Purs like a kitten...

[FastWoman]

Thanks! Yes, I insulated the fuel rail. I covered it in rubber hose, slit down its length. The small length along the line of injectors has a wide gap, along which I strung the wiring. I wrapped it all up with silicone rubber tape, and I ran the wiring to a pigtail with a 12 pin waterproof connector that connects just under the throttle linkage. The reason for the insulation is that I'm fairly certain my fuel boils on hot days, just after shutting down the engine. It really doesn't take much heat for fuel to boil. I figure this is a way to minimize hard starting -- that and a primer switch.

More pics early next week...

[sblake01]

I never had any of those problems and both my 78 280Z and my 79 810 got better gas mileage than mentioned above. The 810 got 21-24 while the Z got 23-26. Neither of them failed emissions testing during my ownership and ran proprely throughout the RPM range. cozye mentioned wear and I'm wondering if that doesn't have something to do with it. My cars were both somewhat low mileage plus the fact that the EFI parts that replaced were new, never used parts that I purchased from Norm at OEM Surplus back when he still had those parts. So much of what I've read here has to do with trying to adjust or somehow compensate for things that wouldn't be happening if everything was working the way it was designed. And I do see some 'running in circles' as mentioned above and even some overthinking as I mentioned in another thread. I didn't have adjustable pressure regulators, insulated fuel rails, etc. My cars worked fine without those things as they were designed to. I know that's not an asnwer, it's just an observation.

Edited November 5, 2010 by sblake01

[cozye]

I never had any of those problems and both my 78 280Z and my 79 810 got better gas mileage than mentioned above. The 810 got 21-24 while the Z got 23-26. Neither of them failed emissions testing during my ownership and ran proprely throughout the RPM range. cozye mentioned wear and I'm wondering if that doesn't have something to do with it. My cars were both somewhat low mileage plus the fact that the EFI parts that replaced were new, never used parts that I purchased from Norm at OEM Surplus back when he still had those parts. So much of what I've read here has to do with trying to adjust or somehow compensate for things that wouldn't be happening if everything was working the way it was designed. And I do see some 'running in circles' as mentioned above and even some overthinking as I mentioned in another thread. I didn't have adjustable pressure regulators, insulated fuel rails, etc. My cars worked fine without those things as they were designed to. I know that's not an asnwer, it's just an observation.

Yeah, you have some valid points. I feel like I've been running in circles on what seems to be the same issue for weeks. Tonight I will be coming full circle again, jacking the car up and trying to find an intake leak from the bottom. I've tried countless times to find an intake leak on this car, and like fastwoman I have new intake gasket, etc.. I've plugged all the vacuum lines and ruled out any external vacuum leak source. But the truth of the matter is that it sounds like an intake leak, smells like an intake leak, and feels like an intake leak. It's just very frustrating when you bathe the thing in carb spray, do boost tests, smoke tests, etc.. and cant find a darn leak. Especially when you know you just put a new Nissan gasket on. I'm wondering if the EGR plumbing isn't leaking internally some how. I've got a new EGR valve on mine because the old one did have a minor diaphram leak but the plumbing is still the same old rusty cast iron.

Personally I just keep getting distracted by all these other possiblities with the EFI etc.. Last night however, I had my AFM apart "again" and fingered the potentiometer to the best idling position to observe vacuum and listen more carefully. For sure it runs smoother, but I did still notice a slight occasional miss. Also I still couldn't get the vacuum over 17.5 no matter how much fuel I added to the mixture. Considering I've seen threads of guys with 15-20psi less compression than me on the same motor getting 18.5 vacuum, I've got to think that there is still some source of unmetered air getting into the intake system (head or manifold) some how.

Still running in circles.

Check out this copy and paste from another thread:

"This problem was present on a 76 that I just rebuilt. The problem was the valves. A valvejob cleared it up nicely. The N42 head (76 has it) has soft valve seats (unless it's already been rebuilt, but they can still be done wrong...) what happens is the seats sink into the head until they come out of adjustment. the valves can never be adjusted properly in this condition. In the case of the 76 I just finished, the car ran rough until just over 2200 and then ran "fine" up to 5500. I say "fine" because after the rebuild the car runs "awesome". Do what ZuperDave tells you, do a compression test (do it right) do a leakdown test (do it right) then put a vaccum gauge on it and it will tell you a lot about the condition of the car. If it's not eating oil and you've adjusted the timing this is where you are headed. One other thing. One (or more) of the o-rings on the injectors could be covering up the spray patterns if it wasn't installed properly. Or, if you are using an intake manifold gasket without the injector holes in it (has happened before) your car will run like @!#$ too.

"

[Z train]

Mr.Blake-wasn't your 810 a stck car?

[sblake01]

Yes, it was a 5 speed.

[Z train]

Then your milage & mine more or less jive as mine is an automatic

[cozye]

Just FYI fastwoman. I tried another ECU tonight, another AFM and went over my entire intake with propane again and still couldn't not find anything. At this point I've ruled out everything I can think of externally replaceable. Debating on pulling the head off personally.

[Z train]

Cozye-define"occassional miss".

[cozye]

idle stumbles around, you hear a slight popping in the exhaust, but it's not to any particular rhythm like a standard miss. When you drive it, it will stumble and hesitate randomly at lower rpm. There is a video of it in the thread I started over in the help me forum.

[cozye]

fastwoman, any progress? I did leak down testing and ruled out any cylinder head issues. I'm still stumped.

[FastWoman]

I'm still shaking off the trip to see my stepson. I slept in late. Gawd, those kids can drink! Anyway, no progress to report. I'll probably start back in on the car tomorrow.

Cozye, I doubt your issue could have anything to do with the major mechanicals, as your engine runs great if you give it a fuel/air mix it likes. It's got to be something that would impact the fuel/air mixture.

Anyway, my stepson gave me an aluminum beer can, which I did not have , and I'll be re-calibrating the AFM per the Atlantic Z article. I'm convinced that messing with the AFM spring is not the answer. This adjustment will of course make the engine run lean again.

Then I'll be double-checking the entire intake system for leaks by pressurizing it lightly through the throttle body. I'd be very surprised if I found any. Then if I don't find anything remarkable, I'll pull the fuel rail back off and flow test the injectors, which I really should have done in the first place, prior to installation. With that information I should have a better idea what my next step should be. There's a distinct possibility that I simply have the wrong type of injectors. If so, then I'll need to get a correct set or determine whether the set I have can be made to operate correctly under a different fuel pressure. Of course that would mean an adjustable FPR -- cheaper than a new set of injectors, I imagine.

Anyway, I promise I'll post updates and eventually my solution, whatever it is.

[cozye]

Just curious what kind of vacuum you can pull if you richen it up to the best idle? The most I can get is 17 or 17.5 if I richen it up as much as possible. This motor should pull at least 18 or more, so that's why I'm still not convinced it's fuel only.