FastWoman

Draz, the fuel pump relay would have no way of "knowing" whether you were stepping on the accelerator. I would be amazed if that's your problem. I believe the '77 Z does cut off the fuel pump via a switch in the AFM. (I might be wrong about this, so check an online FSM.) If so, that's quite likely your problem. You can pop the black cover on the side of the AFM to see what the fuel pump kill switch is doing when you hit the accelerator. Maybe it's out of position somehow? The only other thing I can think of is that you have a bad connection somewhere, and when the engine rocks, or when something flexes or vibrates the wrong way, the connection is lost. I haven't forgotten that this problem is temperature related, and that draws attention somewhat away from the AFM and more towards the wiring (thinking of thermal expansion). Maybe move around your engine bay wiring harnesses gently (and carefully) with the engine running, to see if you can kill the engine somehow. FAIW, Datsun's fuel pump wiring and electrical connections are marginally inadequate. I finally had to abandon the firewall connector in my fuel pump circuit because it kept arcing and melting. I snipped that wire and connected it through a bullet connector instead. You may need to do some fault tracing at various points in the wiring to see what happens when you replicate the problem. Let's get a bit creative in our methods here. Try this to see where your problem lies: First, disconnect the (+) wire to your fuel pump, and attach another long wire. Connect the other end of that wire to your battery. Your fuel pump will then run, irregardless of the state of anything else in your car. Now start up your engine and see if you can replicate the problem by hitting the accelerator. If you can, then it's definitely the fuel pump (for some weird reason). If not, then you know it's something in the electrical supply. The next step, if it's electrical, is to fault trace. Check numerous points in your wiring to see where the power drops out when you hit the gas: -- Fuel pump wire at the connector that would be connected to the fuel pump terminal. -- Fuel pump wire at both sides of the big firewall connector. You should be able to poke your mutimeter probe into the backside of the connector. -- Fuel pump relay coil wire. -- The signal from the AFM's fuel pump kill switch -- Other points I don't know on the '77. (Check a '77 FSM.) If you keep tracing, you should turn up the fault somewhere.

Draztik, I doubt an auto parts store can check your Datsun ignition module. However, you can test your ignition by putting a timing light on the coil wire. Step on the gas to see whether the flashes stop before your engine dies. If everything is working right, you should get sparks/flashes up until the moment the engine stops rotating. If you lose sparks/flashes before the engine stops, then it could be an ignition problem. I say "could" be, because you might also be fouling your plugs with an excessive fuel/air ratio and might be killing your spark that way. That said, if your fuel pressure drops all the way down when you step on the gas, then you're losing your fuel pump power for some reason. I think that's your problem, not the ignition. Can you step on the gas very briefly to make the engine hesitate, but then back off and get the engine to continue running? If so, what happens to the fuel pressure? Does it drop and then return to normal? Remember that the output of the fuel pump doesn't increase when the engine is under load, contrary to what people might want to believe. Fuel is constantly circulated under pressure, and the engine load simply affects the return volume. If there were any fuel flow bottlenecks (e.g. a clogged filter), you'd see them equally under any conditions. The peak load on the pump would be at peak fuel pressure, when the manifold vacuum is zero. If it can hold steady at 36 psi with the vacuum line removed (not pinched), then it can meet any demands placed on it. I suspect your problem might be electrical. You might put a mechanical multimeter on your fuel pump line to see what it does. (Mechanical meters show voltage fluctuations faster than digital ones.) Is the power interrupted when you step on the gas? Does the power flutter for any reason?

Thanks, guys! Those will be on today's shopping list. I haven't been able to do more work and won't for a while. Rain! Lots of it! I can't even paint because the place is dripping in humidity. I'm glad I shot some fogging oil in the intake ports after pulling the intake. Maybe I'll work on the little parts -- throttle body, AFM, etc. My radiator shop guy says he can extract (and possibly helicoil) my frozen/broken screws/bolts. He's starting to be my one-stop resource.

