jeromio Posted January 30, 2002 Share Posted January 30, 2002 Still trying to settle on the fuel lines. I'm going to be using all the stock components from the FBody: fuel pump, regulator, rail - probably even the tank. So, it makes sense to go with the stock fuel line size, 3/8 feed and 5/16 return, right? I don't want to move to the next size up, 1/2 inch, and risk having a pressure drop (need 56psi). The problem is that although I can source 3/8 and 5/16 hardline, no one (that I've found) stocks -5 AN fittings or lines. SO, here's my question: can anybody see a problem with running the same size return as feed, eg 3/8? The other bonus to doing this is that the hardline comes in 25 foot lengths (20 for stainless), and the braided seems to come in 3ft, so I could save myself some dollars and a whole bunch of extra tubing that I wouldn't need (since I only need like 10ft hardline and 18in soft). Quote Link to comment Share on other sites More sharing options...
Guest zfan Posted January 30, 2002 Share Posted January 30, 2002 Actually I think stock was 5/16" but I could be wrong. zfan..Mike Quote Link to comment Share on other sites More sharing options...
jeromio Posted January 30, 2002 Author Share Posted January 30, 2002 On the FBody (Camaro/TransAm)? I'm pretty sure it's 3/8. The stock line on the 240 may be 5/16..... Quote Link to comment Share on other sites More sharing options...
Dan Juday Posted January 31, 2002 Share Posted January 31, 2002 I could not think of any reason a 3/8 return would not work just fine. That's what I did. 3/8 supply, 3/8 return. The only problem I had was determining which was which when I had to connect one of them to the pump. Don't get that wrong. Quote Link to comment Share on other sites More sharing options...
stony Posted January 31, 2002 Share Posted January 31, 2002 not sure where it is but there is a flow formula out there that can determine maz flow and HP of a particular size fuel tubing according to fuel pressure Quote Link to comment Share on other sites More sharing options...
Mike kZ Posted January 31, 2002 Share Posted January 31, 2002 I'm also using 3/8 supply and 3/8 return. The only problem I'm having is keeping the fuel pressure in the line, I'm running fuel injection. So the engine has to turn over a few times until the pressure is back up, unlike a stock system that a half turn of the engine and it starts. Quote Link to comment Share on other sites More sharing options...
Modern Motorsports Ltd Posted January 31, 2002 Share Posted January 31, 2002 "the engine has to turn over a few times until the pressure is back up" Mike, is your EFI wired up so it runs your fuel pump for 2-3 seconds after you turn your key to 'on'? Proflo is designed that way and mine works fine. If it's been a week or more (Xmas)then I just turn my key to on 2 or 3 x's to get it pressurized up. Typical day to day I often don't even wait the 2-3 seconds it would run if I turned to 'start', fires right up. (although my motors never 'fire' as quick as first few months, at that time it's almost zero turnover and it's running...always get's a little longer with hours on the engine (like a 1/2 second or so)). Quote Link to comment Share on other sites More sharing options...
Mike kZ Posted January 31, 2002 Share Posted January 31, 2002 Ya Ross, mine is wired that way. But if I leave it over night then start the car, it takes a few turns of the engine until it starts. If I turn it off then start it again a few minutes later, it starts right away. It looks like the fuel drains back to the tank over night. Any ideas? Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted January 31, 2002 Share Posted January 31, 2002 Are you using like a oil pressure fuel cutout switch (just a thought, I'm not sure if its used on LT1 or injected installs, unfortunately I'm still a carb guy..), is it delaying your pump coming on until it see's pressure? Just a thought. Regards, Lone Quote Link to comment Share on other sites More sharing options...
Mike kZ Posted January 31, 2002 Share Posted January 31, 2002 Ross: If I turn the key on and off a few times it primes, and I have fuel pressure no problem. I guess I was kinda expecting to just turn the key and vroom, a half a turn later and the engine comes to life, like a modern EFI car. Lone: The pump is working normal, I just lose fuel pressure in the line over night. It drains back to the tank. It does have a low oil pressure cut out though. Quote Link to comment Share on other sites More sharing options...
Ray Posted January 31, 2002 Share Posted January 31, 2002 If you need a good source for a set of lines look at Chevy Subs they have a rear tank and long fuel lines and they are 3/8. ...... Quote Link to comment Share on other sites More sharing options...
Modern Motorsports Ltd Posted February 1, 2002 Share Posted February 1, 2002 Mike kZ, I know mine drains back somewhat but to what degree I'm not sure. Have you tried turning your key from off to on 2 or 3x's allowing your fuel pump to run it's 3 seconds each time, to see if that primes your pump long enough to load up the fuel line adequately? If that doesn't solve it or is unsuitable you may want to put a momentary switch in to prime your fuel pump, not an uncommon feature in a custom rod. You may have an existing button/knob you're not using that can be 'cloaked' to serve this function. Or you could source out a check valve for your fuel line or pump which do exist. Quote Link to comment Share on other sites More sharing options...
stony Posted February 1, 2002 Share Posted February 1, 2002 M if the all injection pumps are the same there should be a check valve that keeps pressure in the system for a while. at least this is true with a 89 rx-7 turbo. my 7 would do the same thing your descibing. the book also says injectors may be leaking. and that couple of seconds it take to start the first time is because of the rich condition in the manifold for the first couple of cranks... just guessing here i never did change anything and it never ever gave me any other problems besides needing a couple of cranks in the morning Quote Link to comment Share on other sites More sharing options...
Mike kZ Posted April 15, 2002 Share Posted April 15, 2002 Update!....I fixed the fuel returning to the tank problem. I bought an AN inline one way check valve, it lets fuel go from the tank to engine, but stops the fuel from returning to the tank. Now it starts right up every time. I installed it between the tank and fuel pump, right behind an inline fuel filter. Quote Link to comment Share on other sites More sharing options...
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