Captain Obvious

Thanks for the info guys. Brubaker, sorry I couldn't help you with your trim question though.

cygnusx1, That's a great bottom line summary you posted above. I'm beaming with confidence in my 280 now! C'mon spring!!

Yeah, that's what's really got me stumped. I had the exact same thing but it was because I was lean at midrange due to the carb mods I made and the needles I was running. I switched to the N-27's and it went away. And you're running a richer needle than I am on my 260. Sounds like you're lean, but you shouldn't be. Wish I had your silver bullet!

I'm missing that chrome trim strip completely. Car came to me that way. Can you put it in after the window has been installed, or does it have to go in before you place the window into the frame? (I, thankfully, know nothing about glass.) Also, if you don't mind... What did you pay for the entire chrome trim? I don't particularly love the strip, but it looks goofy without it. I would have preferred a window seal that had no groove for the strip at all.

Now that you mention it, I don't usually actually time my cranking time. I was guessing with my ten second estimate. So out of curiosity, I timed it this afternoon. Today was the first start in about two weeks: First cold start - about four seconds. Warm restarts - Less than one second. Granted, I'm running the flat top SU's which supposedly aren't as good as the round tops, but I'm content. Even thirty seconds of straight cranking without so much as a "pop" would seem like an eternity to me. I'd be looking for a problem!

It's not the fuel pumps fault. You guys are missing my point... When you shut the car off, the carb bowls are full to the proper level. When you go to restart the car a couple days later, the bowls should still be full to the proper level. You don't need ANY fuel pump when you first start the car because the bowls are already full! You should not HAVE to pull fuel from the tank. And it's not like that fuel in the bowls gets sucked in all that quickly. How do I know this? Because there has been occasion where I want to pull the carbs off my car and I want them to be as empty as possible before I pull them. Just less mess, that's all. So I disconnect and plug the fuel input lines to the carbs and then start the engine. It will idle for a good minute or so before it starts to sputter from fuel starvation. In other words, when you first start your car, you should have about a minutes worth of fuel already in the carbs. It should be able to run for quite a while with NO fuel pump before it runs dry. So, if your bowl levels are already low, or if you're percolating the fuel out of the bowls on hot shut-off, or if you've got very low compression, or a weak spark, or your carbs aren't functioning properly, or, or, or... The point is that the underlying problem is not the fuel pump.

Before you get all wrapped up in fuel pumps trying to fix this issue, I will point out that it should not be that difficult to start the car after sitting for just a few days. I can let my 260Z sit for two weeks and it will start within the first ten seconds. Later that same day once the engine has been "freshly started", it will fire off within the first two seconds, so I do see a reduction in cranking. But having to crank for a minute or so? Come on! Requiring 60 seconds of cranking to get the car to start after sitting for two or three days? That's a problem. And not the kind of problem that a fuel pump should be used to fix. The only problem a fuel pump "could" fix is if your float bowls are going dry over a couple days of sitting... And if that's the problem, then you better spend some time trying to figure why your float bowls are going dry after sitting just a couple of days.

Haha! Read? Who said anything about reading? I figured it would take me 1000 hrs to reverse engineer the whole thing. :pirate: So. Simply out of misplaced academic interest... If one WERE to switch over to a new technology system like this on a stock engine, what would be the expected improvements? Should there be improvements in performance, economy, drivability, emissions? All of the above?

Haha! Against my better judgment, I clicked. I knew I shouldn't have, but I clicked anyway. :stupid: You know there's absolutely no way I could buy this thing and not spend 1000 hrs figuring exactly how it works and why. And then another 1000 hrs with the custom design improvements. I need another project like I need a hole in the head!! Yeah, that would be an interesting question in PA. The car is old enough that it is completely exempt from emissions testing, but I'm not sure how PennDOT would interpret an old car with a new system. I suspect they wouldn't care. Old enough to be exempt? Then it's exempt. That would be my guess.