... but the fuel rail is the same! Something isn't quite right, between your fuel pump, your fuel pressure regulator, and your fuel pressure gauge. You could test your fuel pump by hooking the pressure gauge directly to the output of the pump (i.e. disconnecting the fuel supply to the fuel rail). You should get a much higher reading, perhaps 40 psi. Assuming the pump is good... Your fuel pump should produce a constant output, regardless of engine load (because the excess fuel is recirculated). However, the fuel pressure will be regulated in relation to intake manifold vacuum, so that the pressure difference between the fuel rail and the intake manifold is held constant. As a result, the fuel pressure as measured in relation to atmospheric pressure will fluctuate with engine vacuum. That said, when you pull the vacuum line off of the FPR, it should regulate at a constant 36 psi, not a constant 30 psi. Either the pressure is wrong, or the gauge is inaccurate. (Either is a possibility.)

Your fuel pressure will drop when you kill the engine if your fuel pump check valve is bad, your cold start injector is stuck or dribbles, or your main injectors dribble. It's normal to lose some pressure when you kill the engine, but it's supposed to be a rather slow process, and it should continue until your pressure is 0. Just a thought: I don't know whether your '77 is wired like my '78, as there was an evolution of fuel pump control mechanisms with each year. With mine ('78), the fuel pump is energized when you're cranking the engine and stays running if there is either output from the alternator or oil pressure. If the fuel pump CONTROL relay (different from the fuel pump relay) were bad on my '78, or if the connections to it were bad, I think I would have fuel pressure only when cranking the engine, and then the engine would die immediately after starting (like yours). Do you have a FSM for your '77 Z?

I don't know the '79 ZX wiring, but I have a '78 Z. None of my fusible links were engineered to blow at any amperage as low as 20A. I think they're rated maybe 40A and up (from memory). You'll find info about fusible link gauges buried in this thread: http://www.classiczcars.com/forums/showthread.php?t=35588 A short in the cap on your ignition coil might cause both the cap and your fusible link to smoke. The noise suppression capacitors/condensers are cheap. Pick up a new one, and see if that fixes the problem. You'll of course need to reinstall or replace your fusible link wire.

Ztrain, I thought you meant this stuff on the gasket: http://www.permatex.com/products/automotive/automotive_gasketing/gasket_sealants/auto_Permatex_Copper_Spray-A-Gasket_Hi-Temp_Adhesive_Sealant.htm I've known people to spray their gaskets with copper spray of some sort. I guess this is it. Apparently it improves heat transfer and fills surface irregularities. Is it worth using? But I guess you're really talking about this: http://www.permatex.com/products/automotive/automotive_gasketing/gasket_makers/auto_permatex_ultra_copper_maximum_temperature_rtv_silicone_gasket_maker.htm Use one or the other? Both? Thanks for the tips regarding the antisieze. I'll look for the copper variety and will use it sparingly for the SS fasteners in aluminum. I presume I should use the ordinary aluminum-based antisieze for the non-stainless hardware used to bolt the manifolds to the head? BTW, no time to work on my car this weekend. We've been busy visiting solar homes. I'll probably get back to work on the Z tomorrow. Thanks again, guys! Very much!

Thanks, Zdude! I didn't have a name for the spray. Now, with a name, I was able to look it up and see what it does. It certainly sounds worth doing, both on the Z and on our powerboat (which is also lying in pieces). Antisieze it is -- lots of it!

