FastWoman

I had a fuel pump fail that way. My car would idle fine in the driveway, but when I drove it, the engine would eventually falter and then die. It turns out the fuel pump ran fine until it heated up. Then pressure and volume would fall off. You might be able to recreate this problem in the driveway, without even running your engine. Pull off your return line, and connect a long fuel hose that you can run back to the filler neck of your gas tank. Connect a fuel pressure gauge between your fuel filter and the fuel rail. Finally, hot-wire your pump, and run it with the ignition off. Pressure should read about 36 psi, and you should get a healthy rate of fuel flow from the end of the return hose into your gas tank. Let the pump crank for a while, and see if pressure starts to fall and return fuel flow starts to decline. If your pump is like mine was, pressure will fall quite low, and there will be no return fuel flow at all. And BTW, I'm a bit concerned about "blue smoke from the exhaust." Perhaps you mean black or gray smoke? Blue smoke would suggest oil burning. Also check that your coolant temp sensor has a good connection. If that circuit goes open, then you can enter an extremely rich condition that would have your exhaust belching black smoke.

OK, fuel isn't cut at WOT above 3k with the TPS unplugged. It IS cut at WOT above 3k with the TPS connected. Therefore we can assume there is a connection (perhaps a very high impedance one) between pins 2 and 18 when the TPS is connected to the ECU and the throttle is wide open. Somehow, some way, THIS IS YOUR PROBLEM. We know the TPS mediates this connection, but we cannot assume we have isolated the source of this connection to either the TPS, the ECU, or the wiring inbetween. We have these possibilities that I can see: (1) There is a high impedance salt bridge between 2 and 18 in the TPS. (See suggestions above for washing electrolytes from the TPS.) What resistance range did you use on your multimeter? If you used something like a 200 Ohm range, you're not likely to see the sort of salt bridge I'm talking about. You should use the highest possible resistance range on your meter. (2) Your middle contact (18) floats off idle and below WOT (which is really just a "healthy" throttle, not necessarily to the floor). Perhaps the contact is hovering close enough to the 2 contact to bump it when the engine is vibrating hard. If the middle contact floats pretty evenly between 2 and 3, I'd say there's very little likelihood of the contact bumping. I've never heard of it. (3) I'm tentatively ruling out a wiring problem that shorts pin 3 to pin 2 or that reverses pins 2 and 3, based on your observation that 2 and 18 have continuity at idle and at no other throttle position. However, I'm ASSUMING you mean that 2 has continuity WITH 18 and not with something else. I suggest, again, that you reconfirm 2 (idle contact) runs to 2, 3 (WOT contact) runs to 3, and 18 (center contact) runs to 18, and that none of these is shorted to ground. (4) You re-flowed the solder on the ECU boards. I suggested a while ago, but I don't think you've investigated the possibility, that you might have introduced a solder bridge between pins 2 and 3 on the ECU board. That would be easy to do. If you have done this, then at either idle or WOT, there would be continuity between pins 2, 3, and 18. Otherwise there would only be continuity between pins 2 and 3. Of course unplugging the TPS would eliminate any continuity between 2/3 and 18, so the ECU wouldn't enter into a fuel cut state above 3k. I suggest you test for continuity between pins 2 and 3 of the ECU (not the 35 pin connector). If continuity exists, then there's your problem. (5) I suppose it's possible there's a solder bridge upstream from the 35 pin connector and its board contacts. Without a schematic of the ECU, it would be difficult to identify possible trouble spots. The adjacent contacts 2 and 3 sound as likely a trouble spot as I can imagine. BTW, I don't think anybody has a schematic. The ECU uses proprietary chips in oil cans, so even if you can map out all the traces and small components, god only knows what's inside the oil cans.

I disagree: CAN you? No, at least in most states, according to the law, if you're going to drive the car on public roads. I don't know whether Kansas is such a state. BTW, there's at least one reason the EGR wouldn't be controlled by the AFM output. That would require some sort of electrical servo as an output from the ECU, meaning more complexity required of Bosch's EFI. The EGR system is designed as a purely mechanical system, and that's something Nissan could do on their own, without requiring design changes from another company.

Here's a thought: If the ECU has so high an input impedance on the TPS circuit that a bit of water between the contacts can cause trip the logic, then it might also be sensitive to a buildup of electrolytes over the years, perhaps from exposure to road salt. (I note that you're in west Ohio.) Considering this, I would recommend you remove the TPS, scrub it down with gasoline. Let dry. Then wash with detergent and water. Finally, soak the switch overnight in distilled water (because electrolytes might be sandwiched between parts), do a final rinse in distilled water, and let dry. Re-lube. Reinstall.

Mixel, that racket sounds like an exhaust leak at the exhaust manifold gasket. It is EXACTLY the same sort of tapping sound (yes, that sounds like knocking/rattling metal parts) as I had on a 318 in our boat. The exhaust risers were fussy to bolt down with the stainless studs, and they would develop leaks every 2 years or so, so I'm very familiar with this noise. What I learned with that boat is that leaking exhaust gasses erode gaskets and even metal, so your having tightened the #6 bolts would likely not have fixed the leak. You've got to pull the intake/exhaust manifolds and replace the gasket. Anyway, it's an exhaust leak. I'd bet money on it.

