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EFI Fuel piping for a 931.

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Joined: 27 Sep 2005
Posts: 235
Location: Rockville, MD

PostPosted: Tue Nov 20, 2007 2:56 am    Post subject: EFI Fuel piping for a 931. Reply with quote

Here's how I did my fuel lines on a 931:

Disconnected the hard lines right under the master cylinder. PAIN IN THE GRRR, but it's worth it. You need to remove the intake manifold to do it; I cheated, mine was already off I removed the fittings all the way up to the male fitting. Remove the stock fuel filter and the hard lines running under the windshield. Use 19mm, 17mm, and (I think) 14mm wrenches. A small but grippy pipe wrench or pliers would help, too.

**** DON'T BE LAZY AND REMOVE THOSE LINES AND OEM FILTER. If you run your soft lines from OEM locations, it's only a matter of time before you'll SET YOUR CAR ON FIRE. When you don't HAVE to do it, don't run your lines over the exhaust. I had an Rx-7 which had fuel lines running over the exhaust manifold from the factory, one loose clamp and I had to bring out some marshmallows. Speaking of which, keep buckets of water and fire extinguishers on hand. ****

Anyway. All the way on the other end of the car, where factory soft lines connect to the hard lines, unbolt both female fittings. Remove the line from the feed fitting, but keep a short cut of that hard plasticky return line (right up to the barb) for the return fitting.

You can then simply bolt these up, under the master cylinder. Use lots of twist, esp. on the pressure side, make sure it won't leak.

Feed side has a 5/16 barb fitting. I used about 3 feet of high-pressure hose going up to the intake manifold, then a big inline fuel filter (1999 Nissan Maxima gives you a nice, big filter with 5/16 size fittings). The filter has a couple layers of tape and a home depot hose clamp around it, which clamps it to a L-shaped bracket, which is then bolted to the side of the intake manifold for a nice, solid mounting (use existing bolt holes). Then it's another ~4-5 inches of hose going into Todd's fuel rail.

When you get the rail, make sure that you install both fittings tightly. Use teflon tape (found at Home Depot, for example), it really keeps those leaks away. Point both ends towards the driver's side of the car.

I used an el cheapo ebay fuel pressure regulator with a gauge - amazingly, it works good, despite the cheesy chrome looks. You want to mount it as close to the rail as possible. Mine uses about 2 inches of high-pressure hose, and mounts on an intake manifold nut, with a flange. You'll need to angle it away from the alternator to prevent rubbing.

For the return line, you have three options, all are equally good/bad.

Option A) Like I did it, you leave about an inch of the OEM hose on the barb, and then put the 5/16 line over it. Since it's not a pressurized line, you'll be totally fine - it'll hold, just clamp it down.

Option B) Clean the barb and use a 5/16 to 1/4 inch adapter. More secure, but you get an extra break point in the line. The adapter will also be the most restrictive point, but unless you're running a huge pump, that shouldn't be an issue.

Option C) Probably the best one, you CAREFULLY split the male nut on the line with a dremel, and you fit a 5/16 hose right over the metal line, without using the female fitting with the barb. I considered it, but then got lazy and just used option A. Alternatively, you can just tape/glue the male nut to the line so that it won't rattle.

Finally, you'll get plenty of fuel line cushions from removing the two lines that go around the engine bay. Use them whenever you see a potential for your fuel lines to rub or touch anything. Use zip ties and/or brackets to keep the lines from flopping around.

You'll need about 4 feet of high-pressure 5/16 inch hose, and another ~3 feet of low-pressure hose, same diameter. You'll also need a pressure regulator set to 45 PSI, 8 fuel line clamps, an L bracket, a 2.5" OD clamp, fuel filter for 1999 Maxima, and, of course, the rail and injectors The rail and injector cups you can get from Todd (endwrench), and the cheapest properly sized injectors are 36lb/hr low-impedance injectors from Ford Mustang Cobra Turbo (mid 80's), or the equivalent Turbo Thunderbird. They have brown tops, and they are the right size and shape(DSM injectors won't work, btw). I recommend getting new o-rings and end caps.
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