Heat soaking
 

I ran into some trouble on a hot day at the end of last summer when I was out driving my 68 Firebird.

I got stuck in traffic for a long time, stop and go, stop and go.
After about 45 minutes my temp light was lit (I've got idiot lights).
So I put my foot on the gas a little bit to raise the idle to about 2000 rpm and the light went out after a while.
This happened a number of times.

Eventually I got tired of this and pulled over to wait until the traffic eased up.
I shut the car off and raised the hood to let the engine cool down.

After about two hours the traffic was ok again and I thought I would be on my way.
But when I turned the key nothing happened.
The solenoid didn't even click.

I checked the battery which was fine but the starter was dead.
In the end I had to call a tow truck to get home (the car has an automatic, so I couldn't push-start it).
When I got home a number of hours later, the starter still was dead.

The next day it worked again!
I've done a couple of test runs to get the engine properly warmed up, so far no problems.

Something similar happened 10-15 years ago, but then I only had to let the car cool down for an hour or so and then it ran again.
After that I changed the internals of the solenoid and installed the missing heat shield for the solenoid.
No problems since then, until now.

My question is this: what is it that causes problems like this?
Is it mechanical problems, like the plunger in the solenoid expanding from the heat and getting stuck maybe?
Or is it electrical in the way that the wires to the solenoid gets so hot that the resistance in them gets really high and the voltage to the solenoid drops so much it doesn't even engage?

I'd like to figure this out instead of just buying a new starter to see if that solves the problem.

Any input would be much appreciated.
/Johan

Hard to say what the cause was, heat will reduce voltage but the starter wouldnt be totally dead from it, should still click or turn slow.

Sound like the solenoid is on its way out & the heat just made it show up, could be related to what you said about heat causing it to get stuck.

I have had a bad starter/solenoid on my cars before & friends, if it happens again what probably would have saved you is to crawl under the car or reach your arm in if you cant get under it and bang on the starter with a hammer or end of a big ratchet etc while someone turns the key, if it is something getting stuck that will usually make it work a few more times. Saved myself & others more than once doing that.

There's any number of issues at play here, including simple heat soak, but I had the same thing happen on my wife's chevelle. The solenoid on the starter was going out and it would only operate at ambient temperature. A starter change fixed the issue.

I'd have your starter tested and replace if necessary.

A simple test is when this takes place ( takes two people or a mirror) is to see if your headlights dim when trying to crank the motor .

If they do then the solenoid is closing and trying to spin the starter.

If your lights nearly crap out or go very dim then you have a battery and or connection issue.

If your lights do not dim then your starter solenoid is not closing.

I used to get Delco 1000 CCA batteries and that pretty much solved starting problems with Pontiac 455 engines. I also changed the stock gauge negative ground to the next biggest cable.

Another thing to consider is that at idle and low RPM, the alt doesn't put out very much and may not keep the battery charged.

You can always do a remote solenoid too, or go to a mini starter.

If you heat up at idle or low speeds, might consider raising you idle RPM a little and/or more initial timing. If you're running vacuum advance (which you should), make sure you use manifold vacuum for the source.



.

I had what I thought was pretty bad heat soak problems with the factory starter. But, it never took hours or days to recover. Still, I went to a mini starter and never looked back.

Also to reinforce what HWYSTR455 said above, if you are currently running your VA (assuming you're running VA) from ported vacuum, it will run cooler at idle by switching to manifold. Remember that the factory used manifold until emission concerns led them to switch to ported. That seems like a no brainer to me.

Thanks for all the replies.

I should probably have said that I haven't driven the car all that much since I replaced the internals of the solenoid (car was off the road for a number of years during resto).
But even so, you have convinced me that the solenoid seems like the most probable cause of the problem.

And since trying to rebuild the solenoid didn't do the trick I think I will buy a new starter and hope that solves it :)

When I got my RobMc mini starter I installed it so the solenoid was clocked 180 from vertical. It is away from the heat of the headers and engine block.

