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Old 02-01-2010, 10:56 AM
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Leaking NPT fittings on fuel lines...

I can't get my Mallory fuel pressure regulator to stop leaking fuel. The thing continues to leak where the fuel feed and carb feed lines connect. The return line and plugs are fine.

I've tried teflon paste and teflon tape with no luck. I've wrapped the tape the opposite direction of the threads -still no luck. I've also swapped out the NPT fittings for different ones.

I'm considering using some Permatex Indian Head Gasket Shellac Compound on those fittings. Any thoughts?

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Old 02-01-2010, 12:58 PM
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Ayuh,... You could Try it,... I'd try #2...

My 1st Guess is, the housing has a fine Crack that leaks after the pressure of the fitting,+ the fuel opens it abit....
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Old 02-01-2010, 01:11 PM
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I have the same problem with my Russell fuel block just weeps constantly.
I have now got an Earls block ready to fit, the outlets on this have rubber O rings.
This one would stop the hassle an Aeromotive piece, this one has male inlet/outlets.
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Old 02-01-2010, 10:10 PM
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What model of regulator are you using, some models use AN fittings not NPT.

Here's the instructions for all of them.

BTW don't use tape...big no-no on fuel lines, causes hung float needles and a fire.
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Old 02-01-2010, 11:41 PM
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I guess I should read the original post twice before answering.........
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Old 02-02-2010, 03:21 AM
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If it isn't the wrong thread like 4-jaw mentioned, I use stuff called yamibond on the base of my 2-stroke motorbike cylinders to prevent leaks. It's amazing how well it works (even with a very slight misalginment of the cases and the engine pressure). You should be able to get it at a yamaha motorbike dealer. I'd be surprised if it doesn't stop your leak. It is fuel resistant.
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Old 02-02-2010, 04:05 AM
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I use regular pipe joint compound most of the time, but the best sealer for that type use is a product called Gasoila, it is made specifically for NPT joints in fuel systems,
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Old 02-05-2010, 07:03 AM
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Thanks guys. This is the $89 Mallory return-style regulator from Summit/Jegs.

Well, I pulled the regulator out again and the threads are pretty bad on the ports that were leaking - and they never really looked that good to begin with now that I think back.

I called Summit, and they sent me a new one because the old one was less than a year old and still had a manufacturers warranty (Summit rocks!). The new one looks somewhat better, but the threads of the new one still had metal shavings in them

I'll go over all the threads and then reassemble it using all new adapters and one of the suggested sealers. Fingers crossed...
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Old 02-05-2010, 07:54 AM
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Every single Mallory product I've EVER used has failed or given me trouble, I won't use ANYTHING with that name on it any more. Maybe Summit would swap it out for the Holley 12-803BP? Lots of V8 S10 guys using them on carbed trucks with the OE TBI pump with no problems,
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Old 02-05-2010, 01:25 PM
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fuel pump ???

i'll assume your running an elect pump... 8 yrs ago when i finished my bucket i had the same problem.. i sent it back for a refund.. went to pep boys and got one off the shelf for $40 bucks.. it puts out 4 to 5psi so no reg is needed... and have never had a problem.. bill
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