280Z Difficulty starting

[Hodgimus-maximus]

You don't have to wait to test your csv all you have to do is unplugs your water temp sensor and it will behave like its 30 below

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[Marios280Z]

You don't have to wait to test your csv all you have to do is unplugs your water temp sensor and it will behave like its 30 below

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Awesome! I will try that.

[Hodgimus-maximus]

Awesome! I will try that.

ummm if you want more adjustability wire up a potentiometer in its place and you can test what it behaves like at different temperatures. A 10k potentiometer will let you test it between -20 F to 90 F

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[Captain Obvious]

Belay that order... There is no link between the water temp sensor and the cold start valve.

 

If you unplug the water temp sensor it will run pig rich. You might get it to fire off faster because the ECU will stuff in a whole lot more fuel due to the cold temperature it perceives, but that huge amount of extra fuel will drown the engine after it starts.

 

Problem is your car intermittently stumbles on the start. If you pull the water temp sensor, it is going to run like crap, but you won't know exactly why it's running like crap. You won't know if it's only because the water temp sensor is disconnected or if it's the combination of the temp sensor being disconnected in addition to what has been causing your start stumble from before.

 

About the only thing you could do WRT to the temp sensor is for you to pull the temp sensor connector and have someone else (preferably in pajamas) crank the engine. Then the instant it fires off, put the temp sensor back in place while being careful that you don't get your hand into the fan.

 

Then if it starts great with the temp sensor disconnected, was it because the temp sensor was off, or was it simply one of those times when your car started just fine?  How many days is your helper willing to run that test? 

[Captain Obvious]

Measured again at the starter big terminals where the battery cables connect was showing around 10-11 V during cranking (unlike the 6-7V that my volt meter showed me earlier). The car started rather quick so there wasn't really much time for observation.

 

My (meter) seems to be "slow" when it comes to displaying voltage.

 

Not unexpected. Makes me think that the 6-7 volts you measured the other day was a function of the update rate of your digital voltmeter. Some voltmeters have an update rate of one second or more and that makes quick measurements like this impossible.

 

If you got 10-11 volts (while cranking) delivered at the starter end of the big cables, then I think you're cables and battery are fine.

[Captain Obvious]

Haha! And I just saw Zed Head's guru list. I'm no guru, but I'm honored to be even mentioned in the same sentence with such good company!  Not sure I can handle the pressure.....

[Marios280Z]

Belay that order... There is no link between the water temp sensor and the cold start valve.

 

If you unplug the water temp sensor it will run pig rich. You might get it to fire off faster because the ECU will stuff in a whole lot more fuel due to the cold temperature it perceives, but that huge amount of extra fuel will drown the engine after it starts.

 

Problem is your car intermittently stumbles on the start. If you pull the water temp sensor, it is going to run like crap, but you won't know exactly why it's running like crap. You won't know if it's only because the water temp sensor is disconnected or if it's the combination of the temp sensor being disconnected in addition to what has been causing your start stumble from before.

 

About the only thing you could do WRT to the temp sensor is for you to pull the temp sensor connector and have someone else (preferably in pajamas) crank the engine. Then the instant it fires off, put the temp sensor back in place while being careful that you don't get your hand into the fan.

 

Then if it starts great with the temp sensor disconnected, was it because the temp sensor was off, or was it simply one of those times when your car started just fine?  How many days is your helper willing to run that test? 

 Thanks CO.  I will not run the car without the water temp sensor connected, but I will try to start it that way. I may even repeat the CSV-in-the-jar test to see if I even get any fuel out of it.

 

My helper should be OK with running those type of test for a while.. After all she was the one that said, quote: "You would be stupid not to get this car for that price".

[Marios280Z]

Not unexpected. Makes me think that the 6-7 volts you measured the other day was a function of the update rate of your digital voltmeter. Some voltmeters have an update rate of one second or more and that makes quick measurements like this impossible.

 

If you got 10-11 volts (while cranking) delivered at the starter end of the big cables, then I think you're cables and battery are fine.

From what  I saw I tend to believe my battery and at leas the cables work OK.

 

BTW, you are doing just fine with handling the pressure. I  on the other hand, may have a problem if we don't solve this problem soon and you guys will ask me to pull the engine out and start disassembling it.

[Hodgimus-maximus]

my bad forget which one is which sensor did what, always found them to be redundant. you can take out the thermo time switch and place it in some ice water and then put it back and and try or just jump the wires for the theme time switch with a 10 ohm resistor and the cold start valve should work.

[Zed Head]

Since you're above CSV activation temperature, but the engine does try to start, you might look at the other enrichments.  I've studied the chart and the descriptions and sometimes misinterpret what they're saying, and can't always tell when exactly things happen, but they're still worth a ponder.

 

"Start enrichment" is the CSV contribution I believe.  In the past I thought that it might be more time on the injection pulse but probably not.

 

"After start" enrichment is an interesting one.  Seems to fit your time frame but it's not clear what parameters put it in to action.  Maybe the "idle" switch along with the Start signal?  Maybe just the Start signal?  Who knows?

 

"Idle enrichment" seems easy enough.  If the idle switch is actuated the ECU adds time to the injection pulse for more fuel.

 

So there's two things that might affect behavior right after starting, both connected to the idle switch.  Were it my car, I'd check the throttle position valve [TPV (aka TPS)].  They have contacts inside, not well protected from the elements.  They get dirty.  Maybe you're missing your idle enrichment.

 

Check at the ECU connector first, where the signal gets used.

 

Here's another link to a useful book, which hsows how to check everything at the ECU connector, maybe easier to work through than the FSM.  Use the 280Z/ZX Electronic Fuel Injection Guide.  Third one down.

 

http://www.xenonzcar.com/s30/otherguides.html

 

[Zed Head]

Kind of funny - I misinterpreted the chart again.  It actually shows CSV enrichment as separate from Start enrichment.  So Start enrichment is probably always there hot or cold, maybe to varying levels depending on temperature.  Since the system is designed to be started with the throttle closed, idle switch actuated, I wouldn't be surprised if your idle switch is dirty or maladjusted and part of the problem.  Also wouldn't be surprised if ti was fine and not your problem.

[Marios280Z]

Thanks Zed Head. I do have the book you are referring, 280Z/ZX Electronic Fuel Injection Guide. I read through it once, but obviously will have to read again and perform some tests. Now I have these couple of things to check:

 

1) CSV-in-the-jar test with water temp sensor disconnected.

2) Throttle Position Sensor clean up and test.