280Z Difficulty starting

[Chickenman]

The ECU does have a primitive " Clear flooding : circuitry, at least my 1976 has it and I would suspect a 1978 has it. But it usually involves holding the throttle at WOT while cranking. That triggers the WOT TPS signal and combined with Thermo-time switch heating length will reduce fuel injected during cranking.

 

Now the Thermo-time switch is very interesting. It is designed to heat up very quickly and is supposed to be on for only a maximum of 12 seconds ( according to EFI Bible and FSM ). However, they are a bimetallic strip with a heater, and can get wildly inaccurate with age. Some open the circuit too soon and others get sticky contacts and stay on too long.

 

When I was working at Nissan as a Partsman in the late 70's, we went through a lot of Thermo-time switches in the Service Departments. They were always causing issues, both with Hot starts and Cold starts. A resistance check doesn't tell you much, as it's the bending rate of the Bi-metallic strip that always went out of spec. Might be worthwhile installing a new Thermo-time switch.

 

In fact, I may just do that on my 280Z as I have a persistent Rich running at start up. The Thermo-time switch is the only switch that I haven't replaced. 

 

All to be gone when I get my Haltech stand alone system installed this winter.

[Marios280Z]

Very interesting observations and theories both on the Clear Flooding and the starter. So now looks like I will have to replace my starter...?    I already have to replace, in the near future, my radiator that started to slowly leak at the very top and only during operation (most likely due to increased pressure in the system).  I cannot even take my girl to autocross to test here new shoes because of that radiator 

Is there a way to test and verify that the starter is really giving up?  And if so, is there typically a way to fix it, of course pending the damage that  I would find?

 

The stupid thermotime switch is also over $100!! Crap...

[Marios280Z]

Now the Thermo-time switch is very interesting. It is designed to heat up very quickly and is supposed to be on for only a maximum of 12 seconds ( according to EFI Bible and FSM ). However, they are a bimetallic strip with a heater, and can get wildly inaccurate with age. Some open the circuit too soon and others get sticky contacts and stay on too long.

 This is very interesting and almost fits my situation to a T. I have NEVER heard my CSV click and spray the fuel until I did the CSV-in-the-jar test with the thermotime switch put in the freezer for about 10 minutes (see my description few post earlier). At the same time my temps here were typically above 70. I did have couple of days in low 60 when  I left the car outside and I still had a trouble starting (I'm guessing my CSV never sprayed extra fuel despite lower temps).

[Zed Head]

I hold my throttle wide open to start the engine faster when it's cold out, since I've removed my CSV.  All the ECU knows is that the engine needs 27% more fuel when the TPV is on full throttle.  It works, and I've never seen any documentation anywhere that there is special circuitry to reduce fuel enrichment by holding the throttle open and using the starting circuit.  And the 1978 system is essentially identical to the earlier systems in functionality.  I've had all of the various ECU's from 75 to 78 in my car and they behave the same way.

 

I've seen other people describe this flood-clearing mode for other cars but Nissan is pretty clear in the FSM's about when enrichment happens and when fuel cut happens.  I just went through the 1995 Pathfinder EFEC chapter and can't find any reference to fuel cut, except for during deceleration or high-speed operation (RPM limiter, maybe?).

 

Flood-clearing on a modern EFI system would be kind of ironic anyway.  The system is designed to adjust timing, and fuel, and engine speed to start and keep running reliably every time.  The odds of flooding before starting are small.

[Zed Head]

Mario, you should really wait until you've at least gone through that tank of gasoline.  You're spending a lot of time on something that might not be caused by your car at all.  People get bad fuel all of the time.  EuroDat found gallons of water in his tank, no idea where it came from.  

 

The FSM suggests that the thermotime switch provides power when the sensor is somewhere between 57 to 72 degrees F.  If you're at 70 degrees you're at the high end, odds are a new one on't provide power either..  Try wiring in a switch to the CSV before spending $100 on something that many people throw away.

[Marios280Z]

Zed Head,  I get your point about the fuel, but I have gone through few tanks of gas so far with the same problem. EuroDat must have pissed his neighbor pretty bad, maybe his exhaust is to loud ?

 

Yes, I saw that 52-72, and the 'somewhere " doesn't make me feel comfortable. I also believe it says somewhere in that section that one can "adjust" that, but I have not seen anywhere the procedure for adjustment. Also, according to what Chickenman experienced first hand, those units tend to fail, in which case the range goes out the window. I know a lot of people get rid of the CSV...Not sure I'm ready for it yet. Trust me,  I don't want to spend the money on thermotime switch either. Putting a switch sounds like a noble idea, but it will only mask the issue I'm having. I will proceed with WTS signal trace first, make sure all is good, and check its resistance against the old one...

 

Any hints on that starter discussion above?

[siteunseen]

I'm probably light years behind saying this, but have you sanded your thermotime sensor to look like new brass?

[Marios280Z]

I'm probably light years behind saying this, but have you sanded your thermotime sensor to look like new brass?

Nope...It is still brass color, just not shiny...There was no residue on it so I did not sand it down.

