KDMatt

Did you ever check your reaction disc? Be careful you don't lose it in the booster if you mess with the rod!

+1 This is exactly what it sounds like to me. I think he mentioned that he replaced the booster -- I can't remember since it's been a while, but replacement boosters typically include new rods don't they? I think I remember seeing that OP's replacement booster was for a 2+2, which might explain why the rod length changed.

Spendy? Oh yes. They don't make them anymore, so I had to track down a NOS one on eBay. About 80 bucks... but worth the peace of mind. Alright, so there's a green wire with dark green stripes that runs through the whole deal on the passenger side, and that's the positive lead for the fuel pump. Alright. I'll try to track down these junctions, check their conditions, and check voltage. Thank you for this diagram! Where did it come from?

Correct. That's the one I replaced. Small, silver, and under the driver's side panel, just above the ECU --- This thing: The t'ed wire I'm talking about comes off of that. IIRC, on the '76, this relay controls the fuel pump as well as power to the EFI stuff, like the auxiliary air regulator. That is to say, with this thing removed, absolutely nothing happens when you turn the key to on or even try to click the starter. Could you elaborate on the "connector next to the passenger seat" though...? I'm keeping a multimeter in my car right now so, if it happens again, I can jump out and see if the pump is getting power or not. I fiddled with the little T'ed in wire, made sure it was nice and snug, and took the car out for a little cruise... mixed driving... so far no issues. :/

I just replaced the relay though. I never had a problem with it, even with the old one I had that had gotten a bit mangled. If I'm not mistaken, the wires that got bypassed/T-ed are the ones for the AFM shutoff switch.

Hey guys, thank you for the replies! Going into the meat of this business with the fuel pump... my understanding of the L-Jetronic system in this car was that the pressure in the system was maintained by the FPR in the middle of the OEM rail... otherwise there is nothing to keep all the fuel from running back down the return line. I'm assuming the check-valve is what maintains pressure while the pump is powered and running? As I said before, right now I have an aftermarket FPR and aftermarket fuel-rail in the car. As far as I'm aware the design of the former is supposed to let it depressurize while the car is off. @Chickenman I'll double-check my connections, but this car hasn't seen a lot of action since the pump was replaced, so given my cursory glance I didn't see a whole lot of corrosion... No harm in pulling the contacts to look though I guess. The new filter's only been on there a week and I didn't see any obvious signs of debris. @Zed Head As far as the the wiring modifications go... the P/O used some of those goofy T-joints to do it and added a removable connection between the two ends... My guess is that he wanted to make a rudimentary kill-switch because when I pull the plugs loose from each other, the fuel pump no longer runs... in fact the symptoms are identical to what happened to me. Now, I'm not going to say this is my "smoking gun," ... but the randomness of the "dying" as well as the sudden onset of it (and sudden complete recovery) certainly seem consistent with an electrical issue... and since this wire is near my clutching leg it's conceivable it got knocked loose enough to kill the pump. Dunno, it's a working theory for now. I'll need to find some time to take the car out to see if I can duplicate the problem.

Thanks for the quick replies! @siteunseen -- the pump still only runs when the key is switched to "ON" so it shouldn't have abnormally high wear or use on it... Plus it's not very old. Thanks for the well-wishes. @Zed Head -- car's a '76, and yes I can tell when the pump is running because it makes audible noise... In fact, my roommate has walked into the garage many times while I'm tinkering and asked what that "buzzing noise" is from the back of the car... in that respect, in addition to the flatlined FPR readout, it's easy to tell when the pump isn't running. A previous owner bypassed the shutoff by jumping a couple of wires together on the fuel-relay harness... I couldn't tel you exactly which ones or how since I didn't do the work. It's been a fortuitous modification (since the aftermarket fuel-rail doesn't hold pressure like the OEM one does... it can be useful to give the system a few extra seconds to 'charge' before I try to start the car) so I haven't touched it. Easy way to tell if it's the fuel pump? It didn't feel hot to the touch... isn't the old trick a bit like a bad starter? Give it a few gentle taps with a wrench and if it starts moving again you know the bearings or something inside have seized? Your comment on the ECU definitely made he gulp. I'm still battling some running issues with this thing and it could definitely point to the ECU as a smoking gun... I think I still need more evidence though... :/ Did the L28 ECU stay pretty much the same from 75 to 83? I know a few local ZX guys that might have an extra one from an S130 laying around.

So I've finally started driving my Z again after about 5 weeks of extensive rehab. Today was her first day to the office and back home... About a mile from my house (on a slower main thoroughfare) the motor suddenly died. Some notes on the modifications that have been made to the car: 1 - The fuel pump shutoff has been bypassed, so the pump will begin to run as soon as the key is switched "ON" and continue to run until the key has been switched "OFF" 2 - The stock fuel rail has been removed in favor of a solid billet-aluminum one with an adjustable FPR that provides a fuel-pressure read-out. 3 - The OEM fuel pump was replaced about 5 years ago with an aftermarket/universal one that has, until now, given me now problems. 4 - At the same time, the tank was pulled, given an acid-bath, and recoated/sealed. There is now a small plastic filter between the pump and the tank. I just replaced the fuel pump relay with a NIB NOS one since my original one had been pretty mangled. The contacts on the pump are clean and all of my fuses look okay. Since the car had been sitting for a couple of years, the tank was drained and fresh gas was put in just last week. The filter from the tank to the pump was changed at the same time. The main symptom I noticed, when I pulled off to the side of the road, after it died the first time was that with the key ON the pump wasn't running. The fuel gauge on the FPR was also flatlined, but had occasional jumps up in pressure. The engine was also at operating temperature -- having just finished a 45 minute commute home in rush-hour traffic. Somehow, some way, when I started cranking, after a few attempts, the car was convinced to idle... and I limped home... It died two more times on the way. I suppose the next step would be to keep a multi-meter with me in the car to see if, the next time it dies, there's still voltage at the pump. I'm not eager to just "drive it until it dies again" though... God knows where I'm going to end up if I do that. What are some of your guys' immediate thoughts on this? Anything else that could be worth checking beyond all the stuff I just mentioned? Thanks in advance.

