77 280z cannot start, injectors not functioning?

[ISPKI]

Hello folks!

 

I am so close to getting my 77 280z back on the road. Here is my current situation:

 

I took my car off the road to diagnose an issue with it running poorly. While I was working on it, I decided to do some upgrades and replace some things. It now has a distributor from a 280zx (E12-80 module), a new coil, spark plugs, cap, rotor, spark plug wires, fuse block in place of fusible links with midi fuses, header pipes, cleaned intake manifold and replace manifold gasket, throttle body cleaned inside and out, throttle body gasket, cleaned injectors and replaced seals and bolts, new weather proof injector plugs, TB plug, AFM plug, water temp plugs, water temp sensor, thermotime switch and thermal transmitter are all new with fresh wire connectors and connections, thermostat is new, housing and gaskets are all new, new battery, new cables on just about everything, new starter. The list goes on and on.

 

Anyways, my car will not start without spraying starter fluid in it. I have good, strong spark and the car runs with the starter fluid but it will not start/run on it's own. I tested the injectors by tapping a jumper wire from the negative post on the coil to ground with the key turned to "on". I tapped it about twenty times but could not hear a peep out of the injectors. What I am finding to be odd is that, when I first turn the key to start, it has a brief second of ignition and then looses it. I am assuming that is from the cold start injector.

 

I went through tests 1,3,5,6,7,8,9 in the FSM and it passed all of them (continuity tests).

 

I just did test #2 - Testing pin 3 to pin 18 while depressing throttle pedal fully. I should have continuity when the pedal is fully depressed which I do not. I DO have continuity when pedal is not depressed, but as soon as I press the pedal, I lose it. I checked EF-38 diagram and it shows that circuit runs from pin 35 to the negative battery terminal and is spliced into by #72, 49, 5, 16, 17 so I am assuming that is just a primary ground wire for the system. Is this the same 8 gauge wire that had a fusible link wired into it that connected to the "-" on the Battery? I will continue testing to try and find it. I guess I can just test for continuity between the #35 pin on the harness side and the
negative battery terminal to figure it out.

[ISPKI]

MMMk, brief update. The test in question (#2) refers to throttle valve switch which I read is in the TPS. I did rewire this 3 pin plug along with the other plugs in the system so maybe I wired it up wrong? I unplugged the TPS plug and re did the test just to make sure I was on the right track and I had no continuity at all regardless of the pedal being pressed or not so I know that is the item in question now. Problem is, I have no idea what to do about the wiring.

 

The question is: if the TPS is bad or wired incorrectly, would that prevent the vehicle from firing the injectors?

[ISPKI]

Checked the TPS and wiring. Opened it up to check function and it looks to be operating perfectly. Checked the wires and I had #2 and #3 switched. I cut the wires a few inches back (I also noticed that the wires are imprinted with their ECU pin# which is really cool), switched them and reconnected them. Now the vehicle passes test#2...but it still does not start and run on it's own.

 

I am sort of running out of options. I have spark, I have fuel pressure going into the rail (holds steady at 37 PSI) but I have nothing coming out of the injectors, and no click coming from the injectors. I checked the dropping resistors and their connections and they are very clean. I checked the power relay above the ECU and it clicks when the key is turned to "on".

[NewZed]

Does the tachometer show engine RPM while trying to start?  Or while it's running on Starting Fluid?

[ISPKI]

Yes, the tach functions. I checked the resistor for it as I recall it being wrapped in electrical tape which seemed odd to me. Its connections are clean and doesn't seem damaged at all.

[ctc]

If you take an ejector plug off, with the key on, do you have +12v on one pin and continuity to ground on the other?

Edited October 29, 2013 by ctc

[NewZed]

ECU's do go bad sometimes, though not often.  They use similar transistors to the ones in the ignition module to drive the injectors.  I had one die on me while driving.  I got two or three restarts out of it to get me closer to home then it was dead for good.  And, recently, someone on another forum has reported the symptoms of a dying ECU.  It happens.  That's probably where you're at on FSM troubleshooting, "if all these tests pass, replace the ECU".

[ISPKI]

Hah, yes I am nearing the dreaded "get a new ECU" step zed. I just replaced the fusible links (what was left of them) that ran from the battery cables to the dropping resistors. Had to cut about a foot of wire off until I found some decently clean wire. Tried to start it and it fired up for about 2 seconds and then turned off. Maybe it had some fuel left over from the cold start injector.

