Dave WM

we just want to see what happens to confirm the FPR is working at all the way it should. ZH is clearly a faster typist than me :)

one last comment on the 36/30 pressures, this assumes a "normal" running engine. for your case I would tend to think the 30 may be a little bit higher (but still less than the 36) since no doubt your engine is not operating in an idle mode. So you may end up with a 36/33 but the running pressure MUST be lower at idle. It may help if you happen to have a vacuum gauge you could hook up at the brake port.

assuming an intake manifold vacuum (typical of a NA engine at idle) it should rise without vacuum. so disconnect and it goes up.

if you had one, I would go so far as to hookup a vacuum line only to the FPR, like a mini vac used for bleeding breaks. You should be able to drop the pressure (flow more return fuel to the tank) by increasing the vacuum.

cant help as my internet connection will not support videos right now, ZH is on it, do exactly what he ask. and no you have to disconnect the vacuum line AT the FPR.

12.34 with the fuel pump running is not that bad. But it still is a good idea to have a new battery if its even suspect. I replace my battery every 3 years or so even if it test ok. I use a napa legend series fyi. Now back to the original problem. Just to be sure do the pressure checks again, this time with the running, then turn it off and get a engine off (pull the solenoid key to start) this way the batt will have a fresh charge on it. I just want to see those odd readings again that you had previously shown. If that is still the case then you need to check that return line and if ok it almost has to be something wrong with the FPR. You can test I have a test showing compressed air to trigger the 36 psi bleed off. In your case you would need to supply a vacuum as well to confirm the FPR operation. took a long time to type this, did not see the videos yet

that's a weak battery, get a good healthy new one, make sure you have good quality cables (not the kind that clamp on the wire) Make sure the ground connection from the batter cable to the chassis is good. Little things like this can add up and make chasing odd problems an issue. I was able to find a nice positive lead with TWO extra aux leads all molded into the cable at a local car parts store. One problem at a time. you clearly have a weak battery, so the engine off voltage will drop even more with the load of the pump. Next when the alt is working (engine on) the voltage jumps up and the pump will have power running thru it, increasing the fuel pressure. This is why its important not to jump ahead like I already did. get one thing resolved at a time. 1st now is it get a proper working voltage out of the battery. a fully charged battery should be something like 12.8 min (no load), is does not sound like a lot but 12.13 is not healthy. It will be interesting to see the voltages pump on engine off and pump on engine on. Ultimately you need to get the system working as described 36 psi engine off pump on, 30psi engine on. If that is not happening its pointless to move on to other test. the efi is a open loop system with no ability to compensate for out of spec conditions. the pressure must be correct, the sensors must be correct for the entire system to work (think ZH has already mentioned this). Modern cars with O2 sensors and real computers and adapt and keep a car running with all kinds of system failures (but then you get that dreaded "check engine"). You can still check the return line while working the battery issue out, it only takes a min to disconnect the line in the engine bay, remove the fuel tank filler cap, and make sure you can blow air back thru it. Worst case the line is blocked, not easy to fix. If its ok and the battery supply is ok, then the FPR maybe not regulating properly. this would require more test with a controlled vacuum source to make sure the problem is with the FPR. again no point in any other test till you get the 36/30 engine off/engine on with the pump running. 38PSI at idle is more fuel pressure than with the engine at wide open was designed for. no wonder the plugs foul.

Indeed that I odd. get a battery reading with the engine running vs not running. should be about 12v with just the pump running (engine off) with it idling I would expect to see 14v MAX. typical behavior would be about 36 psi engine off pump on. Start the engine idle, and drop to about 30 psi as the vacuum is applied to the FPR thru the small vacuum line. I like ZH more likely guess of low voltage from a weak battery OR bad battery cables. Make sure you have a quality set of battery cables. also agree that pressure could cause higher FPR reading but can not see how you could get a positive pressure in manifold in a NA engine.

One last thing, you did replace the vacuum line on the FPR to the intake manifold right?

watch the video. his video, not mine.

don't bother with any other checks until this is resolved.

This is how it should behave, starter disabled by pulling solenoid spade off, turning key to START. We need to know the pressure with the engine not running but the pump running. This is to check the fuel pressure with the FPR reading NO vacuum. Don't worry about the bleed off discussion, if it holds for even just a few minutes its fine. A problem would be a very quick (1 min) drop to zero. I would guess that would be a leak, but having no serious leaks to detect I am guessing about the time. There is VERY little fuel in rubber hoses that could expand and hold pressure so I would not expect it to last for a very long time. At this point no need to concern until the fuel pressure is correct per the above video, engine off pump on.

that fuel pressure is way too high. did you check it with the engine OFF and the fuel pump running. do this by removing the start solenoid spade connector (so the starter will not operate when turning the key to the START position. while holding the key in the start position get a reading. You should hear the pump running. Note the fuel pressure. Should be 36 psi. Do that and report back. One step at a time. I have some ideas as to what the issue is, but its best to not speculate with possible solutions until test results known. I am guessing the last pic is after shut down and bleed off of some of the pressure with the pump NOT running.

