Click no crank, truck won't start

rockola1971 said:

First verify you dont have a wire pinched in between tranny and engine block then check everywhere else that a wire or its harness is was not damaged or pinched when engine was installed. Visually inspect every inch of wiring harness. If I read you correctly you said you had blown a fuse while the key was in the "Run" position. You have 2 wires in series with that 40a fuse. One coming from the battery (red) to the Start Relay and one from the Start Relay to the Starter terminal S and that wire is Purple. The 40A fuse has nothing to do with anything in your starter motor but the solenoid. The 40A IGN A fuse does NOT provide power to the starter motor itself. You could have a positive wire full of corrosion but just cant see it because of the insulation but I would think that it would be peeking out at you atleast on one end if it were that bad. Clean both ends and connection point of negative and positive wire! Measure resistance of positive wire to ground while connected and you should see infinite resistance. Then disconnect wire positive at battery and starter and then check resistance to ground to verify no rub throughs or touching ground or pinched. You should see infinite resistance there too. Do the same with the Purple wire and treat it same as the red wire positive and same tests. To isolate it you will have to disconnect it from the starter relay. It is also possible that your starter relay coil or solenoid coil partially shorted (not to ground) which lowers its resistance but increases its amp draw. Starter Relay contacts could also be burnt or even partially welded with so much carbon built up that it wont turn starter over until you start moving the contacts by energizing the start relay when ignition is switched to crank. This is going to be a fun one but should be an easy diagnose with a multimeter.
Need resistance measurements of starter and solenoid coils to calculate amp draw to rule those being a partially shorted mess (Not to ground). A coil melted down to itself but still electrically continuous could easily draw double the amount of amperage. All it takes is its resistance to drop in half. Current then doubles.

Edited for previous brain and vision fart.

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MassHoe04 said:

Sorry to hear of your fan belt mishap!
Hurts just thinking about that one...
Since you have been able to keep all 10 fingers, I would bet that there is a new level of respect for moving parts.

Just to clarify...

Exactly when does the fuse blow?
On/Run/Start?

I still think we have something with the solenoid here...
Especially, if blowing the fuse happens on Start. Solenoid is energized on start and pulls a lot of current.
You indicated it was the 40A fuse, which @rockola1971 mentioned was protecting the solenoid.
You hear rattling inside the solenoid (could be a loose screw or piece of metal floating around in there).

I'm sure @rockola1971 will be able to help get you through specific electrical diagnostic steps to pinpoint this for you.

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Matthew Jeschke said:

Sorry isn't all in one post. I made last post then some reason your comments showed up.


Thanks!!!! I was trying to measure coil resistance yesterday but couldn't seem to get anywhere.

Do you know coil resistance in the solenoid? I get on the solenoid:

Switch to ground post 0.4 Ohms (purple to starter ground strap)
Switch to supply post Open Circuit (purple to red post)
Supply to ground post Open Circuit (red to starter ground strap)



It blows fuse when key is turned to crank position. Yeah I'm pretty thankful I still have my fingers and can type now. Took some chunks of flesh which seems to be healing back up but other than that really thankful I'm okay.

I will try to summarize everything in a video

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Matthew Jeschke said:

Thanks @Doubeleive and @MassHoe04.



So as in a mechanical load? The bench tester at parts store didn't apply a mechanical load.

A short certainly crossed my mind. I do static continuity / voltage tests. They were all good. I also took starter off and tested again.

Unfortunately, I should have done more dynamic tests. I bought a power probe. Just touching probe (not pulling up or down w/ rocker button) seemed to eliminate the problem. I touched the probe to the body, which would actually indicate a bad ground?

I noticed the mounting surface of starter (to block) was dirty when I pulled it off. However, probing bolts and the bolt holes in block was good connectivity.

I guess I need to test some more stuff. Probably put starter back on.

Thermal breaker versus fuse?

Yeah, tired of blowing fuses. It's getting expensive to diagnose. Any idea if those thermal breakers work? I just don't want to pull too many amps and break something trying.

40A Thermal breaker

I wonder if I replace it regardless as "preventative maintenance", Although it's $75 I think this is the cable here?

AC Delco 2SX781B

Although multiple options for starter cable which is confusing. What is this??

Standard Motor Products A446L

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Matthew Jeschke said:

I got measurements with starter out of truck but does seem really low.

I pulled the starter and secondary wire to cranking motor. Secondary wire for all intensive purposes seems fine.

I think in hindsight, click no start symptom points to issue with solenoid or power side starter relay circuit (purple wire). Kind of wasted some time pulling the secondary cable.

Thanks for help.

Here's a video for those who are interested but most everything is in the post

Link to Video

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