Zed Head

It is fun to turn that knob and get an immediate effect. Too bad you're short a few fingers for a while, might make it difficult. I wish we had more tuning tools that were so simple.

Car and year would help. I have a 76 and all I see is a body-colored panel that flows with the body lines, with nothing on it. I think that there's a notch in it for the exhaust pipe. Your description of what you're thinking about is not very good.

No problem. Get some bullet connectors and about 8 ft of wire also and you can just unplug the wires to the coolant temp sensor (bullet type) then plug in the potentiometer wires, with no wire cutting, and mount the pot inside the cabin. Tune while driving. If it doesn't work, just unplug it and go back to where your were, no damage. Good luck.

I don't think that you ever really said what you're trying to do, but it looks like you're trying to make things richer. I agree with FastWoman, that adjusting the spring in the AFM will affect low RPM and high RPM (low and high air flow) differently so is not an ideal way to do things. Adding a resistor will make things richer at all air flow levels. I used a 5k-ohm audio taper potentiometer (volume knob) from Radio Shack, part #271-1720 to adjust the resistance. I installed it originally just to be able to add lots of fuel to try and fix the hot start problem, but then found it was very useful when I ended up with a lean AFM, that had a lean flat spot at low RPM. Basically right after taking off from a dead stop, the engine ran through a flat spot then jumped ahead when it hit the good spot. The pot allowed me to tune out the flat spot, but it also turned out the whole curve was lean so it ended up as a really nice tuning tool, for my specific lean-running AFM. For the record, previously I had had a rich-running AFM on the engine but had no way to adjust besides an adjustable FPR. Which leaked down as described. Anyway, get the audio-taper model, the linear model is much harder to control. And 5k is really too much range, I only use the first 1/4 turn of the knob, so a smaller range would probably work even better.

You can only make the mixture richer by adding an inline resistor. But, as grantf suggested, it looks like you still have basic problems to get right before any tweaking should be considered. Your fuel pressure, for instance, should not be jumping to 40 psi. Maybe you're just seeing the needle bounce. You can test it by removing the vacuum line from the FPR while the engine is running, or removing the wire from the solenoid and turning the key to Start. It should be about 36 - 38 psi. If you can't get the engine to die or almost die by turning the idle screw in then you have a vacuum leak somewhere. If you have a vacuum leak and it's still running rich, then you have a fuel enrichment problem, either through too high fuel pressure or something like the TPS or coolant temperature sensor circuit. Lots of basics to get right before tweaking the AFM or installing a resistor. There's really no way around it. I've not read any posts where someone reported that they tested and measured the circuits described in the Engine Fuel chapter, and wished that they hadn't because t was a big waste of time. It's worth doing. The fuel pressure dropping to zero is more of an irritation than a problem to worry about. It's pretty common and there are fixes for it, but that's not your main problem. Get a meter and start probing. Good luck.

It is a magnetic pickup coil, probably off of a 260Z or a 280Z. Somewhere on this forum there is a spreadsheet of all of the Z(X) distributors from points-style to ZX style, with part numbers for each. The part numbers are in the FSMs also, if you wanted to take guess and open up the Electrical chapter. Before you get too carried away, take the breaker plate off and see if the ball bearings are still there and free to move.

I'm sure that you realize this already, but your knowledge of automobiles is not much. You have a jury-rigged fuel pump, a jury-rigged "sensor" to stop the high idle speed and smoke coming from a part that should only get power when the key is turned to Start. You're changing parts and getting ready to change more but don't have a good reason why. It looks like you're testing things by looking and touching, I don't see any meter readings. I don't see any signs that you're really making any progress, I wouldn't be surprised if your next post said "problem solved , the car burned to the ground". You have a serious dilemma, I would spend your free time trying to find a good mechanic or getting a meter and learning how to use it. Sorry, but you really are in danger of destroying the car.

