rossman Posted February 2, 2012 Author Share Posted February 2, 2012 (edited) A tip I got from a former AP mechanic (now engineer) is to apply a small amount of oil or grease to the sealing faces, torque the joint, back off and re-torque. This process helps seat and seal the joint. Edited February 2, 2012 by rossman Quote Link to comment Share on other sites More sharing options...
Cannonball89 Posted February 2, 2012 Share Posted February 2, 2012 Are you sure that your fittings on your air compressor are sound? That could be the source of your slow leak at this point. Quote Link to comment Share on other sites More sharing options...
rossman Posted February 2, 2012 Author Share Posted February 2, 2012 Are you sure that your fittings on your air compressor are sound? That could be the source of your slow leak at this point. The set-up has a shut-off valve between the fuel system and the compressor. That valve is closed when checking for leaks, essentially isolating the compressor from the fuel system. I've checked every fitting including the gauge and shut-off valve with soapy water. There is no indication of a leak, no foaming, no bubbles, nothing. I guess it's possible the shut-off valve or gauge has an internal leak. The shut-off valve is new but the valve was cannibalized from my tire pressure gauge. Quote Link to comment Share on other sites More sharing options...
Tony D Posted February 2, 2012 Share Posted February 2, 2012 Is the air hot when you put it in the system? PV=nRT if it's even slightly hot or near discharge temperature when put into a low-volume system as it rapidly cools you can loose pressure. Does it stabilise at some point or continue dropping? Put the air in, then not the pressure and walk away for an hour. Note the pressure at 1 hour and again in the morning. If it's truly leaking, there will be a steady drop, to the stasis point... If it's heat it will drop a pound or two, then stay there "forever". Quote Link to comment Share on other sites More sharing options...
rossman Posted February 5, 2012 Author Share Posted February 5, 2012 (edited) So it's loosing < 1 psi/hour when pressurized to ~60 psi. There was one loose fitting and a couple of extrusion marks that weren't removed completely. I've only tested it for approx. 1 hour increments so some of that loss may be due to heat as Tony suggested. Right now it is pressurized to 59 psi. I'll take another reading later this evening or in the morning. The Snoop that I ordered should be here tomorrow. Will Snoop find a leak this slow? Edited February 6, 2012 by rossman Quote Link to comment Share on other sites More sharing options...
Tony D Posted February 6, 2012 Share Posted February 6, 2012 Why don't you check back in a couple of... waitaminit, it's been 19 hours...WHAT was the drop overnight? Hell wait for the full 24 hours and check it a day later, it should be within 0.5psig of where it was after that first hour after it all equalized (assuming it's the same temperature and climactic conditions as yesterday at that time!) Quote Link to comment Share on other sites More sharing options...
rossman Posted February 6, 2012 Author Share Posted February 6, 2012 I just checked it - 32 psi. Quote Link to comment Share on other sites More sharing options...
akeboshi Posted February 8, 2012 Share Posted February 8, 2012 (edited) How did the leak testing go? You will definitely be able to find the leak with the "snoop" leak detecting compound. I leak test with this stuff weekly. I pressuize the system im leak testing to 170 psi for 1 hour and then I vacuum drop test to make sure. If it drops more than 5000 microns in an hour then, I repressurize and do it all again. It never fails! Too bad Im just now reading this, I could have gotten you some snoop for free.... Edited February 8, 2012 by akeboshi Quote Link to comment Share on other sites More sharing options...
rossman Posted February 8, 2012 Author Share Posted February 8, 2012 How did the leak testing go? You will definitely be able to find the leak with the "snoop" leak detecting compound. I leak test with this stuff weekly. I pressuize the system im leak testing to 170 psi for 1 hour and then I vacuum drop test to make sure. If it drops more than 5000 microns in an hour then, I repressurize and do it all again. It never fails! Too bad Im just now reading this, I could have gotten you some snoop for free.... I just got the Snoop today. Testing will resume in the morning... You know you're obsessed with your car when you get up at 4 AM to work on it because you have no other time during the day! Free is always good. I paid $14 with shipping for an 8oz bottle from Amazon. I'll be happy if it helps me find these pesky leaks. Quote Link to comment Share on other sites More sharing options...
akeboshi Posted February 8, 2012 Share Posted February 8, 2012 Good luck with the leak hunting. I would wake up at 4am to work on my car too except I go to bed late and Im too lazy to get up that early. I only get 3 hours a day on wed/thurs/friday myself Quote Link to comment Share on other sites More sharing options...
