S2kool Posted March 30, 2016 Share Posted March 30, 2016 (edited) Car is 77 280z So I've been looking into why my fuel pressure drops to 0 after shut down relatively fast from almost instantly to about 30 minuets. After some testing I found that sometimes the stock fpr was stuck open and let the gas bypass into the return and sometimes it would drip slowly taking a bit longer, but ultimately to 0. So I have tried two stock replacements one from autozone and one from Napa, they both let the gas bleed through after shutdown, I know because I removed the return line and used a clear line for the testing, I would prime the fuel pump to build pressure and it will go to 0 in about 15 minuets and I can see the line with gas in it. My question is, are the aftermarket stock replacement ones not supposed to hold pressure at least overnight? My cold start injector and injectors do not leak I have pulled them to observe during the leak down, my fuel pump is new and I have an inline check valve. Thanks! Other than that it runs great, about 30 idle, 40with th vac unplugged. Edited March 30, 2016 by S2kool Quote Link to comment Share on other sites More sharing options...
Pillar Posted March 30, 2016 Share Posted March 30, 2016 I have a 76, and my fuel system has never held pressure after shut-down as long as I have owned it (however I have an original fuel pump that is getting quite tired, so that could be why). It had raised questions for me as well, but all my searching left me with no definitive answer. Some people have claimed that the stock system holds pressure, while others claim that it is normal for it to bleed pressure off. If everything is working properly, and fuel isnt leaking out I wouldnt think there is any reason to worry. You said you had a new pump and that your injectors were not leaking, so if all it is doing is draining back into the gas tank, it is no problem. I will tell you, that my experience (and a lot of others have voiced the same) with the aftermarket "stock" replacement FPRs, is that they are crap. Many people have had them go bad within a year. Mine actually failed within a week, and it could have potentially caused quite a bit of damage if I hadnt caught the problem. The diaphragm between the vacuum (intake manifold) side and the fuel side blew out, so basically my intake manifold completely filled with fuel to the point that it was pouring out of the air filter. It actually flooded 2 of the cylinders as well (which can brake things like piston rings if it is compressed). Luckily nothing on mine broke and I replaced it immediately with an aftermarket FPR. Not trying to say that all aftermarket "stock" units go bad, but just that they seem to be prone to it. I suggest that if you cant get ahold of an actual Nissan factory FPR, that you just go with a decent aftermarket FPR from someone like Aeromotive. Brand new ones can be had for as little as $150 or so for a decent one (which is actually about the price of a factory Nissan unit last I checked). Quote Link to comment Share on other sites More sharing options...
S2kool Posted March 30, 2016 Author Share Posted March 30, 2016 I see, good to know its not just me, well I know it's supposed to hold because my stock fpr will intermittently hold pressure sometimes and will be 20psi for a couple of days, before it completely went out ,but I can't get any of these aftermarket ones to hold for even an hour, which I found to be weird. I need to fix it because I want to see if this helps my heat soak issues once resolved. Quote Link to comment Share on other sites More sharing options...
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