Starter gets hot, won't crank the engine, solenoid doesn't even click.

COMMON AS DIRT.

The typical problem is that there's enough corrosion on the wire harness, ignition switch, neutral safety switch, etc. powering the purple (fades to pink with heat, time, and oil contamination) wire connected to the "S" terminal of the starter motor, that it won't transmit enough current to activate the pull-in winding of the starter solenoid. Therefore, no "click" of the shift-fork plunger moving toward the copper disc, and therefore no engine cranking.

It can be made worse by having the guts of the starter hot, and the internal windings have higher resistance and perhaps even some mechanical binding of the armature. But the real issue is the lack of sufficient power to the "S" terminal, which is easily verified with a voltmeter on the "S" terminal when cranking. If there's excessive voltage drop...you've found the issue. The "S" terminal is not easily accessible for connecting the voltmeter leads. Consider getting 3--4--5 feet of primary wire, putting a ring terminal on one end, and bolting it to the "S" terminal on the starter solenoid along with the existing wire. Then you can do your voltage testing at the other end of that new, clean, "diagnostic" wire, up in the engine compartment where it's easily accessible. This can be a temporary installation, removed when you fix the problem...or...IF YOU'RE CAREFUL ABOUT ROUTING AND SECURING THE WIRE so it doesn't ground or get burned by exhaust heat, it can be permanent. Realistically, with a Ford solenoid on the fender, there's no reason to leave that wire in place.

You "could" trace that purple wire backwards through the bulkhead connector, past the neutral safety switch, to the ignition switch, and then back to the battery. Clean every contact, clean every connection, replace all the corroded wire. This is clearly the best solution. It's also a heap of work.

The typical "fix" is to put a "Ford" solenoid on the fender, and use the Ford solenoid to power the starter. The "S" terminal gets power from the bigass battery cable via a short copper link, or short jumper wire. The "S" terminal therefore has all the voltage/current it needs.

The "Ford" solenoid doesn't need as much power as the Delco solenoid, so it works fine even with reduced power due to all the corroded connections in the circuit.

The downside to the "Ford" solenoid is that A. it's ugly, and B. it's not compatible with SOME "Mini starters" such as the Delco PG260.

An upside to the "Ford" solenoid is that it gives you a convenient place under the hood to crank the engine during compression tests and other diagnostic work; and the bigass power cable going to the starter is now only powered when the engine is cranking. (IF your vehicle uses the starter solenoid as a connection for routing power to other devices, you'll have to extend and move those wires to the Ford solenoid.)

@ Schurkey : Thanks for your detailed analysis.
It sounds reasonable.

My car is a numbers matching very original car though, so I don't think I want to go the solenoid on the fender route.

I like your suggested way to use a voltmeter to verify if this is the actual problem. The only thing is to know what is an acceptable voltage at the terminal. Is it 12 V, or maybe 11,5 V or what?

I've had already thought about installing a temporary wire from the S-terminal to the battery (without connecting it) to have as a back-up if I end up in the same situation again. That way I would both get home and know for sure that it is the original wire to the S-terminal that is the cause of the problem.

Do you think that could work?

/Johan

"I've had already thought about installing a temporary wire from the S-terminal to the battery (without connecting it) to have as a back-up if I end up in the same situation again. That way I would both get home and know for sure that it is the original wire to the S-terminal that is the cause of the problem."

Sure, you could use it to try and crank the engine when you have the problem. You need to be careful if you have a manual transmission, especially, or even an automatic, if you leave it in gear. The car may start up and take off once started.

I had the same kind of intermittent issue one time, added the wire. Once the problem showed up, using the test wire, the solenoid did not pull in. The problem turned out to be a broken brush holder in the starter motor.

George

@ George: That's actually good advice about not having the car in gear since the safety contacts for the TH400 will be bypassed. Thanks for the heads up!

