Paulytunes

Update: My 280Z will not start. I am getting 0 PSIG on the fuel pressure gauge on the fuel oil supply line. I was able to source a replacement fuel damper and plumbed up everything. Troubleshooting per the Fuel Injection and Factory Service Manual led me to find the following: All wiring connections are as intended - I did not find any plugs or harnesses disconnected. The fuel pump is not getting power when I start the car. No voltage is present at the fuel pump across the power and ground terminals when the key is in the "On" position. No voltage is present at the wiring harness under the passenger seat at the green wire and black ground when the key is in the "On" position. The fuel pump relay clicks when I try to start the car. The fuel pump operates when I run a direct line from the positive battery terminal to the pump. All of troubleshooting checks from the "Engine won't Start" section of the Fuel Injection Bible pass and my efforts lead to quote "try a different ECU." I was able to source a second ECU on eBay, but it yields the same result. My taillights and license plate lights do not work (not getting power). Running a separate ground wire from the fuel pump negative terminal to a chassis ground does not resolve the no starting condition. Based on my findings above, I am not sure what my issue is or to diagnose why I am not getting any power to the pump. Anyone have a similar problem and can diagnose? I thought maybe it was a bad ground, but wouldn't the separate ground wire have resolved the problem? From what I understand, the main ground that the fuel pump, taillights, etc. are connected to requires removal of the gas tank to access. I was hoping to avoid this, but if it is my next step, so be it. Also, when the previous damper failed, it did drip gasoline on to the pump and terminals. This is because on 1976 280Zs, the damper is above the pump and the whole kit (damper, pump, hoses, wiring) is mounted to an L shaped bracket that is mounted with three screws to the chassis. This was changed in 1977 and 1978 models to a flat plate that mounts to the chassis but places the damper and pump side-by-side. I'm guessing this was an improvement that would have reduced the possibility of a failed damper leaking fuel onto the pump. Could that wetting of the pump terminals have ruined my ground wire or power wire to the pump? How likely is it that my remanufactured aftermarket ECU and the eBay replacement (which was started to be from a 1976 2+2 4 speed, just like mine) are both bad and presenting the same exact issue?

I should also mention that my 280Z does not have the vacuum switching valve shown in most of the diagrams and photos I have seen in the FSM, other manuals, photos, etc. It seems one of the previous owners removed it. Is there a vacuum line that should be connected to it, and if so, should I plug that if the vacuum switching valve isn't there? I wouldn't think that this would cause my current issues. But it does appear that this was the vacuum line that the previous owner placed on to the dashpot nipple.

Over the past few months, I have been trying to continue to troubleshoot my high idle issues. I had it parked and applied throttle. It was stuttering and backfiring at high rpms, and then I noticed a hissing sound coming from the rear. I looked below, saw a puddle of gasoline on the garage floor, and found that my fuel damper had sprung a leak. This is the second one to fail since I replaced the aftermarket fuel pump with a slightly used OEM fuel pump. I came to find that the fuel dampers are incredibly hard (if not impossible) to find. It looks like the damper is no longer manufactured. An internet search revealed that these were also used on BMWs. But any mention of these 3 letters in the part search seems to add a 3x multiplier to the cost and it is also not available after hours of scouring the internet. So I ended up buying an aftermarket damper from Z Car Depot and made by Radium Engineering. Once I had the aftermarket damper in hand, I plumbed everything up and resumed troubleshooting. The new damper fixed the high idling problem, as it only idles high when cold, but then eventually settles down to ~800rpm when warmed up. It has a hard time keeping from stalling once the idle drops, and this is regardless of what adjustments I make to the idle speed screw. Applying throttle leads to backfiring and stuttering around 3000rpm, usually followed by a stall. This was the status yesterday. I troubleshooted more today and noticed that I somehow was missing the Air Flow Meter ground wire connection, so I fixed that. Now when I try to start it, I can get it to start, but stalling is almost immediate. Also, applying throttle has no effect, other than forcing a stall. I also noticed the pressure gauge I installed between the fuel filter and engine fuel supply tubing is now frozen at 10 psig. I also read through the "Purs like a kitten thread" (sic) and other threads found by searching, tried much of the troubleshooting in the FSM and Fuel Injection Bible, and other service manuals, but I have not been able to find a smoking gun or root cause of my issue. I can certainly relate to all those "that have been to hell and back with the factory EFI system," as someone said in one of the numerous posts I read. I am also beginning to think either my 280Z or I am cursed. Anyone know of a good Datsun mechanic in the Baltimore, MD area? I don't want to give up, but I am starting to lose hope.