Whoa! NEVER run the engine with the battery disconnected!! That's a good way to fry your electronics. (Yes, I realize the 260 has fewer electronic components than a 280, but even so, it's really hard on the electrical system.) Get a multimeter. You can get a cheap meter for $15 at Radio Shack or at your local auto parts store. I've even bought some for $5, just to throw in the glove boxes for emergency diagnostics. Start your engine, and measure the voltage across the battery terminals. It should be in the neighborhood of 14 - 14.5 V. If it is, your alternator and voltage regulator are good for the moment. You might also run the engine until the alternator gets warm, and then take another reading. It should still be in that voltage range. If you don't get voltage in that range, either the alternator or the voltage regulator is bad. As one can cause the other to fail, most people replace these items together. That's probably wise. Now stop your engine, and take the same measurement. The voltage of a fully charged battery should be in the neighborhood of 12.7 V. If you can't charge your battery to that voltage, something is probably wrong with it. A voltage of 12.0 V would mean the battery is half discharged, and you should try never to run your battery below this point. Note that a bad alternator is a great way to kill a perfectly good battery. If you ran your voltage down to maybe 10 V, it would have been almost fully discharged, and your battery will have lost much of its plate area. Let's say you get a good voltage reading (12V or higher) on your battery. Now try starting your car. Does your engine crank energetically? If so, the battery is good -- or at least good "enough." What sort of noise are you hearing? As for your weird electrical symptoms. Check all of your grounds to see that they are really grounded. Visually inspect your wiring harnesses to whatever extent you can. Are there any places that have been unwrapped and/or rewrapped? If so, unwrap them to see what is underneath. Do you see any strange bulges where creative wiring might have been performed by the previous owner? If so, open it up to see what it is. Are there any burnt/charred areas? If so, open them up. Whatever looks fine can be rewrapped with electrical tape. Pay special attention around the wiring to the stereo (which I'm presuming is aftermarket and therefore has suspect wiring -- because hardly anybody does good installation work). This wiring is in the vicinity of the hazard switch (at least on the 280Z), which is part of the turn signal wiring. Look carefully in this area for shorts and disconnected grounds.

Yikes! No WAY can I afford an electronic gauge! Oh well... Mechanical it is...

Oh, also... I remember seeing a set of stainless screws and bolts for the Z. Where would I have seen that? I'm starting to think it would be a very good idea to buy it before reassembling all this stuff! Update: I've found zcarcreations.com, but they appear not to be in business anymore (no ebay auctions, no prices quoted). I have an email out to them. Another update 9/25: I found www.boltdepot.com, which sells SS fastener assortments. I bought about $150 worth of metric SS screws, bolts, nuts, washers, etc. We'll see how far that goes.

Zedhead, thanks so much for the real world info! You've confirmed or reinforced a few of my suspicions (e.g. dribbly injectors, flooded manifold) and have pointed me to things I hadn't even considered (FPR running differently hot vs. cold). I have two stock FPRs -- the one from my car and one I pulled off of an '81 ZX intake (a gift from Geezer). They are a few PSI off from each other. I think Geezer's is probably more accurate, and mine is probably low. Anyway, this tells me that at least one of them isn't quite right. Also thanks for the great info on fuel pressure gauges. I might look for an electric one. I hope they're not too pricey. I'm not bothered that the Aeromotive FPR won't hold pressure after shutdown. I've gotten into the habit of priming before starting anyway. I actually installed a switch to do that. I did the same thing on our carbureted powerboat, putting an electric fuel pump inline just for that purpose. (BTW, the powerboat is my other project that's in a million pieces -- leaking intake and exhaust manifold gaskets and a carb that needs attention. Now THAT project is great fun regarding rust. It has a saltwater-cooled 318 inboard. The Z is easy by comparison. ) I forgot to mention yesterday that the underside of the intake manifold gasket (i.e. the side nearer to the exhaust) appeared to be rather degraded. The insides of my intake manifold are black with soot (is that normal?), and there are areas on the mating surfaces (manifold to head) where I don't have any identifiable gasket material and which are also covered in black soot. By comparison, other areas are pretty, clean, shiny aluminum. I guess that would qualify as a massive intake leak? I also found a split in the boot between my AFM and throttle body. It's of course possible I put it there in the removal process. I had been terrified to remove the boot for inspection before (because it's old and fragile) but had run a mirror around it and was satisfied it was good. Anyway I do have an NOS spare for the reinstall, and I suppose I'll be buying another spare now. (Is there any aftermarket source for these things?) Although I'm not there yet, I'll ask now: Is there any way I should treat the new intake/exhaust gasket? I've heard of people spraying them with copper spray. I have no idea what this does. The part is MSA's, if that makes any difference. Also I was planning to use liberal amounts of antisieze compound on the hardware. However, would the blue threadlock be better? Do I have to worry about the nuts/bolts backing off? Finally, Bart, thanks for finding the crow's foot on Amazon for me! Although I no longer need a 30mm crow's foot, I wouldn't mind having crow's feet for use on the propeller shaft stuffing boxes on our two boats. There's almost no working space down there. In fact when working on the stuffing box on the sailboat, I have to fling myself over the top of the engine and almost hang upside down. It's not a pretty sight!