Thanks for the wayback. I'm not surprised at all that our old L-jet can't compete with modern systems. The advances in electronics since our system was made are simply astounding. Today, one could probably completely replace our entire ECU with a small microcontroller and a couple external components to handle the current required by the injectors. A project I would love to take on... But probably never will. :classic:

Yeah, I understand completely. I don't fault you one bit for trying the seemingly unrelated. I'd be trying anything by now as well. Something else I forgot to ask a while ago... I wanted to confirm the circumstances of the mid-RPM misfire. Does it occur only under light load (like when you are cruising along at a steady speed at 4500 RPM-ish) or does it occur under no load just sitting still with your foot a little bit on the gas pedal? (Or both?) Thanks for the needle info. I've been messing around with my flat-tops and have measured a few different needles recently including the N-27. I should probably post my findings sometime.

A quarter inch out of spec might be enough to be noticeable, but what could a low bowl level do to mid-RPM cruise that wouldn't be worse at high RPM WOT? Hey, I forgot to ask you the other day... When you bought OEM stock needles, what needle number did you buy? Do the new needles even have numbers marked on them? My round tops have N-27's but I believe they ran a couple different numbers over the first few years.

I was assuming 3 and 3, but I was just looking at the FSM and the dropping resistors (6 Ohm) are grouped into 4 and 2. Who knows why, and who knows if that situation continues into the ECU... Seems like it would have been much better from a manufacturing standpoint to use two identical 3 packs of the same resistors, but who knows? Maybe they were able to share the 4 resistor pack with some 4 cylinder engines and the 2 pack is the outlier? I guess as long as they aren't getting anywhere near what the driver transistor is rated for, it probably doesn't matter if it's 3/3 or 4/2. The whole batch fired thing kinda makes me wonder why they didn't just run one big honkin' wire from the ECU to the engine and then split it up there into smaller wires for each injector. Seems like it would be a lot less copper. Maybe they were planning to go to individual injector control at some point and wanted to be ready? Why am I stirring around in the FI pot? Because I just bought a 280 and have to restart all my learning curve over. I just got my head wrapped around the carbs, and now I have to start all over again from practically zero. This one is at the house now... Can't wait for you to see it.

cygnusx1, At the very end of that thread, you mentioned a L-Jet Lobotmy and attached a .zip. What's that all about? http://forums.hybridz.org/index.php/topic/95316-braaps-l6-efi-induction-advice-and-tips/page__st__20 I'm not a member over there... What was that .zip file?

FastWoman, Yeah, I'm very pleased with the collective's opinions of the stock system. At this point I'm planning to do what you suggested and fix what's there. I was expecting more "It's junk. Switch to SU's" kind of replies and I'm very happy that didn't happen. I've done nothing with it yet, and will probably have to wait for warmer weather. First order of business was to decide which horse I was backing. So they're IC's in those packages? Do you remember if you recognized any of the numbers? Something that you could get today in DIP form perhaps? Those flying saucer heat sinks weren't all that unusual... Back then. Heck, there might even be some germanium on that board! Hey, while you're here, what's your take on which pair of cylinders the injectors open on? Luck of the draw when you start the engine "that time" on which pair? I was originally thinking about that when I saw your post in the 280 starts then stalls thread where you were talking about the spark events: http://www.classiczcars.com/forums/showthread.php?44646-76-280z-Starts-then-stalls The question I have is WHICH 3 sparks? Yeah, I saw those too. The big TO-3 transistors using the chassis as a heat sink. If I'm seeing it correctly there are two of them running three injectors off each. I know from the FI bible that they are low side switches so they are open collector outputs dragging one side of each injector to ground to open them.

More great stuff. Thanks everyone. My 280 runs pretty well, but the idle is too high and the fumes are stinky over the entire driving range. Before I spent time trying to see what I could do with the original system, I wanted to figure out if I would be better off working on the L-Jet, or if I should cut the cord and spend that time replacing the system with something better. Not surprisingly, it seems there are some gains to be had with a newer technology replacement. What is surprising however is that the original system still has a good reputation and the gains to be had by newer technology are not that dramatic. The original analog system, if working properly and as intended, seems to have stood the test of time.

