Zed Head

Just wanted to mention it since you said you have a fairly big leak. I'm pretty sure that I replaced the crankshaft seal on the engine currently in my car, and I'm getting a few drops for every week it sits in the garage. I won't know if it was my seal repair or something else until I take it apart again. It was fine for quite a while then I jinx'ed myself by saying I had a leak-free engine.

You're considering several different categories of car. The 240Z is the basic, no frills, carb'ed "pure" sports car that Nissan intended. A 280Z is essentially a refined 240Z, with EFI and its associated blandness. A 300ZX is more like a modern car, smooth, quiet, even more bland. The Porsches are a different kind of car, more "engineered" than the Z's, which tend to take the simple route to accomplish an objective. These are all "old" cars though, compared to the computer-controlled vehicles today. You're going to have to learn on the fly to keep any of them running well, unless you find a shop nearby that can work on one. You might consider that in your choice. Find a shop that can help, then choose a car that fits the shop. Or pick the car you want and learn how to make it work. Some of the ideas you're throwing out are a bit exotic and knowledge-intensive, like the RB26 or the twin turbo 300ZX. Even a carb'ed 240Z takes some learning.

Do you have target specs? Like CR, cam lift, duration, etc. Just curious. With that dome it seems like you'd be running high CR and with the valve cutouts, high lift and duration. It's definitely not a factory spec. 8.8 CR engine, I'd guess. Curious. The specs. make the power. It's an odd looking piston shape, but not clear what it's supposed to be doing.

Check the mating surface on the crankshaft for wear. I have an old 240Z propeller shaft with a groove worn in it from a bad seal that didn't get replaced. The metal spring inside can actually break through and contact the sealing surface if it gets bad enough.

Do the number font styles match the other gauges? That might tell you if it's a 1971 gauge. Many emissions devices have a speed detector attached to the speedometer. You might read the various Emission Control chapters to see, or look at wiring diagrams.

Are you replacing the rear main bearing cap seal, or just the round crankshaft seal? Or both?

Sounds like the electrical part of your ignition switch might be messed up. You didn't mention this before though. You implied that key action was normal. If things change with each turn of the key maybe the switch is failing. It can be unplugged also. If the power goes off there's a short inside the switch component.

That's interesting. I tested mine, the "bad" ones that I removed, via a simple multi-meter test and they tested OK. Leaving me wondering what really happened. I still need to put that ECU back in and give it a ride, just to see.

The plug and diode is a good guess. Assume you have one of the MSA or Dave Irwin adapters? The simple test would be to disconnect the T plug at the alternator, engine off, and see if the brake light goes off. You can then also start the engine with the T plug disconnected and see if the engine turns off correctly. It won't hurt to run on just battery power for a little while. If that doesn't show the problem, then you might have a melted wire in a harness somewhere.

Pretty cool. I love a good detective story. I wonder if the transistor bases fail closed, in addition to failing open. Question for CO. Many ECU failures result in richness/flooding. MSA is a site sponsor. I like to let them know what the competition is doing so I gave them a some @'s below.. They have a business to run so have to be profitable, but competing with Cardone is a tough job. Cardone is not known for high quality though, they're more high volume. Beware, that savings might be temporary. And don't forget the member discount at MSA. Somehwere out there is your member number which gives a discount at thier store (not sure of the percentage). It used to be under your username but it seems to have disappeared again. The core charges are the big deal killer though, especially since you don't know if your core is good, until after you send it in. Plus you can't keep the old part for messing with, which is most of the fun with DIY. @Joseph@TheZStore @James@TheZStore

CaliforniaDatsun is a gamble. That''s the problem. If you get a bad part he makes it very difficult to make it right. You got lucky. If you're a gambler, go for it.

Exotic. The top ring land is way down the bore. Are they for a turbo application? Race motor? Can't imagine they'd fit under a stock combustion chamber design. Or will they?

I probably planted the wrong seed in your brain when I said C and E. You want to check voltage on C, and continuity to ground on E. Which you did, directly, and in one step with your method.. The voltage was on C and the path to ground was on E. So those numbers look right. But they don't tell you about the "B" circuit. You're at the point where you'll probably find that a replacement ECU will get you running. Then you'll have to decide if you want to try to fix the ECU. Yours is the first 3 injector problem I've seen. It implies that one of those transistor "B" traces is bad. It seems like the "B" timing circuit should be common to both, otherwise there would be two complete sets of timing circuits, which seems overkill and redundant. So, tracing the two transistor "B" circuits back should find a break, I'd think. My inner engineer is curious. Don't throw the ECU away if you get a good one.

Actually, the C voltage fits what you saw at the ECU connector. The E voltage might be through one of those resistors CO mentioned in that other thread. You can see full voltage if very little current is flowing. Did you check for continuity to ground on the E pin? You can do that with the key off. Anyway, the reality is it doesn't work. The very last thing that Nissan says after all of the other tests fail is "replace ECU". Try a loaner first, then you'll know if you should buy.

