When engaging the ignition, no start, voltmeter moves right on down to zero
 

I'm posting this in case someone else has had this specific problem before: Car cranks , but will not start:

Symptoms: Upon engaging ignition switch, from 12.5 the needle on the dash voltmeter moves right on down to zero. Swapped "in dash" voltmeter with new one. Swapped ignition switch also result the same :

Battery check: 12.66 volts no load. Battery underload (starter engaged) the reading is 10.45 on the multimeter, but when engaging the ignition switch the "in dash" voltmeter moves right on down to zero...But the multimeter at the battery at the same time reads 10.45 .....................................

.CD Box hot wire also reads 10.45 under load (starter cranking):

As if there is a ground somewhere? starter? alternator? regulator? or the coil as from my previous thread?


Ideas appreciated. Thanks

Sounds to me like the battery is bad (bad, not dead). You can have a battery go bad such that the battery will power a few lights, the radio, and other small draw items, but it does not have the amperage to start the car. That sounds like what you are seeing. You can have that verified by most retail auto parts stores. Most have a load tester.

And it can happen very quickly. I have had it happen several times myself and saw it happen to lots of people when I worked at a retail parts store when I was younger.

If the battery is swapped/tested o.k., perhaps the tach is bad and grounding out the coil(?) Try disconnecting, wrap wire and retry.
Not sure where the dash voltmeter gets its voltage from but if there's something on the same fused circuit that's going to ground while cranking, nothing will go through the meter.

There is also the case of a thin/bad connection that shows voltage potential, but won't flow amps. This will heat up the restriction(acting as the load resistor) to the point of fire.

Another idea, not sure if yours has it, but newer cars have a bypass circuit that provides coil juice right from the battery, and not tapped off the starter relay where there could be a drop.

First thing, you say you have power at the cd box, but have you verified the spark output at the plugwires?

Yes, I tried the spark test from the coil lead, and nothing. Which is where I suspected the coil.

I fixed the voltmeter drop by using Early_S_Man's reccomendation of switching the terminal connection on the ignition switch.

masraum: I can leave the headlights on and crank and only a very very slight drop in brightness occurs (using this as my load test.) I use a 2-10-55(start) Century charger, and the charger at the "2", has the indicator in the yellow "charge" as being OK. Is this enough? However, I will take the battery to have a "load" test tomorrow? What should I specifically ask for?

Thanks

HGP (name please?),

Swap another battery in the car if you have one to do a bit of quick trouble shooting. If no change then check your ground straps and battery cables and connections.

Feel that Steve is correct about the battery and a load check will show it however swapping another battery in the car would do the same thing faster. Several components in a cars electrical system have a minimum voltage. Below this they stop working and this may be your problem.

JoeA

OK. I'll take the battery in tomorrow. I can't really take a battery out of another car right now, it's quite time consuming, easier to take the one down to the have it load tested tomorrow.

Thanks

I have to disagree here. It has not been determined if the cd box is working and that any spark is apparent. The only information is that there is power to the cd box, and the starter is cranking the engine, and the lights do not dim while cranking. IMHO, the cd needs to proven good. Does it whine with the key on?

Damon is correct here. If the CD box does not whine when the ignition is turned on before the starter is engaged, then that needs to be corrected.

If the CD box does make noise then a good battery is a must before moving forward.

JoeA

I have an old "blue box" Permatune, that Early_S_Man, in some other threads says(I paraphrase) "is decent".

I understand, these don't make noise. The box is so old (I bet one of the first lines ever to come out) that the Permatune site for identification of the date , doesn't even coorespond to mine. Furthermore, the way the unit is installed looks very professional like factory. The mounting bracket, is not like an add on bracket, but like it came welded in as part of the the engine bay itself.

I re-verified after the battery test/ and coil swap (read below) today, and the hot center "B" connector for the CD box has full voltage upon ignition.

So the number one suspect returns to the old, very old apparently, CD box.

As a side note two questions

1. Could a voltage regulator or the alternator be effecting ignition itself? and
2. What is an "SCR'? Do I have one on a 1969 E?



