Intermittent Starter Fail, Buick

[chimpvalet]

Buddy's son has an odd problem with the starter on his prized '69 Riviera. After shutdown hot it often won't start, just clicks the solenoid. After cooling it gets back online. Recently swapped in a new starter after all wiring had been checked and the replacement does crank noticeably better than the previous one yet the on and off problem remains. Every bit of heatshield possible is in place, so what to look at next? It's a 430 original engine, stock.

Cheers
Steve

[V12MECH]

Did you do a voltage drop test with a quality DVOM on the 50 year old wiring when you checked it.? Especially at block ground and positive terminal at starter.Remove ground wire at block and clean connection point . Load test battery, we have batteries fail that are only a few months old. Do a amp draw test on negative cable hot crank, 300 amp momentary spike that settles to 240 or so cranking would be about right for older V8. New/rebuilt starter today is no guarantee it may not have a defect hot.

[V12MECH]

Something you might try at solenoid small terminal marked "S" when hot, unhook wire, attach to headlamp, ground other end, with key in crank position, headlamp should be bright, if not, you found problem, 50 year old wires or ignition switch, neutral safety switch, etc.

[chimpvalet]

Thanks, those are good points!

[jsgarage]

A number of wonky starter issues come from bad ground cables or their contact to the frame. Some are factory. I've also had cheap rebuilds fail due to them replacing the bakelite insulator in the back of the GM integral solenoid with nylon-looking plastic. Under 150-200 amps current, the contacts really heat up, and the plastic softens. So the hot contact embeds itself in the nylon. Eventually, the contact on the solenoid no longer touches the embedded one, no current and no start. For a poor boy, taking an old starter apart and replacing the rebuild's cheap plastic insulator with OEM (used) bakelite restored the starter to full function for a decade, now.

[Baprace]

Buddy's son has an odd problem with the starter on his prized '69 Riviera. After shutdown hot it often won't start, just clicks the solenoid. After cooling it gets back online. Recently swapped in a new starter after all wiring had been checked and the replacement does crank noticeably better than the previous one yet the on and off problem remains. Every bit of heatshield possible is in place, so what to look at next? It's a 430 original engine, stock.

Cheers
Steve

Years ago, GM had high heat solenoids that were identified by a brown color on the bakelite , now today you can't trust the color because the after market makes brown solenoids that are not high heat. Back in the day there were solenoid heat shields that attached to the solenoid. Also check your connections and make sure the battery cables are big enough to carry enough voltage , a lot of new cables just don't have enough copper wire.

[BCjohnny]

Back when I used to mess with these things on a daily basis, the 10MT Delcos could be susceptible to heat soaking

The one aspect of the design I was never keen on is the solenoid plunger was a loose fit in the sol body, relative to most other designs, with obvious consequences ...... all older Delcos used to be this way, even the European ones

One thing you can do is not switch the sol terminal directly off the IGN switch, put a relay close to the starter with heavy gauge cables and switch that

As said, check the material of the cap, you really need the thermo-setting (Bakelite) plastic type .... an easy test is to gently push a soldering iron into it and if you get smoke and it goes in, you have the wrong cap

Once, when faced with a chronic similar problem, I sleeved the sol plunger and 'fitted' it to the sol body to reduce the clearance, and that did give a marked improvement, although I'd stop short of saying it as a complete cure

[chimpvalet]

I find the remarks on solenoid very interesting. My daily driver Nissan has rapidly gone through 2 rebuilt starters following the OEM's demise at 130k miles. Mechanic suspects the solenoids of course, and I'll share the ideas posted here when I next get in touch.
Thanks