Zed Head

The EFI Bible should really be called EFI Cliffsnotes. The book it's based is the FSM. Notice that the "Bible" always refers you to the Service Manual when there's a problem. Download the FSM and read the Engine Fuel section, along with Body Electrical. It has much more detail specific to your year. There is a separate set of green fusible links (either one or two) for the EFI harness, inline with a wire that comes directly off of the positive post of the battery. It should be clipped to the side of the big metal relay cover right in front of the battery. The ECU fires all of the injectors on every third spark produced by the coil. It "counts" the pulses through a wire from the negative post of the coil. The tachometer circuit plays a part also, if the tachometer is removed the injectors won't fire. You can test the ECU and circuits by connecting a wire to the negative post, turning the key On, and tapping the wire to ground. You should hear the injectors open and close on every third tap. You'll also get a spark at the distributor on every tap. If you can't find the "ignition lead wire" you can test for power to the control unit on Pin 10 at the ECU connector.

#14 in the picture on this link - http://www.carpartsmanual.com/datsuns30/DatsunZIndex/Engine280Z/Accelerator/tabid/1624/Default.aspx

I see that you're trying to do everything from a phone. Find a computer and spend a few minutes on it. On Google, the ignition lead wire shows up as the main wire from the center of the distributor cap. But that will only have power when spark is generated, so it's probably not the one you're looking for. If you're checking for spark, you can do everything you need to do right at the coil, with a voltmeter and a jumper wire.

Take a picture or copy the photo you're talking about and post it. Describe the booklet you're looking at. Describe the problem you're trying to diagnose. OR. Type "ignition lead wire" in to Google and a picture will pop up.

I had a check valve on my return line, but found that it quit working after a short while. It was only designed to hold to about one psi anyway. I know my lines were emptying because I could hear a large quantity of bubbles in the tank for about 20 seconds after I turned on the pump (I have a switch for priming). The best check valve is a fuel pressure regulator. So I dug through a few parts that I've accumulated and found an FPR that regulated and held full pressure with the pump off. Replaced my Aeromotive FPR with it last night and will see how things work now. Hopefully, a good 30+ psi on a full rail of fuel will keep the injector bodies cool enough (that's my hypothesis of the moment that seems to fit the facts) to avoid the hot start problem. Basically using the fuel as a conductive cooling path. Since I first installed the Aeromotive adjustable FPR (I bought it 'cause I knew my stock FPR was bad and the Aeromotive was on CL for cheap at the time, plus I thought adjustability would be nice in the future) I've made quite a few changes and coincidentally ended up with a fuel rail that fits the good regulator, which is the two port, 1978 style. So I am essentially back to a stock 1978 fuel setup, in my 1976 car. I also tested another 78 FPR that I had and it regulated fine but leaked down to 10-15 psi as soon as the pump turned off. With all of the sitting that these old cars tend to do, I suspect that there a lot of marginal FPRs out there, with seats that don't quite seat.

I would check fuel pressure first. With a fuel pressure gauge, you can check your pressure before and after the filter change and know if you did anything. The gauges are a little spendy and you think you won't use it much but the they're a good tool for problem-solving. If it ran for 20 minutes then conked out, a faulty fuel pump might be more likely, or a clogged fuel inlet. If the filter is clogged it will still be clogged when you test pressure. Either way, with a gauge you can confirm pressure before taking it out on the road.

Actually the sensor might have an effect at all temperatures, despite what the FSM says. The FSM says it is essentially out of the picture after 158 degrees F, but it's been shown (see BRAAP's EFI work over on Hybridz) that it still does have some effect at higher temperatures. Plus, it would be surprising for your engine to be fully warmed up after 6-8 blocks, so a shorted temperature sensor would be something to look at. Don't forget fuel pressure, while driving - after 6-8 blocks. Several people have thoguht that they had good pressure but found that the fuel pump was over-heating and losing pressure under load. I've had one in the garage that looked fine for 10 minutes then slowly crapped out. No fuel pressure, no fuel = lean condition. I've read road test reports from the past that talk about the 280Z EFI system's lean surge problem, even when new. If you read Fast Woman and cozye's threads you'll learn about the typical fix (seems to be more prevalent with the 78 cars) of adding a resistor to the water temperature circuit to richen up the mixture, across the whole temperature curve. Another possibility is the AFM. My 76 had similar mid-throttle lean intake popping, bucking and stalling, but much worse than what you describe, it was generally undriveable. In my case, a rebuilt AFM fixed the problem. Take some measurements, cold and fully warmed up and something will probably show itself. You can't get very far with these EFI systems if you don't take measurements.