Firstly, I would not use that mechanic again. Unless you didn't understand what he was saying, he does not seem to have even the basic skills required to work on EFI systems at all. Power in the wires but can't make the pump run, leaky fuel lines stopping fuel from reaching its destination in a 36 psi EFI system with a return line, air in the lines stopping flow, waiting for gravity - all bad. Edited my previous comments and gave the guy the benefit of the doubt. He might be a great mechanic for carb'ed cars. Based on the last statements, that it will run for a few seconds then die, even though the pump is running, it sounds like your injectors might not be firing and the engine is running off of the gas from the cold start valve. Or the fuel pump inlet could be clogged, but it would probably run for a more than a few seconds if so (note that "few" generally means about three). Just guesses. Looking back in the thread, it seems like it hasn't run since the welding was done. Maybe something got fried in the ECU. Keep looking for someone that knows how to work on old EFI systems, not someone excited to work on something they don't understand. Download the FSM, print out the pages of the Engine Fuel chapter and let the real mechanic do some component testing. All of the proper tests are described in the Engine Fuel chapter.

The following should help, in no particular order - Describe the car - year, model, and any modifications. Download the service manual and read the Engine Fuel and Electrical chapters - www.xenons30.com/reference or www.xenons130.com/reference Use capital letter's periods, and commas to make your posts easy and pleasant to read. It shows that you care and makes people more likely to get involved with your problem, and that there's hope that their contributions won't be wasted.

The R200, with 3.54 ratio, is the only differential used for the 1975 to 1978 280Z's. It's shown in the Service Manual. They're hard to rebuild right, from what I've read. They seem to be a noisy design in general, but much of the noise can be isolated with the right bushings, and a little sound deadening material in the back of the car. You might do a little more reading, there are more frustration stories than success, from what I've seen. Are you sure it's the bearings that are making the noise, and have you checked to see if the diff was full of fluid? After 36 years much of it will have escaped through the breather.

I had that leak and had to lay a bead of silicone around the complete perimeter of the glass/seal interface to keep the water out (I really don't want to replace the seal). The water can get in anywhere along the outside edge, gravity takes it down the gap inside the seal between the glass and rubber, it travels inside the seal to the low point and comes out on the inside corner. I tried sealing just the bottom corner, then the whole bottom edge, then the bottom and the sides but apparently there was enough water rolling over the top edge and under the seal through capillary forces to get in and fill the gap inside the seal. For anyone wondering, the way to see if you have this leak is to take a long wide left or right turn after some rain or a washing and watch for the drops of water magically appearing at the inside corner of the window and seal. The water doesn't leave much of trail when it beads up and rolls off the rubber so it's hard to find otherwise.

There's a tiny screw holding the odometer cable in place that has to be loosened. It might be possible with tiny hands but I think that you'll need to remove the tach to get to it. Stick your hand in the tach hole toget to the backof the speedometer. You might find that you can wiggle the cable end and retighten the screw and the odometer starts working again. The tip of the tiny screw fits in to a tiny hole on the end of the cable, locking it down so that it can't slip. You might also be able to slip a stiff piece of paper or plastic or metal between the speedometer edge and the lip of the dash cap to get the tach and/or speedoout. Make a little ramp to slide it past the dash cap edge. A little Armorall to make things slipperier would help too.

I think that the factory put a lot more effort in to tuning the timing than the distributor rebuild companies do. If you look, you'll find the same part number for a whole range of years from the rebuilds, but no vacuum advance data. They are either using a generic, probably mild and safe timing advance, vacuum canister, or each canister has a random advance curve. I think the canister is new though, so it's probably just a mild 10-12 degrees total at high vacuum, to avoid any pinging at all. I can understand the urge for a backup plan. That's how I ended up with the GM HEI module. I installed it just to make sure it would work if my factory module died again, the left it on and kept the factory module as the backup. I'll probably never use it again. CO made a good point about the dual pickup ignition. If you go away from the factory ignition setup you will lose that. On the manual cars, like my 76, it's main purpose seemed to be to keep the idle speed up while the engine got warm. It might have a different purpose on the 74 auto cars. Should be described in the FSM though. I deleted the second pickup on mine and just live with a low idle for a couple of minutes between the AAR closing and the engine reaching full temperature.

