280Z Requires Starting Fluid for Cold Starts

[S30Grit]

Good deal, when I took it off the firewall, it actually looked like the area had gotten some attention recently, but hit it with a wire brush anyway.

And yes, it is a troubleshooting loop at times, but the forums have been very helpful to bounce ideas off of.  With all the bad connections/grounds I've encountered already.  It seems like I could be down this path for a while.

The car has a dead-man switch installed in the cabin and wired to nothing in the engine bay right now.  I'm tempted to wire this up to the CSV so I can manually trigger it instead of using starting fluid lol...

[Captain Obvious]

It's a little late to be doing this, but I'd like to drop back a little... We've all been treating your cold start difficulties as a lack of fuel situation, and I would like to investigate that a little more.

You've mentioned a couple times that the injectors don't seem to be firing when you're trying to start the cold car. Can you provide some more details as to how are you coming to that conclusion?

[Dave WM]

I got money on the IGN switch, I know its new, but was it checked before installing.

let me summarize what I think is the situtation

Runs fine if started with starting fluid. So all systems needed for operation work fine BUT for START

functions of START

FUEL pump ON

IGN relay ON (ECU power and pump)

CSV ON (if cold, but its not cold so OFF in this case)

SPARK ON.

Starter ON

All of these are controlled by that START selection on the key switch. My guess is one of those is not happening hence the need to monitor them all while someone cranks it to isolate. monitor fuel pressure, monitor spark, monitor injectors (clicking).

 

 

 

 

Edited October 22, 2019 by Dave WM

[S30Grit]

2 hours ago, Captain Obvious said:

It's a little late to be doing this, but I'd like to drop back a little... We've all been treating your cold start difficulties as a lack of fuel situation, and I would like to investigate that a little more.

You've mentioned a couple times that the injectors don't seem to be firing when you're trying to start the cold car. Can you provide some more details as to how are you coming to that conclusion?

Yeah, I noticed people were trending that way too.  It could be related to fuel, but as far as I can tell fuel is completely fine as described earlier.

The mechanic used an in-line noid light (allows injector to still be connected up while testing) for the injectors and there was no signal when trying to start the car.  Similarly, I myself have connected an LED to the injector harness (not in-line) and found similar results, by unplugging the injector harness and plugging an LED to both terminals.  No pulse while cranking.  While rotating the key through the ignition, I can get a SUPER short flicker of the LED, but definitely way too short to be consider a "pulse" IMO (hint hint what Dave WM said has a good chance I think).  During cranking, I'm expecting a short and consistent pulse of the LED, but there is simply nothing.  As @Zed Head suggested, it is valuable to know if the injectors are receiving the constant +12v during starting.  If no constant +12v during cranking, then the issue could maybe be on the power-side of the injector (maybe drop resistors).  If there is constant +12v to ground at the harness during cranking, then the issue is likely on the grounding side of the EFI circuit or ECU... I'll be testing that next time I have time.

My thoughts are that at this point, the most common suspects are: Ignition related, drop resistors, or some other EFI wiring/ground problem.  Also, I need to run tests 3-1 through 3-3 according to FSM.  Some ignition and EFI tests should find the culprit, hopefully this weekend.  Thoughts on easiest test to run with most useful results?  I figure thoroughly testing the ignition system AND it's wiring may be a pain.

[S30Grit]

2 hours ago, Dave WM said:

I got money on the IGN switch, I know its new, but was it checked before installing.

 

I'm right there with ya Dave WM!  The guy I bought it from installed the new Ignition Assembly, but I think it's likely either not wired up perfectly, or a ground to the IGN or something isn't strong.  Working alone makes it somewhat of a pain to test the stuff... but hopefully I can confirm some basic ignition wiring and the switch itself soon.

Edited October 22, 2019 by S30Grit

[cgsheen1]

I'm wondering if the ECU isn't getting a good "the engine is turning now - you can start firing the injectors" signal when it's cold. Does your Tach show RPM while cranking? Also, have you checked the ECU plug and socket connections for oxidation. (Going back to the "90% of the problems I've found in these old EFI systems have to do with wiring and connectors"...)

Edited October 22, 2019 by cgsheen1

[S30Grit]

18 minutes ago, cgsheen1 said:

I'm wondering if the ECU isn't getting a good "the engine is turning now - you can start firing the injectors" signal when it's cold. Does your Tach show RPM while cranking?

That's a good point, I'm not sure off the top of my head what the tach is doing, I'll have to get back to you. I think this is supposed to come into the ECU as the "Ignition trigger coil signal"

[Patcon]

You could always try to hot wire the car to eliminate the switch as a problem

[S30Grit]

17 hours ago, Patcon said:

You could always try to hot wire the car to eliminate the switch as a problem

I did look at the ignition wiring last night, might give it a go

[zclocks]

S30 Grit, 

I'm with Dave WM. I had the same problem your having and it turned out to be the ign switch. Perform the testing , out of the car, as Dave's   

video mentioned earlier and pay close attention to the resistance in the start position. Mine was OK on several tries in the start position,

but not consistent. 

 

[S30Grit]

9 minutes ago, zclocks said:

I'm with Dave WM. I had the same problem your having and it turned out to be the ign switch. Perform the testing , out of the car, as Dave's   

video mentioned earlier and pay close attention to the resistance in the start position. Mine was OK on several tries in the start position,

but not consistent. 

Good thinking.  The guy i bought it from left the old ignition switch in the car and I tested it last night.  It had similar behavior to what's shown in @Dave WM's video.  There seemed to be a sweet spot when turning through the "start" range where everything behaved as it should, but outside of that sweet spot, resistance was either infinite or variable.

Has anyone confirmed that test with a new/working ignition switch?  Mostly curious if I should expect the entire range/area when turning past "On" and through "Start" to have no resistance for the marked pins in the FSM? Or is it normal for there to be a slightly more narrow "sweet spot"?

Either way, my old ignition switch has a pretty big and consistent "sweet spot" which seems like it should have been usable...  I haven't checked the new unit that installed in the car now, but I will hopefully this weekend..

[zclocks]

S30 Grit 

Yep, I tested my new switch and it was a solid connection through the complete range of the "Start" portion of the switch. No sweet spot just continunity.

Ron