This is mine (build date of 7/76): One forward plug and one aft plug.

Thanks, I'll look into that. So should that vacuum house then be open to the air or connect to something else that I am not seeing? There's a three way tee, which was always connected to the dashpot nipple, a vacuum port on the bottom of the AFM, and also to the charcoal canister vent on the other side of the engine bay. The dashpot connection does indeed seem to be common, many other L28 engine photos online show it connected.

So after much trial, error, troubleshooting, and going through the Fuel Injection Bible and FSM, I was able to get my 280Z running again. The issues I have now: I stupidly broke the plastic nipple on the stall dashpot while connecting the thermostat sensors and wiring: Idling is pretty high, around 2000rpm at cold start. Occasionally, it will adjust down to 700 to 800 rpm and will sometimes stall. Other times it will stay at 2000 rpm, unless I drive it and can force the RPMs lower with the gearing. When I take it out of gear, it shoots right back up to 2000 rpm. May be due to the temps here, which were between 55 and 60 degrees F today. I was able to temporarily fix the dashpot and reconnect the vacuum hose to it using a smaller diameter tube to insert into the part of the intact plastic and the vacuum hose until I can source a new dashpot assembly. I'll continue to diagnose the high idling and see if this is due to something I am overlooking or a symptom of my rebuilt ECU not performing up to OEM standards.

Zed Head - that is Interesting, thanks for finding that site. The OP never does say what he did with the ECU.

Thanks! This was certainly an unexpected and unfortunate discovery. I wasn't able to track down how to troubleshoot the ECU - those pages are probably long gone or that institutional knowledge died when the company went 6 feet under. I have had nothing but trouble with aftermarket parts that one of the PO's installed - first the fuel pump now this. I guess I am at a crossroads - Do I try to source a working 1976 Datsun 280Z ECU, go down the Resto mod path of installing a FAST ECU or other replacement system, or continue to struggle and troubleshoot with what I have (even though it may be an exercise in futility)?

So as I continue to troubleshoot, I pulled out the ecu to inspect it. When I unscrewed it and examined it, I noticed a qr code. When I scanned it, I am sent to a website that no longer exists. The website was Installapart.com. It appears that Installapart is no longer in business. Were they a rebuilder of ecus? Why did they go out of business? Has anyone here ever heard of Installapart or used their ecu services?

I decided to go back to the beginning of the 1976 FSM (Page EF-21) and attempted to diagnose why the engine cranks but won't start. It listed the AFM test first, so I went ahead and did that. I skipped over the fuel pump (since I recently replaced it), and then moved to the water temperature sensor test. I checked the connections at the AFM and Water Temp Sensor, both were snug. Bullet connections are snug too. I'm at a loss as to why I am not getting any continuity unless I am either doing the test wrong or I managed to really fry the wiring after I accidently and inadvertently wet the connections and burned up the fusible links.

Update: so I tested the temperature transmitter. It has the appropriate resistance for the coolant temperature. However, when I test the connection pins at the wiring harness, I get zero continuity. This is for pins 6 and 8, 7 and 8, 8 and 9, and pin 13 and ground. This leads me to believe that maybe the wiring harness is possibly bad. Could I have ruined the whole harness when I unintentionally gave the lower thermostat housing wiring connections a coolant shower and blew out my fusible links? If so, I feel like an idiot and that one's partially on me. Also partially on whichever previous owner decided to over bore the thermostat bolt, and Nissan for using non-waterproof electrical connections under a gasketed connections for coolant. 🤦‍♂️

Thanks! I will test the resistance at the ECU next. I'll be looking for a higher resistance reading since it is starting to get cooler here and my garage is not insulated.

