tank pressure
12-10-2007, 11:07 AM
#1
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tank pressure
when i remove my fuel tank cap no matter full of diesel of empty it realeases pressure, do we have a hose that is supposed to release pressure, if so mine might be clogged, or is this normal?
12-10-2007, 11:12 AM
#2
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I have never noticed any pressure from mine... I have had my tank out and there is a hose (with a check valve) that vents off pressure... I think it is in there and prevents spillage if the truck rolls over...at least that is what it looks like it does.... something might be clogged...
12-10-2007, 05:21 PM
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Mine used to be very difficult to fill. I never noticed any pressure but I am sure it was there. It would trip the fill hose automatic cut off. It once took me a half hour to get enough fuel in the thing. I took it to a dodge place and they disconnected the inlet hose and freed up the floating ball. They said if it did it again to rap on the assembly until the problem goes away. That was three years ago and I have not had a problem. It is probably caused by gummy fuel.
12-10-2007, 05:35 PM
#7
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Like already said, the tank is vented with a roll-over ball-valve in the vent-line.
If your cap is building pressure, this vent is choked up somewhere.
Actually, what you all are experiencing is more likely VACUUM, rather than pressure.
When the vent gets completely plugged, the engine will run until the tank gets enough vacuum build-up that the lift-pump cannot overide it, thus shutting off the flow of fuel and killing the engine.
If your cap is building pressure, this vent is choked up somewhere.
Actually, what you all are experiencing is more likely VACUUM, rather than pressure.
When the vent gets completely plugged, the engine will run until the tank gets enough vacuum build-up that the lift-pump cannot overide it, thus shutting off the flow of fuel and killing the engine.
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12-10-2007, 06:32 PM
#9
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The picture that BC847 posted is perfect... that "thing" is located on top of the gas tank... It is not easy to get to... about an hour to get it out and another couple to put it back...Be patient ...
12-10-2007, 07:14 PM
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I've seen this a few times. What usually causes this is diesel fuel attracting dirt in the nipple of the vent, eventually clogging it altogether over time. I have had great luck by using a mityvac hand vacuum pump with a brake bleed canister on that port with the fuel cap removed. spray a little penetrating oil in there let it set for a few minutes. Then, pull a vacuum on the port (which happens if there is a problem), most of the time you'll have the vacuum suddenly release and find the gunk in the line or canister. No pulling the tank, problem solved.
12-10-2007, 07:40 PM
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BC847, do you have that big honkin hose as your new fuel delivery? Looks like its' plumbed into the spare bung, yet I see a quick connect next to it. How does the plastic hold what looks like a brass bulkhead fitting? Seems like it would crack to pieces with the vibs of the Cummins? I've been passively trying to plan a clean Holley Blue pump install on the frame at the tank, but I have all plastic lines and dont want to cut 'em to get the pump in there. I want OE looks and durability.
12-10-2007, 07:48 PM
#13
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My fuel system amounts to a piston lift-pump ~ https://www.dieseltruckresource.com/...ad.php?t=93722
That's been modified to provide higher pressure/volume ~ https://www.dieseltruckresource.com/...d.php?t=176472
The plumbing is all 3/8" ID from the actual fuel pick-up in the tank all the way to the IP ~ https://www.dieseltruckresource.com/...d.php?t=151190
I also run the larger fuel filter ~ https://www.dieseltruckresource.com/...6&postcount=16
The fuel plumbing is connected everywhere via AN fittings. The OEM fuel return line is still used in it's original setup. The OEM fuel supply line is now used as the bypass style fuel pressure regulator's return line.
That's been modified to provide higher pressure/volume ~ https://www.dieseltruckresource.com/...d.php?t=176472
The plumbing is all 3/8" ID from the actual fuel pick-up in the tank all the way to the IP ~ https://www.dieseltruckresource.com/...d.php?t=151190
I also run the larger fuel filter ~ https://www.dieseltruckresource.com/...6&postcount=16
The fuel plumbing is connected everywhere via AN fittings. The OEM fuel return line is still used in it's original setup. The OEM fuel supply line is now used as the bypass style fuel pressure regulator's return line.
12-10-2007, 10:33 PM
#14
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Another thing to check is your fuel filler cap. The filler cap should release pressure between 1.5 and 2.0 psi. You might check to see if the cap needs to be replaced.