Every suggestion in this thread is worth checking, even if the problem goes away. Get a meter and a pen and paper and go through the tests in the Engine Fuel chapter. Almost guaranteed that you will find somethings that can be improved and your engine will run better when you're done. If you read through the chapter first you can put a table together that will show what the measurements at the pins at the ECU connector should be. For some reason Nissan broke the testing up in to testing continuity at the ECU first, then real numbers at the component itself. Easier just to measure real numbers at the ECU. For example, measure resistance at the ECU pins for the coolant temp. sensor, instead of just continuity. Don't skip the fuel pressure check either, that would be another cause of lean running. You might have a weak pump. And a sign of a plugged exhaust is a lack of pulsing at the tail pipe.

Could also be the TPS. Read the Engine Fuel chapter, it describes how the ECU delivers "full enrichment" above a certain throttle opening based on the signal from the TPS. Shows how to test it also. No throttle signal to the ECU, no enrichment, lean mixture, popping and surging. Maybe.

If the Z stuff is the same, this option might work. It's light-weight so shipping shouldn't be too bad. Bottom of the page. They take phone calls and credit card numbers. Seattle, WA. http://www.datsunstore.com/index.php/page/2/sort/2a/cName/7578-280-z3-weatherstripping-3

If you know the year of the distributor, you can find the advance curves, and details about automatic versus manual in the Electrical chapter of the FSM. Along with diagrams and drawings of how things work and go together. I don't think that the ZX vacuum canister will fit on the Z distributor. It's different. www.xenons30.com/reference www.xenons130.com/reference

Thanks for the kudos clouds. Good that you found a mechanic that can trace a circuit and figure things out. Plus take things apart and fix them. A rare find, from what I've read on these forums.

Note the comment about "details may differ" - http://atlanticz.ca/zclub/techtips/distributor/index.html If you have the 260Z electronic ignition with VR distributor, you could use the GM HEI module in place of the stock module. Cheaper, and just as effective. Check the advance mechanism on both distributors. If either doesn't move, take some time to break the rust on the ball bearings loose before forcing it. You might be able to get it moving again without breaking the plastic bearing cage.

Actually, I think it will allow you to send more shock load to the differential. Less mass to damp engine engagement through the clutch. Probably won't matter unless you're drag-racing, although I could see a higher modulus material transmitting higher frequency noise. Might be noisier, but I haven't seen any accounts. I have read stories about the aluminum shafts not liking harsh treatment through the clutch. Apparently the u-joint yokes can get damaged. You can buy a slip yoke and have a new steel shaft made for ~$250 bucks easy I would guess. I have found a local guy, up the Gorge (Portland talk...) who would shorten one for $90, which turned out to be essentially building it over again after cutting it. A good shop could probably source the yoke too. Just take your old one in and say "make me a copy of this, please". You might be spending more money than necessary for a relatively simple part.

The alternative to the full harness would be one of FricFrac's repair kits. http://forums.hybridz.org/index.php/topic/104419-s30-and-s130-wiring-harness-repair-kits-you-need-this-if-you-have-an-l28e-or-l28et/#entry1020367 You said that you were gauging interest so it seems like a good thing to know before you get too far in to it. He is a member here and posts occasionally.

I would look in the service manual and compare the vacuum and centrifugal timing curves first. The later year 280ZX distributors had some pretty aggressive vacuum advance curves, for emissions and fuel mileage purposes. The wiring diagrams are in the manuals also and will show you the differences between the two types.

The purpose of the FPR is to maintain a constant pressure differential between the fuel in the injector and the environment at the tip. So that the ECU can control fuel supply accurately with injector open time. So if pressure goes down in the manifold (vacuum reading goes up) then fuel pressure in the rail will go down also. If pressure goes up n the manifold (boost) then pressure goes up in the fuel rail. The FPR in your link in Post #3 should work fine as long as you want to go richer than stock in your tuning, which it looks like you do. Actually, it looks about like what FastWoman was describing, a stock regulator that's been modified to allow spring pressure adjustment. 45 psi is actually a pretty big increase over stock and should supply about 12% more fuel than 36 psi. The unanswered question about the Summit FPR is whether or not it will leak down like the Aeromotive and your EBay FPR.

They just had a thing on the local TV news about that same EBay ad - using "sex" to sell cars, is it right? The owner, Ridley himself, said everybody does it, and gave the Carls's Junior ad for BBQ as an example. Weird.

Fastwoman was talking about inches of vacuum here, in Post #47, but in the previous post, #46, it looks like you're reporting RPM. Have you measured intake vacuum yet?