Zed Head

I think I saw some of the responses on your other thread. Some of the irritation might come from the fact that you're not including any of the helpful information from the other replies. You're ignoring what's been said and quoting Wikipedia. Maybe you could put some time in to compiling what you've learned so that people see their help being acknowledged. It seems like you'll keep asking the same question until you get an answer that you're looking for. "Describing differences" is very vague. What is the purpose of your question? Maybe someone can help you get their instead of citing differences. Tom Monroe's How To Rebuild Your Datsun Engine book says that the the L20A is a six cylinder engine that was not sold in the USA. There's a difference. The L20B is a 4 cylinder engine. The 1972 FSM shows an L20A as an option for the 240Z though, which seems odd if it wasn't sold in the USA. Maybe Canada got it. I included a picture of the L20A specs. I collected all of this in 5 minutes with my paper book and the internet. If you could do the same, people could fill in the gaps instead of starting from scratch every time you ask. What do you know and what are your sources. Just trying to help you out. Compile what you know and show it.

The 36 psi with pump only (engine not running) shows that the pump and regulator and relays can work correctly. That is actually normal, and is one of the standard tests of the system. But that's with everything cold. One thing you could try to see if it's electrical is to just hard wire the pump directly to battery power. If it works, then you know that you have an electrical problem. I had an AFM problem once, on the road, and used the back window defroster circuit to run my pump. They're conveniently close (two connections at the top of the window), can handle the current and have a switch (the defrost switch). You can run the wires out of the hatch. Or you can find a way to wire it in at the relay. You're kind of at that point where you need to break the problem in to pieces.

You're getting closer. If you could have measured fuel pressure while it was running well, then when it was not, you would know a lot more. Instead of a direct nipple, a T-fitting might have been better, with the gauge left under the hood in a cool spot while driving. If the problem was the fuel pump relay you would have seen low fuel pressure. But even watching the incorrect number on the bad gauge would help. If it shows 20 psi when it's running well, and 20 psi when it cuts out, then you could reasonably assume that it's not lack of fuel pressure causing the problem. The 40 psi is on the low end for maximum fuel pressure but it's close to the spec. for the bypass on the factory stock Nissan pump. Did you get a brand new Nissan fuel pump or an aftermarket pump? The aftermarket pumps typically will reach 90 psi. The Nissan pumps have an internal bypass that kicks in at 43 - 64 psi. I would T that gauge in between the filter and the rail, and take another drive. Take a note of fuel pressure several times while it's running well, then as soon as it cuts out get another. Proper fuel pressure is critical and you just don't have any good data on what it really is when the problem happens. You have to get good numbers to understand what the system is missing.

Makes sense. I see also that sccanf's has an extra D315, right below the burned diode. Missing in yours. Looks like a tough puzzle. I wonder if one of the old Nissan diagnostic testers would help with the project.

You're right, I assumed that the green on the ends was a stripe. There's not enough information in your picture to tell. I wonder if there was enough variation in components that the final parts were chosen based on test results. Add up a bunch of plus tolerances or minuses and maybe the end result is out of product spec. Just a thought. Considering the injector open times are so small, it's incredible that they could build a functional board "solder by number" alone. Who knows.

Interesting that the resistors in the upper left of your picture are different than the ones in Post #21. I have several ECU's that I've collected. I'm going to open them up and see how things compare, so if anyone wants a picture I can get it. I actually fixed one that had the two (or one of the) main injectors go bad by replacing them with my best guess. The failure symptoms, holding the injectors open, seemed to indicate that and I got lucky. I know very little about electronics.

Here's another thread on shift kits that I just came across. Not that a shift kit is necessary, just posting because automatic transmission threads are few. I think it's the same guy. DIY Stage III Shift Kit Installation for S30 and S130 Jatco Autos - Drivetrain - HybridZ

Channeling Occam (actually William - I had to look it up) and Einstein and KISS - are you sure that the throttle blade is opening completely? It's called a throttle for a reason.

The 280ZX drive shaft won't work in a 240Z, the length is wrong, but the 280ZX transmission and differential will work with a 240Z drive shaft. That's probably what you have. Unless somebody had a 280ZX drive shaft cut to fit, which seems unlikely. You can get replacement u-joints at the local parts store (cheap), or MSA or the dealer (expensive). Don't forget that Nissan calls it a propeller shaft. The drive shafts are the two on the sides of the diff.