Did they fail in the same way? CO knows his stuff. I'd take him up on his loaner offer. Maybe he'll swap that transistor for you just to see what happens . I'm not sure but I think that the transistors should have a direct connection to the injectors. You should be able to take a meter and see voltage on the "C" leg, I believe. It should be hot when the injectors are, and the "E" leg should be connected to ground. "B" is the activater, controlled by the timing circuitry. (Give me a grade CO...). So you can check C and E by plugging in the ECU and turning on the key. Be careful with the meter probes.

The gasket alone, dry, should be fine on the cover. On the bolts, make sure that there are no burrs on the mating surfaces from past lock washer damage, clean them up, scrape off damaged paint (Nissan clamped directly on fresh paint but it tends to chip off after disassembly.) and don't use any thread locker. Make sure the lock washers are in good shape. But new ones if you're not sure. Some of us (me for sure, I think others) put a spongy material in the cover vent to stop oil droplets from leaving and oiling up the diff. You might consider it while its apart.

I have a vague memory of exploring the source of those O'Reilly's heads in the past. I think that they source them and rebuild them when orders come in. I just called O"Reillys and asked about one. They said that they special order it from Power Torque and it should show up in one week. I got on the Google and found these. Very recent. There's always somethin;... https://power-torque-engines.pissedconsumer.com/ http://www.bbb.org/dallas/business-reviews/engines-rebuild-and-exchange/power-torque-engines-in-grand-prairie-tx-90405420/complaints Hate to be a downer. They might do great with high volume stuff like small block chevys. So many ways to go wrong with the L6 head though. Cam lobes, valve seats, cracks...

The 11 600-000 number looks right. You have what might be a second source ECU, or a replacement, from Bosch, with a "K" instead of an "A". You got a picture of the bottom of the transistors. They're above the picture I cut out of yours. You can see the ribbons. The screw heads are of the screws holding the transistors. Here's a copy of the ECU guide, showing the Nissan "A" numbers.

You're unlikely to find a place that has rebuilt 5 speeds "in stock". Your best route will probably be to find a decent used one and take it to a shop that knows what's what. And that 5th gear would be a .745. .75 would come from your rounding method, which can vary depending on profession.

It's a perfect bathroom library book. You can learn something in just a paragraph. Don't even want to think about mobile phone/super computers in the bathroom...

Post #37 here has the part # for the transistor - http://www.classiczcars.com/topic/56143-super-rich-plugs-fouled/?page=2 You can also read our past ramblings, insights, and conclusions about ECU problems. Might be entertaining.

I'll dig up the number. The connections from the transistor pins to the board are fairly fragile looking metal ribbons. Very easy to see, the two transistors are on the top edge of the assembly. ~Quarter-size. I could see one of the ribbons getting damaged if somebody poked around in there. You never know. Besides that, you'll want the part number for the ECU. There are several.

You might want to wait until you know which camshaft you'll be using before you buy lash pads. If you get a reground cam profile, the lash pads will be different than with a stock camshaft. Also, waiting until the head has been inspected is a good idea too since it's possible that it's warped or cracked or eroded internally. It might not be worth rebuilding. The basic process and steps, in order, is/are described in the "How to Rebuild" book that site linked to (which you really should have bought before you even started. It's very thorough). If you find the right shop/mechanic they'll know the details of lash pads and rocker arm wipe patterns and other details. If you get the wrong one they might try to guess their way through and they can make a mess of things. Somebody on another forum got a single bad/tight rocker arm and ruined his camshaft. When things are right they're very durable. When things are off, they can fail quickly.

Just for fun, you might take the ECU cover off and make sure the transistor wires are intact, and/or not shorted. The ECU location can get moist if a leak develops at the windshield. I actually have some part numbers for a replacement transistor and did replace both on a bad ECU. But probably for the wrong reasons, they tested okay afterward. It was probably something else. Your situation though, with three dead injectors, looks like maybe a single transistor or its wiring.

That looks like the replacement relay for the original JECS relay. Which is actually based on the Bosch system. It's actually two relays in one, EFI and fuel pump. Despite all of the pins it's a fairly simple relay. If you get the readings that you should at the ECU connector, don't worry about it. Many people "assume" and replace, it's hard to resist. If you get tricky, you can ground the injectors individually at the ECU connector, just like it would, to test the complete circuit of wires, power and injectors. I made some male pins to use in the connector from a flattened piece of solid core copper wire. Makes it easy to get an alligator clip connected to supply power and ground. Forgot to say - there's a procedure for testing the EFI relay, if you get odd numbers. In the FSM, Engine Fuel chapter, and probably in that EFI book too.