Starter works fine but car catches after you let off on the starter

[Jerry]

I was reading the archives about poor starting but the symptoms are different in my car. The starter turns the engine very well but the car does not catch and run till you let off on the starter. This sounds to me like the voltage needed for the ignition system is being used by the starter. Car runs great once it fires.
I put a voltage test on the battery:
1. No load= 12.0 v
2. While starting the car, 10.5-11v
3. Once running and the charging system takes over, 13.8v

The battery is an Optima and there is no date stamp on it, but I am guessing it is 7-8 years old. My next test is to jump the car and see if it starts better. But, any other items you can suggest to test?

Jerry

 

[AH100M]

Are you getting spark while it's cranking? Easy to check that first.

 

[Hangtown Healey]

Try another ignition switch or temporarily a separate ignition switch and separate starter button. Do you have a ballast resistor on the coil for some reason?

 

[DerekJ]

Should be more like 12.5 volts, at least.

 

[Jerry]

No ballast on the car, I may have an extra ignition switch, I will try that and test the ignition wires.

Jerry

 

[steveg]

You could run a temporary separate hot wire from the solenoid connection to the primary connection on the coil (the one from the ignition switch) thus routing around the ignition switch. If the car starts when cranking the ignition part of the switch is bad or the wire is broken somewhere between the ignition switch and the coil.

If there's enough voltage to crank the starter motor, there's enough for a spark, so the voltage may be a little low, but that's not the problem.

 

[RAC68]

Hi Jerry,

I also believe you have a faulty ignition switch an suggest the internal key contacts are either out of line or partially burned. When the ignition is turned to the start position, it makes contact with the starter but misses the ignition contact. When released to the run position, it relaxes and realigns to makes contact with the ignition contact to direct power to the coil.

To check this condition, place a voltage meter on the coil and turn the key to the start position. If voltage is not registered at the coil, change the switch.

Good luck,
Ray (64BJ8P1)

 

[CraigC]

Being an auto mechanic by day and a Healey enthusiast by night, I too suspect a burnt contact in the ignition switch. Ray has the proper test procedure if you are at home/shop with a voltmeter. If not, a convenient work-around is available if your car is fitted with a starter solenoid with the push button on the back side. Try starting normally. If the no-start while cranking exists, put gearbox in neutral, set parking brake, leave the ignition "on" , open hood and manually activate starter solenoid. If it fires up normally, head straight to the switch.

 

[CraigC]

Should be more like 12.5 volts, at least.

Derek, while cranking an engine, the starter motor is putting a huge load on the battery. It is quite normal for a healthy battery with a no load voltage of 12.6 to drop into the mid-10 volt range while the starter spins the engine. How low it drops is dependent on starter, battery, cable and connection condition as well as the engine you are trying to spin. I have a big block Chevy with 10-1 compression in a boat. It pulls in excess of 200 amps cranking. A low compression Sprite 948 probably pulls less than 80. if I were to crank each with the same battery, the Chevy would pull down a lot farther than the Sprite.

 

[DerekJ]

Craig, his battery shows 12.0 volts with no load, not 12.6v.

 

[Keoke]

The battery is an Optima and there is no date stamp on it, but I am guessing it is 7-8 years old.

Replace it.

 

[CraigC]

Craig, his battery shows 12.0 volts with no load, not 12.6v.

Ooops. For some reason I thought you were refering to his 10.5-11 volts while cranking. That's what I get for reading a thread at work and responding hours later from home.

Still would not be too concerned with that voltage since cranking volts are perfectly acceptable. Could just be low from repeatedly testing the starting issue.

 

[Jerry]

Update on the issue: I charged the battery up over night. It read 12.4 when I took the charger off, and 2 hours later was down to 12.2. I put the voltage meter on the coil and during cranking, the meter read 9.5-10, but started right away after charging so not a fair test. Unless you look at the charging of the battery and then a quick start as the test that tells me the battery is weak. So I will wait two days and try again just to prove it is the battery. At least a battery is easier to change than the ignition switch. Besides if I was getting voltage to the coil during cranking, it is probably NOT the ignition switch.

Jerry

 

[RAC68]

Hi Jerry,

It is a good sign that power is reaching the coil when the ignition is switched to the start position. However, if the contact is partially burned, the flow of power may not be sufficient for ignition.. As you have in indicated, a fully charged battery putting out spec levels of power will be necessary to test to a conclusion.

I also have an ageing Optima red-top battery and find that a deep charge is required to bring it up to power. Although a charge set to a standard setting will indicate a fully charged battery condition, without being placed on a deep charge non-maintenance charging setting, it will loos power very quickly and could hamper your ignition test with incorrect conclusions.

Good luck,
Ray (64BJ8P1)

 

[Jerry]

Update on the fix: I installed the new battery and it started like the old days. I kept a voltage meter on the old battery and the voltage dropped below 12v. New battery as expected was 12.8v.

Nice to have it fixed. thanks for your suggestions.

Jerry