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Testing for air Leaks in fuel lines...


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As you may know from my previous posting that I have this strange sound like a hoot sound and can watch my fuel pressure drop when it happens. I have completed the fuel tank access door in the truck bed so I full freedom to diagnose any issues. So now I want to blow a small amount of air pressure into the fuel line at the top of the tank to check for leaks in the suction side. Will it do any damage to the vp diaphram or other components if I blow about 10 psi into the fuel delivery lines to check on leaks?I removed the fuel module/ anti slosh tube and found my draw straw partially blocked by the fuel module housing. it was too near the side so part of the plastic housing and was partially blocking the bottom of the draw straw. Also I found the 1/2'' draw straw was cut with a tubing cutter that reduced the I.D. size where cut. So I used a tool to trim a slight bevel to the inside of the DS and got it to a full 1/2''.I cannot find the problem yet with the hoot sound and sudden pressure drop, but want those interested to know I have the intank screens cut out for better flow to the draw straw inside the module.Any suggestions are very welcome... this site provides free Mopar Care for my truck and I appreciate it from all it's members. Nancy Pelosie hands off!

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I have never heard any one mention that it would hurt the vp. So I would not think it would. Might need others opinions on that. You said the ds was cut with a tubing cutter. It should be cut with a slight angle or some notches added so it want suck to the bottom of the tank. Might that be causing your problem?

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I have never heard any one mention that it would hurt the vp. So I would not think it would. Might need others opinions on that. You said the ds was cut with a tubing cutter. It should be cut with a slight angle or some notches added so it want suck to the bottom of the tank. Might that be causing your problem?

That's good thought Dripley. That straw might be at the bottom of the tank. Wish the rain would stop it makes me lazy.
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I agree with Dripley. From what your describing I would say the straw is indeed sticking to the tank. Have you noticed if it is "hooting" at you under full throttle, over large bumps, potholes. Randomly? I'm wondering if there is a catalyst for the hoot so to speak, perfect conditions if you will. What is the duration of the pressure loss?

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It is very sporadic and just momentary. It does it more frequent going up a hill and gettin' on it a little harder. You can watch the pressure gauge bouncing at the same time. I can also get it to do it more frequent on mountain road turns. If you hit a spot with lots of switch backs, it will do it more often even though it's level ground and the tank's half full.

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You have a lot of variables that could be taking place. Since you have easy access to yours I would think the easy resolve is simply to pull the straw, cut it at an angle and that eliminates the suction to the bottom of the tank as your culprit and will make your system function better and as its supposed to. (I may have misunderstood, I thought I read you only cleaned up the improper cut to eliminate the reduction in ID, rather than cutting at an angle which is a small degree of angle by the way, 15*-30* depending on what you prefer, start small) If you still have the HOOT after that, then go see a doctor.....wait test for leaks. You could just pressurize the tank via the filler neck, just be careful as it does not take much to do it. Wrap a shop rag (clean one) around the blow gun connected to the air compressor and fill her up.

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IIRC Moparman has a pic of his draw straw and its not cut an an angle, he cut notches in the bottom of the tube. So even if the tube touched the bottom of the tank, there were "windows" where fuel could still get sucked in.

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