[Zed Head]

I looked at your post #35 video and think that maybe the starter issue  is the starter letting go when the engine first pops.  Hard to tell, but the big buzz when it doesn't start seems wrong.  Usually the starter gear will stay extended and engaged as long as you hold the key to Start.  There's a ratchet mechanism in the starter gear that will let it spin when the engine starts.  But that wouldn't fix the slow start problem, it would just make it less aggravating.  It's the waiting for the starter to stop spinning that's irritating.  So really you have two irritations combined - the slow start and the wait for the starter gear.

 

It looks like you've checked everything and it's all working to spec. but you're still not getting enough fuel at Start to kick the engine off quickly.  If the CSV is not squirting because the thermotime switch is open, that means the injectors aren't squirting enough.  Which might be because the Start enrichment designed in to the ECU, through injector open duration, is not enough.  Either the enrichment is not working or it's just not set high enough.

 

OR, and here's another stretch, the starter issue and the slow start issue are caused by the same thing: low voltage.  But I think that you showed that voltage was okay, although I can't remember if you used a meter on the starter or just looked at the dash gauge (there's a lot of pages here!).

 

OR, another stretch, your weird "priming" behavior is a sign of a messed-up fuel pump control relay.  Slow to stop power, but also slow to provide power.  Kind of back to EuroDat's comment in #25.  Maybe when you hit Start, the pump doesn't get power for just long enough to cause the slow starting.  Try providing full-time power with jumpers and see if it starts quickly.

 

I'd try the last one first.  It's pretty easy.  You might be able to jump the fuel pump relay plug in the cabin instead of running a bunch of wire to the pump.  Just let it run, that's what it does when you're driving.  Won't hurt.

[Marios280Z]

I'd try the last one first.  It's pretty easy.  You might be able to jump the fuel pump relay plug in the cabin instead of running a bunch of wire to the pump.  Just let it run, that's what it does when you're driving.  Won't hurt.

 That fuel pump relay, I must be blind because I didn't see it in the cabin. Where is it? It is not hidden in the engine bay under black metal cover on the right side of the engine, just in front of the battery, is it? Those are EFI relays, correct?

 

It looks like you've checked everything and it's all working to spec. but you're still not getting enough fuel at Start to kick the engine off quickly.  If the CSV is not squirting because the thermotime switch is open, that means the injectors aren't squirting enough.  Which might be because the Start enrichment designed in to the ECU, through injector open duration, is not enough.  Either the enrichment is not working or it's just not set high enough.

The low enrichment during start is what has always been on my mind when I started doing all these tests. I just don't understand why. I think it is also emphasized by incorrect CSV operation.

 

As I recall correctly, my voltage at the starter when cranking was acceptable as concluded by one of you guys here. The starter definitely makes this "big buzz" as you accurately described it. It has been doing that even more often recently and it prevents me from holding the key in the START position therefore not allowing for a longer cranking .

[Zed Head]

The control relay and the pump relay are both in the engine bay under that cover.  There's a diagram on page BE-6 (edit - went ahead and added that picture too).

 

I don't know how comfortable you are with wiring but a jumper wire at the connector (circled in the attached drawing) should run the pump just fine and completely bypass the control relay.  A paper clip might do the job but make sure it doesn't touch any metal.  It's connected directly to the battery and could short.  As soon as you jump it the pump will run.

 

While you're there, take a look at the control relay.  If it's dirty and corroded it might need a good cleaning.  They can be disassembled.  But try the jumper wire first, that will tell the story on the control relay quality.

 

CO might have some comments.  He has dug much deeper in to the system.  

 

I'm suggesting this because it would be easy if you don't mind playing with electricity.  A few screws, remove a plug, add a paper clip.  More knowledge.

Edited August 20, 2015 by Zed Head

[Chickenman]

Copy and paste from the FSM about Thermo-time switch operation:

 

 

The thermotime switch is ON when
the cooling water temperature is below
specification. This implies, however,
that repeated operation of the ignition
switch may result in excessively thick
mixture and consequent troubles in
engine operation. To prevent this, the
bimetal is equipped with a heater.
Electric current flows through the
heater while the ignition switch is in
the start position, and warms up the
bimetal. Through repeated operation
of the ignition switch, then, the bimetal is sufficiently warmed up to
open the thermotime switch, thus
stopping excessive injection of fuel
from the cold start valve.
 

Just some food for thought...    I don't think this is the end all solution. Just one reason. why you shouldn't turn the key repeatably on and off.  It is just not necessary under normal conditions. It's probable that you have several small problems compounding each other. IE:

 

1: You're losing fuel pressure in the Fuel rail for some reason. I think that has been established. Either a leaking injector ( most likely ), leaking check valve in Fuel Pump or leaking Fuel Pressure regulator

 

2: Starter kicking out too early is not allowing fuel pressure to prime the fuel rail. Combined with the loss of fuel pressure this makes the car a B***ch to start. Could be a starter solenoid problem or even a low battery,  The starter solenoids usually get tired and the hold in coil cannot hold the Bendix gear engaged properly. 

 

I have a brand new starter on my 280Z and even with the battery almost dead flat it stays engaged while cranking. It never " kicks out " like yours does.

Edited August 21, 2015 by Chickenman