280Z Difficulty starting

[Marios280Z]

I've heard of the propane method as well. I tried it once on my motorcycle and didn't get any effect, but that was because I didn't have any leaks.

 

So I can attest to the popularity, but haven't experienced the results personally.

 Ha,ha, well, I did not have propane but I did have starter fluid. This morning when I fired it up cold  I sprayed around the vac hoses  I could see, especially around fittings. I sprayed around the AFM boot as well.  I did not get any reaction from the engine :/ I guess it's a good think, but this still didn't point me to the cause of my issue 

[Captain Obvious]

So no new info there, huh?

 

While you have the starter fluid handy... Next time it fails to start on the first attempt, before you try a second time, maybe pull off a vacuum hose and give it a shot of the starter fluid and then put the hose back on. Try to get a sense if it's looking for more fuel or not. If it fires right up to a steady(er) idle on the second attempt, it would be an indication that it's lean.

 

Just trying to gather info....
 

[Marios280Z]

Right now looks like I have the CSV-in-the-jar test to do with the thermotime switch cooled off in the freezer. Perhaps the vacuum test if I can get my hands on one of them vacuum gauges.  Other than that what else is there...? There is no way  I didn't already look at the faulty item and concluded it was "good". I guess I have not looked at the condition of the pickup coil in the distributor. I could do it this weekend. 

Also, I'd like to challenge you guys with the question that I believe is linked to this issue. Why is my idle RPM so "low" right after starting the car? It is as if the ECU did not recognize initial starting condition and did not follow with the enrichment period as indicated in the graph in post #70 by ZedHead. What about the air temperature sensor in the AFM? Could that effect the richness/leanness of the fuel mixture in a way that would affect starting? What about that water temp sensor I replaced? It has new connector as well, it tests OK at the sensor with the resistance matching FSM specs, but what if the signal gets interrupted between the sensor and the ECU? At he same time if that was the case, wouldn't I have other driveability problems? 

[Marios280Z]

So no new info there, huh?

 

While you have the starter fluid handy... Next time it fails to start on the first attempt, before you try a second time, maybe pull off a vacuum hose and give it a shot of the starter fluid and then put the hose back on. Try to get a sense if it's looking for more fuel or not. If it fires right up to a steady(er) idle on the second attempt, it would be an indication that it's lean.

 

Just trying to gather info....

 

Will do.

[Captain Obvious]

Why is your RPM so low right after starting? My guess would be because internal combustion engines are never really happy at idle. They're unstable down that far and they're unstable when their cold. They're particularly unstable when they're cold AND turning slow. Sometimes they have trouble getting themselves into a more stable state. I saw in one of your videos that once it finally caught and continued to run, it stumbled for a couple seconds, but once you hit the gas, it steadied out to a 1000 RPM smooth idle? Did I see that right?

 

The "Start Enrichment" supplied by the ECU is a real thing, but it's not a huge adder. It's a circuit in there that charges up when the key is turned to START and then slowly decays over a period of maybe thirty seconds or so after the key has been returned to ON.

 

Air temp sensor or water temp sensors will definitely affect mixture, but here's the thing... The higher the resistance, the more fuel. And it's a lot easier to fault to a higher resistance than a lower one. Dirty connectors and open wires contribute to higher resistance. About the only thing you could do to get LOWER resistance is short one of your sensor wires to ground which is unlikely. In other words... If the signal gets interrupted, you'll run rich, not lean.

 

Once it starts, does it make black smoke? How do the plugs look?  I'm still trying to figure out if you're running rich or lean.

[Marios280Z]

Why is your RPM so low right after starting? My guess would be because internal combustion engines are never really happy at idle. They're unstable down that far and they're unstable when their cold. They're particularly unstable when they're cold AND turning slow. Sometimes they have trouble getting themselves into a more stable state. I saw in one of your videos that once it finally caught and continued to run, it stumbled for a couple seconds, but once you hit the gas, it steadied out to a 1000 RPM smooth idle? Did I see that right?

It stumbles almost every time when I have hard time starting. I tend not to add any gas, but sometimes  I do when I see it is "almost there" to overcome the stumble.  I believe the video you refer to is the one when I had my idle screw set open pretty wide. After engine warmed up it would idle at or just above 1000rpm with that setting.

 

I have not seen any unusual and excessive smoke out of my pipes (never saw anything black). If anything, there is a small amount of white smoke, but pretty much only in the mornings when it is a bit cooler (60s) and somewhat humid.

 

Spark plugs...  I got obsessed with them when I first got the car.Watched hours of videos to "learn" how to read them, and the more I watched the more I got confused with different approaches and reading techniques. Some said look at this portion of the plug, others said that portion of the spark didn't matter. At the end of the day I went and spoke with a local car guy, who races track and has an  army of vehicles, including some MGs, Porshes, Hondas, and others. He also builds his engines for some of the cars, like MG, so i trusted he knew what he was talking about. He looked at my spark plug first hand (and at that point it was pretty new spark plug that I replaced). He said they looked really good. We then went for a ride, and except for a dry clutch bearing he did not identify anything wrong with how the car was driving.

