Loud screeching instead of starting (randomly)

[KFunk740]

Every once in a while when I turn the key in my truck, it just makes a loud screeching noise from somewhere in the engine.  Doesn't even feel like its attempting to start.  Then I let off the key, and do it again, it usually starts right up like normal.  Its usually on cold starts, but today after stopping at a taco stand, it did it for a while.  2nd attempt still made the screeching sound, then on third try it started right up no problem.

 

My initial thought is that there are some bad teeth on ring gear or starter pinion.  I'm thinking about pulling starter to inspect teeth, and looking to find sources/compatibility for both.  It's got a J13 with an original 4-speed floor tranny (probably original tranny, as it has original style slave cylinder).  If I end up pulling tranny to swap ring gear, might as well get new clutch too.

 

However, are there any other possible explanations?  Could a failing starter motor or solenoid just make screeching sounds like that too?  I would think if the pinion were just spinning against chewed up teeth, then I would have to roll the truck a little to get to new teeth.  But no, next good start turns easy.

I also can't even tell if its even turning the motor at all when it does the screeching, when I assume it would be shaking it around some as one grinds against the other.  

I could easily bench test starter too, but then I figure its probably not going to exhibit issue on bench since its fine for 95% of starts anyways.  

Can I use a starter solenoid, pinion, or motor from other years of trucks if necessary?  I'm assuming I need 520 parts, and don't see any full starter assemblies on rockauto.com for the 520.

I suppose I better double-check battery cables leading to starter too to make sure they are making good connection.  

Battery is near new, and it did it with previous battery as well.  

 

Thanks for the help.  At least I can use my hand crank if necessary, but not sure if I can even start it with that when its cold.

[hobospyder]

Starter sylonoid might not be engaging all the way. Remove starter and check the teeth on the starter gear and the flywheel. Had this happen with a newer vehicle before, replaced starter, fixed issue. But not so easy with a 320

[datzenmike]

In order of cost and complexity....

 

Possibly you have a weak 12 signal from the key to the solenoid. Borrow a remote starter switch and mount in the cab. Use it and see fi the problem goes away. If it does, you can use the weak start signal to power a relay connected to the battery for a stronger 12 volts to the solenoid.

 

The solenoid has two functions. It connects a high amperage current to the starter windings and forces the starter pinion gear out to engage the flywheel. It might be iffy or the sliding parts rusty and sticky. Remove the starter and inspect this and the gear and starter ring for wear.

 

Weak battery. 

[Stoffregen Motorsports]

The screeching could actually be the motor, while the gear is not engaged. A worn out motor will make noises like that as the bearings get dirty and wear, or start to seize up.

 

Why the gear is not being actuated is a different matter. Could be a bad solenoid or, as Mike said, a low battery, could be dirty or corroded, could have a broken spring.

 

Best to pull the starter and bench test it with either a good battery or a battery charger and see if A- the solenoid pops, or B- if the motor spins freely.

[KFunk740]

In order of cost and complexity....

 

Possibly you have a weak 12 signal from the key to the solenoid. Borrow a remote starter switch and mount in the cab. Use it and see fi the problem goes away. If it does, you can use the weak start signal to power a relay connected to the battery for a stronger 12 volts to the solenoid.

 

The solenoid has two functions. It connects a high amperage current to the starter windings and forces the starter pinion gear out to engage the flywheel. It might be iffy or the sliding parts rusty and sticky. Remove the starter and inspect this and the gear and starter ring for wear.

 

 

Better yet, I could just run a 12V jumper straight to the solenoid, or maybe even just lay a screwdriver across the two posts (I've done this often in my old BMW, not sure if can be done in Datsun).  I don't have a remote starter handy.  Should probably get one sometime, too.

The problem is the intermittency, that most of the time there's no problem to resolve.  It'll start right now with the key easy, or I'm sure any other way I want to start it.

 

I'll probably just have to pop open solenoid and/or starter to look for dirty/corroded terminals.  Tempted to just order a solenoid off ebay or Rockauto, as I'm seeing a lot in the $35 range.  Gotta look at my starter again to verify I buy the right type.   

 

Battery stays on battery tender all the time, and nearly new.  Got voltmeter in cigarette lighter to keep an eye on it.