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corey_49

Ignition Problems when Hot

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I have just installed a new alternator (https://zcardepot.com/electrical/battery/alternator-high-amp-90-240z-260z-280z.html?search=alternator) and external regulator delete (http://www.thezstore.com/page/TZS/PROD/classic10l/12-4067).  I had the car running beautifully for one day, or the best it has ever run for me, then ignition problem only when hot.  The car will run fine when first starting up or idling and you can cruise along fine for short time.  When you start to rev the engine up and put it through its entire RPM range I only get 2-4 shots at full throttle up to 6500rpm.  Once hot I lose all power and it stumbles, kind of like really bad timing, constant misfire, or running of 5 cylinders.  The car wants to die and if you stop moving or allow the car to idle the engine will stall, I have to keep the engine rpm above 1000 rpm and baby it home.  I can get up to about 30mph but that is about it.  I can stop and keep the car idling for a short time and the car will eventually idle for itself, after about 5 minutes I get about 30 seconds of use maxing out around 2500-3000 rpm and then back to the same problem.  Or I turn the car off and take a break for half hour and get about 3-5 minutes of normal driving before the problem persists. 

 

The ignition system

Ignition Coil:  Crane PS-20 Performance Coil

http://www.thezstore.com/page/TZS/PROD/classic11f03/12-4051

Plug wires:Taylor Thundervolt 50 Racing 10.4mm

http://www.thezstore.com/page/TZS/PROD/classic11k/12-4169

Spark plugs:  NGK BPR6ES

Everything else is stock for a 240z (auto transmission distributor)

 

1) Battery is old and kind of dead, have replacement just need to change some things.  This is my first step

2) Change Spark plugs, they are about 4 years old and have about 5000-7000 miles on them.

3) Swap out new alternator for old set up.

 

Any ideas/ solutions would be a great help as I am at a loss and don’t know where to go from here.

 

P.S. anyone have an original Distributor for a 240z Manual transmission version as I want to convert to electrical points set up.  Located near Toronto Canada.  Thx

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Why did you describe your new alternator and regulator-delete system?  You're implying that they might be part of your problem.  Did the ignition system work well before the alternator change?  Has the engine ever run well?  

 

How do you know it's not a fuel problem?  Did you know that some of the early cars have the electric fuel pump power supplied by the external regulator?

 

Just adding some focus.

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Posted (edited)

In short I have the same problem. Try replacing your coil. Only $35 bucks. Autozone has them. Also, check all connections for corrosion, as mentioned fuel filter, battery voltage when the car starts acting up.

Edited by steve260z

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The car is a 1971 240z, and the car ran fine before with the original 40 amp alternator but when i installed the 90 amp i noticed an improvement, small but noticeable.  I don't think it is a fuel problem because i still have the mechanical fuel pump and a clean filter. 

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Have you confirmed that the new alternator is regulating correctly?  Could be that it's not and you fried something with high voltage.  Easy to check with a meter at the battery.  Even new parts can be bad.  Or your S circuit might not be complete.  Best confirm.

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When the car is idling i take a multimeter to the battery and it reads 14.24-14.36 volts.  I rev up the engine and it stays more or less the same.  The S circuit could be a problem as it is connected to original wiring.  when this symptom started i drove the car about 1 hour the day before and about 20 minutes the day of before it started acting up.  what do you think i could of fried?

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Those numbers look right.  ~14.3 volts.  Probably haven't fried anything.

 

That voltage passes through the coil.  Too high could damage it.  But your numbers look fine.

 

Could just be coincidence.  When did you last change the points and condenser, and set gap or dwell?  A condenser can overheat and short, causing ignition problems.  Or your points might be burned.  Give it a tuneup and see if there's a difference.`

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Posted (edited)

Compare your voltage from the heavy power lead on the alternator to the voltage at the battery. If the wiring is stock, the power flows from the alternator to the fuse box through the ammeter back to the battery. I had 1 volt drop on my 240z between the alternator to the battery and it melted one of the connectors under the dash.