Also interesting to hear about your experience and it is exactly to find out if the problem is with the solenoid or the actual starter motor I wanted to use this extra wire.

Thanks for your input.
/Johan

Open-circuit voltage at the battery terminals should be 12.6--12.8 depending on the battery construction. I guess Absorbed Glass Mat (AGM) batteries tend to be on the higher end of that scale.

Under the heavy load of cranking the engine, voltage at the battery can drop to 9-ish volts, but higher voltage is better. A light load on the battery--the ignition system, starter solenoid, maybe brake lights--voltage at the battery might be 12.3--12.5, something like that.

So your voltage at the "S" terminal will be in relation to the voltage available at the battery (system voltage). I'd be uncomfortable with lower voltage than 1/4 volt below "system voltage" at the moment. 1/2 volt down is probably excessive, 2 or 3 or 5 volts down from whatever the battery voltage is, is beyond excessive.

The BEST way to check this is via a "Voltage Drop" (VD) test. As you know, "VD" is to be avoided (or with electrical circuitry, minimized.) Connect voltmeter + lead to battery +. Connect voltmeter - lead to the "S" terminal, or to your extended "diagnostic" wire which is connected to the "S" terminal. Crank engine, (or at least turn key to "Crank") read voltmeter. Voltmeter shows the difference between voltage at the battery vs. voltage at the "S" terminal. You'd expect a reading of ~1/4--1/2 volt when the key is turned, but I bet your vehicle has more VD, with higher voltage showing on the voltmeter.


Absolutely...given that the additional wire has to be routed and secured to avoid chafing/burning, or accidental contact with the battery; and that when connected to the battery +, it's going to crank the engine even if the car is in-gear, and even if the ignition is not turned on. If the ignition is on, the engine should start and run.

I've had two friends that had significant problems with vehicles that started because the neutral safety switch was bypassed. One got lucky, when the car took off, it "only" destroyed the bigass wheeled battery charger that was in front of the car. The other guy was injured. The wire you're considering will do the same as a bypassed neutral safety switch.

I had hot start problem in my 63 421 GP back in early 70s. Here what it was the bushings in the starter were egg shaped. Heat expansion on armature.I bought bushings and tool to install, worked.

Thank you for the tip on how to measure voltage drop.
I like this a lot since I can do this at home in the garage without having to wait for the problem to show up again.
And I can use the same wire for measuring as for getting full voltage to the solenoid if needed (making sure to work safe of course).

If the voltage drop shows acceptable numbers I can move on to restoring or replacing the solenoid and/or starter motor.

I have to say that it is fantastic to be able to get great free advice like this from experienced people.

Makes me think that there might be hope for humanity after all :)

/Johan

I had my car in the Middle East in Qatar for the first 17 years. Boy did I get familiar with this routine. I used to stand outside my kids' school pouring water down the driver's side of the engine to cool the starter faster. It really got old in the summer.

Eventually I put in an IMI mini starter from our sponsor. That was it. Never had a problem again. I understand your ride is original and you're trying to keep it that way but it's pretty hard to see the starter motor from most angles... :) Anyway, for what it is worth the big GM starters are known for this in hot climates. If you have to keep the big starter then, like everyone here has said, you need to address all the other factors as well as you can:
* Good quality good condition wiring from battery to starter and good earth cable from motor to chassis
* Good quality high amp battery
* Good charging system and alternator
* Consider adding the little (sometimes hard to find) GM heat shield to the solenoid on the starter (or just wrap it in heat tape)
* Replace your solenoid with a fresh one of good quality -- the contacts get more worn with age and take more current to work

Best of luck!

Sam

Sam, thanks for your input and checklist.

I have addressed the last two points on the list, the solenoid was some time ago but it can't have seen more than a hundred starts or so.

I think I will start with doing the voltage drop test and then take it from there.
I will for sure keep your list in mind.

Who knows, maybe I will end up switching to a mini starter if nothing else works.

/Johan