Rossiz, your putting your fuse block and relays in the cabin was a great idea. Relays are pretty well protected even in the hood compartment, but those fuses do get bathed in rainwater. My solution to the moisture issue was to put a band of clear packing tape over the top of the acrylic fuse block. You can't really see it, and it forms a pretty good umbrella. But inside the cabin would have been much, much better. I might relocate mine someday.

Txvepr, my fusible link blocks were broken apart, and because they are contiguous with the wires you mention, there's no way to replace them without finding junkyard replacements and splicing them in. Of course the ECU fusible links to which Tomo is referring are more easily replaceable with generic components. Anyway, Tomo, I easily justified replacing the awful, broken-apart mess of fusible link junk that came with my car (hanging from the dangly wires) because there were no OEM replacement parts available -- not even a pair of decent, used, wrecking yard blocks. And after having done the conversion, I am so much happier with the proper fuses. I've got current, voltage, POWER! Some of this is due to some rebuilding I did of the wiring tree (the mess Txvepr refers to). I ran a 4 ga alternator wire straight to the fuse block, which did away with all of the goofy OEM white-wire splicing internal to the harness. While I was at it, I also wired in some headlight relays, and now I have bright, white lights. Woohoo! I believe your car is a DD, just like mine. Considering that, I highly recommend these mods!

A single MIA injector isn't going to cause your engine to cut out completely above 3kRPM. It will give your exhaust a chugging sound, and you will lose 1/6 of your power throughout the power band. But no, it won't cause your engine to drop out. A non-working injector also will not affect the fuel/air ratio balance. The cylinders that are running will be getting the same mix as they would if the #5 injector were working. Your injectors could just be gummed up with varnish. If there's any flow at all through your #5, there's hope for cleaning it up. (A stuck injector might free up once it gets hot. Does it show a normal resistance across its contacts?) I once cleaned up a gummy intake by running some Chemtool B12 through it. It took a bit of persistence, but it finally paid off. Have you taken the cover off of the TPS to see if anything is amiss? Have you confirmed the correct signals at the big ECU connector when you move the accelerator pedal?

Your high fuel pressure reading could be an inaccurate fuel pressure gauge. You might try confirming with another gauge. You might be able to borrow one from an auto parts store. (You leave a deposit with them that gets refunded when you return the gauge.) It's entirely possible your engine was running lean, and then you added enough resistance to make it run rich. Or perhaps it was running rich, and you made it run richer. Any of that is possible. You really have to adjust the potentiometer to maximize the vacuum and performance -- and to give the plugs a nice mocha color. The cutting out issue does sound like the TPS. Perhaps the previous owner/mechanic rewired it incorrectly, or perhaps it's broken. It sounds to me like it's sending a throttle-closed signal to the ECU when you step on the pedal. If the engine is turning above 3k or so, the ECU will then cut fuel. You should check this switch very carefully to make certain it's doing what it should. You should check it both visually and with a meter at the big ECU connector. Another thought: When you reflowed the solder on the ECU PCBs, is it at all possible that you introduced a short between traces leading to the TPS? It might be worth a look.

Well, I grant you they don't look OEM. Fuses are better overcurrent protection devices than fusible links, IMO. They are not so crusty/rickety, and they don't create as great a voltage drop (which is really pretty minimal with either). Here are all of my main fuses, BTW -- substituted for all 6 fusible links, plus stereo, plus alternator...

Some people want a perfect car to polish and admire -- and to drive to car shows on odd weekends. And that's OK. I once bought an extremely nice show-type Mustang and learned that such a car is, for ME, absolutely no fun to own. I was constantly scared I would scratch it or get a door ping. So it sat in the garage a lot. My current Z is not perfect. She looks good, but she's got a few rusty spots, a couple of small scratches, and a ding in the hood where I forgot to remove a socket before closing the hood. @#$%!!! So if the car gets a door ding in a parking lot, I'll curse about it, but I'll get over it by nightfall. Otherwise I have the car in excellent running condition, because it would bother me greatly if it wasn't. My car is "just right" -- for ME. It's a car I enjoy using. I would not enjoy it if it were perfect, and that's perhaps one reason I'm reluctant to lay into body work. I'll also mention that a car is no fun TO ME if I don't put something of myself into it -- a repair here, a small mod there -- something that's MINE. I think I bonded with my car in a big way with regard to the brakes and the EFI. Not everyone is like this, but many people are. I'm not saying your thinking should be just like mine. Rather, I'm raising a couple of issues you might want to consider. Will $7-10k get you a nice Z? Yes, absolutely! Towards the $7k end, it won't be perfect, but it will be very nice, especially in Utah. You might find some nice cars in Arizona. I think your expectations seem reasonable. If you want a perfect car and don't care how much you have contributed to that perfection, the best thing you can do is to find a car that is already perfect -- that someone else has restored. You will likely buy it for less money than they have into it.

WOW! That's the rustiest car I've ever seen! I hope your welding guy takes lots of pics for us, so that we can marvel at his workmanship!

Nice!

