Voltage drop while cranking. Alternator?

[Paul Thomas]

I have had intermitent start-up ignition problems lately. I thought it was gone but now the car wont start at all. And i could not drive it to Hershey.

When i turn the key on, fuel pump runs, 13-16 volts at the ignition hot lead.

Turn the key to start and the motor turns over great but the voltage at the ignition hot lead drops to around 2 volts. Not enough to power the crankfire. I talked to Richard Clewett (great guy by the way), he is sending a relay he says i should have anyway and it might be the fix. I am open to other possibilities.

Could it be my alternator? Voltage regulator? Diodes?

Paul

[Tim Walsh]

Have you taken your battery to your FLAPS and had it tested? Cranking a car takes LOTS of juice, but 2 volts is pretty low. I don't think it would be the alt since it just supplies maintence to your battery. You can run for an hour or more just on a fresh battery without an alternator

[Fl Ted]

If you've got 13-16 volts with the ignition on and engine not running, you've got a voltmeter thats reading about 4 volts high!! The battery will only read about 12-12.7 volts by itself, 13.75 to14.25 with alternator running. Battery voltage will drop to 11-7 volts while cranking, lower than 7 volts, your batt is bad. Something is loading down your ign circuit.
When you're reading the 2v @ the ign hot wire, is the wire connected or dissconnected? If its connected, whatever it's connected to is the culprit. If it's dissconnected, it's something up-stream. Get the wiring diagram and trace upstream.

[Paul Thomas]

Checked both batteries and they are good. I pulled the alternator earlier to check all of the conections and the voltage regulator. All of the connections were tight but the red wire ends look like ***** so i am going to replace them.

The voltage regulator is available from Pelican. Wires going into and out of the regulator have some sort of brown goop on the wires. I may take a pic if anyone has any further insight.

Paul

[asphaltgambler]

Could it be my alternator? Voltage regulator? Diodes? -No these components do enter the picture until the engine fires and the alt starts to charge.

Your voltage problem is upon start /crank. A good battery should maintain @ 11 volts while cranking (at the batt terminals) I'm not sure where (terminal)you are measuring this low voltage, please clarify.

[Paul Thomas]

I tested the voltage before and during cranking at the red power wire that goes my crankfire. I am realitively certain that it goes from the battery to the ignition switch to the coilpacks.

Richard Clewett suggested i put in a relay regardless. He thinks that may be the problem, but it hasnt been one in 5 years.

The alternator is out and i am having it checked on Monday just to rule it out. I understand what you're saying, i just want to narrow it down a bit. Something is draining my voltage while cranking.

Paul

[911pcars]

"Checked both batteries and they are good."

Please describe the test(s).

Better yet, connect a voltmeter directly onto the battery posts, then retest. If it stays above 9 volts during cranking, the battery is okay. Then look elsewhere for the voltage drop to the ignition system (only during cranking).

If the ignition hot lead has 13-16 volts with ignition ON, but drops to 2 volts during cranking, something is wrong. I don't know what's going on upstream.

Points-based ignition systems use a resistor on the primary circuit to drop running voltage to about 9 volts. However, during cranking, this circuit receives a full 12 volts via a bypass circuit on the starter solenoid. If this is your setup, the bypass circuit could have excessive resistance which results in only 2 volts available (loose, dirty connector).

My guess,
Sherwood

[Fl Ted]

Paul: you haven't answered the key question yet. The ign wire that you're getting the 2v on while cranking, is it connected? and if so, what is it connected to? Is it connected to the "crankfire" box, or are you measuring at the ign switch, or what?
If, as you state in your previous post,"something is draining my voltage while cranking" you would be cranking slowly or not at all. You should check your cranking voltage just so you know what it is as a referance, but if its turning over at its usual speed, than its safe to assume that the battery is GOOD. The alternator has NOTHING to do with this problem, as the engine has to be RUNNING before the alternator does anything!
At this point, I would suspect a bad/corroded connection. Check the fuse for the crankfire for loosness or corrosion. Again, is that ign wire connected or disconnected when you measure the 2 v????

[rick-l]

Let me make sure I understand this

1) Starter turns the engine just fine meaning the battery and alternator are just fine.
2) when you run the starter the voltage at the input to the ignition control module drops to 2 volts, less than needed to function.
3) this configuration has worked but has deteriorated over time to where it now does not function.

Where does that power wire come from? It sounds like it is on the starter terminal, not the best. More likely is the ground point you selected for measurement is on the wrong end of a corroded chassis ground connection, possibly a clue to resolving the problem.

Does the car run if you push start it?

[Paul Thomas]

Thanks for everyones input. I have a list of things to check tomorrow when i have an extra pair of hands.

Ted, when i measured the voltage at the ignition power wire, it was still connected to the Electromotive. Unhooking and checking again is at the top of my list.

Rick, i am relatively sure that the power wire goes from the battery to the ignition switch, to the engine bay. I am going to disconect it and confirm. I believe that the car would run if roll started, but since my house is on a hill, i am not willing to bet on it.

Thanks again,
Paul