Lots of detail about the engine but only "stops pulling" on the problem. Not much to go on. Does the tachometer needle do anything odd? Does the engine sound different? Do the RPM continue to rise just a much slower rate? How high can you go in RPM? Also, you don't say if you have a mechanical or electric fuel pump. The mechanical pumps pump more volume at higher RPM and control pressure through a relief valve. The electric may or may not use a regulator. What do you have? And points aren't rebuilt, just replaced, with gap or dwell set when installed. Could be a point gap problem. If the points don't stay open long enough (dwell) you'll get a weak spark. You should probably just do a basic tune-up before buying a gauge.

Is the engine running when the charge light comes on? Or is everything off? The reverse switch just completes a circuit, allowing power to flow through the reverse lamps. Seems like you might have a short somewhere between the switch and the lights, maybe drawing enough current to overload the alternator at idle, or actually shorted through the Charge lamp wire.

The liquid-filled gauges are known to be sensitive to heat. Many have warning labels that say so. But they're cheap and durable. The dry gauges are sensitive to vibration. So really, even though people use them, there is no gauge that is really suitable for long-term use on a fuel rail. It's just too hot and vibrationy. If it were me, I would get another gauge, that's in the right price range, stick it on the rail, and check pressure cold using just the pump. It if reads 36-37 psi, you'll know that the other gauge was bad and you can look for other issues. If it it still won't hold 36-37 psi, then you need to figure out why your new FPR is isn't R'ing. You have a new FPR and a new pump, you should easily see 36-37 psi immediately by turning the key to start with the solenoid wire disconnected. You could also borrow a fuel pressure a gauge and just use it temporarily, in-line between the filter and the rail. Then you'll know if you need to replace your rail gauge.

All we can really say is that three(?) people with FJ707T injectors and headers do not have the heat soak problem. FastWoman said that she remembered an occasional heat soak problem with the FJ3's, so maybe it's just the design of the 707T's versus the standard pintle design. Still unclear. It is interesting though that the big parts stores seem to be narrowing their selection down to that design, in three different brands. Maybe they know something. Need more data. Back to perfect......

I would replace the rail gauge with the new gauge first. I think that your gauge is bad. A quick swap will at least confirm that you have a problem. The gauge before the filter would show if you had a clogged filter (big pressure drop), but the FPR should still take pressure to 36-37 psi with no vacuum hose connected. A clogged filter would just make things take longer but pressure would still get there. The fact that the vacuum hose causes an 8 psi change is normal, the starting point is just off. 36-37 (no vacuum hose) and 28-29 (vacuum hose) psi will be what a good gauge will probably show. Your fuel supply is probably fine and your problem cause is somewhere else. Again, sorry for the bad advice, I just assumed that the pressure numbers reported were good. Should have asked, since I have three gauges of my own that I swap around to the various devices that use them, just to be sure they're all working correctly, because a bad gauge screwed me up for a few months on a bad FPR.

Backfilling with a realization - the Standard brand FJ3 injector has the "normal" pintle valve nozzle. Only the FJ707T has the odd-looking nozzle. Weirdly, the more expensive BWD injector has the odd-looking nozzle, BWD 57519P - Fuel Injector | O'Reilly Auto Parts, and the cheaper one has the usual type, BWD 27519 - Fuel Injector - MFI | O'Reilly Auto Parts In case it matters... Here's another, from Autozone, that appears to have the odd nozzle. It's the only one they sell. Different brand, GP Sorensen. http://www.autozone.com/autozone/parts/GP-Sorensen-Fuel-Injector/1978-Nissan-Datsun-280Z/_/N-ivfvlZ8vd08?itemIdentifier=79726_2390_0_

Many other old car nuts use the GM HEI module in place of their more expensive or outdated ignition modules. If you search the web you'll find a lot to read, and there are a few threads on this forum that describe it's use with the 280Z's. It was developed at about the same time as the ZX module though and has about the same capabilities as far as I can tell. They're both "smart" modules that control current to avoid system overheating. Actually, the 1978 ignition module was also pretty modern, I believe, it did not use a ballast and point gap was specified at ~.040", which is the typical high energy ignition setting. The main advantage of the GM over the 78 Z and the ZX modules is cost, since it is a widely used part. ~$20 versus ~$100 or more. Those three are probably about the same performance-wise. I get the impression though that the ZX distributor with its six point pickup, might be more precise than the Z distributor. There might be other advantages there also. Check by your fusebox. You might have your original 1978 module in place, ready to be re-used.

