Scratching my head on this one. No ignition while cranking unless...

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Scratching my head on this one. No ignition while cranking unless...

Post  738drvr on January 4th 2015, 8:59 pm

All MSD system. 6-AL2 with start retard. Billet distributor locked out at 32 degrees.

Car will fire right up and run fine while using a remote start switch on the start solenoid with the key in the run position. If you try and start the car with the key, no ignition just engine cranking over.

What gives? Tried a different start solenoid and it did the very same thing. Ignition only when jumping between the S pole on the solenoid and the hot battery connection. Replace the 12V switched wire and the solenoid will crank the engine but no ignition.

All fuses are good. All connections are good. Worked great up until Friday of last week. Weird.
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Re: Scratching my head on this one. No ignition while cranking unless...

Post  FalconEh on January 4th 2015, 9:02 pm

At what voltage?
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Re: Scratching my head on this one. No ignition while cranking unless...

Post  QtrWarrior on January 4th 2015, 9:05 pm

Contacts in the key switch..
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Re: Scratching my head on this one. No ignition while cranking unless...

Post  FalconEh on January 4th 2015, 9:12 pm

I will elaborate a little here, when you jump the terminals on the solenoid it bypasses everything else, so if you have 11.85 volts at the ignition, you may have 12.00V at the solenoid which is what the MSD requires, the Duraspark is more forgiving when it comes to voltage, you need to be really close to 12V for the MSD to fire, if you can jump the car from the solenoid and put a meter on the battery it should tell you if the charging system is working properly, when running it should be around 14.1V if it is 13+ and climbing the charging system is working and your battery(s) are too low for an ignition start, if it shows less then likely you have developed a charging problem.
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Re: Scratching my head on this one. No ignition while cranking unless...

Post  DFI429 on January 4th 2015, 10:30 pm

QtrWarrior wrote:Contacts in the key switch..


X2... Common denominator is the key switch contacts - sounds like the common contact that should carry run to start has lost its' start portion. Hence why it starts when you leave the key ON, and jump the solenoid. Voltage is important too, but the repeatability points towards the switch.
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Re: Scratching my head on this one. No ignition while cranking unless...

Post  maverick on January 4th 2015, 11:00 pm

QtrWarrior wrote:Contacts in the key switch..

X3. Not all that uncommon. Replace the ignition switch.
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Re: Scratching my head on this one. No ignition while cranking unless...

Post  738drvr on January 4th 2015, 11:15 pm

Just picked up an ignition switch and key tumbler. Will report back in a bit. Battery voltage is good.
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Re: Scratching my head on this one. No ignition while cranking unless...

Post  738drvr on January 5th 2015, 12:26 am

New ignition switch and a new keyswitch/tumbler.

No change. Shocked
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Re: Scratching my head on this one. No ignition while cranking unless...

Post  738drvr on January 5th 2015, 12:28 am

Still can't understand why it fires from the solenoid but not the key when cranking. No power to the box when in crank position on the key.

I'm going to break out the meter and the 1978 wiring diagram(I do have it).

Looks like a late night.

Any more suggestions?

Thanks.
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Re: Scratching my head on this one. No ignition while cranking unless...

Post  738drvr on January 5th 2015, 12:39 am

10.99-11.01v while cranking. Measured at the battery. Cranks like a 302. The box is wired directly to the battery with 10 gauge wire +/-. I'll measure the voltage while cranking at the 12v wire to the box from the fuse panel.
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Re: Scratching my head on this one. No ignition while cranking unless...

Post  738drvr on January 5th 2015, 1:16 am

Moved wires to 12v hot always even while cranking.

She fired right up. Not sure why it ran wired the other way but it did.

Thanks guys for the help.
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