Slant Six Forum

B150 Fuel Filling Madness
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Author:  Sonic Purity [ Thu Sep 03, 2015 4:05 pm ]
Post subject:  B150 Fuel Filling Madness

Author:  afastcuda1970 [ Thu Sep 03, 2015 11:26 pm ]
Post subject: 

People would often leave the gas caps at the station on older Dodges and would use a red shop towel as a replacement. The shop towels would find their way down the filler neck and cause the problems you have described. I have removed more than 1 shop towel from filler necks.

Author:  Reed [ Thu Sep 03, 2015 11:52 pm ]
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My brother has an 83 Dodge van with a slant six an the plastic gas tank. it ha absolutely no problems filling with gas. It sounds to me like you have a blockage in the vent or fill systems on your gas tank.

Author:  Sonic Purity [ Sun Sep 06, 2015 11:46 am ]
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Reed wrote:
My brother has an 83 Dodge van with a slant six an the plastic gas tank. it ha absolutely no problems filling with gas. It sounds to me like you have a blockage in the vent or fill systems on your gas tank.

Good to know that there’s a similar vehicle with no issues. As i mentioned, it has always been an issue for me since i got the vehicle used, and it seems to be much worse now. There shouldn’t be any difference between a California and Federal back at the filler and tank, should there?

I doubt there’s anything like a shop rag in there, and i’m pretty sure i checked the filler for being clear when i last had the tank out, but at this point, pretty sure isn’t good enough. I’m going to wait until the tank is more empty and open things up again, checking everything from gas cap to tank for the filler, and all vent lines. There’s some kind of vent line way up near the top of the filler pipe (near the gas cap) which i’ve never physically looked at, and it’s time now. I don’t know how to test the rollover valve on the tank to the vent line, but i guess if it is blocked, that could be a/the problem.

This thread is probably going to die until i get the fuel level down and have time to really dig in. I look forward to any additional contributions.


Author:  Reed [ Sun Sep 06, 2015 12:27 pm ]
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I recommend you trace all the vacuum lines under the van and make sure they are clear. Then replace the filters in the charcoal canisters and make sure all the hoses are routed correctly under the hood.

80s era emissions packages for California were an nightmare of hoses. The worst vehicle i ever worked on for this was a 1984 Ford E-150 that had a 351 W with a California High Altitude emissions package. Total spaghetti all over the engine.

Author:  Sonic Purity [ Sun Sep 06, 2015 2:16 pm ]
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Author:  Reed [ Sun Sep 06, 2015 3:25 pm ]
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You may have more stringent vapor recover nozzles on the fuel pumps in California than I do here in Washington State. Heck, in Washington if you go to a gas station on an Indian Reservation or even gas stations in small out of the way areas you can find fuel pumps without ANY vapor recovery systems on the nozzle. I know that on older cars I often have to get the angle of the nozzle just right and only use the slow fill-up speed to get them to work with the modern fuel vapor recovery nozzles.

Have you tried filling it up with a gas can? Does it back up and overflow if you use just a regular emergency gas can?

My 1983 factory service manual for Dodge vans does not give much info about troubleshooting the evaporation control system or the rollover valve. Here is all it says about the rollover valve:

"As fuel evaporates or when thermal expansion occurs in the tank, vapors are metered into the vent hose through the rollover valve. The restrictor is located in the rubber vent hose near the ECS dome mounted on top of the fuel tank. The rollover valve also prevents liquid fuel from entering the vent tube."

I would drop the tank and inspect the rollover valve and the restrictor. If you have access, you can cut a hole in the floor of the van and go in through the top to avoid dropping the gas tank. I owned a 79 Dodge van where a previous owner had done this. Just be sure that you can re-seal the hole to prevent exhaust and fuel vapors from getting in the van.

The rollover valve is the smaller of the two circular things going into the fuel tank. The larger circular thing is the sending unit. I also recommend checking the vent tube for blockage.

Author:  SlantSixDan [ Sun Sep 06, 2015 7:44 pm ]
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Sonic Purity wrote:
Thank you for the advice. I not only traced, but replaced every single vacuum line with silicone hose

Could be part of the problem. Silicone hose is not the correct material for prolonged exposure to gasoline liquid or vapour.

Author:  matv91 [ Tue Sep 08, 2015 6:16 pm ]
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Reading bulletin no. 14-06A-78 August 9 1978 Subject 36 gallon plastic fuel tank Venting and filling. My scaner is broke. Any way under, Slow filling of tank, Bulletin says Filler vent line too long or improperly routed-it sags or kinks allowing fuel to get trapped restricting the air from venting out the filler tube when filling.See illustrations 2 and 4. The filler vent hose conects at top of tank and goes to top of filler hose or tube. Now my guess work. A low spot in line will over time fill up with condensed water or fuel vapor. Sorta liked the trap under kitchen sink.This is what illustration 2 shows. Illustration 4 has a section of vent hose conected to metal tube[brake line]. For a short distance and then back to hose prevent kinks.