The stock 280Z modules seem to last about 35 years, and ~100 - 200K miles. So do the ZX modules, change 35 to 30. The GM HEI module is a cheap, reliable alternative. 123ignition has a module in a programmable distributor that apparently is reliable (based on reports from users of the other cars it's used in). What car are you working with, what distributor are you using to drive the MSD (points or reluctor) and how much are you willing to change? The MSD is one of the few external modules designed to be a "bolt-on, wire-in" system. Others, like Crane, work the same way but they appear to use the same general design as MSD. Might even be the same product under a different name. Lots of options. Many will require a distributor change though. Your heat problem might just show a need for a different location for the MSD module.

Actually, I am running now with the pot either completely open (knob stopped out) or a slight resistance. The tension on the knob is high, it's vibration resistant. And the pot is behind the hood release handle in the cabin, so ranges from 60 - 80 F probably. The changes are from outside the pot, I believe, either fuel or 1970's components. Always ready for a new experiment though. Interested to see what happens.

Curious as to what your plan is. Maybe some small adjustable pots in place of resistors, for tuning purposes? I have a 5K taper potentiometer in my car and it is a little touchy, but I've also noticed that the performance seems to change occasionally for no obvious reason. Maybe with tanks of fuel, but hard to tell. I drive my car almost every day and can go a tank or two with out touching the knob, but occasionally I have to add a little fuel to cover a lean spot, or reduce it to change the smell of the exhaust. Who knows, it might also be ECU temperature itself causing some drift, but something is going on.

You've given some good details but not the big picture. Is this car new to you, maybe just arrived, sitting in the driveway and you're trying to get it running? It's never run right for you, or you've had it for a while and this is a new problem? It could be flooding due to coolant temperature sensor circuit problems. When it's cold, the extra fuel is good for starting. Then it runs for a little while until the engine is too hot to use the fuel. Then there's too much fuel on the restart since the engine is warm. There are some tricks that you could probably try with your fuel pump relay, or pinching the fuel supply line, but the best thing to do is the standard advice of "get the FSM and a meter and do some testing". If you have a meter and download the manual, many people here can run you through the circuits to test. IT's not that hard and you'll learn a lot. Test before starting after the two day wait, then test when it won't restart. Something will show up. Unfortunately, the parts are so inter-connected that it's easy to get mis-led. It's rare that someone's first guess is the right one. Fuel pressure testing is also important. FPR's have been known to be affected by heat.

I would go all the way and put a bench seat and column shifter in there. Then you can cruise with an arm free for your passenger. Haha. The residual hoses attached to the radiator imply that it's the stock radiator unless someone was getting fancy with oil cooling. Looks like it was a factory auto car. The typical mod for autos were called "shift kits". I searched the Google and found a few links. Shift kits for auto Zeds Technical Information Page ..... Transmission Jatco Valve Body Shift Kit Installation 3N71B & 4N71B Datsun 240Z VL Turbo - DragTimes.com

Is this a car sitting in the driveway running for a few minutes, or are you driving it around then turning it off? Are there high RPM involved? The ECU's have been known to go bad, though it's not common, and typically die by dumping too much fuel. Either cracked solder joints, or bad injector transistors.

Look at the shift linkage in the Craig's List ad. It's different than later transmissions. People called it "monkey motion" because it felt different when shifting, apparently. I've never tried one. Probably not what you really wanted anyway. Looks like you ended up at the right place. A free 4 speed just for shipping. Can't beat that.

I think that the OP wants a "monkey motion" 4 speed.

The third wire is for the second pickup in the distributor. There's a whole separate circuit in the ignition module to advance the timing when cold. Lots of engineering and work for a small thing that they got rid of later. I just realized that I could have used those wires and junction box for my injector cooling fan and my coolant circuit potentiometer. Three wires in the harness, running from the engine bay to the cabin. Pretty handy.