Another question... The system is batch fired and all six injectors open at the same time once per engine revolution. The timing on this is accomplished by picking off a signal from the ignition coil. The ECU pulses the injectors once for every three spark events. The question is... Which three spark events? The injectors could seemingly open on sparking 1+4, or 2+5, or 3+6 depending on how the engine ended up when it shut off last time? Luck of the draw on which pair? Probably doesn't matter, but just unusual by today's standards that the ECU wouldn't have an absolute timing mark in addition to the relative one.

Excellent! That's some great stuff! I haven't dug through all of it, but it's clear that it is in fact analog. Dig those metal can transistors with the flying saucer heat sinks. Very 70's. :laugh: I don't see any trimpots or other adjustments for calibration. They must have been pretty consistent. I would have expected some factory adjustability. The pictures of the L-jet on that geeky probing site are very different than the ones you posted. I'm guessing that there were different variations of the L-Jet over the years but the basic block diagram is probably similar for all of them.

I'm having a little trouble justifying a typical vacuum leak. You said your idle is perfect, and I would expect the impact of your typical "constant" vacuum leak to decrease as you give it pedal. That's why I was trying to think of more atypical vacuum leak sources that might get worse off idle. Well whatever you find, I'm pullin' for ya!!

Yeah, the PCV "rattle" and blow through tests only goes so far. Capping it and going for a drive would be a better test. What happens when you go more than 3 turns out on the nozzle? It goes so rich that the car won't run at all? I'm with you on the exhaust leak and fuel delivery stuff. If you are OK at full throttle, then it's not fuel delivery, and anything downstream of the exhaust valve (like a headpipe leak) isn't going to give you any significant performance impact. Popping noise maybe, but no performance changes. So. Let me jump ahead a little just for cuiosity... So you put the wideband on and it shows you are very lean at midrange. What are you going to do then? And conversely, if the wideband shows you are very rich at midrange. What then? What's "the plan" in either event? :bulb:

sblake01, I'm not sure what you meant by "nothing but circuit boards" and equating that to an analog design. Both an analog and a digital design could utilize a circuit board. "Digital" doesn't have to look like a PC. You're right about 'micro', but it's time relative, right? Haha! So, just to be sure. Another way to ask the same question... Are there any software programmable devices inside that box, or not? Z train, is this the post you were talking about? http://www.classiczcars.com/forums/showthread.php?36903-280Z-ZX-ECM-tech

Thanks all. That's exactly the kind of info I was looking for. I'm not surprised at all that newer systems from today are much better than the L-Jet using technology from the early 70's. And it also makes sense that the stock system will run out of adjustability if you make significant enough engine modifications that it's not expecting. Another question... Is the L-Jet brain analog or digital? In other words, is there a microprocessor in there, or is the whole thing done analog? I suspect it's digital, but just have to ask. I just bought a 280 and now I gotta start my whole learning curve over again.

If the 280Z fuel injection system is in good shape and is working as originally intended, do people consider it a "good" system? Another way to ask that question is... If everything is working properly, is there any reason to be wanting something different or is the original Bosch system the best choice for a stock 280Z motor? I do see people pulling the FI system off and replacing with carbs, but that seems to only be in cases where the FI isn't working properly. What about when it IS working properly? Do people feel the reason to change to something else? I assume the FI system is expected to: Provide better gas mileage vs carbs. Provide better drivability over seasonal temperature swings vs. carbs Produce lower emissions vs carbs. What about performance vs. carbs?

72 FSM (EF-26) says to use 10W-30, but not SAE 30. They must have expected that SAE 30 would be too thick when cold, but the multigrade would be suitable. As for the evap system, I just refreshed my memory on the early (flow guide style) systems and after further review, my mistake... I cannot come up with any reasonable explanations how the (early) evap system could cause any extra air around the carbs into the engine. Later carbon canister style, yes. But the flow guide style like what you have? No.

Yeah, I'm with you. I would expect that "SU oil" would be perfect for the SU's!! I haven't downloaded all the different years of FSM's. I got 72, 73, and 74, so I don't know what 71 calls for. Another straw... I just noticed in your sig that you've done some changes to your evap system? What can you tell us about that? I can imagine scenarios where the evap system could allow too much air under certain conditions but still appear to be working correctly at idle.