(from the other thread....now consolidating to this one thread>>>>>>>

"Well here's the results of the battery: Tested by two places including a battery specialty house. Including under load. the battery is good.

Unfortunately the replacement coil has no effect. spark test with coil lead off also has NO spark.So:

Good battery
Good coil
Distributor rotates OK
Starter cranks normal
Full power at CD box both with and without load.

That leaves option of R&R CD box
(I do not know what an SCR is??? and if my 1969 has one or how to test itand how to test the voltage regulator? I have a small rectangular box on the sidewall with "Motorola" on it..is this the regulator ? and can it be tested amd replaced with a compatible regulator?" )

Sounds like it's time for the car to go to the local Porsche shop!

- Too much "dart throwing" -

Thanks, but almost impossible where I live.

I live close to 50 miles (100 both ways), to the nearest Porsche shop. I'm going on four years and I've determined to do everything myself.

( This far, I have completed all myself, from simple battery installation, to dropping the engine, installing new flywheel, starter, clutch R&R, ignition switch (NLA) R&R, total axle R&R for CV boots and repack joints, welding of alternator hub shaft, timing points, cap, plugs, speedometer "noise" repair, LED auxillary lights install, new fuel pump and pump relocation. throttle linkage, etc., and on......)

Electical stuff is mostly new to me though.................

I've got a feeling it's the way you connected your indash voltmeter. The starter motor voltage drop at the battery appears normal.

How did you connect the voltmeter? It sounds like you connected the + side to the ground side of an accessory. When cranking, the accessory uses up the 12 volts and the meter thus reads zero (0).

Try disconnecting the voltmeter and see if that makes any difference. However, you've done other things with the electrical system so there might be other solutions. The no-spark situation might have nothing to do with the voltmeter. Maybe something else.

Sherwood

If you would post your location, either in this thread, or on your profile, it might help. There are a lot of us around and just could be someone near you who has some spare parts or who is more familiar with the system who could lend a hand.

Am not really familiar with the Permatune box, only the factory unit. Have one of the Permatune units on a British car but different setup from the 911.

JoeA

I ran the voltmeter on this car for at least a year with no problems. I tried the disconnect of the meter yesterday but still did not change the situation. But I'll try again anyway.

One more test will be to disconnect the alternator and regulator, at the starter (?) or at least the regulator leads. And try the start with only the battery. Is this possible?

Then finally order a money back guarantee for a CD box, that I can get same day "shipped.

Thanks for the responses.

Did you verify the input to the ignition box from the distributor? Does this car hve points? Since you suspect a problem in the dash I would also disconect the wire that goes to the tach.

Your primary electrical malfunction sounds like the ignition system. If the CD box has normal voltage, is ok and the distributor can trigger and distribute, then there should be spark.

Anything else is something else.

Sherwood

Time has returned to "what was."

"Little Bull" rages again! "original "blue box" Permatune ok.

Some key words that brought solution(s):

"Load", "Primary" (and secondary), "coils don't fail often",
"flash over", "grounded", "voltmeter"(location)

I prepared about 4 hours or so, yesterday to work, on re-starting the car. I prepared to possibly have to swap in a new box, but it was not to be. I examined a number of threads at this site relating to ignition, and together with an Ignition Systems book I just purchased, decided that the problem (my amateur theory)might be in the secondary coil winding output.

No. 1: The points APPEARED great, but I put in new ones
No. 2: The rotor, I switch for a cleaner one.
No. 3. Replaced the distributor cap.

Result: fired right up.
Benefits (thanks to everyone who contributed ideas)
1. Car starts
2. learned amounts about my ignition
3. learned alot about battery load(s)
4. Primary and secondary output
5. Cleaned my CD box (outside), and with curiosity looked on the inside:

http://forums.pelicanparts.com/uploa...1097736219.jpg

Glad to hear its running again! Now you will probably not have any electrical problems for the next several years!

JoeA

so you figure the rotor rpm limiter "opened"?
How about an ohm resistance test for entertainment.