Starts right up, then falls on its face.

[SteveJ]

I ran through the fsm yes.

Check again. Read the EF section.

From the chart below, taken from the trouble shooting section, it sounds like the AAR, as Captain Obvious suggested. Note that it gives the symptom of "Engine stalls" and several sections to inspect, including the Air regulator system condition. Note 2 below says "Check this item when trouble occurs during warming-up." That sounds like a great place to start. There are also lots of other things it suggests to inspect. Go through the tests. Tell us the results. My guess is that the good Captain or someone else can help you narrow down the culprits if you still can't isolate the problem.

[Zed Head]

The video sounds a little bit like low fuel pressure, from the fuel pump stopping when the key is let go. 78 uses the alternator or the oil pressure to keep the fuel pump running, either one. Maybe your switch is bad and/or the alternator is not kicking in soon enough. Watch your voltmeter and see if it jumps above where it sat before starting.

[z_ya]

I just replaced the alternator like 3 days ago, but this has been happening since I have bought the car it's just something annoying that I'd like to fix. My fuel pump kicks on when the key is switched to on even if the engine is not running the fuel pump is. I'll run through the FSM again just to double check everything.

[siteunseen]

How long since you've changed the fuel filter by the radiator?

[Oiluj]

How long since you've changed the fuel filter by the radiator?

My thought exactly! I alsways like to start with the simple stuff...

[FastWoman]

Nathan, that's how MOST cars used to run back in the day! So instead of getting self-conscious, you might pop the hood, jiggle or tap some random part, try starting (successfully) again, shrug, and say, "Heh... antique sports cars!"

My guess would be fuel rail leak-down as well.

Edited January 8, 2013 by FastWoman

[z_ya]

I just changed the fuel filter, but silly me i forgot to hook the cold start injector after purging it so I guess I will find out tomorrow for sure if that fixed it. And FastWoman, It is normal for my car to need me on the throttle right at start even though it is fuel injected? I do love the antique sports car feel though I love how everyone looks at it and takes pictures of it even though the paint is sun faded an cracked. I love the exhaust note as well I'm extremely happy to own a first gen Z and don't ever see myself getting rid of it. And thanks for all the advice guys I'm still a "rookie" to Z cars and since the closest Nissan dealership is approx. 100 miles away this forum is the next best thing to that.

[SteveJ]

It is normal for my car to need me on the throttle right at start even though it is fuel injected?

No, it is not normal.

[FastWoman]

That's actually how most of the carbureted cars ran. Most fuel injected cars did start and run, without any re-start or throttle-goosing necessary. Both carb and EFI ran great when new/fresh, of course. It's just that it took much more deterioration/wear/tear/time/corrosion/whatever for an EFI engine to get to that point. They were less fussy. Anyway, my comment was meant mostly jokingly.

Only speaking for myself, my car starts and runs at the first turn of the key, regardless of temperature, but its EFI is in unusually good shape for an L-Jet system. Many L-Jet 280s have mysterious hot-restart issues, but even these can be resolved with enough fiddling. Fuel rail pressure leak-down is another really common problem and could be responsible for your initial starting issues.

[Wade Nelson]

Sounds like it's losing fuel pressure.

You need a gauge on a fuel line to tell.

I concur. Before you buy ONE SINGLE PART put a fuel pressure gauge on it and see what's going on. Then you'll be in a position of knowledge to decide what step to take next.

I might point out I waited until I had done 3-4 OTHER things before finally putting a FP gauge on mine, all of which wasted time and $, on a related problem.

[z_ya]

the fuel filter did not fix it. i was suggested the cold start or afm

[FastWoman]

Nathan, go to the hardware store, and buy a cheap water pressure gauge ($5-10 in the well pump section), a brass "T" that it will screw into, and two 5/16" nipples that will also screw into it. Then insert the gauge inline between the fuel filter and fuel rail. The gauge won't be dead-on accurate (being a cheap gauge), but it will be good for monitoring what generally goes on with your fuel pressure. You can leave it permanently installed.

When you shut down the engine, the fuel pressure should remain high, in the neighborhood of 29 psi (36.3 minus 7.something for idle vacuum). It should ideally stay there forever, until you restart the car. Mine will retain pressure for at least a week (the longest I've gone between runs). A tiny bit of leakdown is normal. I think if you lose half of your pressure over a period of maybe several hours, you have a minor problem, or you can at least improve the situation. There's a check valve on the fuel pump that prevents backflow, and there is the fuel pressure regulator that prevents pressure release to the return line. And then all your injectors must also be tight as well.

What you might find with the hot-restart problem (if you have it) is that fuel pressure rises after engine shut-down, as fuel is heated, expands, and (controversially) may become vaporized by the engine heat. (Our engines run at very low fuel pressure and were not designed for modern ethanol gas.) The pressure will rise to 36.3 (?) psi, at which point excess pressure (and fuel) will be spilled to the return line through the fuel pressure regulator. Then the engine will cool, and the gasoline will condense, causing pressure to fall, possibly to a vacuum. At that point air may be drawn into the fuel rail, if there is any leakage in the injectors. Then on startup, your system is injecting air, rather than fuel, and it takes a while for the air to clear. (Or so one theory goes.)

Another hot restart theory is that gasoline in the injector pintle is superheated and flashes to vapor when the injector opens, so less fuel is delivered as a vapor than as a liquid. The situation resolves when the injector is cooled by the vaporizing fuel. You won't see this issue reflected as much in the fuel pressure.

I'm uncertain from your description whether this is a hot restart issue you're describing or just a restart issue. Is the engine hardest to restart maybe a half hour after shutdown and then easier after it's been sitting overnight? If so, then it's hot restart and may relate to fuel pressure leakdown, combined with heat soaking of the fuel injection rail. If it's an ordinary restart issue, then it may simply be fuel pressure leakdown by itself. Either way, the cure involves resolving all of the sources of leakdown. If it's a hot restart issue, you might have some additional success by changing fuel formulations, installing a 280ZX blower (for cooling, not for forced induction), insulating your fuel rail, and/or changing out the aluminum insulators at the base of each injector to the plastic type.

PS the cold start valve is only actuated when the engine temperature is below 50degF.

Edited January 10, 2013 by FastWoman