280Z Difficulty starting

[Hodgimus-maximus]

Well Looks like you either have a problem with your battery or the starter, there shouldn't be more than a 1 or 2 volt drop between battery voltage and the voltage at stater when cranking.  Check to make sure you have good clean connections at the starter and make sure the battery cables are in good shape. I can't remember if you had your battery tested or not but i suggest you stop somewhere and have it tested when it is fully charged.

[Zed Head]

You're kind of at the "think" portion of the typical learning process.  Usually starts with Do.  Do-think-do-think-do...etc.

 

You have the tools and you're taking measurements but some of them are done using incorrect methods.  Working on old EFI can be tough if you haven't had some lessons in basic electrical concepts but it's possible to learn on the job.  

 

The two things you're looking at now are voltage and resistance.  Voltage is typically measured from a component's electrical contacts to a ground point, which is any metal body or engine part.  The battery's negative post is connected to the body and engine, so you're actually measuring the supply of voltage from the battery by this method.  Resistance can be measured between any two points and is used to determine either how good the path to the component or to ground is, or to see if a component has the proper resistance for its function (the coil, for example).

 

Sorry to get all teachy, but your methods show some lack.  No offense.  The more times you run through the do-think cycle the more comfortable you'll be with the troubleshooting process.  Even the pros have to stop and think occasionally.

[Hodgimus-maximus]

oh I almost forgot, check if your battery leads are bad or not you should measure the voltage drop across them while the engine is cranking. If the drop is more than 0.25 Volts there is either a  bad connection or the leads are bad, most likely there is a bad connection.

[Captain Obvious]

Listening to the speed at which the starter cranks the motor over doesn't lead me to believe there's a problem with the battery cables or the starter. It sounds like a healthy typical speed spin.

 

The battery and cables "sound" fine to me. (If I can legally do that...) 

[Captain Obvious]

And reading back a little, I'm guessing the reason we're talking about battery cables at all is this:

 

When I measure the voltage across the starter at the two big terminals, it was reading 13V, as I would expect since they get direct connection from the battery. However, when measured in the same way but during my wife cranking the engine (still in pajamas), the voltage was reading around 6-7V.

 

I'm not sure what you meant by "terminals". Are you measuring where the two large battery cables connect to the starter (One on the starter solenoid and one on the mounting bolt that holds the starter to the engine)? Or are you measuring on the two threaded posts sticking out of the starter solenoid?

Edited August 11, 2015 by Captain Obvious

[Marios280Z]

Sorry to get all teachy, but your methods show some lack.  No offense.  The more times you run through the do-think cycle the more comfortable you'll be with the troubleshooting process.  Even the pros have to stop and think occasionally.

 No offense taken Zed Hed. One of the reasons that I got the car was to learn about engines and cars and I'm here for the same reason, so it's all good.

Edited August 11, 2015 by Marios280Z

[Marios280Z]

oh I almost forgot, check if your battery leads are bad or not you should measure the voltage drop across them while the engine is cranking. If the drop is more than 0.25 Volts there is either a  bad connection or the leads are bad, most likely there is a bad connection.

When I first got the car I had to some battery refreshment since the connectors at the battery terminals were pretty corroded. So I installed new clamp for a positive terminal and cleaned well the negative terminal. This weekend when I cleaned all the ground terminals per atlanticzcar DIY, I also cleaned ALL the connections to the starter, so they are nice and clean.

[EuroDat]

Marios280Z, To answer your question in post 48. Yes, thats what I meant. You can test for resistance by measuring voltage drop along your power supply starting at the battery terminal.

If you start with one probe in the centre of the (+) battery post and the other probe on the outside of the terminal, you will measure any resistance across the terminal when its cranking. If you see a voltage reading, clean the terminal and retest.

Then follow the cable to the starter and repeat the test with one probe on the centre of the battery post and the other on the starter terminal. Any voltage reading would be a bad cable or dirty terminal at the starter.

The starter solenoid is a little different because you are measuring across an open and closed contact. You will read battery voltage when you move the probe the the next terminal until cranking. You should read 0 volts when cranking. If you see some voltage then the solenoid contacts are dirty.

Once you have done the positive side test the negitive the same way.

One way to understand it better is to think in terms of hydraulics or your fuel system for that matter. Voltage is pressure and resistance is a restriction in the line. If a filter gets block it builds up pressure across the filter. Thats what you are looking for with voltage readings. Just like the hydraulic system, you will not see any pressure (voltage) when the system is at rest. That is why you need to crank the engine.

