FastWoman

Very interesting... although I looked at the diagram of the damper in the FSM, and it would appear to operate differently from how the little writeup indicated. In the Datsun damper, it's not necessary for the diaphram to be moved by fuel pressure in order for fuel to flow. Maybe a different' design?

Looking at your pics, I see your EFI retrofit. Is that a MegaSquirt system? Please share all your experiences with it. A few of us have been talking about making the conversion. Oh.... And welcome!

Wait a minute, there! There's nothing humble about a 280. No need to make apologetic sounds. Some people prefer the 280 to the 240. You've got fuel injection, which is a wonderful thing when it works right. In fact your '75 has the very FIRST fuel injection in the Datsun lineage, and although it's not the BEST fuel injection, I personally believe the intake system on that year is the prettiest. Also, while the 240 may be a better sportscar, the 280 is a better GT. If you're actually going to drive the thing on a daily basis, as I do, that's a very good thing. Both models (and also the transitional 260) are good machines and good examples of what they are. So be proud! Don't think of your 280 wistfully as a 240 look-alike with different bumpers. Think of it as a 280!

Well, I fall on the side of "rip the crusty old junk out," but it's a matter of preference. If you keep your fusible links, I'd replace with new. You can still get the little things. You can also buy fusible link material to roll your own. In my case it made sense to replace with MaxiFuses because my fusible link assemblies were broken (fractured bases) and just hanging on the end of the wiring harness. I have to say I love my MaxiFuses, but if my fusible link assemblies had started off in good condition, I'd have probably kept them. Darom, do fuel dampers actually get clogged up? I thought that was a pretty trouble-free part. FAIW, I've read on this list where one person had a plugged up metal fuel line and had to replace it. When I was diagnosing my own system, I simply opened it up past the fuel filter and ran the pump. I got plenty of volume, so I was satisfied I didn't have any restriction of flow anywhere.

Yay! You can do it, honest! We'll be here for you.

To be clear, if there's a vacuum in the line to the FPR, and you pinch it, there's STILL a vacuum in the line. You actually have to PULL THE LINE OFF to relieve the vacuum. It's never a bad time to replace old hoses and filters, but I wouldn't replace a fuel pump "just because." It's expensive. First verify that it's failed -- either that it can't support maybe a 45 psi static pressure or that it produces inadequate flow.

Yeah, cold start injector -- possible! Mine was sticking open at one time. Maybe one of the 6 main injectors sticking open and fouling its cylinder? Check all of your plugs to see if any of them are fuel-soaked.

On second thought, that would just throw (a lot of) extra gas into the intake. You'd probably be blowing black smoke out the exhaust.

A ruptured diaphram in the fuel pressure regulator? Pull the vacuum line off of the FPR and see if there's gas in it.

Just a guess, but maybe an electrical specialist could straighten out your instruments and flashers for $500 or so. Or maybe your brother-in-law could help. It would seem a pity to sell a car just because it's got a few electrical issues.

Eric, I'd honestly have said the same thing, except that I've experienced otherwise. Before I got my engine straight, I was scratching my head quite a lot that my engine was backfiring through the intake (suggesting lean), and yet my plugs were quite black (suggesting rich). It turns out that my engine really was running lean to the extent that I had incomplete combustion going on, hence soot, hence black plugs. So at least in my experience, black means rich or extremely lean, and white/chalky means slightly to moderately lean. Weird, I know... and few people are prepared to believe it. BTW, kinking/pinching the vacuum line to the FPR doesn't really indicate much, as there is nothing relieving the vacuum from the FPR. The line has to be pulled off to relieve vacuum on the part.

Nah, don't sell -- unless you really don't like the car, that is. Heck, the electrical stuff isn't all that hard, particularly in a 240. The worst case is that you rip out every wire in the car and start fresh. Many of the connectors can be found here: http://www.vintageconnections.com/ You can substitute non-original styles of connectors in many places, e.g. where one harness plugs into another. If you have no other choice, you can re-use old connectors by snipping the wires and splicing them into your new wiring. Learn to crimp and solder. It's not rocket science -- videos on YouTube. Don't know where do the wires go? Download a free copy of the factory service manual here: http://www.xenons30.com/ I believe you can find wiring diagrams there too. Your car couldn't be much worse than my 1977 cabin cruiser when I bought it. (Note: Large cabin cruisers live in the salt water around here. Wrap your imagination around what the wiring might look like after a few decades.) I rewired the entire boat from bow to stern. It took me about a day.

