in the first diagram for my application is on the passenger side, and as high as the rear shelf was was the key. Non vented cap. Can fill it now with no drips. the most common was parking nose down after fill up. Also, it is a 70 tank on a 69 with an extra nipple due to the supplier Mopar Ed in the Central Valley jerking me around. Capped it.

 

[cudak888]

Ok, my confidence level is up then!

I have a wanted post up right now for the filler neck (I don't want to modify the one in the car at present) and soon as I've secured one, I'll order some tube and get to bending once everything arrives.

-Kurt

 

[moparedtn]

My similar situation ('68 GTX) was solved when I dug into the parts books and found a vented gas cap that fit correctly.
Issue resolved.
I have the two vent tubes in the factory (in the trunk, one of 'em) position.

 

[cudak888]

My similar situation ('68 GTX) was solved when I dug into the parts books and found a vented gas cap that fit correctly.
Issue resolved.
I have the two vent tubes in the factory (in the trunk, one of 'em) position.

Two-way vented cap? Factory part? Aftermarket? Which parts book? Got a pic, if nothing else?

(As you can see, you've got my attention now).

-Kurt

 

[moparedtn]

Two-way vented cap? Factory part? Aftermarket? Which parts book? Got a pic, if nothing else?

(As you can see, you've got my attention now).

-Kurt

Heh, looks like.
Seems like the counter guy and I came up with something off a Ford. Big goofy chrome looking thing. Let me go out in the garage and find the box...