Author:  matv91 [ Tue Sep 08, 2015 8:09 pm ]
Post subject:  Rollover vapor seperator valve

From chrysler technical guide. The rollover/vapor valve contains a single check ball,which uses gravity for two functions .Fiure 11-5.[steel ball sorta like in a carb at bottom of accelerator pump well]. With the vechicle upright the weight of the ball seals the lower passage,vapor separator seat. This seals tank pressure until vapor pressure can raise the ball for venting to the canister. The design prevents liqid from passing,thus separating liquid from vapor. If the vehicle rolls over, the ball will block the upper outlet [rollover position seat]. Gravity will hold the ball in position and stop fuel leakage from the tank.

Author:  Sonic Purity [ Mon Sep 21, 2015 6:01 pm ]
Post subject:  B150 Fuel Filling Madness Update

Author:  Reed [ Mon Sep 21, 2015 6:54 pm ]
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I will be anxiously awaiting more findings from you. I appreciate your efforts to make an informed and logical diagnosis of the problem. Keep researching and posting links and findings.

Author:  azray [ Mon Sep 21, 2015 11:26 pm ]
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With the fill tube at the bottom of the tank ,once the fuel rises above the pipe level, all the air in the tank must exit only through the vent . The vent must not be large enough to allow the full volume of nozzle flow to enter the tank, So the fuel is backing up in the fill pipe.

I think it needs a larger vent, or slower fill flow.

I don't think You would have this problem if the fill pipe would have entered the tank at the top.

There should be no restriction allowing air out of the top of the tank vent

Author:  Sonic Purity [ Fri Oct 02, 2015 8:44 pm ]
Post subject: 

I have too much information to put into one post, so get ready for a flurry of posts from me focusing on single aspects of this issue. Hopefully they’ll be easier to read/respond to that way.

Author:  Sonic Purity [ Fri Oct 02, 2015 8:48 pm ]
Post subject:  Rollover/Vent Valve and Line

* I may need to do more thorough rollover valve testing, if i can figure out how to get the valve out of the tank without breaking it.

Lacking testing information, i attempted to test the flow through the valve and a short section of rubber hose to open air (disconnected from the hard line and the charcoal canisters). Here are my assumptions and math:

10 gallons = 1.34 cu. ft., thus 10 GPM flow rate = 1.34 CFM.
My air compressor says it flows at 4.0 SCFM at 40 PSI. I have no information on the flow rate of the standard rubber-tipped blowing nozzle.

4/1.34 =2.985, so basically the air compressor supplies air at 3 times the flow rate of liquid gasoline, or the equivalent of 30 GPM, other than i have no specs on the air nozzle. So the venting needs to bleed all the way down in 3 times the air input time, or less (sooner).

1.34 CFM/4 SCFM @ 40 PSI * 60 = 20 sec. of air input for the equivalent of 10 gallons in a minute.
5 gallons in half a minute would be 10 sec. of air.
2.5 gallons in 1/4 minute would be 5 sec. of air.

I blocked off all other gas tank openings, to only test the flow of this one vent line. Then i used the air compressor to fill the tank with air at 40 PSI for 5 seconds. If the vent line cleared this air in 15 seconds or fewer (3 times as long, since i’m effectively pumping in air at the equivalent of 30 GPM and we only need to clear 10 GPM), all should be well.

    Aside: with only 5 seconds of air, the plastic tank bulged alarmingly. Had it been metal, i could have permanently damaged it.

With the original rollover/vent valve, this took approximately 54 seconds to bleed down to zero air pressure—far too long. The brand-new replacement rollover/vent valve (see below) took far, far longer: i stopped counting at about 155 seconds, and the tank was still not empty (but was slowly venting down).

Conclusion: upon further consideration i don’t think it’s relevant to my issue, and here’s why:
    * The hose and hard line off this valve is 3/16", which will limit flow.
    * The valve (old and new; see below) has built-in restriction, by design. The Stockel book SS Dan has recommended for years shows a .060" orifice (Fig. 5-62, p. 115, 1978 edition).

If anything, the new, working rollover/vent valve may make things worse.
This venting system is necessary and important for the proper operation of the vehicle, but it has no means of flowing anywhere near enough for refueling, which is where i’m having issues.


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