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Discussion Starter · #1 ·
Haven't been back here for awhile, but I wanna pick some brains:

Just picked up an '83 280ZX as a mini-project that I intend to daily in the summer while I build my 'big' project. Fuel in the tank was probably a decade or more old, so I drained the tank. Pump was shot, so I did an in-tank pump mod which works wonderfully. found out the injectors were plugged solid and didn't work anymore, so I figured that while I was replacing them, that I might as well go for the billet rail with pressure gauge and some modern o-ring injectors to simplify things a bit and eliminate the chance of heat-soaking the fuel rail...

Problem is, the car floods like crazy when I attempt to start it. Fuel pressure hits around 38-ish PSI when the pump cycles on, which is nice and healthy, and it settles at ~32PSI when it shuts off, which is no problem. CHTS is reading where it should, and TPS is doing what it should. AFM boots and such, while dry on the outside, still seal.

I'm using the old Ford 190cc orange/yellow top injectors because they were there and I figured "similar flow rate to stock". Thing is, they're high-impedance (saturated) style, and the OEM units, as we know, are low-impedance (peak/hold). I thought this wouldn't be a huge problem since the extra resistance shouldn't fry anything, unlike if you set it up the other way around.

Being an '83, the resistor pack is built into the ECU, so I can't bypass them. All I want is to get this thing to run and stay running without drowning itself. So my question is: Is there really no low-impedance, o-ring style injector out there that's comparable to the stock ones? Am I really stuck with either going standalone (expensive) or back to stock injectors and rail (overly complicated)? Trying to adhere to a budget, here.
 

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honestly dude, I think you should just put in stock 280zx injectors and a stock fuel pump where it belongs. your putting upgrades on things that weren't working to begin with in their original state. for testing and diagnosis purposes, put the stock fuel rail back on any other stock items that may have been removed. put the engine back in its original state (if you can) and start there.... then, and only then, should you go for bigger upgrades. btw, is your car turbo or NA?

Bon
 

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1983 280ZX Turbo
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I'm a big fan of stock parts, and this situation is a reason. With changed injectors and pump, you have no real way of testing against any specifications. I second the vote to go back to stock.
 

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Discussion Starter · #4 ·
I've already confirmed that the pump is fine, and the regulator is doing what it should. Car is an N/A. I'm thinking about going back to the stock rail and injectors, as much as I don't want to deal with hot start problems inherent with that rail design. I chose the injectors I did because they're supposed to be the same flow rate as the stock units.
 

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Devil’s advocate here. How does an aftermarket fuel rail fix the hot start problem? It’ll get cooked just like the oem, or even quicker if it aluminum.

Not sure if it was mentioned yet but what about the possibility of the cold start valve being stuck open or leaking. Fairly easy to check.


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Discussion Starter · #6 ·
The common problem, as had been observed and said many times over the years, the loop-style fuel rail had been known to absorb more heat from the engine because the fuel in the rail has to travel farther around, over the heat source, before returning to the tank, causing a vapor-lock condition on hot-start.

One would then rationalize, then, that the less time the fuel spends in the rail over the heat source, and the straighter the path, the less likely this would happen.

On the subject of the cold-start injector, I temporarily bypassed it altogether, initially, and it still flooded. Hooked it up after and checked, no leaks pressurized.

Threw a set of stock injectors back in (dug around for used ones in a friend's box because mine were toast), and whadya know, it runs. Maybe should have done this from the beginning.

I have plans to do eventual upgrades away from the stock L-Jet system, and I figured that upgrading the fuel rail now would allow me to use more common injectors, prevent the heat-soak issue these engines are known for, and give me more options down the road. I tried using the injectors I did because I figured "hey, 190cc/min,which is what everyone is saying the stock ones are, so they should work, right?" Can you blame me for trying to think ahead?

Thanks for the input, folks. You gave me a good reminder to slow down and take this thing a step at a time.
 

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prevent the heat-soak issue these engines are known for, and give me more options down the road.
I'm sorry dude, but I don't quite understand this.... what known-for heat soak issues are you talking about?
I've been driving L28 powered Z's for twenty years now and I have never ever had a problem with heat soak or vapor lock... like never. I removed the hair-dryer cooler thing from both of my 280zx's and I even drove one of those cars cross country, all the way from Utah to North Carolina.. never had a single heat soak issue. My 76 280z has never had heat soak related issues. My Z31's don't have heat soak issues.