Great news!

you also should make sure all the heat shielding is in place, will help a lot with the splitting.

ah yes suspension you will get a lot of advice there. Your biggest decision will be stock or modify. I find stock very satisfactory as I am more of a driver vs a racer. in the stock configuration the ride is pretty rough, its a very connected to the road kind of car. Making it stiffer for "performance" would be unbearable to my old bones. I never hear anyone mention a smoother ride with suspension upgrades. AC is some fun stuff, its a very very simple system, works marginally well (not great but much better than the old 240z pull thru evap). you got to decide if you want to stick with R12 or 134a, The only real upgrade you could do is maybe a PF condenser. brand new evaps are available but expensive. The biggest complaint seems to be the volume of air flow in really hot climates. here in the sub tropics middle of summer (95f 80%humidity) can really require more than the system can handle, at best you will not sweat in the car. In LA you should be ok with the lower humidity. Looking forward to some threads on these topics once you get the current problem worked out.

sent out another email requesting an update on the status of the 280z dash, will report what I hear.

1st things 1st, check fuel pressure. rich running is a function of two things duty cycle (ECU) and fuel pressure (FPR). Best practice is to check the pressure 1st. Duty cycle is controlled by the ECU with inputs from the AFM/water temp sensor/throttle position sensor. Clearing internal fuel leaks into the intake will require leak testing of the fuel injectors. you have cleared the FPR of leaking fuel, that leaves the injectors and the cold start system. if everything checks out, the ECU itself become suspect, but that is prob the least likely to be a problem. Its solid state, lives inside the cabin so has a easy life. after rich running is resolved air leaks can be looked into, generally speaking they would allow unmetered air in a system that would account for rough idle but not rich mixtures. The split hose on the valve cover would prob make it run BETTER since its allowing air in when something else is allowing too much fuel in. Sounds like a combination of problems exist keeping the FI from ideal, so you may have some set back in performance before it all gets better. All the above being said the easiest thing to check and the most likely to be causing the issue is a defective water temp sensor. they live in a wet environment, can corrode and generally fail in a high resistance reading resulting in rich run. HOPEFULLY no one has messed with the calibration of the AFM. There is really no reason for it to become "UN" calibrated. In the electronics world we have tuned circuits that often become in operative due to "screw driver" drift... people can't seem to resist tweeking things in an attempt to resolve a problem. Tuned circuits have a very definite "peak" that can be ruined by the slightest turn. Now the AFM is not a tuned circuit like I have described but it can still be messed up I would think.

Once you get it sorted out the EFI works very well. The only odd thing that seems systemic is the hot restart issue. Its manageable by simply popping the hood up at filling stations. Seems both the carb and EFI had issues with this. Eventually Datsun came up with cooling vents and cooling fans that help keep the hot restart issue at bay. There is even mention in the owner manual about it, recommending holding full throttle while cranking when the conditions are very hot. Other things to look into, the water pump, keep a close listen to it, check it for play in the shaft (try and shake the fan side to side). I have had two Z's both water pumps went out on me while on a long drive. Usual warnings about breaking bolts apply during replacement (there are two bolts that are very long and skinny, easy to break). Use what ever technique you like to prevent breakage. this applies to a LOT of the bolts on a Datsun of this vintage. Personally I like my induction flameless heater. My 75 is not a DD either, but I do get out on the weekends to take it up to highway speeds, and have had a few long trips (over 400 miles) with no issues after the water pump replacement. just use common sense, hoses, belts (not too tight), no water pressure cleaning under the hood etc... These cars are so simple to work on and not a lot to go wrong once you work out the EFI I find it to be very reliable. Back in the day Datsun was very well regarded for reliability and economy. I owned a 1972 Datsun 1200 for my college car, it was perfect for that. I miss that car it was the definition of "basis transportation" 35mpg back in the oil shortage days came in real handy.

have some vacuum tube handy, if that is the OE piece it will be hard. I used some hemostats to get at it to remove, can be a bit of a bear. after confirming leakage from that you can just replace with some new stuff, much easier to slide into place if its the type with the real short piece.

the oil cap off runs better confirms the rich fuel mix, unmetered air entering thru oil fill hole. a couple things look for gas leaks (no engine fires) from ALL the rubber hoses, if they have been replaced I hope it was with FI rated hoses. do the engine off fuel pressure (36 psi with fuel pump on engine NOT running). The process requires disconnecting the starter solenoid (spade connector small on starter) so the engine will not turn over, then key to START position until fuel pressure comes up, should be full pressure in a matter of seconds. should be 36psi (sea level). Release key and watch pressure. It should hold for at least a few minutes, if it drops off instantly then you have a leaking injector or FPR or something else. Try that and report back.

too funny!

got the sparkler working

Remember the episode of TNG where the alien race spoke only in metaphors? you can kinda do that by old TV shows if you have an extensive enough "vocabulary" to recall. Darmok. here is one for you: ghost/phantoms/specters...

Yea it was like a contact high watching the others relate to his talking about the craving (x files) no more cole slaw for me. Gotta give the lady shrink credit for hanging in there at the end.