I really don't know much about oil pumps, I've never even had mine off, let alone apart, but the FSM, EL section, suggests that the pump should still turn with no gasket. Clearance is measured from the base of the pump body down to the rotor, implying that there is clearance without a gasket. This is from the 1976 FSM, which is better illustrated than the 1973 FSM. Just an observation.

Beware those tires. Rubber will age and degrade just through oxidation alone, even out of the sun, no matter how much Armorall you apply. 38 years is way old.

Blue might actually be referring to the book "How to Modify Your Nissan & Datsun OHC Engine" by Frank Honsowetz. On page 15 he describes enlarging the oil-jet from 2.0 mm to 3.17 mm to increase oil flow to the head, but it's in reference to big cams and high spring pressures. Some people, over on Hybridz, have suggested that there is plenty of flow to support both spray-bar and internal oiling. Others suggest drilling out the oil-jet to be sure. Your oil pump condition is probably a factor also, considering the lower flow at low RPM. Seems like Rebello would know about drilling out the oil-jet. Probably worth a discussion since he suggested it. p.s. the flat head of a good bolt should (did, in my case) provide enough pressure to seal the spray bar, with gasket, to the tower. The pressure in the bar is reduced due to the oil-jet restriction. The gasket on my 1976 spray bar was well-compressed and showed no signs of distortion or leakage. It was smashed flat like a typical old gasket, very evenly. No signs of uneven load.

Disconnect the small wire at the starter solenoid, the one that pulls right off, and turn the key to Start. The fuel pump safety circuits are bypassed at Start and you should hear the fuel pump run. If you have a fuel pressure gauge you can measure pressure this way also. It should be ~36 psi.

I've been having the "hot start" problem recently. Here is an interesting thread on the topic - http://forums.hybridz.org/index.php/topic/76282-heat-soak-vapor-lock-problem/page__p__746890__hl__%2Bvapor+%2Block+%2Binjectors__fromsearch__1#entry746890 The thread above spends a lot of time on defining the words and terms, but hot injectors seem to be the common point. I am leaning toward cygnusx1's theory that the problem is actually caused by overheated injector bodies causing the fuel to vaporize as it passes through, or percolate while it's in the channel. This actually results in a lean condition. You might have noticed that you don't really smell any excess gas, it just runs like it's flooded. A miss is a miss, lean or rich. I've had a pretty good lean backfire through the intake when this happened. I used to think the problem was leaking injectors, but the lack of fumes fits a lean running situation better. One change that I made recently was to the holders around the injector bodies. In the past, I had the one piece holder, recently I went to the two piece holder, with the aluminum upper ring and phenolic lower. I almost never had the problem before, I'm having it more often now. Maybe the two piece holder lets the injector body get hotter while sitting. It is also a different engine, but the EFI, intake and exhaust system are the same. I think that the Nissan engineers attempt to fix the problem was the injector fans, controlled by coolant temperature. I've insulated my injectors within the last week to keep them from absorbing radiant heat when the car is sitting, but still have had the problem. Still looking for ways to avoid an injector cooling fan retrofit, but I have one and might try it. Edit - I also have an Aeromotive FPR that leaks down rapidly. So maybe the dry injectors do not get the cooling that a "filled" injector would.

I took a look here - http://www.carpartsmanual.com/datsuns30/DatsunZIndex/Engine280Z/CamshaftValveMechanism/tabid/1603/Default.aspx - and here - http://www.carpartsmanual.com/datsunS30/DatsunZIndex/Engine240Z260Z/CamshaftValveMechanism/tabid/1565/Default.aspx - and see that the 240/260 spray bar is different from the 280Z. Doesn't show a stock gasket on either, so I'm not sure why mine has one (two actually). 30 ounce has a point though, you might do some preventative brazing on your stock tube while you have it out, if you don't want to spring for a custom billet bar.