Now I get that this is only my own personal experience, but seriously I've never seen this problem. None of my Z car friends seem have this problem. and I never really ever see posts on here regarding heat soak issues with these engines. From what I understand, heat soak and vapor lock problems tend to occur more commonly on American engine designs. and you know what, I could be totally wrong here or just really lucky with my own cars.

stick with the factory stuff on your Z. your budget and wallet will thank you.
and your car's engine it will run the way it was designed to run and I would be very surprised if you actually ever have a heat soak issue with it.

Bon
 

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Discussion Starter · #8 ·
I've actually had it happen to me on my '76 once. Very hot summer day back in '09. Coolant temps were great but the car was starving for fuel and died on me. Had to park it under an overpass with the hood open for about 15 minutes before it cooled down enough to stay running again. That's when I decided to put vents in the hood. Hadn't a problem since the install.

Now, I can imagine this being one of the reasons why the cars from '77-up had vented hoods, and why the ZX even had the injector cooling fans installed. I guess it all depends on several factors regarding weather/ambient temperature, and how long the car has been driven. I'm just going based on experience and what I've read.

The low-budget thing is for the initial "see if it's worth it" part of the build. Now that I've determined a healthy engine, functioning fuel system, and enough salvageable chassis to justify my time and money, now I can comfortably ease into the project proper.

That said, I'd have preferred running the L-Jet system for a while anyway. The '76 I used to have treated me good outside that incident. Maybe I won't have a day's problem with the ZX, but I was erring on the side of caution.
 

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Yeah. Agreed.
I always thought there was a reason behind the 77 year installing hood vents from then on. Makes sense. My 76 doesn't have them. I have been running turbo on that car and it hasn't had any issue, but that's not to say that it won't. I just wonder if nissan's fuel rail design was really flawed and they never really fixed it. didn't the carbed cars have a lot of issues with heat soak? being their location right above the exhaust manifold?
You know, its funny... after 7 years with hood vents, they went back to ventless hoods on the 300zx (except the induction scoop on the 84/85 turbos) and they all seem to run okay. They must have done something to completely remedy the heat soak issues on that car... new engine, new design, fuel system etc...

as far as the L-jetronic fuel injection goes, I think Bosche made a nice design for the time and it works. its just old technology that's all. I like how Japan opted to use a reliable German design for it. Smart buggers.
good luck in whatever you decide to do on your project. hope you can get it running good soon.

Bon
 

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I can relate to the hot start issue. I run totally stock engine and efi, 93 oct non ethonal gas, and if I drive fast for an extended time, then stop and for about 5-30 min, restarting will sometimes be tricky (in the summer time that is where temps are often 95 plus and humidity is 70% or better). I have ZERO issues if I just pop the hood up for 5-10 min. typically my car starts in a fraction of second cranking, I like the bosch L jet tronic system. When every I stop to get gas I pop the hood (good idea anyway, check for leaks oil/water level, just like back in the day). If I park and leave it for over 1 hour I generally do not have restart issues. Cold starts are always perfect down to freezing temps (not much lower as it just does not get too cold in florida).

oh the problem when it happens is long crank times followed with a very rough idle to the point where it barely runs. in about 10-15 seconds it clears up. You can shorten the crank time when this happens by just pressing the throttle wide open during cranking. Generally this take care of the issue if you did not pop the hood. The owners manual covers this procedure.


The build quality of the ECU is impressive, all very high quality parts, NO electrolytic caps to dry out and since its located inside the cabin, no corrosion to worry about. I think the best thing you can do for a Z car is keep it in a good dry garage.

oops I just saw this was for a ZX, My car is a 75 280z
 

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Discussion Starter · #11 ·
Same basic principles, Dave, so don't worry about it. My 75 Project is getting all the new tech, turbo L-series, etc., but this one is probably going to be a much tamer build, overall (some minor mechanical/electrical updates, but mostly cosmetic). I want to make this a relatively stylish daily driver during the summer months, and the N/A L-series is great for that purpose.

Got it running much better today, albeit very rich, but I'll figure it out as I go, I guess. Thanks again for the input, folks.
 
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