KD, something suddenly going wonky does sound most likely like something electrical. Yes, it's very common for something to go out suddenly -- to break, as it were. So it might not be a long-term drift problem like Cozye and I experienced with our ECUs. I think I described the yogurt cup test in that long "purs like a kitten" thread. It's simple, though: Simply remove the AFM, and stuff something like a yogurt cup (Yotastic brand worked for me) in the AFM-to-throttle body boot to block off all air flow. Pull the brake booster vacuum line loose, and hook a clean hose (that you don't mind putting your mouth on) to the intake manifold at that fitting. Then pressurize the entire intake system (including crank case, valve cover, and probably a couple of cylinders with open intake valves) by blowing hard into the tube. You might have to hold the cup to keep it from popping out of the boot like a cork. By doing this, you'll be able to feel how fast air leaks out of the entire intake system. Now pull off the tiny vacuum line next to the brake booster line, which runs along the firewall to the opposite fender and feeds the HVAC system. With that fitting open, try inflating the intake system again, and note how fast the air leaks back out. The second time, you are introducing a known leak that is small enough to be of only minor consequence to the fuel/air ratio. If your system is tight, you will notice a substantial difference in air leakage rate between your two tests. Also most of the air you blow into the intake on the second test will shoot right back out of the smaller HVAC fitting. If your intake is not tight, the air will probably leak out quickly either way. If the total of your leakage in the first test is substantially less than the leakage through the HVAC fitting in your second test, then you don't have any vacuum leaks large enough to worry about.

Front right could be an alternator bearing. It does sound like a bearing that's gone south.

Been there, done that. Look for my "purs like a kitten" thread, and dig through it. It seems as though some of these old ECUs drift in their calibrations, delivering shorter pulses to the injectors than they should. You can "fool" them back into proper calibration by adding resistance to the coolant temp sensor circuit. But before you go altering the CTS circuit, make certain your fuel pressure is right. You say you're getting lots of return (healthy pump), and your running pressure is probably about right (30); however, you should pull the vacuum line from the FPR and verify that the pressure increases to 36.3 psi. Also plug the return line and verify that the pressure rises to approx 45 psi or higher (further testing your pump). Then I think you'll have the rest of the story on your pump/FPR situation. Also, to rule out the possibility of any pesky vacuum leaks, perform my "yogurt cup test." If you have any leak anywhere, you'll know it.

Given your backfire (through the intake), blackish plugs, and low fuel pressure, I'd say you're running extremely lean. Of course the question is "why." If I were you, I'd just start going over the system from stem to stern, looking for whatever. It could be any combination of problems, but I'm betting it's more than one -- or even a few.

You're off to a good start up there in Canuckistan. Pretty engine bay.

How bad is "pretty bad?" Does it just have a small hole or two around the rear fenders, or is it a complete basket case, with holes in the floorboards, rocker panels, doors, frame rails, etc. Almost all of these cars have a bit of rust somewhere. The question is, "How much?"

Yeah, not likely the thermotime, if only because the problem presents itself in a warm engine after the engine has been running fine for a while. However, you can't automatically eliminate the cold start valve just by unplugging it. Sometimes these things jam open a bit and dribble/spray fuel even when they shouldn't. Hook up a fuel pressure gauge, and see how fast your fuel pressure drops off after you've shut off the engine. If everything is tight, your pressure should hold for hours, or even days. If not, it will peter away fairly quickly. That said, your cold start valve isn't going to suddenly open when the engine is warm. Whatever your problem is, it would appear to be electrical, and it might even be your electrically connectors. After suffering decades of harsh use, the electrical connectors under our hoods are usually pretty crusty and crumbly. Try cleaning up all your connections with DeOxit (best) or some other contact cleaner. You might also need some very fine (e.g. 600 grit) sandpaper to polish contacts and/or a tiny screwdriver to scrape corrosion. If the plastic body crumbles on one of your two-conductor connectors, you can buy new off of Ebay. Just do a search for "injector connector 280Z." There's some seller ("forest," as I recall) who sells some pretty good kits. I'd frankly replace all my connectors if I were you. Old connectors are trouble.

