68 Camaro starting problem

[mikefamig]

I started this topic in another message thread and decided to move it here where it belongs.
 
Here is the original post
 
Right now I am spending my spare time struggling with an electrical problem in my old 68 Chevy and I'm going to go waaay off topic because I think htat you may be able to help me. 
 
There is a problem with the starting circuit that I haven't been able to correct. I'm getting a large voltage drop between the battery and the starter solenoid that comes and goes. For years it would occur only when the engine was hot and then recently it failed altogether. I went through the circuit replacing switches and cleaning up connections and now it is back to a hot engine problem or at least it seems that way at the moment. In the past few weeks it has been failing randomly both hot and cold as if it has an intermittent connection but I haven't been able to find it. It is very hard to find because it is not consistent.
 
In addition to the possibility of an intermittent connection it has been suggested to me that the problem is that the electromagnet in the starter solenoid is getting hot causing the resistance in the wire windings to rise and causing the solenoid to fail to energize. When I put a volt meter at the solenoid when the problem occurs the voltage is about 8vdc which is a 4.5vdc drop from battery voltage and not enough to energize the solenoid. If it is true that the resistance had risen in the solenoid due to heat wouldn't I see less of a voltage drop due to less of a load created by the solenoid? When the system is operating correctly the voltage at the solenoid is about 10 - 10.5 volts.
 
Mike.

 

[mikefamig]

  here's a pic of the car

 

[wkearney99]

I've owned boats for years and starting gremlins are the bane of most owners experiences.  Quite often it's due to failure within the heavy gauge wires connecting everything.  Right, not just at the connectors, but inside the insulation.  The symptom is you can usually start the engines just fine if there's more than 10 minutes between attempts.  Otherwise, the drain of current pulling through the corroded section causes it to heat up and that causes voltage drop (leading to it heating up more, repeat...).
 
Heat ends up being a factor as the engine compartment tends to get pretty warm.  Vapor lock is also a hassle, but that's another troubleshooting adventure.  Where you can crank forever without getting it to catch.
 
I find it's sometimes simplest/fastest/cheapest to take the wiring question out of the equation, if you haven't already.  Along the process of replacing that wire you typically also find and have a chance to correct, a bunch of other things.  Like the wire harness being poorly anchored, or too close to heat sources (manifolds, etc).  At the same time you're getting clean connectors and likely cleaning their posts better.
 
Same thing goes for solenoids, sometimes it's more effective to rip-and-replace vs repeatedly getting stranded.

 

[mikefamig]

To get up to date....
 
Here is a post that I made to a Camaro forum that I frequent that summarizes the problem and the circuit. It is in reply to a guy who is troubleshooting the same problem with his car. At the time of this posting I thought that I had solved my problem but it has since returned:
 
 
I'm in the middle of troubleshooting the same problem. Mine would fail occasionally and mostly gave me trouble when the engine was hot and recently it stopped working altogether. I think that I traced my problem to a combination of old dirty connections with the worst of them being in the console wiring harness to the neutral safety switch.

The problem is that not enough power is getting to the starter solenoid to activate it. This can be caused by a weak battery or one or more bad connections between the battery and the starter solenoid switch.  It can also be a bad connection between the body of the solenoid switch and the negative battery post.

After studying the wiring diagram I learned that the starter solenoid circuit is as follows:

1 fusible link from battery + to terminal post on the radiator support near the battery.
2 wire from terminal post to horn relay
3 wire from horn relay to the bulkhead connector on the firewall behind the power brake booster
4 wire from the bulkhead connector to the ignition switch
5 wire from ignition switch to the neutral safety switch in the floor console (auto transmission)
6 wire from the neutral safety switch back to the bulkhead connector
7 wire from the bulkhead connector to the starter solenoid

Any and all of these connections can get dirty and cause resistance in the circuit that adds up to a problem.  Or as stated previously it could be as simple as a weak battery or bad battery cable connection.
 
Mike

 

[mikefamig]

I've owned boats for years and starting gremlins are the bane of most owners experiences.  Quite often it's due to failure within the heavy gauge wires connecting everything.  Right, not just at the connectors, but inside the insulation.  The symptom is you can usually start the engines just fine if there's more than 10 minutes between attempts.  Otherwise, the drain of current pulling through the corroded section causes it to heat up and that causes voltage drop (leading to it heating up more, repeat...).
 