I happen to have a 1976 spray bar in a box in the garage and just took a look at it. It does have a gasket at the interface. Not a precision piece, essentially a square of gasket material with two holes, one for the oil and one for the bolt. Pretty sure the head has never been touched. p.s. don't forget the hole for the oil.

It won't disrupt anything, it's a straight bolt-in swap. But it might not make a difference. What are the problems with the starter you have?

An alternative is that this is your second car, for fun and a hobby. Buy it, race it around, get some tickets, slide it in to a ditch or two on those icy MN roads, fix it and modify it in the winter and do it again in the summer time. Just a thought. The car isn't really very practical as it sits, especially since you don't know a ton about cars, but it looks like some fun. Someone planning to put all of those race parts on a stock car might easily spend over $5,000. The coil over work and brakes are easily over $3,000, just looking at comparable internet prices. If you were planning to go that route, this might be a deal, if not, they're just wasted parts.

Go racing?

Assume that the engine is worthless and see what the rest looks like. No rust, paint looks good, seats in decent shape, 5 speed, coil-overs, decent dash. Looks like some standard L24 performance mods on the engine. But it could be worn out by now. Find out when it last drove so you'll have an idea of whether or not the various hydraulic parts will need replacing. Over 2 years in MN and the fluids will probably have absorbed moisture. Might need new calipers, master cylinders and slave cylinder. Also find out what "needs some work". The $25,000 number is irrelevant, only the $5,000 number matters.

Z train is right, I was off target on the pilot bushing. The crankshaft, pilot bushing and input shaft are all spinning at the same speed when the clutch is engaged, so it wouldn't make a noise while you're cruising. Examine the the things that all spin at the same speed as the crankshaft or come in to contact with it and you might come up with something. Maybe your throwout bearing is touching the springs. Z train, did you mean input shaft? Isn't the output shaft spinning at a speed proportional to road speed, independent of RPM?

Doesn't seem like a common noise. Has the car been sitting or driven regularly? Is it always 2800 RPM, no matter what gear or just 2800 RPM in a certain gear? Have you checked the fluid level in the transmission? Could be the pilot bushing.

You could put a small rheostat in line somewhere and adjust it up until you get desired performance. Or get a few resistors and do trial and error to see what you need. That way you can just go for it and make it work, but still be safe on the wiring. Plus, the heater circuit might already have a fuse in-line, or you could/should add one.

It's inside the alternator case.

I think that the spherical shape of the stock "washers" is designed to take up any thickness differences and equalize the load between the intake and exhaust manifold flanges. A flat surfaced shoulder bolt will only put pressure on the highest surface, plus it will put a bending load on the bolt if there is a thickness mismatch. Might work if both flanges at every location are of the same thickness.

Piling on: If you use the RT-style mount with the Energy Suspension GM transmission mount, suspension work is super-easy. The differential will hang from the mount instead of sitting on the cross member. You can remove the Nissan front diff mount entirely. No need to support the diff to change bushing or stuts or springs. Just one more benefit. I noticed when I was working on the clunk problem also, that if you strap the diff down too tight it can be drawn down on to the cross member, generating more diff whine and vibration in the cabin. In my case, the mount was so worn that it wasn't really holding the diff nose from moving up or down.

yoshi, you didn't say if your ZX is a manual or automatic transmission. If it's a manual, and you have a fuel supply problem, it wouldn't be so RPM specific. Try changing gears and see if the problem is speed or RPM related. You mentioned a new throttle body. Why did you change the stock one? Did you go for a larger TB for "more power"? Upgraded FPR? If you're running the stock ECU, what features of a different FPR would be an upgrade? Seems like there might be more to your story. Have you been upgrading for performance, or is this a stock 1980 280ZX? Ted, you didn't really say what the solution to your problem was. Did you have EFI on your 240Z?