Never mind! So I got this idea: Take off the heat shield around the master brake cylinder, and put a 12" Crescent wrench on the nut. There's just enough room to place it around the brake lines. (Yikes!) Then tie a rope through the hole in the end of the wrench's handle (a bowlin knot, of course). Wrap the other end of the rope around the end of the intake near the throttle body. Snug up the rope tightly, and then pull the length of rope upwards. The mechanical advantage on the wrench is enormous, and the pull is smooth and controlled. It worked. The nut came loose. Of course I had been soaking the nut for days with solvents and then hit it with a blow torch before trying to loosen it. That having been done, I removed the remaining nuts/bolts on my intake and successfully removed it with not a single broken stud. I also removed several bolts on the exhaust. Having gotten the intake off, I gave all the remaining exhaust bolts another good soaking, and I'll try pulling that manifold tomorrow. So far nothing broken! Yea! I'm feeling a bit more encouraged now.

Question for both of you: I'm trying to take this mess apart now. My next step (and impasse) is to disconnect the EGR pipe between the two manifolds. (This is a '78 model, BTW, if that makes any difference.) I can't get any ordinary wrench in there anywhere. I'm thinking the best approach would be a crowfoot wrench on the big nut just below the back of the intake. The nut is 30mm, and my largest crowfoot wrench is 22mm. I'll need to go tool shopping to get a 30mm crowfoot, and the sets aren't cheap. (I might get an SAE set with a 1 3/16" wrench, which is 30.16 mm.) It's also a long trip into town. So is that nut (the largest one) the easiest to get loose? I'm thinking it should be, but before I buy tools to use on it, it would be great to know I'm on the right track. Or is there any other approach that's better than a 30mm crowfoot wrench? Thanks, guys!

Ztrain, I have a gauge I often have temporarily installed inline. I don't think it would last very long as a permanent installation, but I don't mind driving around with it for a day or two or three. Just altering the plumbing isn't much of a mod, functionally. If I can set the stock pressure, nothing has really changed. Right?

Ztrain, I recently replaced my check valve, and it made a MAJOR difference. The Nissan check valves are NLA, but you can MAYBE still find a Volvo or Saab check valve that fit and function the same: See here: http://www.classiczcars.com/forums/showthread.php?t=36255&highlight=volvo+check+valve Unfortunately when I had sourced out the Volvo check valves (which were plentiful) in public view, they almost immediately went NLA. I was lucky to buy just one.

Thanks for the encouragement, Dana. I keep looking back on that last screw and thinking, gee, maybe I should have soaked it for a week, or maybe I should have used two nuts and a socket, instead of a small vice grip. I keep kicking myself over it, but I know I gave it my (almost) best effort. The thing about it, though, was that the first couple of turns were only moderately difficult -- with a screwdriver, even. As I said, though, the manifolds have to come off anyway. I've had the manifold bolts soaking in PBlaster (thanks for the suggestion, Bart). I'll probably give them a try today. I've already studied the AFM adjustment info on the Atlantic Z website. That's a great resource they've got. Right now I'm looking at my system much the same way you probably are -- a mixture of malfunctions, some of which lean the mixture, some of which enrichen the mixture -- all of which work in combination together and in opposition to give me a (poorly) running and somewhat unresponsive engine. I did pull the cold start valve yesterday, and it appears to be stuck open. I also noticed some damage to the lower EGR gasket, which I hadn't replaced when I replaced my EGR valve. (The big iron spacer was stuck in place, so I didn't think it was necessary.) There may be a leak in the intake manifold gasket for all I know. I found another small leak where a fitting was loose. I'm sure I'll discover lots of interesting stuff. My general approach will be to go through the entire system, component by component, to ensure that it is mechanically and electrically sound. Then I'll see how it runs and make my final adjustments to the AFM. That said, I'm considering a minor redesign of my fuel rail (see thread in the EFI section). I'm considering incorporating an adjustable fuel pressure regulator in that design. That can be used to fine-tune fuel/air ratio a bit more easily than cracking open the AFM. What do you think? I've found these nice looking regulators on Ebay, but they seem maybe "too" inexpensive. I presume they're made in China: http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=170535789792&viewitem=&sspagename=STRK%3AMESINDXX%3AIT Also with such a broad adjustment range of 0 - 140 psi, I wonder how accurately I'd be able to adjust the fuel pressure.