 

There was  a specific engine noise at high RPM  I went to him to talk about, but that is an item for a separate forum topic that I may bring to your attention when we figure out this starting issue. At the end of the day he concluded that it was nothing mechanical but rather some strange resonance between 4500-5500 rpm that causes high frequency vibration of something in the exhaust part of the engine.  

[rcb280z]

"QUOTE" the mornings when it is a bit cooler (60s). If thats the case your CSV should fire.

[Marios280Z]

This weekend was hot and humid and I really didn't have much time to spend in the steamy garage to do chilled thermotime switch testing. I did receive new oil temp sensor in the mail on Friday, since my old one was leaking oil, so I did replace that. I also quickly took off distributor cap off and the router and take a look at the pick up coil, but since I did not have any particular instructions and did not really know what to look for, I did not mess with it and did not attempt to remove it.

 

Tomorrow morning I will try to use starter fluid to at least figure out if the engine runs a bit lean or rich while starting.

[Marios280Z]

Late last weekend I disconnected the AFM for the second time now. I made sure again that the flap was moving OK, I looked at the boot connecting it to the throttle body looking for significant cracks. I did see slight rubber cracks, but nothing was all the way through. Again having the throttle body available I used electrical connector cleaner and cleaned it some more. Last time I did this the car fired up twice in the row, after sitting in the garage over night and then next day after sitting outside at work. 

 

OK, so my morning test was inconclusive.  I wasn't quite awake and I sprayed the starting fluid before I even attempt to start the car to see if she would give my hard time. Needless to say she fired right up. Coincidence? Did it have to do with the fact that I pulled the AFM? Or was it the starting fluid? Or was she just happy to see me? The weather was questionable so I turned her off and took my other car and left her in the garage for the day.

 

When I came back from work I primed the fuel pressure and cranked the engine (no starting fluid), and she fired right up...

I decided to do more CSV investigation. I pulled CSV out and stuck it in the jar. Disconnected the starter and turn the key to start. I could hear the fuel pump running, but there was nothing coming out of the CSV. Note, it was about 79 degrees outside. So I did the fuel pressure discharge per FSM. Still with the CSV in the jar I unplugged the CSV connector and using two leads I connected the CSV itself to the battery, at which point I heard audible click and the fuel was discharged from the fuel lines via the CSV to the jar. This proves that CSV, as long as it gets the right signal, works properly.

So then I moved to thermotimeswitch, I pulled it out, plugged the hole and put the switch inside my freezer for about 10minutes. Pulled it out and quickly installed it where it belongs. With the electrical connector back on the CSV (still in the jar) and the starter still disconnected I turn the key to start for a second or so. I did get solid spray of fuel out of the CSV. But when I immediately turn the key to start for the second time, the CSV would not spray. Perhaps that was just enough time for the thermotimeswitch to warm up and open the circuit. Just to make sure, I then moved to the thermotimeswithc connector, unplugged it and provided voltage from the batter to the connector. CSV responded nicely with a solid spray.

This proved that:

1) My CSV is working properly and as long as there is voltage and fuel it will spray.

2) The wiring connection between the CSV, the ignition key and the thermotimeswitch is all good

3) I'm not 100% convinced that my thermotimeswitch is working correctly.It just seems that it warmed up quite fast effectively disabling CSV.

 

I will still play with starting fluid AFTER she gives me hard time starting to.

[Captain Obvious]

It sounds like your thermotime and cold start valve are working exactly as intended. I don't remember how long it takes the thermotime to self warm due to the internal heating coil, but I thought it was a pretty short period of time even when the engine was truly cold.  I took a quick look through the FSM and I found the temperatures involved, but I didn't see anywhere where those temperatures were translated to "time". I think I had seen some numbers somewhere, but haven't turned those up. Ten to fifteen seconds sticks in my mind on an honestly cold engine.

 

The point of all that is... I'm not surprised at all that your thermotime switch went open so quickly. That thing started warming up the instant you took it out of the freezer, and after installation, the conduction rate to your ambient temp engine would be huge. You got one quick shot before you went above the threshold and the thermotime opened.

 

And BTW, it sounds like you've got a good handle on how the system is supposed to work and you're doing a good job of testing things and evaluating the results. You'll figure this out.  

[Marios280Z]

And BTW, it sounds like you've got a good handle on how the system is supposed to work and you're doing a good job of testing things and evaluating the results. You'll figure this out.  

Thanks CO. Like I said earlier, I'm here to learn.

 

Yesterday after coming back from work I attempted to start the car.  When at first try it gave me hard time, I then sprayed starting fluid. She fired right up. This leads me to believe that I may be running lean at least at the start up. I decided to pull the spark plugs to take a look at them. Keep in mind that the car has not been driven in few days now and all I have been doing was starting it cold and running no longer than 1 minute at the time, never reaching operating temperature. From what I understand to get a good indication of what's  going on in the cylinder by looking at the spark plug, the car needs to be driven at operational temperature for a while and than turned off and spark plugs pulled out. SO what you are about to see is just an indication of what takes place on cold engine. I will try and do the same after getting the car up and running at operation temps.

 

[Marios280Z]

Here is a short video of my spark plugs after running the car at operational temperature. Any thoughts?

 

Edited August 20, 2015 by Marios280Z