Fuel Injection Issues

[Yaboyolin]

Hey guys, I've got a 78 280z that won't start. I think I've narrowed it down to the ECU but I'm not positive. I've read through the manual thing but FI is something I've never touched before, always had carbs. Basically the power relay is clicking, the air regulator has power, the injectors fluctuate a little with a voltmeter on it, but only a couple of volts. I tried the injector sound test with a screwdriver and that doesn't seem to give me anything. The pressure regulator doesn't buzz like it said it should in the manual, but I have no idea why it would buzz at it doesn't have any power running to it. I know the fuel pump works, it has a manual switch and you can hear it run. Sorry for the newb question, but just looking to get some insight as this is the only thing keeping my Z off the road. 

[S30Driver]

When did the motor last start & run?

To start with ... Verify you have a charged battery, (voltage is important with FI), then verify spark, and if so, see if it will run on a shot starter fluid.

[Yaboyolin]

No idea when it last ran. I do have a nice spark and it will run on SF. The PO stated that the fuel pump was new and hooked up correctly, but I crawled underneath the car to check this just now and discovered that the pump was connected backwards and is leaking like a siv. So I'll replace that in the next couple days and get back to you. I assume not getting gas to the engine is probably an issue when it comes to combustion engines 

is there anything I can also check while I wait on a fuel pump? 

Edited March 7, 2017 by Yaboyolin

[SteveJ]

The voltage on the injectors will only fluctuate about 2 volts when they are firing. You might consider getting a fuel pressure gauge to install on the fuel line in the engine bay. Get one that goes to 60 PSI. From your follow-up, it sounds like you didn't have pressurized fuel in the rail. I'm not an expert on fuel injection, but I'm thinking the injectors might not be making much of a clicking sound if there isn't fuel in them.

In the meantime, download the FSM for your car. You can get it from this site or from the link in my signature.

[Yaboyolin]

Right, there was no fuel getting through the line. Now how exactly do you bleed the injectors? Or do you even have to? I know it's a must with diesels. And how do I check the pressure regulator?

[SteveJ]

I would prime the fuel line. The fuel filter is probably the easiest access point.

[Yaboyolin]

Alright, a little update on the car. It has fuel all the way to the injectors and runs on ether. There is a small fluctuation of power on the injectors, but it's hard to read with a voltmeter because they bounce from 0 to 3 volts back and forth, not sure if the voltmeter doesn't have enough time to read the voltage as it's digital or if that's all I'm getting for power. The issue seems to be that it's not injecting fuel into the engine, so what now?  

[Zed Head]

Check Pin 1 for connection to the coil's negative terminal.  That's what the ECU monitors to know when to open the injectors.

Might be worthwhile to go through the tests in the EFI book.  Your fluctuations could just be the coil changing the voltage drop when it sparks.

 

[Yaboyolin]

Alright, another update. Pin 1 has power, I swapped ECUs with a running 1977 Datsun and it still isn't firing. I've read through the manual and according to all my tests it's the ECU. So why isn't it firing? 

[Yaboyolin]

What is this thing and is it important? 

[Yaboyolin]

Terminal 10 on the ECU connected pin was reading no voltage and it's  my understanding that the thing in the photo above is the injector relay, which isn't working. So I'm replacing that and will report back.

[SteveJ]

2 hours ago, Yaboyolin said:

What is this thing and is it important? 

That is what's left of a relay. It's only important if you need the circuit it was switching to work. Where was it plugged in? What are the wire colors at that plug?