Well, maybe not vapor lock, then. I know gasoline boils very easily, but I also realize it can be compressed back to its liquid state. However, I do get air in my fuel rail, whichever way that might happen, and if the car is sitting at even the slightest angle, it's harder to purge it. (I installed a priming switch on my fuel pump system, so I do know this.) I had been confused as to why the air isn't generally purged rather quickly by priming. (It sometimes takes maybe 10 sec of priming). However, the bifurcated flow path explains it. Billy, I've been going through all that stuff! Thanks for the help, though!

Hogie, been there, done that with my '75 at a much earlier age. I might have even driven a lot like you at the time! Like you, I wanted to get to summer break before launching into the clutch. My 280 was my only car, and I needed it to commute about 30 mi to and from school. Fortunately the terrain was relatively flat -- no hills to climb, at least at higher speeds. I decided to stretch the clutch life as far as it would go (not causing damage to the FW, just like you.) I did make it to summer break with "sensible" driving. I think it was about 6 months -- probably about 5000 mi of city driving. It was getting pretty slippy towards the end, particularly in 4th gear (4 sp transmission). There was no damage to the flywheel, perhaps because there was never a time it slipped that I didn't know it, so I could back off of the accelerator to stop the slippage. Here's what I'd recommend: 1. Make sure you can hear your engine (i.e. keep the volume down), so that you'll know when the clutch is slipping. 2. Drive in lower gears when you can't avoid slippage in higher gears. 3. Engage your clutch as quickly as possible, without much gas. 4. Use your brakes more, and don't downshift into your stops. With a bit of care and thought, I think you should make it to winter break.

It wouldn't apply to you in Oregon, but just a note to folks in hot places like Texas: I installed a half cap on my '75 long ago (in Texas, of course), and it looked great. The problem was that the Texas heat caused the plastic to soften and sag. As a result, you could see the contour of a zig-zaggy line of caulk from one end of the dash to the other. The moral: If you live in a really hot climate, be careful how you cement the thing down!

Hi all, I had a eureka moment this morning in my half-groggy state. (Apparently I had been dreaming about fuel injectors, seized screws and bolts, and other frustrations all night. Go figure.) My '78 has this problem that it sometimes gets vapor locked and also sometimes gets air (as opposed to fuel vapor) in the injector rail. The result is hard starting. Part of the problem is worn injectors (which I'm trying to replace). Part of the problem is heat. I figure it this way: I drive to where I'm going and shut down. Then the area over the intake gets quite hot, and the fuel in the injection rail boils. Fuel is ejected to the return line via the pressure regulator and/or dribbles out through worn injectors into the intake manifold. Then the engine cools, and the fuel vapor condenses, creating a vacuum in the injection rail. Air is then drawn from the intake manifold, through the worn injectors, into the injector rail. When I go to restart the car, all the air has to be purged before the engine will run right. It takes several attempted starts, and the engine will run very roughly (on only a few cylinders) until it smooths out. I think I'm learning this is a fairly common problem. Apparently this problem can also occur without fuel vaporization if the fuel pump check valve is bad. Gravity will pull the fuel from the rail, and apparently there is enough air leakage from even newer injectors as to allow air to enter the fuel rail from the intake manifold. But here's what I figured out this morning: When you get air in your fuel rail for any reason, Bosch's "trumpet" design does not help you to purge it. If one end of the fuel rail is any higher than the other (which it probably is), then the air will settle at that end. Fuel enters one side of the trumpet (i.e. not the end, but the side), and it ordinarily flows around both ends of the trumpet to the 6 injectors. The excess flows from the trumpet on the other side (not end) and is returned via the fuel pressure regulator to the tank. However, when there's a big air pocket in the higher end of the trumpet, the fuel will only flow around the lower end of the trumpet (the one without the air pocket. Thus the air pocket will not be flushed by the normal circulation of the fuel. Instead, the air will have to be purged through the injectors. A much smarter design would be a system without a bifurcated route. Fuel would be introduced into one end of a straight line (e.g. the aluminum billet rails), flow past the 6 injectors, exit the other end, travel directly to the pressure regulator, and then return to the tank. That way any air pockets would be purged by the normal flow of fuel through the rail, not having to be bled through the injectors. The aluminum billet fuel rails I've seen seem to be dead-end streets, perhaps with the pressure regulation occuring prior to the rail. (Am I correct about this?) This would require purging of the air through the injectors and could be even worse than Bosch's "trumpet." The secret to purging air and fuel vapor is to put the fuel pressure regulator on the far side of the injectors. Anyway, even though I have a new check valve and will soon have new injectors under the hood, I think I'm going to redesign the rail system. Anyone know where I can find a pre-made aluminum billet rail, or do I have to make my own?