Tony D Posted February 8, 2012 Share Posted February 8, 2012 I would think Swagelock has some distribution near Seabrook TX! Jeebus... It's probably the best stuff for leak checking there is...you may want to consider a higher pressure to 'induce' leaks. The system you have set up should hold several hundred pounds! Quote Link to comment Share on other sites More sharing options...
rossman Posted February 9, 2012 Author Share Posted February 9, 2012 (edited) Snoop helped find 2 small leaks. One in the fuel system and one of the gauge adapter fittings. I fixed both of those leaks and re-pressurized the system to 75 psi. I check every fitting and hose connection again, twice. There was no indication of a leak. So, I let it sit overnight. Unfortunately it's still losing pressure. This morning it was at 65 psi after sitting pressurized for 7 hours. The next step is to pressurize the system up to 180 psi (compressor maximum) to induce a leak as Tony stated. Should I be worried about the other components like the FPR, injectors and pump at this pressure? I don't want to blow out their seals. Edited February 9, 2012 by rossman Quote Link to comment Share on other sites More sharing options...
rossman Posted February 9, 2012 Author Share Posted February 9, 2012 (edited) I talked with the Aeromotive tech rep today. He did not recommend pressurizing the pump over ~80 psi for fear of damaging the end plates due to their relatively large flat surface areas. He commented that the pressure degradation could be due to permeation thru the rubber hose (Earl's Prolite 350). He also thought that the leak rate was slow enough that I probably wouldn't have any fuel leak issues. Worst case I would need to re-seat the a fitting or two. I'm still skeptical. I'm going to bypass the pump and regulator next go round and pressurize to 180 psi. If that doesn't result in any indications then I'll press on with fuel. Edited February 9, 2012 by rossman Quote Link to comment Share on other sites More sharing options...
Tony D Posted February 12, 2012 Share Posted February 12, 2012 That is a good observation---my statements were based on checking hardline. That is what I thought was being pressurized, I didn't realize there were hoses involved (especially not rubber-based hoses as opposed to Teflon-lined SS-Braided!) Yes, permeation through the rubber is possible. A N2 check would probably be more accurate. The O2 component of "Air" can permeate through the "holes" in rubber hoses, or in some cases be 'consumed' by the rubber in an Oxygenated/Oxidising process. Once the O2 is passivated through interacting with active components in the system (meaning up to 19% of "Air" can be lost!) the pressure drop should be stopped. It's been this long, you may just want to see where the pressure goes over a week's time, or use some N2 for a check to see if you get the same kind of drop. If you have a welding setup, the Nitrogen or Argon would give similar results. There should be no appreciable migration through diaphragms at these pressures with pure Nitrogen or Argon. It may be possible with air, and a 19% volume drop will result in significant pressure loss over the time the migration occurs. Good to see you found more leaks with the snoop, though! With such small system volume though, any sort of migration or seep can cause a significant drop in pressure. If you get it below 5psi overnight, and it can hold steady through a week of sitting I would say you will not have any fuel leaks. Curiously now, did you use Loctite 567 PST on NPT Threaded fittings or Teflon Tape? If you didn't use anaerobic sealants on threaded connections like NPT,ISO fittings and they are not O-Ring sealed my bet is this would be the last place to find your leaks. They will be very small and will only get worse over time. Teflon Tape sucks, the Anaerobic sealants from Loctite work miracles on pesky threaded joints! Press on! Quote Link to comment Share on other sites More sharing options...
