Inside an FPR - the valve

[Zed Head]

Messing around with things and I cut an FPR open, mainly for the mounting bracket, but also to see what the valve looks like. It's a steel tube mated against a steel disc, both highly polished and very flat. You can see how a little bit of crud or even just a hair could cause it to leak.

[Captain Obvious]

Thanks for that pic. That's a cool shot. The only one of these I have is the one on my car or I would have dissected one. Thanks for taking care of this.

I've been working on a fuel presure leakdown issue with my 280 and after fixing a few things I've got it to the point now that it takes about an hour to drop to zero. I've traced most of the remaining leakdown to my FPR and I haven't decided if it's worth trying to make it any better. All I have to do is outlast the temp crest on a hot shutdown day and I think I already have that beat at an hour.

Still bugs me though...

[Zed Head]

Glad you got some value from it. I have an adjustable Aeromotive regulator that leaks down in seconds. It uses a big ~3/8" diameter steel ball in the diaphragm seated on a hole in the aluminum body of the bottom half. Terrible design for sealing. I even tried to fix it by lapping in a better seat in the aluminum but it's impossible. I'll probably sell it to somebody for use with carbs (it has a low rate spring for carb usage). That's what got me interested though.

On your leak-down problem - I have cracked the fuel lines on 280Z's and ZX's in the wrecking yards that I'm sure had sat for months. They were still holding pressure. You might consider buying used Nissan wrecking yard parts. Easy to test the leak-down of the pump check-valve and the FPR with a pair of side-cutters, aka "dikes". Just make sure the cut is pointed the right way, and cover your eyes.

Having a system that holds pressure for days, weeks or months is really nice. That's why I never went back to that Aeromotive FPR even though I'd like to have it to do some fine tuning. Too aggravating.

[superlen]

Zed,

Thanks for the pic. I bought a chiwanese adjustable online but haven't plumbed it in yet. I wondered what the quality might be. Hopefully, it will work out. Wiring a "prime" circuit in would also help out the leak down.

Len

[Captain Obvious]

My original leakdown was like yours... Instant. I traced the majority to a bad check valve back at the fuel pump and a minor leak in one of the lines in the engine compartment. I replaced the check valve (story there that I'll get to hopefully soon) and repaired the leak in the line. That got me to an hour. Prior to that work, I was boiling the fuel in the rail on very hot shutdowns and creating a bubble that needed to pump out before pressure would build in the lines. That resulted in a long cranking time and embarrassment in the parking lot. Now that I've got the leakdown to an hour, I don't have that problem anymore because an hour is long enough to get me past the temperature crest on the hot shutdowns.

So my hot restart issues are conquered, but I'm with ya on the junkyard cars... I've split the fuel line on countless cars in junkyards over the past year and most of them still have plenty of pressure. Some of these cars I know for a fact have been there for months. That tells me that it's certainly possible. And even though I don't really NEED it, since I know it's possible, I want it.

So my FPR isn't anywhere near as bad as your aftermarket Aeromotive, but I know from clamping off the return line that my FPR is the next largest contributor to my leakdown. I get up to maybe ten hours of line pressure with the FPR blocked off. Beyond that, I'll probably go with a fuel pump prime as Lenny mentioned.

[cesar280z]

So what would be a good brand..at least no leaking?