Zed Head

"Primes" usually means that it activates for a few seconds then turns off. Kind of sounding like you might have some fuel pump relay problems. The pump should not get any power until you turn the key to Start or the engine is running. Relay testing is shown in the FSM.

1982 280ZX

Does anybody have the micofiche CD? Might have more drawings.

It's a dilemma. 1976 Fsm Carpartsmanual #20 Nissanpartsdeal 54776

Are you positive that this is real? Seems odd. Still not clear how exactly you blocked off the supply and return lines to the fuel rail. Your problem really sounds like either an FPR that leaks down quickly or a bad check valve in the fuel pump. Pretty common and slow starts in the morning are the symptom. If you didn't get a good seal on your supply and return lines they could still be leaking. In short, sounds like a fuel pressure leak-down problem.

Did you block the CSV? Not really clear what "both hoses" means either. Also, not clear what the problem is. You mentioned a labored start, and a start up time/stutter, and a lower fast idle, but what would you like to be better? You probably mentioned it in another thread, it seems like you've described it before. Can't remember what car you have either. I think that, generally, raw fuel in the intake manifold or cylinders will cause the engine to start up faster. That's what the CSV is for, to squirt a load of raw fuel in to the manifold. Might be that you have a weak spark problem instead. Not sure. Anyway, give fresh description of the problem and something might show.

Start at the battery, then the fusible links, and onward...

That must mean something. At least it gives hope that the pump is good. Get used to poking around with your meter and working from the wiring diagram.

What does "tried" mean? Have you verified that you have a good ground at the pump? You need power and ground to get current to flow through the pump, to make it spin. Sometimes a tap on the pump body will get it spinning if it has power and ground. Might help to put a list together and check things off as you test them. You're kind of jumping around from thing to thing. Being methodical is important for working on these old cars.

The noise in the video just sounded like the starter re-engaging when the engine fired once. Pretty common when having starting problems. You're not really following a good plan. To test your pump, pull the yellow wire from the starter and turn the key to Start. You should hear the pump run. If you have a gauge connected you should see the needle move. If you want to leave the pump running, turn the key on, and move the AFM weight. Ideally you would actually get a fuel pressure number. With a $30 eBay pump it's possible that you won't get full pressure or that the pump will overheat quickly. Who knows. Letting the pump run with a gauge connected will answer that question. It will also tell you if your hoses are connected correctly. Testing the engine with starter fluid is pretty simple, but if you want to save a few dollars, just pour some gasoline directly in to the intake manifold through one of the vacuum ports. It's dangerous, of course, but it's the same method carb guys use, except they pour it through the carb throats. You can also use carb cleaner through a vacuum port.

Maybe you had residual combustion byproducts in the block. Or maybe you just have a small leak that shows on the test, but is not the cause of the gushing. You're trying to assign two separate results to the same cause. Might not be the case.

Check that the other wire, the one that does not have 12 volts, has a good ground. No ground, no spin.

That's some good diagnostic work there. Magnaflux is the typical crack test method, I believe. Looks like they've expanded their methods. Might give you some ideas. https://www.magnaflux.com/Magnaflux I wonder how your engine would have run as a daily driver? Pretty sure I've sen threads about gushing coolant and much discussion about "burping" the engines. Maybe they just had cracked heads. Ouch.

Cylinder pressure pushing gases into the coolant channels would be much higher than coolant pressure the other way. Plus gases are less viscous than water. Interesting problem. Good to have two engines to compare. Here's a thread with some chopped up heads that might show you where a crack or erosion could cause problems. https://forums.hybridz.org/topic/59029-head-cooling-on-cylinder-5-solutions/page/2/

Actually, that guy is showing that somebody didn't install the rotor correctly. It wasn't pressed down far enough and seated. That's a "user error" video, unless 123 installs the rotor before shipping. Then it's a 123 rotor install error. Trust but verify.

The Hybridz guys have lots of stories of breaking things on their modified engines, especially the turbo guys. Knocking/detonation can break things right away, apparently, on these engines. Detonation is one of the main problems they try to avoid. Seems like 123 just needs better instructions and higher quality caps. Stores like this one are what the forum is all about though, aren't they? Save somebody else a headache. Verify timing with a light, don't trust the instructions.

The voltmeter should always work even with the key off. Sounds like you've lost connection through your main fusible link. there's a fuse also but I can't tell which one it is. There's better diagram below this one.

Some people swap in the 3.9 just for better pickup in 1st gear. 4th gear is 1:1 in both transmissions. If the engine is running well you probably won't mind the high revs. I've had my ZX 5 speed with 3.9 on the local freeways at ~60 mph in 4th and it's not bad. Probably won't bother you. You might find yourself starting out in 2nd gear though, with the 3.321 1st gear in the 4 speed. It will be like having a 3 speed.

A hot spot, boiling, creates a vapor pocket. Just like air in the system. Pumping compresses the vapor pocket, just like it compresses an air bubble. Seems plausible.

@Mark Maras it's just a regular distributor with timing control inside. It does all six at once, like moving the breaker plate on a regular distributor. Here's a pretty good review of detonation. Timing, heat, lean mixture...all can lead to detonation. https://www.enginelabs.com/news/detonation-what-causes-it-and-how-to-control-it-using-efi/

I think that lower vacuum when revving is a sign of a leak. At higher air flow the leak gets overpowered. Don't forget the EGR system. It's a known problem.

It's sounding like it might be a detonation problem, from too much advance. Still haven't seen the initial timing, just the instructions for installing the distributor. Seems like a 50:50 fault. 123's instructions aren't clear, but, on the other hand. verifying timing is a basic automotive skill. And the L series engines are known to be detonation prone, so knowing your timing is even more important. One of those live and learn things.

I was thinking the same thing but got distracted when he said it wasn't like brake fade. Boiling and brake fade are different things. Boiling would kill the pressure immediately. I was going to suggest that a brake line might be close to an exhaust pipe or engine part, which might explain why it comes on so soon. Check all of the lines, shield the MC from heat, make sure that the brake fluid is pure and fresh.

Maybe your CSV and/or thermotime switch is drawing too much current. It's on a parallel circuit with Pin 4. Instead of covering Pin 4, maybe disconnect the CSV and thermotime switch. It might delay starting but it should start if that's the problem. I don't have a CSV anymore and my car starts. I usally give it about 5 crank/spins, wait about 30 seconds for fuel to vaporize then start it up. You might also try starting fluid just to see if you have a no-spark or a weak spark or an injection problem. Finally, I just remembered that I had a starting problem once, but it was when things were hot. My EFI relay was fried and opened up when it got hot. So, the EFI and fuel pump relay's are a possibility too.

Pretty sure he describes it in the what will it make video. Tried to find where he talked about timing but my computer sucks for videos. https://www.classiczcars.com/forums/topic/58542-home-built-z-full-video-build/?&page=27#comments