Tony D Posted February 12, 2012 Share Posted February 12, 2012 Remember the new oxygenated fuels are eating up fuel lines! Same for air... Might be a stretch, may not be! Quote Link to comment Share on other sites More sharing options...
rossman Posted February 12, 2012 Author Share Posted February 12, 2012 (edited) What I've been referring to as my "fuel system" consists of the following components: Fuel tank with sump at the rear 3/4 NPT to -10 AN 90 degree fitting 5/8" 316 stainless tube to the front of the tank -10 male union Earls -10 ProLite hose with straight -10 swivel seal fittings -10 AN male to -10 ORB fitting Aeromotive fuel filter (100 micron) -10 AN union with 0-rings on each end Aeromotive A1000 Fuel pump -10 ORB to -10 AN male fitting 5/8" stainless tube 180 degree bend -10 male union Earls -10 ProLite Hose with straight -10 swivel seal fittings -10 male union 5/8" stainless tube up the transmission tunnel to the firewall behind the valve cover -10 AN male to -10 ORB fitting Aeromotive 40 micron filter -10 AN male to -10 ORB fitting Earls -10 ProLite hose with one straight -10 swivel seal fitting and one -10 90 degree swivel seal fitting -10 to 1/2" NPT fitting Pallnet -10 Fuel rail with o-ring'd injectors -10 to 1/2: NPT fitting 5/8" stainless tube around the front of the valve cover -10 male union Earls -10 ProLite hose with -10 AN male to -10 ORB fitting Aeromotive A1000 FPR -6 ORB to -8 AN male fitting 1/2" 316 stainless tube all the way back to the front of the fuel tank -8 male union Earls -8 ProLite hose with straight -8 swivel seal fittings -8 to -10 AN male union 5/8" 316 stainless tube from the from the front to the back fuel tank 3/4 NPT to -10 AN 90 degree fitting Fuel tank sump There is about 36" of ProLite hose in the system. I've been pressure testing everything but the fuel tank. Curiously now, did you use Loctite 567 PST on NPT Threaded fittings or Teflon Tape? I used Locktite PST on the threads to the fuel rail, fuel pressure gauge & fuel tank. PTFE tape was used on the temporary test fittings (gauge and valve fittings). There are several fittings to get from 3/4 NPT at the tank fitting to 1/4 NPT at the gauge...all potential leak/permeation sources. Edited February 12, 2012 by rossman Quote Link to comment Share on other sites More sharing options...
Tony D Posted February 12, 2012 Share Posted February 12, 2012 "PTFE tape was used on the temporary test fittings (gauge and valve fittings)." Oh yeah, that will leak! Quote Link to comment Share on other sites More sharing options...
rossman Posted February 12, 2012 Author Share Posted February 12, 2012 Yeah, I may be chasing my tail at this point! Quote Link to comment Share on other sites More sharing options...
rossman Posted April 25, 2012 Author Share Posted April 25, 2012 (edited) This morning I got up under the car with the pump running and FPR set at 43 PSI. There was no evidence of any leaks. The pump hasn't been run for any extended periods of time (>30 min) so I'm going to continue to check. So far so good. Edited April 25, 2012 by rossman Quote Link to comment Share on other sites More sharing options...
rossman Posted April 25, 2012 Author Share Posted April 25, 2012 Also, I ended up replacing the 90 degree machined fittings at the tank with 90 degree bent tube type fittings. The pump was noisy and required higher than normal voltage to maintain 43 PSI. I contacted Aeormotive for help. The tech help guy immediately honed in on the tank fitting and recommended that I change them. The sharp corners created by the intersecting drill bores in the fitting cause cavitation on the intake side which leads to poor pump performance. I changed the fittings to XRP high flow fittings. The voltage is now in spec and the noise dropped noticeably. Quote Link to comment Share on other sites More sharing options...
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