I think I was just in a hurry before and didn't have all of the lobes/cylinders at TDC, so as you might imagine some of the clearances were off. Now that they're all correct to 'cold-spec' (after sitting for a few days) it's nice and quiet like it ought to be. I just use a 14mm wrench, and 17mm wrench, along with the go/no-go method on the feeler gauges... and yeah, the locknut tends to move the adjustment out of spec -- I figured that out the hard way, but that wasn't why it was out of spec -- it was out of spec because I wasn't being fastidious about the rotation of the cam lobes. Anyway, I think all is well in the kingdom now. Thanks guys!

Sorry about the delay. I had to finish installing all my new shocks and springs this week. I re-checked the valve lash and you guys were right. Some of them were WAY out of spec. Not sure how that happened, but after re-adjusting the ones that had gone wonky the whole thing quieted down considerably. Now I just need to re-tune a bit more... adjust fuel mixture and what have you... getting a bit of backfire out of the intake, but I doubt that's related to this particular project.

Correct. The seals are replaced, the engine is all back together, and it's running ... very smoothly too I might add. I gave it some fresh gas and a fresh filter this weekend so I could correctly tune the ignition timing and fuel pressure (because adjustable FPR), and I would venture to say this is the nicest I have ever had this motor running... save for the added noise. The extra noise I've picked up is definitely from the valve/cam area -- I've had this car for 11 years and have never been able to hear valve or cam noise from inside the cabin of the car while driving. I suppose there's no harm in cracking it back open now that it's undergone a few cold/hot cycles to see if perhaps the clearances have gotten tighter or something. I didn't get any of the tappets/rockers mixed up when I put it all back together (because I did one at a time) ... only thing I can think of that even stood a chance of being put back together wrong would be the little circular lash-pads that live on top of the valve keepers. I tried to keep them all in the same orientation they came out in, but my magnetic puller might have flipped a couple. I've read in other threads that these little things can be a source of noise. Thoughts?

So, before we let this thread fall into the annals of CZC.com history... ... is the valve ticking/tapping in and of itself anything to worry about if the car seems to be running well otherwise? I'm assuming at some point I should just plan to replace the tappets, lash-pads, and retaining springs in the future, but for the time being the engine isn't going to self-destruct, right? I've only ever dealt with 'ticking' on cars with hydraulic lifters, which is a different ballgame.

I read this out loud. The glare I got from across the room was priceless. "You're not getting any more cars until we move" ... which doesn't mean never!!

I got lucky on the Trans Am project. She and I are big Knight Rider fans, so when I told her I had the opportunity to get a great deal on an '82 Trans Am, she was the very first person to tell me I should do it, haha... Between her and our housemate, we've got 5 cars here... If I showed up with a sixth there would definitely be hell to pay. ... I might get a free pass if it were a Delorean though... in any case! I probably won't start driving this car on the regular until at least next week... so I'll just let it run like this for a while, and then re-adjust the lash after it's had a chance to "settle in."

For sure! I don't think this thing has ever run this well in the 11 years I've owned it. It already feels like a completely different car and I'm not even finished! New shocks and springs this weekend (stay tuned for THAT thread, lol) -- I just needed to stop being a chicken about diving in there and just getting it done. After years of working on various other cars... a Beemer, couple of Honda motors, the T/A, my Mustang, I remembered how delightfully simple this 40-year-old Nissan powertrain is... kind of keeps things in perspective. Besides, she turned 40 this year. She's in the throws of a midlife crisis and demands some attention! "Next Datsun project" though... just don't tell my other half. I've been itching to get a Roadster... and if I had the room I probably wouldn't hesitate... but she would kill me if I came home with another project, haha! No, after the Z is back in good working order, my next focus will be on that third-gen Trans Am in my garage - the whole powertrain is coming out. Here's the video I took of the the car running -- I know I'm probably just being paranoid. I've heard motors that tick way worse than this one does. Don't mind me mumbling something about ticking and fuel injectors ... also don't mind the missing stuff on the valve cover. I was in a hurry to get the car running again so I skipped a few things. It was 2 AM! https://drive.google.com/file/d/0B7_bZL8NqxIAejB3aGNHekgzTEU/view?usp=sharing @rossiz I have not done a "hot" adjustment... I don't think I could adjust them fast enough for all of them to remain the same temperature. Needless to say I adjusted all of them to cold specs as I put the rockers and lashes back together - it'd been a few years since I'd last done it.