Well, your fuel pressure APPEARS to be a few psi low. As Cozye suggests, it would tell us more if you could pull the vacuum line off of the FPR. Then the fuel pressure should read right at 36.3 psi, give or take. He's also suggesting you pull out all your plugs and photograph their working ends, keeping them in order from #1 to #6. You can "read the plugs" to help diagnose fuel/air mixture problems. I suspect his theory is that your engine has too little fuel pressure, therefore too little fuel, therefore too lean a mix, therefore somewhat white and chalky looking plugs. However, if it's running EXTREMELY lean, then there will be a lot of incomplete combustion, a lot of unburnt hydrocarbons, and rather black plugs, appearing almost as though your engine were running very rich. Anyway a picture of your plugs would be helpful.

Well, since my last post on this subject, my fuel pump died, and I've replaced it. The new (OEM) pump makes a soft whine that you can barely hear. When you start the car, you can no longer hear it over the engine. I suspect the pump would be a lot louder if it weren't mounted with those HUGE rubber bushings. You might check the bushings to make sure they're still intact. Also there are some metal tabs designed to "catch" the pump if the bushings were to rip/detach/fail. Perhaps you've got some metal-to-metal contact there? They should float inside their respective holes. There should be no metal-to-metal contact at all.

The first turn of the day, out of my driveway, when I straighten out my wheel quickly from a hard turn, I often get a loud "honk" as the steering shaft vibrates around in the column. That's on my list of to-do things. I presume I have to pull the entire column and slather it with grease. I don't have suggestions/solutions for you. This is just a sympathy post.

Cesar, pay attention to the weather and the heat inside your car. Remember that both your ECU and your ignition module are INSIDE the cabin of the car, just inside the kick panels. So if your car has been baking in the sun, both of these components will be starting out a bit on the hot side when you start your car. If the weather is a bit more fair, and if your car has been sitting in the shade, your IM and ECU will be less heat-stressed. I don't know whether that would coincide with when your engine messes up, but it's something to watch. These intermittent problems are the worst! I hope whatever the problem is, that it just FAILS for you, so that you can track it down.

Your capitalization and punctuation were very good; however, I cannot give you full credit for your response, because it is an incomplete sentence. 5th, I think that would be "... uncle, Jack, off his horse." (You omitted a comma.) Grammar aside, your engine has to get pretty warm to start messing up. I was thinking it might be a fuel/air ratio issue, but now considering how warm you have to get it, it does sound more like a heat-related component failure such as Steve is suggesting. I'd probably look at the ignition module, coil, and ECU, as he suggests.

Chris, I bought a '75 Z long, long ago, during my college years. It had a very beat-up front end and some hard-as-concrete rally struts. I soon replaced the rally struts with KYB gas struts, and that made the ride much more comfortable, but the front end was still very sloppy. The more work I did on it to take slop/play out of the system, the worse a shimmy I got at higher speeds. I had a really good mechanic work on the car, 'cuz I was over my head. He did a lot of head scratching and then "borrowed" a set of wheels/tires from another Z to test my front end. The ride became tight and smooth as silk. My tires were new (and good). The culprit was actually the cheap rims, whose lug holes were slightly off center. When a tire shop would spin them up to balance them, I think it was by the center hole. When they went on my car, they were centered (differently) by the lug nuts. The reason the problem felt worse, the more I corrected problems with the front end, was that there was less "forgiveness" with less slop/play. The jury was out regarding what caused the front end to be so beat up. It might have been hard driving with the concrete rally struts, but my guess is that the off-center rims resulted in the hardest long-term wear.