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Old 11-29-2020, 06:21 PM
TexasJ TexasJ is offline
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Default Fpr bb shim and fuel pressure gauge install question

Hi guys, not sure if this is the right place for this question. If not let me know.

Anyway, I just did the bb fuel pressure regulator shim mod where you put a bb in between the plunger and spring that's located under the 19mm bolt on the driver side of the fuel bowl/fpr housing. Underneath that 19mm bolt there is a schrader valve for testing your fuel pressure. I saw a mod awhile back about removing the schrader valve and using several 1/8 npt fittings to branch off of the area the schrader valve screws into, in order to add in a liquid filled fuel pressure gauge, and then a 90 elbow at the end where you re-attach the schrader valve so you can still hook up a removeable gauge. So basically what you have when you're done is a line comming off of the fpr with 2 branches, one branch goes to the pressure gauge, the other goes to the schrader valve. I did this several months back and put everything together dry, and when I tested it I was leaking fuel from the new brass fittings. Then I used regular plumbers tape and the diesel tore right through that, causing it to still leak. I did some researching online and found that rector #5 was able to be used in diesel applications. So I got some of that and finally got around to trying again today. I thoroughly coated all the threads with it, not too much, not too little. Then I attached everything to the fpr and let it sit for about 30 mins before cranking the engine to test for leaks. When I did, it was immediately clear that every fitting was leaking.

My question is, how much should I tighten these fittings down? I don't want to damage them or warp the threads, so I've been getting them "snug" but not super tight. Is that the reason it's still leaking? Is it just not tight enough? I can't think of anything else. When I remove the whole assembly and just reattach the schrader valve directly to the fpr housing it seals just fine. Even when dry! But it seems no matter what I do these brass fittings continue to leak.
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Old 11-29-2020, 07:32 PM
Patrick Feeley's Avatar
Patrick Feeley Patrick Feeley is offline
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Location: Tehachapi, CA
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They are probably all tapered pipe threads. You can tighten them down pretty hard except for the fitting going into the regulator housing. If you tighten that one too much, you will crack the housing. Use some pipe dope or tape rated for the fuel/oil. Cheers!
1997 F250 SC 4x4, E4OD, 4.10 LS, Basically Stock, Relocated Block Heater Plug, External Trans Filter, Tru-Cool Max, I/C Mounted but not Plumbed

SOLD - 1994 F350 CC DRW 2WD PSD, 5 Speed, 4.10 LS, SBC Con-O, Baldwin Filter, Tymar HPX Hose, DPPI DP, Bilsteins, $12 AIC, Coolant Filter, Explorer Overhead Console, A-Pillar w/ISSPRO Black Ice, EV Boost, and EV Pyro, Modified Pedestal, Gutted EBPV.
Old 12-03-2020, 02:50 AM
TexasJ TexasJ is offline
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Thanks for the reply! I pulled all the fittings apart and cleaned the threads, then re applied the rectorseal #5 (a pipe dope that is rated for diesel) and tightened the brass fittings WAY down. I tightened the one that goes into the fpr housing finger tight, then 2 full turns past that. Thankfully only one fitting leaked, so I tightened that one down quite a bit more and it stopped leaking. I was surprised how much tighter you can get those brass fittings, so that was definitely my issue. Thanks for your reply!

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