280Z Requires Starting Fluid for Cold Starts

[S30Grit]

Hi All,

I'm new to the forums and recently acquired a 280Z!  I'm really excited about the car, but I did make the purchase with it not running.  The interesting (and very bizarre) issue I'm having is that the engine refuses to start on it's own when it's cold.  The weird part is that with a quick spray of starting fluid (3 sec), the car starts up and RUNS instantly and idles/revs using it's own EFI without problem.  If I leave the engine idling for a couple minutes (not even up to op. temp.), then kill the engine, it will subsequently start on it's own without the need of starting fluid.  It appears to only be cold starts where the car refuses to start on it's own.  After letting the engine fully warm up, I can start the engine just fine several hours later without starter fluid.  But fully "cold" starts it will always fail without starting fluid.

A trusted mechanic and myself have tried several things, and consulting the FSM as well.  I'll be working more thoroughly through the full EFI troubleshooting FSM this weekend to make sure we haven't missed something.

During a failing cold start, what is known:

• Fuel pressure is correct/consistent at the fuel injectors during priming and starting sequence
• Spark is present
• Timing of the engine seems fine once it's started/idling via spray
• Fuel Injectors simply appear to NOT be receiving a signal to fire during startup (in-line light test was done). [obvious red herring here].  The weird part is that obviously after the starter spray is used and the engine starts, the fuel injectors start working.

Previous owner and myself have thrown a few new parts at it without necessarily diagnosing each component: Spark plugs/wires, starter motor, battery, fuel pump/filter/regulator, some vacuum hoses.

Troubleshooting done already, that has not changed the symptoms:

• Swapped in a different ECU (although I did notice that the ECU part number appears to be for an automatic A11-601000 while the car is a manual.  But after reading, apparently the ECU's are actually the same)
• Cleaned misc. electrical connections everywhere I can think of (although I know I'm missing some areas)
• Checking fuses and fusible links
• Swapped in new EFI relay
• Unplugging a few sensors/connections to remove those variables (typically in isolation): thermotine, temp sensor, CSV.  My understanding is that regardless of this configuration, the injectors should be getting a signal to fire on startup anyways though.

Seems like an electrical gremlin, but running out of ideas to kill it, other than hooking up a NOS system as my starter fluid (kidding).  I'll be spending a lot of time with the multimeter it seems, but any ideas what component/wiring could cause this?

Edited October 17, 2019 by S30Grit

[Dave WM]

start switch

 

Edited October 17, 2019 by Dave WM

[Dave WM]

the only happens when cold is odd, exactly how cold is it where you are?

Have you confirmed the CSV is operating IF the temps are indeed cold? generally it is not turned on unless its less that 70f?

Try listening for the injectors rather than looking at lights. I used a stethoscope.

[jonathanrussell]

If it were me, the first thing I would check is the cold start valve and thermotime switch. If you pull the cold start valve harness and connect positive and negative to the two cold start valve terminals, does the cold start valve spray? If yes, and you manually spray the cold start valve when the car is cold, does it start?

[S30Grit]

Thanks for the quick responses.  I'll definitely check out each of these things this weekend.

It's been 80+ F where I'm located at (SF bay area).  Maybe a dumb question: Is it correct to assume that the CSV is only used in conjunction with the normal injectors? i.e. never in isolation?  I didn't see this operation described in the FSM.  If CSV and normal injectors are only used simultaneously, then I'm still very puzzled why the injectors aren't getting signaled to spray on cold starts.  The mechanic used a specialty light for injectors (not a simple test light), I can try listening to the injectors but I'll expect a similar result. 

This weekend will be more chilly, below 70F in the morning for sure.. either way, I'll see if the CSV is 1) getting signal to spray and 2) actually spraying. And depending on those results, 3) manually triggering the CSV to spray and attempt to start.  I won't be expecting the ECU to trigger it to spray if the coolant is above 70F, like Dave WM said - which could point to a water temp sensor issue if I'm not mistaken.

[siteunseen]

I think it would be a good idea to take a pic of the driver's side of your motor and post it.  It's amazing what will "jump out" at these guys if it's wrong.  I'm mainly wanting to see how your AAR hoses are routed.  In '78 Nissan changed it around to keep some gunk out of the Auxiliary Air Regulator like this picture.  That thing keeps the idle high until it warms up then closes off the extra air and then the idle drops.  Here's a shot of the bullet connectors that get plugged up wrong a lot of times too.  

Welcome to the forum!  You won't find a nicer or more helpful group.  

Edited October 17, 2019 by siteunseen

[S30Grit]

Sure thing, here's two images.  I'll take a closer look at your image and compare, but first glance looks ok?  And yes, mine is a '78, hopefully plumbed up like one.

 

[siteunseen]

Your cold start isn't plugged up in the first pic. Looks like it is in #2.

Edited October 17, 2019 by siteunseen

[Zed Head]

3 hours ago, S30Grit said:

I won't be expecting the ECU to trigger it to spray if the coolant is above 70F, like Dave WM said - which could point to a water temp sensor issue if I'm not mistaken.

The ECU has nothing to do with the CSV.  The CSV system is its own little separate control system, with power supplied to it and controlled via the thermotime switch.  No ECU involvement, no coolant temperature sensor involvement.  There is a "signal" that supposedly goes to the ECU, in the diagram, but many of us have realized that the ECU's don't have a wire to that pin.  It seems to be a diagram mistake that Nissan never fixed.  The thermotime switch is a thermally actuated relay that grounds through the switch body.  Check the ground circuit.  The wiring diagram can be confusing if you don't know that.  There is power through a heater wire around a bimetallic strip, that opens and closes the relay contact points, and also power to the CSV injector. It's pretty ingenious but still looks crude.

I removed my CSV and had delayed starting when it got colder or the car sat for a while.  So I changed my starting procedure to giving the engine a good 5 or 6 revolutions on a first crank then letting it sit for about 20-30 seconds so the gasoline from the injectors could vaporize.  Then it typically would start normally.  You might try that as a test for or as a way to get by without starting fluid.

[Zed Head]

Also, I never realized this and don't know how it's done, but, apparently, the thermotime switch is adjustable.  Weird.

[Dave WM]

4 hours ago, jonathanrussell said:

 

don't think its adj just a range that it happens to operate in. I know you can buy different spec ones, I got one for a VW that operates up to 85f

[Zed Head]

I'm just reading the words in the FSM.