car won't start!

As a layman, I don't have the chops to carry on a discussion of jump starting a car and the technical details of the potential dangers, I can simply state from 40 years of driving experience that I've never had any kind of catastrophic system failure following the jump starting of a car.

I can't imagine how many times I've done it over the years, and not always by strictly following the procedure of grounding to the vehicle, not the battery, and then connecting the hot lead to the hot on the battery, etc.

I've done it with my Dino, I've done it with many other cars, from late 60's models to current ones, without experiencing any kind of disasters.

I even did it with my 360. Although in that case I did carefully follow the instructions of my mechanic, as failure of the dash gauges can result from improper jumping.

I'll continue to follow the discussion here, but sometimes I think we over think it. Can't you just see the two guys by the side of the road in 1973 with a dead Dino arguing induction and mega volt backlash from a jump start?

DM

 

Thank you all for the advice. I think it fair to err on the side of caution if you still have original or older electronic ignitions.

Going back to the non starting issue, my car is a terrible hot starter and I have used a jump start pack on it many times to help the engine turn a little faster if the battery starts to weaken.

I have friend here in the UK with three 70s V12 cars and he has fitted new starter motors from www.ferraristarters.com to all of them. I have to say they work really well. He & I use the same mechanic who has suggested to me that one of these would really help with my Dino starting issues. I have ordered one and will report my findings when fitted.

Mark

www.markshannon.net

 

Adrian - thank you for your understanding of my concern, and receiving my comments as intended; constructive and pedagogical. (Why use a long word when a diminutive one will work as well?)

You are correct that the internal resistance of a lead-acid battery increases as charge (voltage) decreases. However, while the change can be as great as 40% between full charge and depleted (depleted internal resistance being greater), the absolute numbers are in milli-Ohms. Furthermore, the consequence of (relatively) high internal resistance of the battery is a diminished voltage to the remainder of the system. Voltage dropped (owing to Ohm's Law) in the battery is not available to the starter, lights, etc.

The alternator will see a diminished load, and will generate more current into the battery. But the Dinoplex is an non-participating bystander simply observing voltage fluctuations (all lower).

Nonetheless, I respect your experience, and advise others to follow your advice.

Mark - with regard to gear reduction starters - Best thing since sliced bread. Period.

Jim S.

 

Jim,
What you are saying above is all true and correct, but you and Adrian seem to be talking about different scenarios.
You did say that you welcome a discussion of the failure mechanism involved in jump starting, so here is my contribution:

Adrian is absolutely correct about the dangers of jumpstarting. The induced voltage transients resulting from simply connecting and disconnecting the jumper cables, are entirely capable of damaging the Dinoplex or any other semiconductor device connected to the 12 V system. Not every time, and perhaps not even most of the time, but the danger is definitely there.

The reason for those voltage transients are not intuitive or obvious, but for me, at least, they become clear when you think about the extreme case, which Ferrari specifically is warning against: Disconnecting the battery when the car is running. So, let us look at that scenario first.

I think we can all agree that a current through an inductive device builds up a magnetic field, which represents energy. When you suddenly interrupt that current, that energy must go somewhere, and with an open circuit, the energy has nowhere to go. To comply with the laws of physics, the voltage will simply rise and rise, until it finds a path to discharge, and thus dump the energy (converting it into heat actually). That is how high voltage transients are created from what is otherwise a low voltage system. Inductive kick back, simply. Hardly controversial, and something we can all agree on.

If someone would be foolish enough to disconnect the battery of a Dino when the car is running, what would happen?
The alternator is probably charging the battery with a substantial current, perhaps twenty amps or so. The alternator is a highly inductive device. In fact, it is nothing but an inductance. Disconnecting the battery under these conditions, is the textbook case for creating induced high voltage transients described above. The energy built up in the alternator coils will have no place to go. In early alternators, the transients would kill the diodes and discharge that way. Later alternators have better protection and better diodes, and will probably survive. Instead, the entire 12 V system in the Dino will be exposed to the high voltage spikes, and that, unfortunately, includes the Dinoplex. Hence the warning from Ferrari.