Not saying this is the issue but it is possible that the alternator is putting out more than what your battery voltage says IF the flow of power is stock.

Run an additional heavy wire from the alternator terminal to the battery so the charging current doesn't have to run through the dash. This is even more important if you have additional accessories like electric fans etc. run from the battery. Ask me how I know ! Downside is the ammeter wont read correctly as it will be partially bypassed.

Edited by BJSZED

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The initial plan was to switch over to electrical points (https://zcardepot.com/engine/ignition/pertronix-ignitor-ii-electronic-ignition-conversion.html) however that part only works with the manual transmission version, as the auto has a different backing plate.  I just changed the points and set the gap to 0.020" inbetween the 0.018 and 0.022" specked out.  The  condenser was replaced about 4-5 years ago about 5000-7000 miles.  

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The car will run fine when first starting up or idling and you can cruise along fine for short time.  When you start to rev the engine up and put it through its entire RPM range I only get 2-4 shots at full throttle up to 6500rpm.  Once hot I lose all power and it stumbles, kind of like really bad timing, constant misfire, or running of 5 cylinders. 

 

I can stop and keep the car idling for a short time and the car will eventually idle for itself, after about 5 minutes I get about 30 seconds of use maxing out around 2500-3000 rpm and then back to the same problem. 

 

Still seems non-ignition-related, unless the coil is overheating like steve260z suggested.  If you can stop and let the engine cool off but still at operating temperature, and the problem comes back after 30 seconds, that doesn't really sound electrical.

 

Bad fuel pump  or clogged fuel lines come to mind.  Can you confirm fuel flow and check float bowl levels when the problem happens?  Seems like you've decided it's ignition but haven't checked the other stuff.

 

You could get a 280Z distributor and a GM HEI module and have a better ignition system than that Pertronix unit, for about the same cost.

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Posted (edited)

For the record, here is my deal which I'm chasing down:

 

Ok..Have a stroker with triple Weber 40s, Datsun distributor, 34 degrees all in, carter low pressure fuel pump, plugs look good, brand new fuel filter, dead headed carbs, old return line vented to atmosphere, Crane ignition module...Think thats most of important parts, just ask for whatever I've neglected to mention.
After 10 minutes of driving, when I come to a stop the car will act like its going to die or will die. This occurs about 50% of the time. If this does not occur I can let the car idle in the driveway and it will start acting like its going to die and will eventually within the next 30 minutes. I can then restart in the car with about a 4 or 5 second crank. Now, if its not in this state of just dying I can turn the car off and restart with a 1 or 2 second start...I think the clues lie here in this 4-5 second crank to start. Now, I've but a voltmeter on the battery as the car dies and the meter reads a consistent 14-14.3 volts while running and dying. When the car dies I can still hear the carter fuel pump running. When it dies the O2 meter will drop down to about 10 AFR from the usually 12 at idle. Now, not sure if this richness is caused by the actual problem or just the result of low bouncing idle at the point of dying which would mess with the vacuum signal the carb sees. Obviously I'm freaking stumped. As mentioned above the 4-5 second crank time on restart is interesting. I've been thinking maybe the fuel is getting too hot, pump is crapping out (only 5K miles on it), all kind of esoteric different Weber ideas and many other ideas...

 

And the thread...http://forums.hybridz.org/topic/127405-strange-dying-issuetake-a-shot/

Edited by steve260z

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Corey, I used to have a 260 that had BOTH the mechanical fuel pump and the electrical pump. I had similar symptoms to what you are describing and it turns out that there is a small cylindrical screen inside the electric fuel pump. If you have this I would strongly suggest checking it. Even if it isn't the issue it's a good thing to check on occasion.

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P.S. anyone have an original Distributor for a 240z Manual transmission version as I want to convert to electrical points set up.  Located near Toronto Canada.  Thx

Oddly, I believe I do.  I can shoot you some pics if you want to check it out.

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