For my 1975 Ford I have done a complete replacement of the electrical system with a Painless Wire Kit and engine components for my rebuild. I have worked on the ignition system for the past couple of weeks and I have exhausted all of what I know to check, so I am open for some input to get this monster finally started.


When I turn the ignition key the Starter Solenoid just gives a loud “clunk”, even when I just run a wire from the positive side terminal to the “I”.

Grounding checks from the positive post:
Battery post to post there is 12.2V
- battery post to engine grounding point is 11.97V
Engine block to frame ground is 11.97
Engine block to cab is 11.68

There is < 1V on the cable to the starter when the ignition key is turned.

Replaced the Solenoid resulted in a “clunk” still, I pulled the starter and took it to be checked and it passed. When I was reinstalling the starter I just hooked up the cable and let it hang on the ground still not turning with a “clunk” from the solenoid.

Triple checked the wire connections from the schematics.

If there is anything else that I need to check please let me know and in advance thank you for the help.

 

If I'm not mistaken, the I terminal supplies full voltage to the coil.

The Ignition switch start wire should be attached to the S terminal.

Not sure why the relay/solenoid would be doing the clunk thing with the I terminal, as in theory it should be isolated from the relay/solenoids winding...

Can you use jumper cables to bypass the solenoid to activate the starter? What about a jumper on the S terminal? The S terminal should provide a clunk and the starter should activate. Doing at least these things should provide some clues to where the problem lies.

edit: Be careful if you try the jumper cables thing! don't wanna get tangled up with the engines fan or burn down your truck...

 

Sure are losing a lot of voltage. Try a voltage drop test across the cables and connections to find out where.

 

easiest check would be to make sure solenoid mounting bracket has good ground, good 12v connection from batt + to left, large post...then jump 12v from the large post to the s terminal...it should click and send 12v to other larger teminal and the I terminal...

 

Either the block isn't grounded well or your cable from the solenoid to starter is bad...

 

ZarK-eh, I was mistaken it is the “S” post that I am Jumping from the positive terminal to the “S”. I have tried a 6 gauge wire jump from the positive side of the Solenoid to the post going to the starter and it does nothing, only to the S terminal do I get the clunking noise.

Tedster the cable is only a year old but I will do a voltage drop check tomorrow morning.

Dlburch the negative battery cable is connected straight to the block . it is 12.2 V from + battery post to the – battery post. I will scuff up the paint under the mounting bracket as the fender has been painted.

Thank you for the input and I will get back first thing in the morning as I have to head off to work now.

 

Not just a cable include the starter itself for example. One common issue, did you paint the block as part of the rebuild? Place one end of the voltmeter at the negative battery post and the other end at clean metal at the starter case. Measure voltage during cranking.

 

Seems like it might be the cable from the starter relay/solenoid to the starter that maybe the problem.

How do you feel about using jumper cables to jump from the battery + to the starter lug? If it turns over then check the cables, but if it doesn't check the starter.

Of course do this with manual transmission in neutral or auto transmission in park... And expect a few sparks when making contact...

 

Make the last connection at the starter, away from the battery if you want to try that. Sparks near battery is Not Good.

 

This is what I was able to do this morning before I had to head off to work today, I scuffed under the Solenoid and even put a 12g grounding wire to a grounding stud I have for accessories resulted in a click at the solenoid when trying to start it.

I noticed one thing and I believe it is due to me having the red lead on the negative post and the black lead on the starter lug which resulted in a -.12V when the ignition key was turned. I still feel that at least 12V DC is getting to the starter but why is the motor not engaging.

Tomorrow I am going to the store and get a new cable from the Solenoid to the Starter as it is cheap and I did not have time to check the voltage drop across it today.

I checked the ground again from the – terminal on the battery to each of the grounding points where a grounding strap is attached and they all read at 0 V or near to it. The previous check was from the Positive battery terminal to the grounding attachments.

Again Thank You for the input and if there is anything else that I need to check, please let me know.

 

To check grounds, measure resistance (near 0Ω) rather than voltage. 0V doesn't tell you anything except that it's not hot.

First one to check: battery - post to starter: anywhere on the exposed metal part that mounts to the block.

 

I checked the resistance from the - terminal to the starter and I had 1.6Mega Ohm's.

I also looked online for diagrams on the solenoid and there were several examples of a jumper wire on the starter its self from the main lug to an "S" connection on the starter. I have 2 smaller little terminals on the starter also. Anyone know of this and should I put a jumper as illustrated?

 

Resistance (ohms) check of high current cables and connections drawing hundreds of amps aren't particularly useful, they have to be tested while under load for voltage drop. (In the case of the starting circuit, while cranking)

Anything more than a few tenths of a volt under load is excessive. Voltage drop testing is easy but usually misunderstood, the voltmeter isn't placed across the battery or pos/neg connection but across a single cable leg or connection. For example, the negative battery post itself, and the negative battery cable terminal, or the neg battery post and cable terminal at the block, the battery post and the block itself. Each connection has the potential to be a show stopper, or when all voltage drops added together especially. Cable crimps are notorious for this as they age. The voltage drop is actually expressed as a positive voltage on the meter.

Anything starting out with a "19" in front of the year deserves new cables all the way around at this point on general principles. They are cheap and save lots of headaches.

 

once you ensure the starter is grounded well (not sure based on your resistance reading) and you have the jumper in the right place, you should get crank...

 

As a first step they are - dude just measured *megaohms* of resistance. There's clearly a significant grounding issue here if that measurement is correct.

Get the ground issue fixed to where you can't measure more than an ohm of resistance at most between those points, and then we can move on.

(Caveat: make sure you have a good connection with the multimeter - stab the contacts in hard and scratch 'em around a bit - otherwise, you could measure more resistance than is really there, due to poor surface contact)