Heat ends up being a factor as the engine compartment tends to get pretty warm.  Vapor lock is also a hassle, but that's another troubleshooting adventure.  Where you can crank forever without getting it to catch.
 
I find it's sometimes simplest/fastest/cheapest to take the wiring question out of the equation, if you haven't already.  Along the process of replacing that wire you typically also find and have a chance to correct, a bunch of other things.  Like the wire harness being poorly anchored, or too close to heat sources (manifolds, etc).  At the same time you're getting clean connectors and likely cleaning their posts better.
 
Same thing goes for solenoids, sometimes it's more effective to rip-and-replace vs repeatedly getting stranded.

 
Yes I have considered the effect that heat is having on the wires. I have also heard of what is commonly called "heat soak" that affects the windings in the solenoid. I don't understand the behavior of electricity in windings like electric motors and electromagnets. It has to do with flux and induction that I don't know a lot about.
 
Mike.

 

[mikefamig]

Update
 
I worked on the car lst evening and maybe made some progress. Most of my effort so far was trying to improve power to the solenoid by improving connections and replacing the ignition switch and neutral safety switch which were both original parts. Lasyt night I tried something different.
 
It was brought to my attention that this ws a common problem in old GM cars that GM was aware of. One fix that they came up with was a shorter weaker spring for the solenoid which made it easier to activate requiring less power. So I rounded up two old starters that I had under work benches for years and removed all of the solenoid springs. Then I removed the starter from the car and removed that solenoid spring and all three springs were different lengths.
 
I installed the shortest spring which interestingly came from one of the old starters which has the Delco logo on it.
 
The car is starting again but I will have to take it for a ride and see what happens.
 
Mike.

 

[wkearney99]

The basic problem is electrons meeting obstacles along the circuit.  This leads to heat, which usually further increases the obstacles.  Meanwhile the device being powered is still calling for a lot of current, further exacerbating the heat buildup problem.  Eventually something fails and lets out the magic smoke.  Electromagnet windings cause some degree of heat as a normal result of how an induction circuit works.  Magnets are also affected by heat and excessive amount of it can cause them to fail to work as expected.  
 
Starters on small blocks tend to live in a pretty bad position in most engine compartments.  And getting flexibly-insulated cabling to them suffers as a result.  That and the engine motion (vibration, road conditons and acceleration torque) is causing intermittent stress on the cabling (both the wires in the bundle and the insulating jacket).  Eventually something fails, but not always in the most obvious part of the circuit.  

 

[mikefamig]

The basic problem is electrons meeting obstacles along the circuit.  This leads to heat, which usually further increases the obstacles.  Meanwhile the device being powered is still calling for a lot of current, further exacerbating the heat buildup problem.  Eventually something fails and lets out the magic smoke.  Electromagnet windings cause some degree of heat as a normal result of how an induction circuit works.  Magnets are also affected by heat and excessive amount of it can cause them to fail to work as expected.  
 
Starters on small blocks tend to live in a pretty bad position in most engine compartments.  And getting flexibly-insulated cabling to them suffers as a result.  That and the engine motion (vibration, road conditons and acceleration torque) is causing intermittent stress on the cabling (both the wires in the bundle and the insulating jacket).  Eventually something fails, but not always in the most obvious part of the circuit.  

 
Part of me wishes thatI could get a little smoke from a wire, at least then I'd have a direction to go in.
 
I tore this car apart and traced the entire circuit. I had the gauges out of the dash and the console apart and inspected every connection. i even pulled the fuse box from the firewall and cleaned up the bulkhead connector and have not found any apparent problem. There was some corrosion and I replaced the ignition switch and neutral safety switch and still the same.
 
When the problem occurs I have taken voltage drop tests and they just confuse me. For instance there is a 12awg wire from the battery to the horn relay. The voltage drop in that wire is almost a full 1 volt. So I took a new wire and jumped that wire and still the same problem. Then I would take a voltage test at the next available connection and the drop is even more. And the voltage drop gets greater with each connection as I move farther away from the positive battery post.
 
I have jumped wires across switches and sections of wire because they each showed a significant voltage drop and always the same. The problem persists.
 