Yes, download the service manual. It's absolutely the most important resource you can have. It's light years beyond what you would find in a Haynes or Chilton's. However, the first thing you should check out is fusible links under "body electrical." I'd bet good money you have a bad fusible link.

You replace it with a MaxiFuse! But seriously, I suspect the fusible link was sold with the connectors on the end. But there's no reason you can't pull yours apart. You might get lucky and find the right connector to re-insert into the shell.

Hey, if anyone's interested, I ran across this water-tight 12-pin electrical connector on ebay that looks like the one I used as a main disconnect for my 6 injectors on my fuel rail: 1 Sets 12 Pin Waterproof Electrical Wire Connector Plug DT04 12P and DT06 12S | eBay This allowed me to create a fuel rail wiring harness, bound tightly to the rail, with one large pigtail coming off of it to attach to the main EFI harness.

Zed, to be more accurate, I have a split rubber hose over my rail, wrapped with silicone rubber tape. The intent was certainly to insulate, but I don't know how effective the rubber really is. It's entirely possible that if I remove it, my hot restart will go away (and my intake manifold will take a small aesthetic setback).

Well, mrj45, it doesn't really have to go on the firewall. If you can direct your eyes to siteunseen's photo just prior to his extraordinarily top-heavy fishing companion with the small, golden bandages tied to her body, you'll notice that the return line comes off of a "T" at the back end of the fuel rail. The hose coming off the driver side of the "T" feeds the cold start valve. An alternative configuration might be to have a hose running from the back of the rail to a "T" near the cold start valve. Then mount a FPR to a bracket in that same area, fed from the "T" and emptying to the hardlines that run around the front of the head. If you want to make it neater, put a barb connector into a 7th hole just behind the #6 injector, so that the return hose drops down beside the line of injectors. Then put a plug in the end hole. Better still, figure out some way to bracket a hard, stainless return line in parallel with the fuel rail. There's something seductive about the plumbing of an engine if done neatly. ----------------------- And speaking of "clean," Tomo, those hardlines and your FPR look quite fetching! Do they just polish up like that, or are they chromed?

With an adjustable regulator of the vacuum compensated variety (e.g. an Aeromotive unit), you would be able to tweak the fuel/air ratio simply by adjusting pressure. However, as already mentioned, these sorts of FPRs leak down after engine shutoff, which would surely worsen the hot restart issue.

With a solid weld? No. There would be very efficient heat conduction through the aluminum. However, you could attach two rails together with a few brackets (perhaps a welded assembly), so that there's mostly air between the two rails. That would work fairly well. Or you could bracket a return tube below the rail.

Geeez! Come on, guys!

Gold, after you shut down your engine, I think that IS the case, that the engine is hotter than the surrounding air. After fuel flow stops, the injectors and the fuel inside them are probably heated rather quickly to the temp of the cylinder head and underlying exhaust manifold. On another note, I notice that Blue suggested a two-hole fuel rail design, above, whereby one hole is the supply and the other hole is the return. Although this sounds like a good idea on the surface and certainly neatens the engine bay, it would not be a good idea with respect to cooling the fuel rail with fresh fuel during startup. A two-hole rail would essentially become a countercurrent heat exchanger. Cool fuel entering the rail would be warmed by hot fuel exiting the rail, resulting in a somewhat static heat gradient between #1 (cool) and #6 (hot). If hot fuel is tapped off of the #6 end instead, and returned around the back end of the engine, it does not have the opportunity to transfer heat back to the incoming fuel. BTW, countercurrent heat exchange is how a duck can go paddling around in ice-cold water with its big, webbed feet and not lose its body heat to the water. Blood flowing to the feet is cooled by returning blood, which is re-warmed before re-entering the rest of the body. The duck's feet are ice cold, and there's very little body heat to be lost. Lessons from nature!

My car was pretty clean, except that it came with one aftermarket mouse nest atop the intake manifold. Fortunately the little buggers didn't nibble any wiring. I think the PO's only sin -- a minor one -- was to stick a number of parts in place with silicone caulk (e.g. the chrome trim piece at the top of the interior arm rest). My favorite, though, was on a boat of ours, not the Z. When I reworked the bilge pump system, I came upon a brick in the forward bilge (and of course removed it). It was a few years later that some guy was eying our boat in drydock. (We were scraping the bottom.) He said, "That boat sure looks familiar!) It turns out it was his late father's decades earlier. We chatted about many aspects of the boat. I mentioned the brick in the bilge, and he said, "Yeah, then that's DEFINITELY Dad's boat!" It turns out he used the brick to weight down the old bilge pump (which should have been screwed in place).

Vintageair is for American vehicles, at least if you want a true retrofit design. I checked their site, and they don't have anything for the Z, so the best you could do is to buy generic components. It would be nice if they did, though. I installed a Vintageair A/C in my '66 Mustang, and it was a very nice retrofit. Maybe if we pestered them about it, they'd branch off into Japanese cars.

Well, I think it's safe to say they're not OEM. I think you can remove them and any of their companions without fear. FAIW, if you're not brave enough to nibble them yourself (I wouldn't be that brave either), just set them out on your back patio and see if the birds eat them.