'66 f100 starting problems
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'66 f100 starting problems
I have a '66 F100 with as 302 and AOD swap. Was going to start the truck today and the relay clicked once, no crank and all the lights stayed on. After that there was no click at the relay with the key turn. I checked voltage to the relay and got 12.21, checked it at the starter and got 12.21, alt was the same and grounds were the same. Does this seem like a bad relay/solenoid or starter? Also with this if i disconnect the battery and let the system discharge, reconnect and try the key again i get the same exact symptoms. Any help would be appreciated I'm at a loss.
More Turbo
Joined: Dec 2019
Posts: 737
Likes: 159
From: Orange County
In my experience - that's very possibly a bad or low battery. The symptoms sound like it's got enough juice to turn on lights but not turn the starter. I've been there and chased other things, then swapped the battery, and voila. A good battery at rest should be something like 12.6V or more. 12.2 would be on the low end of workable. If you have a known-good car battery near, I'd do a quick swap to check that first.
FTE Legend
Joined: Jun 2004
Posts: 31,948
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From: Upstate NY
, Your battery can be bad and still read voltage but it does not have amperage. You could just try jump starting it to eliminate the battery. Often a bad battery will make the solenoid (starter relay), click but not have enough power to turn the starter. That is probably what you need to test first. If still no starter, do you know how to jump across the solenoid (relay)? You have to go from the big wire on one side to the big wire on the other side. You will see some sparks so don't jump and hurt yourself. If you heard a click, it seems like the circuit from the switch is alright. If not start after that, it may well be the starter. However, check the larger ground wire that attaches to the engine. Loose grounds can cause weird problems. Have fun!
Oh yeah, welcome to FTE. There is a lot to learn here even if your truck is running fine!
Oh yeah, welcome to FTE. There is a lot to learn here even if your truck is running fine!
Cargo Master
Joined: Apr 2001
Posts: 2,697
Likes: 46
From: Vancouver
What is the battery voltage while cranking? If it is not at least 9.6V I would suspect the battery, as suggested above. This is presuming all connections are clean and tight.
Try jumper cables to a known-good battery such as one in a diesel truck and see what happens.
A good rule of thumb is that a 12V battery that reads 12V is essentially...dead.
Eric
Try jumper cables to a known-good battery such as one in a diesel truck and see what happens.
A good rule of thumb is that a 12V battery that reads 12V is essentially...dead.
Eric
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New User
Joined: Mar 2021
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The battery was the cranking issue, thank you gentlemen. Now i only have spark during starting and not in the run position. Is the "I" post on the starter relay/solenoid supposed to be my "hot" in the run position and in the start position?
Fleet Mechanic
Joined: Sep 2016
Posts: 1,459
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From: Southern Maryland
The I terminal provides a full 12volts to the coil while cranking. Once the key is returned to the run position, then power to the coil comes from the ignition switch through the pink resistor wire (which drops voltage down to around 9 volts) and then out to the coil on the red/green stripe wire. Start tracing from the ignition switch out to find where you're losing continuity.
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