I want to learn more about electromagnets and "heat soak". Or maybe I have an intermittent wire shorting as RAL suggested earlier.
 
Mike.
 
EDIT
the voltage drop tests above were made with the key in the start position and the circuit under full load.

 

[mikefamig]

I took the car for a test run this morning and could not reproduce the problem so installing the shorter spring in teh solenoid seems to have made a difference. I'll call it a cure if it lasts a week or two. I'll be watching the cranking voltage and see what time brings.
 
Mike.

 

[pete_c]

Good news Mike!
 
My old next door neighbor has a '67 Firebird that looks to be like yours (same colors inside and out).
 
He stores it every winter and drives it all summer.  It's been some 15 years now of doing this.

 

[mikefamig]

Good news Mike!
 
My old next door neighbor has a '67 Firebird that looks to be like yours (same colors inside and out).
 
He stores it every winter and drives it all summer.  It's been some 15 years now of doing this.

 
I bought mine in 1988 and have had it since. It needed restoring so I welded new fender wells and quarter panels and door skins on it and painted it with gray epoxy primer. I re-ringed and re-gasketed the engine and drove it that way for twenty years or so and no one ever worked on it but me. It was great that I could throw the dog in the back seat and not worry about the seats and I drove and parked it anywhere without worrying about getting dinged. It was kind of an old hippy type car.
 
Then a few years ago I decided that I could afford to spend some money working on points for style and my wife was embarrassed to be seen in it so I had the body refinished professionally and had the engine rebuilt professionally and now I have a car that I have to cover and hide from the weather and worry where I leave it parked. It runs and  looks better than it ever did but I can't kick it around like I used to. Now it's more of a show car that mostly sits in the garage under cover.
 
Mike.

 

[RAL]

I took the car for a test run this morning and could not reproduce the problem so installing the shorter spring in teh solenoid seems to have made a difference. I'll call it a cure if it lasts a week or two. I'll be watching the cranking voltage and see what time brings.

 
I wouldn't call it a cure, so much as a work around.  The starter isn't getting enough voltage to engage, and by putting in a weaker spring, you allowed it to engage with the lower voltage.   My guess is that it will work for now, even for weeks or months, but whatever the real problem is will get worse over time until the weaker spring won't be good enough, either.

 

[pete_c]

Goggling read that the heat-soak (too much heat was being absorbed by the starter solenoid) problem is an issue many times because the heat shield has been removed.  Someone suggested replacing it with a mini starter.  Other folks have seen this with the heat from headers and proximity to the starter.
 
Here is a mechanics DIY list to fix.
 
1. Install a heat shield
2. Install a high-torque mini-starter
3. Install an external starter solenoid
 
Here is an old trick I learned from a starter re-builder friend...

I had the same problem with my 67 396 car.
The solution was to install a secondary solenoid (slave solenoid)
I mounted it with an oil pan bolt above the starter location.

 

[wkearney99]

Some amount of voltage drop is to be expected, that's just how wire gauge and current draw works.  The thinner the wire, the shorter the distance before you start having voltage drop.  12ga isn't uncommon in cars for this kind of thing.  Provided, of course, that it's not internally corroded after so much time and exposure.  
 
Here's a thought, how new is your battery? 

 

[mikefamig]

I wouldn't call it a cure, so much as a work around.  The starter isn't getting enough voltage to engage, and by putting in a weaker spring, you allowed it to engage with the lower voltage.   My guess is that it will work for now, even for weeks or months, but whatever the real problem is will get worse over time until the weaker spring won't be good enough, either.

I would agree with you if the longer spring was a GM part or at least known to work in a 1968 car. I suspect that the new aftermarket solenoid will work fine long spring and all in a later small block Chevy car with a larger battery cranking amperage rating. It is possible that this problem arose when I installed the new starter and solenoid years ago, I just can't remember that far back. It's an aftermarket solenoid and may not be tested with 1968 cars which had lower powered batteries and alternators than say a similar 1990 chevy that uses the same starter. The short spring that is working now is from an old OEM Delco solenoid that I have had laying around for years and it is much shorter than the aftermarket part.
 
If the problem returns then yes you are correct and especially if it returns to not starting when cold. I'm not celebrating yet.
 
Mike.