Kinda late... But I'll try PB Blaster the next time. Update: I spent the entire afternoon on the rusted fasteners. I extracted the bolt and cleaned up the threads just fine. Then the three injector screws. (These seem to have been rusted in place by a very slow coolant leak the previous owner had let go -- the one to the air bypass.) I've never seen anything rusted in place so badly. I finally drilled the heads, pulled the injectors, and then worked on the long stubs to extract them. The only thing was that the last screw -- the lower #1 injector screw -- would NOT come out. I could turn it back and forth, and I worked it back and forth for maybe an hour, working WD-40 down the hole all the while. I made about 5 turns progress before the screw died of metal fatique and gave way at the base at an odd and rather difficult to drill angle (considering that the throttle linkage tower is in my way). Grrrrrr.... So now I'm trying to figure out what to do. I need to replace the exhaust manifold gasket anyway, so maybe I pull both manifolds and run the intake to a machine shop for them to work their magic?

Hi Jan, I once asked around about whether it's better to use ancient, remanufactured, genuine Nissan injectors or new aftermarket. I got a lot of shoulder shrugging (I think). One person whose opinion I trust said to go with the new injectors. I asked which ones, and he said it didn't matter. I got a set of the GP Sorensen injectors and haven't yet got them on the car. These injectors get very mixed reviews. Some love them. Some hate them. Your remanufactured injectors should have come as a matched set (matched for flow rate). If they didn't, that might be the source of your problem.

Point taken about the solder joints. Bart, the oil filler cap does introduce air after the AFM -- via the hose between the valve cover and the inlet to the throttle body. ktm, you're right, of course. Update: I haven't quite finished removing all of the old fuel rail. I still have 3 frozen injector screws, and one mounting bolt snapped after I had turned it several turns. Still soaking with WD-40, and I'll be drilling out the bolt tomorrow. If the screws still won't turn, then I may end up drilling off the heads, removing the injectors, introducing WD-40 closer to the corrosion, and backing them out with double nuts. It shouldn't be this hard to remove these screws and bolts. I don't think a bit of antisieze compound was used on any of this hardware when the previous owner had a single (yes, one) injector replaced 5 or 6 years ago! I've done injectors before. I've never had this much trouble -- not even close! I'll also check out the cold start valve tomorrow before reassembling. I have a spare valve, so I can clean both and use the better of the two. (I'm optimistic that at least one will be good.) I also have a new filter, so my fuel system will finally be reworked from tank to injector -- clean tank, new hoses, pre-filter, flushed pump, new check valve, cleaned damper, new filter, clean fuel rail, new injectors (with fresh wiring and connectors), cleaned/checked cold start, and cleaned/checked fuel pressure regulator. I went through a lot of crusty/crumbly equipment to get to this point. More tomorrow!

Yikes, Ztrain! Bad solder joints are pretty rare and usually only in subpar equipment! I wouldn't expect such a thing from Hitachi (?). Well, I did pick up a spare '78 ECM a while back. It's an easy thing to try a quick swap. Thanks for that tip!