Now back to the case of jump-starting. It is not nearly as bad as disconnecting the battery, but it does create a similar interruption (sharp reduction) of current from the Dino alternator. In fact, in the donor car it also creates similar transients, which may or may not reach the Dino system via the jumper cable. If there is a small spark or a crackling sound when you remove the jumper cable, it is proof that you created high voltage transients! The currents involved are very high, resulting in powerful transients. The only difference to the example above is that the Dino now has a battery connected. This battery is now supposed to swallow and absorb these transients. The problem is that a lead acid accumulator is a fairly slow device. It can absorb substantial energies and currents, but it takes some time to do it. In microseconds or milliseconds, the battery can not absorb anything. The transients will not even see the battery, they will run right over it and into the 12 V system of the car. The capacitor on the input of the Dinoplex, on the other hand, will look like a short circuit to ground and a perfect path to discharge. The result will be a fried capacitor, like the one in Adrian’s photo.
As Adrian also mentioned, a charged battery will have a lower resistance and perhaps absorb more of the transients, but I would not bet the farm (or the Dinoplex) on it. Jump starting is a crude and unpredictable method, and should be avoided at any price, in my opinion. If it must be done, it is better to use a power pack as Mark Shannon mentioned. The reason is that they usually have an on/off switch, allowing you to connect the cables first, then turn the switch on. It is a cleaner and safer way to connect and disconnect the two batteries.

My only disagreement with Adrian is the recommendation to leave the two batteries connected to each other for ten minutes. Lead acid accumulators should never be connected in parallel for any length of time, at least not without some device to limit or control the current between them. Otherwise, the charging current to the receiving battery could easily become so high that “gassing” could result. That could in turn increase the risk of a battery explosion. Not something that you even want to think about in a Dino!

Lars

 

As you say...The key is to Ground the car, then all the other stuff works itself out.

Scenario, car stalls, no start, switch to emmergency coil, battery too weak to produce any kind of spark. No cell phone, miles from nowwhere
Slip gear into neutral, ignition on, release handbrake, open window and start pushing. Push push, and more push push, jump in aim your foot at the clutch pedal clutch in, slam it into 3rd at the same time, drop the clutch, feel it bite, clutch in before it stalls...keep revs up, catch breath, check heart rate and move on.

 

There must be something else afoot, car should still start and a chronic starting problem must indicate other issues, aside from the starter itself. Just a thought

 

Lars - brilliant explanation. Thank you.

A few comments:

1) When an inductive circuit is "opened" (as proposed by removing the battery), the inductor will attempt to maintain current flow. Voltage across the inductor will equal the source voltage (momentarily) with exponential decay thereafter. It is the inductor that sees this voltage. Other loads will see a diminishing voltage (equal to the product of the exponentially decaying current and the load resistance - Ohm's Law). Thus, in the idealized example of all of the inductance located in the alternator, it is the alternator that will experience this voltage, but a voltage only equal to the original source. Inductors will not multiply voltage. The voltage across the inductor will not "rise and rise", but will instantaneously equal the original source voltage and then decay. This is not a transformer where coupling has taken place.

2) The spark seen in an inductive circuit when the switch is open does not imply vastly high voltage, simply the source voltage across a very small gap (as the switch opens). If the voltage (12 volts, for example) is sufficient to ionize the gas across this minuscule gap, then the spark will grow as ions form.

3) Tapping a battery post with a charger, or ground, almost always results in sparks, and this is at 12 volts.

4) The capacitor in the Dinoplex ALWAYS looks like a short circuit when the ignition is turned on, yet it does not burn up. Indeed, capacitors are designed to appear as zero impedance as a power up transient...current leads voltage.

5) Your explanation is quite sound and consistent with physical principles. We could discuss the physics until the cows come home, but I suspect the real truth will be found in the lab with an oscilloscope on a Dino.

Thanks for educating me. I learned a great deal. I had not considered many of the issues you raise.

Jim S.

 

Yes I agree. It is a hot starting problem that goes away after 20 mins with the engine lid open. However, we are doing lots of other stuff as well.

Mark

 

Mark,

On the basis of about 6 months experience with my dino and a lot of experience with old knackered cars in my youth if you have problems with starting when hot it is likely to be a fuel evaporation in carbs/vapour lock in the fuel line problem.

My dino manual says that what i need to do when starting it hot is to press the throttle on full and crank away until it starts. It has worked every time....so far....I presume that this is a way of drawing colder) fuel into the carbs.

So my conclusion is to keep the dino on a trickle charger when it isn't being used becasue i never know when I need to just turn it over.

As for my old Vauxhall Cavalier and TVR s2 when hot and they didn't start the first thing to do was get my hammer out of the trunk and hit the starter motor solenoid.....more room under their hoods than the dino...

Snowy

 

Sorry, everyone, for taking up too much space here. This will be my last post on this thread, I promise! I just had to respond.