[Marios280Z]

Listening to the speed at which the starter cranks the motor over doesn't lead me to believe there's a problem with the battery cables or the starter. It sounds like a healthy typical speed spin.

 

The battery and cables "sound" fine to me. (If I can legally do that...) 

Glad to hear that.

 

 

I'm not sure what you meant by "terminals". Are you measuring where the two large battery cables connect to the starter (One on the starter solenoid and one on the mounting bolt that holds the starter to the engine)?

YES.

 

Also I double checked my work this evening and had my wife crank the engine for me again (not in her pajamas, so it wasn't as exciting). 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. I think I need to buy a better volt meter. My seems to be "slow" when it comes to displaying voltage. I've used volt meters in the past that were much more eager to show change in voltage than my cheep unit.

 

I also looked at the spark at each spark plug while the engine was running. They all looked the same to me and frankly they looked, well, like a spark... Hard for me to judge whether it was strong and bright or week and thin. Till I got this car I have never looked at the car spark or for that matter experienced the feeling when it arcs to your finger...I knew about spark plugs, what they do, I replaced them, but that's about it. Just never messed with them in today's hi tech cars. I took a video (go figure), and I could post it but after watching it I don't think any helpful conclusion can be drawn.

Other than that I was not able to do any more measurements today. Maybe I will read up in FSM before I go to bed.

Edited August 11, 2015 by Marios280Z

[Marios280Z]

Marios280Z, To answer your question in post 48. Yes, thats what I meant. You can test for resistance by measuring voltage drop along your power supply starting at the battery terminal.

If you start with one probe in the centre of the (+) battery post and the other probe on the outside of the terminal, you will measure any resistance across the terminal when its cranking. If you see a voltage reading, clean the terminal and retest.

Then follow the cable to the starter and repeat the test with one probe on the centre of the battery post and the other on the starter terminal. Any voltage reading would be a bad cable or dirty terminal at the starter.

The starter solenoid is a little different because you are measuring across an open and closed contact. You will read battery voltage when you move the probe the the next terminal until cranking. You should read 0 volts when cranking. If you see some voltage then the solenoid contacts are dirty.

Once you have done the positive side test the negitive the same way.

One way to understand it better is to think in terms of hydraulics or your fuel system for that matter. Voltage is pressure and resistance is a restriction in the line. If a filter gets block it builds up pressure across the filter. Thats what you are looking for with voltage readings. Just like the hydraulic system, you will not see any pressure (voltage) when the system is at rest. That is why you need to crank the engine.

Thanks EuroDat for the explanation. I will trace it down as you described and post the results.

[Zed Head]

 No offense taken Zed Hed. One of the reasons that I got the car was to learn about engines and cars and I'm here for the same reason, so it's all good.

This is good.  You're on the right forum and you picked the right car.  I've often thought that the 280Z EFI system is an excellent starting point for learning about cars and EFI.  Very basic and fundamental, with excellent documentation in the FSM's.  If I was an auto shop teacher, I'd use the 280Z as a teaching aid.

 

Looking back, you might be making a bigger deal out of the starting issue than it really is.  This technology is primitive, compared to today's cars.  The occasional stuttering start is fairly normal, and as I mentioned, could well be a tank of fuel that the system has trouble with.

 

But, if you want to forge ahead - consider the cold start valve (CSV) as CO mentioned in #42.  But look at it both ways, working too well and not working well enough.  It's function is to squirt a load of extra fuel in to the intake manifold, to give a fast start.  Many of us have removed our CSV's because we're okay with an extra second or two of cranking.  But there are times when I realize I could use its benefits (cold day after sitting in the garage for a week or two).  

 

By the way, Captain Obvious and SteveJ are the two electrical/electronics gurus on the forum (no offense to any unknown gurus,sorry for the pressure Steve and CO).  Consider their electrical words most carefully.

[Marios280Z]

Thanks ZedHead for kind words.

 

Frankly, the temps here in Iowa have not been cool enough to truly verify operation of the cold start system. Every time I looked at ti it was over 80 degrees and per FSM the thermotime switch has an upper limit of about 72 degrees. I did notice couple of times that when I left the car outside and not in the garage and the temps were in 60s over night, I had a bit harder time to start it in the morning, harder than after work when sitting outside in 80-90 degrees.

 

I did once (gain it was 80 some degrees), pulled out the CSV out of the intake manifold and placed it in the small jar while my wife cranked the engine. There was no drop of fuel that came out of it. I will be interested to repeat this when it is cooler outside.

 

Mean time I will disconnect my CSV plug as CO indicated in post #42 and will report if there are any changes in behavior.