 

CTC: I checked injectors 1, 2, 5, 6. All had 12.0 volts on one pin and I think continuity to ground on the other. I was getting a number come up on my volt meter that hovered around .740. I am assuming that is the resistance in the circuit. I may need to ask around here and see if anyone has a functioning ECU that I can get cheap. I just do not understand how all the injectors could stop functioning all at once unless the ECU went bad. Alternatively, I do not understand how the car can turn on so long as a fuel source is provided to it if the ECU is in fact, bad. Is it possible to open the ECU and check the transistors for burning or damage?

[ctc]

So the last thing I would do before the new ECU is to install a test light in place of one of the injectors. The fancy word is NOID light, but any low wattage 12 volt non-led bulb will work. Wire it so you can connect it to the two pins of the injector plug. It should flash when the engine is cranked if the injector is receiving a signal.

 

Or you can buy one, google

 

 

OTC 7188 Bosch PFI Noid Lite

Edited November 3, 2013 by ctc

[ISPKI]

Thanks for that tip CTC. Would a turn signal bulb or dome light bulb work? I assume those are fairly low wattage, especially the dome light.

[ctc]

Dome light should work. If you want to be picky, I think around 2 or 3 watts is what you want. You can ohm out the injector and build to get in the ball park.

[ISPKI]

I will stop by the ca parts store tomorrow and snag an interior light of some kind and test the injectors out.

[ISPKI]

I picked up a small bulb from the parts store - 12v, 3.5watt. Wired it up. I checked it by plugging one wire into the + side of the #6 injector plug and touched the other wire to ground, bulb lit up nicely. I plugged the ground wire into the other side of the plug, turned key to "on", then to "start" for a few seconds and the bulb does nothing. So, this tells me that the ECU is not grounding the injectors...but why? Is there any other reason as to why the ECU would not ground the injectors besides the ECU being damaged internally somehow?

 

Is it possible that the actual wiring from the injectors to the ECU is damaged? I will search for the wire schematic but I am running out of time today so if anyone could fill me in on where the ground wire for the injector goes or what else it runs through between the injector and the ECU? It does not look like it goes anywhere except to the ECU and then the ECU grounds to the -BAT terminal correct?

Edited November 4, 2013 by ISPKI

[ISPKI]

I went back and tested the ground connections for the ECU plug. With one end of my multimeter stuffed into the plug on the battery terminal, I tested slot 5, 16,17, and 35. I have no continuity on 5, 16, and 17, but I do have continuity on 35. Guess I will be hunting down ground wires for the rest of the week.

[NewZed]

You can check the wiring from the injector plug to the ECU also from the connector.  Find the pin numbers from the diagram and just measure continuity between the injector connector and the ECU connector.  You've already checked power, the other side of the injector circuit, when you grounded the light bulb.

 

Eyeball the diagram and you'll see that many of those grounds go to a common point.  There's one in the EFI harness, it's screwed to the top edge of the intake manifold, where the harness jumps the gap from the body to the engine.

 

This thread illustrates why once you have the ECU connector in one hand and the meter in the other you might as well spend time testing as many of the circuits as you can.  Grounding is one of those things that seems so simple it's often overlooked.

[ctc]

The ECU "supplies" the ground signal by completing the circuit to ground.  Your wires should show continuity, and check the ohms, between the injector negative and the ECU plug.

[ISPKI]

Well I located the ground wire on the intake. It was in bad shape so I cut it out at the point where the three smaller wires connected from the harness and soldered in a new wire. Still cannot start. I was looking at my ecm and noticed that there are pins on the plug for the ecm that do not have pins matching up to them on the ecm side.

[ctc]

So what was the measured ohms between the ecu plug and the injector plugs (pins 15,33,32,14,30,31)? What pins are missing? Can you post a pic of the ecu pins? Do all the grounds show continuity now?

Edited November 6, 2013 by ctc

[ctc]

So another thing to check, with ECU plug disconnected, Key on, Pins 10 should have 12V.  With the key in the start (cranking) pin 4 should have +12V.  Also double check that 72 has ground as well.  It is the double relay ground, but since the injectors have 12V, it should be ok.  I am using the diagram on EF-25 of the FSM to trace the supply voltage and grounds to the ECU.

[9rider]

Did you check spark plug ? Ignition wire and firing sequence ?