Jim,
The problem of induced high voltage transients is a well known and well documented phenomenon in the electronics industry. Thousands of products have been designed to eliminate or minimize the damage they can do. Hundreds of technical papers have been written about them. I, myself, have observed those high voltage transients on a storage oscilloscope many, many times. I can understand if you quarrel with my attempts at describing and explaining the phenomenon, but I can not understand how you can question whether this, very well known phenomenon exists at all! I believe you are making the mistake of looking at the circuits under steady state conditions. I am describing the events under dynamic conditions during a few hundred milliseconds, events that can be captured on a storage oscilloscope but not on a voltmeter. When I say the voltage is rising, I am talking about the instantaneous, induced voltage across an inductor. It can indeed be shown to behave exactly as I described it.
Anyway, I simply have to comment on your points:

1) The first part is a half-truth, the second part is simply incorrect, in my opinion. Yes, the voltage across an inductor will decay exponentially as you state, but only if you provide a path for the energy to discharge!
If you interrupt that path, the induced voltage across the inductor will indeed rise and rise. The reason can be found in your own words: “It will try to maintain the current through it”. Exactly! If the current is suddenly zero, the voltage must go to infinity to maintain it! It will never reach infinity, but it will certainly try. Normally, the voltage rises to about ten times the supply voltage, around 100 - 150V, but can frequently be double or triple that value before it runs out of steam.
The alternator will produce a massive high voltage transient if you disconnect the battery. Reason: See above. The high voltage transients will reach all components connected to the 12 V supply.

2) 12V with a pure resistive load will never produce much of an arc. Arcing = inductive voltage spikes. Put a scope over it and see.

3) A battery charger will produce exactly the same (albeit smaller) transients as an alternator when the charge current is interrupted – for the same reasons. See above.

4) Of course. But normally it is only 12 to 14V. When the transients come, it is perhaps 200V. That is the difference.

5) Thanks, Jim. Perhaps some time in the future, I will dig out the old oscilloscope from my moving boxes and be able to produce some oscilloscope pictures. You may become a believer… : )


Finally, take a look at what other people say about this problem. This is just one site, chosen at random:
http://www.sto-p.com/pfp/pfp-transients.htm

Lars

 

so the real answer is to trickle charge a battery that's dead.

No massive amperage, no sparking, no problems, right? Just also no immediate gratification, or starting of the car.

And if the battery is dead, zero volts, zero amps, will it trickle charge? And do trickle chargers shut themselves off?

dm

 

Thank you Snowy.

I keep mine with the battery disconnected, I do not trust chargers since someone I know had a fire. The car always starts perfectly when cold or even when warm, so the battery is fully charged up, by the car, way before it gets too hot.

I too use your hot starting method as described in the manual. My friendly mechanic says it is to increase the air quantity as well, but he does say to slowly lift your foot off as the car catches.

Mark

 

Not all trickle chargers turn themselves off, but the new "intelligent" ones do (example, Cetek, etc.). They cycle on and off as required. They are supposed to be safe to leave on all the time.
If you have a completely dead battery, trickle chargers take too long, 24 to 48 hours. It will seem like forever. I use a regular little 10 A charger instead. A completely empty battery will need to be charged overnight.

I disconnect the battery in the Dino when I am away on a trip, or not driving it once a week or so (shame!). When I come back, I put the charger on and watch until the current drops. Usually, one hour or less is enough. The car always starts then. That was not always the case before, when I left the battery connected for weeks at a time. Sometimes it would then behave just like philt68's car: It would seem to crank at more or less normal speeds, but not fire. After some fiddling and looking at spark plugs, etc. it would finally start. Exactly the situation described by philt68.

Since I changed to the disconnect battery/brief charging method, the car always starts happily.

Lars

 

Hi Guys,

Of course this happens when most of you guys are in Monterey. My car suddenly decided not to start. It started fine until now. My fuel pumps come on and I'm pretty sure there's plenty of juice in the battery. Just when I turn the key that final arc...nothing. Only the "brake failure" warning light comes on. But absolutely nothing from the starter. She's been sitting for at least 4 hours so she's not hot at all.

Any ideas?

Thanks,

Manny

 

do you hear a click or clicks or anything when the key is turned that final arc?

 

Just the click of the ignition switch itself. I'm too swamped to bother with it right now (reason I wasn't in Monterey). I dropped the car off this morning at the shop. There were a couple of other minor issues as well. I'll let you know what they find.

 

This is a long shot but can be a good trick...
Reach under the dash on the back of the ignition switch module where the wires are and squeeze the backing forward towards the key face slot. Sometimes the interior electrical connections inside the switch casing get loose. There is a reason that T Rutlands sells a lot of ignition switch backings, they fail to make contacts
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=190176322219

 

The shop called with the cause of the problem. A broken wire. I was swamped so didn't get the details. I'll get the details when I pick up the car.