That's what I was afraid of - the Fast EFI almost looks too good to be true. I also really don't want to stray too far away from stock if I can help it.

So I was running fine through most of the summer, until mid-August when one of the connections to the water temperature sensors broke while I was on my way to support a Cub Scouts event and show the kids my 280Z. Since I was going to be sidelined for awhile waiting for the new switch to arrive from Z Car Depot, I decided now would be a good time to flush out the coolant, replace the thermostat, etc. No good deed goes unpunished. I found one of the thermostat lower housing bolt holes to be over-bored and filled with thread sealer: Of course I discovered this after I had reconnected everything, got my 280Z to start, and then when the T-stat opened, it showered the connections and proceeded to cause a short and burned up my fusible links. So, I ended up ordering a new fusible links, a lower housing, and other parts and again was waiting for them to arrive. I got everything back together and it started but was really rough. I thought maybe I had swapped the thermo-time switch and water temperature sensor connections, but after tracing the wires back using the FSM and 1976 wiring diagram, I verified all was connected as it should be. When the engine is cold, it will start but idle really rough then eventually dies after a minute or two or applying throttle. I did the light test today from page EF-51 of the 1976 FSM, and I notice that there is no difference in brightness from the flashes of the light when cranking when the cold start valve is connected and removed. This was witnessed on the No.1 and No.4 injector connections, as the FSM instructs. The FSM states "if the lamp does not flash, or if the lamp does not become brighter when the cooling water temperature sensor harness connector is removed, it indicates that the control unit is faulty. Replace the control unit, and carry out the inspection again as described above." So my questions are: 1. Is there any other quick ways that I can determine that my ECU has failed. 2. Assuming I have a bad ECU, what is the reliability of used ECUs? Are they similar to the Transistor Ignition Unit where a used one that I find (I assume there is no more NOS available from Nissan) will be living on borrowed time and I could expect to have the same sort of failure at any given time, whether it is days, months, or years down the road? 3. If #2 is true and used ECUs will fail, has anyone tried the FAST EFI ($1,600) or other more reliable/modern fuel injection system that can chime in on their experience and whether this is a recommended option or not? Thanks in advance for any input you may have and thanks for reading.

I think you hit the nail on the head. I'll add that I think the S30's are very well engineered cars that can be worked on with a good set of metric tools and without many specialized tools. My 280Z also doesn't generate the same level of frustration of other older cars that I have owned. Caution: I may be biased and have an unnatural love for Japanese cars. There's no cost cutting measures that are prevalent in American cars (nothing frustrates me more than finding something stupid, like a $75 relay buried behind a dashboard assembly or door handles that just fatigue and break repeatedly, or overheating problems that never go away), no inherent complexity or need for special tools like German cars require, or reliability issues with other European makes. The only issues I have found is that my clumsy, large American hands are often too big to fit in small spaces. I think I said it before, but Japanese cars built up to around the mid-1990's were probably the pinnacle of automotive engineering, and that likely started somewhere around the time of the S30. Unfortunately, this golden age ended in before the new millennium, when Japan started playing the same game that all the other manufacturers do now, with impossibly difficult maintenance items, needless plastic and foam rubber coverings in the engine bay, technology that becomes obsolete in a few years, and components with limited lifespans only designed to last until the warranty expires. It is a joy to open the hood of the 280Z and just look at the L-series inline 6. I also love explaining to my kids or whoever else will listen what each component does and how it functions. I have become somewhat of a self-taught expert, using my mechanical aptitude, reading the factory service manual and fuel injection bible, and also with the help of the great members and resources of this forum. They no longer make cars like the S30 and never will again, which is why I intend to keep mine alive and driving for as long as I am able, as well as trying to cultivate and grow interest with my kids. The next generation will likely not understand how to drive a car with a manual transmission, or without backup cameras, blind spot warning lights, lane assist, traction control, power steering, and all the other electronic nannies that are present on modern cars.