M1009 Starter system

[jimm1009]

August 1984 M1009. Been my D.D. for 190,000 miles and 17 years.
A few weeks ago, my AC Delco starter went into runaway and was severely overheated before I could get the cables disconnected.
Prior to that, I have been having problems with the starter electrically engaging on an intermittent basis.
The typical click click and then it would take off. No problems with batteries or batteries cables. All that stuff is very new and top quality.
I changed the starter and put on a brand new gear reduction starter (12 volt system). I also did the Doghead Relay Modification at the same time.
The very first time that I tried to start the truck after the new starter and relay installation, the system did the same thing to me in that click click click and then it took off.
Since the, I get the click click problem once in a while but it always starts.
Today it gave out and only clicks. The batteries are strong, the new NAPA relay actuates very well, but no joy. I checked the connections for the starter cable and the smaller wires to the relay. The starter is only a month old and again was brand new. It could be the starter but I think not as it is exhibiting the same problem as before the older starter went bad.
I do not see a second relay in the starter system but perhaps there is one.
Note: the starter is not binding as when it correctly on the electrical it spins right up and there is no noise, roughness, etc.
I can't get to the truck right now as I need to go back to the grocery store parking lot and tow it home first.
Once home, I will pull the driver's seat out (better for us heftier guys) and start tinkering.
Am bowing to the masses for any other ideas concerning the older part of the system that could be going bad.
I may replace the starter cable but hate to spend 40 dollars if I don't have to.
If there is only the new NAPA relay and the solenoid on the starter, then either the solenoid is not getting power or the starter is not getting power from the battery but on the firewall. If there is another relay then obviously that could be and probably is the problem. The ignition switch is not new but only about three years old and a genuine AC Delco part.
If there is something that I am missing in the diagrams please point out the reference for me. I have the 20, 20P, 34, and 34P manuals.
Suggestions and ideas are most welcome and appreciated.
jimm1009 here on s.s.
or
jimm1009@yahoo.com

 

[southdave]

recheck your grounding on the doghead relay.. mine did that, had to tight some of grounds with that improvment, I also had several that where lose also.

 

[cpf240]

Is the doghead relay engaging each time when this happens? You can hear it?

I'm asking because I didn't see any mention of checking either the ignition switch linkage or the actual electrical portion of the ignition switch. Perhaps it is sticking on sometimes, causing the runaway condition.

I seem to recall another SS member having the ignition switch hang up, causing the doghead relay to be engaged.

 

[jimm1009]

I can actually feel it in the sheetmetal of the lower dash. The NAPA relay is brand new and very strong. I did clean the grounds from that OEM bracket to the dash and also added an auxiliary ground several years ago but I'll check that too.
In review of myself, I have not checked the grounds bypassing the motor mounts. All the power in the world will not help is I don't have a ground from the starter to the engine and the the engine to the chassis and then to the battery.
Once I get it back home, I will go over all the grounding straps. I know that my tranny ground is not good as when I overhauled it a few months ago, the front bushing had arcing damage and that is from a bad ground too.

I will also install a temporary power wire from the battery to the starter solenoid to simulate power from the key switch and work backwards after checking the grounds, providing I don't find and obvious ground problem.

Thanks for the help so far,
jimm1009

 

[mistaken1]

I changed the starter and put on a brand new gear reduction starter (12 volt system). I also did the Doghead Relay Modification at the same time.

You now have a 12V starter (motor and solenoid) with a doghead relay sending 24V to the 12V starter solenoid?

 

[jimm1009]

No, all 12 volt system. 24 volt starter was stolen in the lot by soldier B before I went to pick it up in the DRMO parking area so I put a 12 starter on it from the get go. Been a 12 volt truck for 17 years now.

jimm1009

 

[jimm1009]

Well I went back to my truck to start checking the grounds and other easy stuff before I hooked up the tow bar and after two attemtps and click. the third time it turned the starter over and fired right up.
Makes me think more about a loose ground. Whe it was hot it opened up and would not make contact.

After three hours of cooling down it was a slightly tighter connection and worked enough to get it started.

It is back home and I'll start tinkering tomorrow to see what is going on.

I will post my results here on what I find.
If it is something amazing, I'll shoot a picture or two but we'll see.

jimm1009

 

[mistaken1]

So the doghead relay is switching 12V to the 12V starter solenoid.

Check the grounds and all the wires at the terminals. Wires and connections can be corroded and measure okay with a meter but when a large amount of current starts to flow (like to turn a starter motor) those high resistance points will drop a lot of voltage and get hot.

If the motor is cold and you get several 'clicks' take an infrared thermometer and check the wires and connections for hot spots. That may be the easiest way to find them.

 

[ryan77]

If you have a 12volt system you dont need the dog head relay take it off and connect the wires together! That might be your problem right there!

 

[jimm1009]

I would normally agree but the old relay was not the problem with regards to the starter solenoid not engaging in the first place. It did this intermittently before and also after and the new relay & new starter were installed.
It was the original, factory installed GM relay before I changed it and it did stick and cause my starter to go into runaway by not releasing the solenoid, or at least that is what I see by the diagrams.
What I am confused about right now is in the figure E-1 of the -34 TM.
The relay also has a lead to the thermo switch which is shown right up near the bus bar. As I understand the system, the thermo swich is supposed to control the glow plug system so that when the engine is hot, the glow plugs do not come on as it would cause premature failure to the plugs with repeated heating via the electrical circuit when they are physically hot while installed in the hot engine that was just shut down.

AS a side note; I went out to start it to move it into the garage due to the rain coming in around noon today and the daxx thing started right up after sitting all night. I think that points to bad grounds that are loose and I will check that this AM but I was trying to study the diagram before getting dirty.
The top lead in the diagram comes from the ignition switch. The 2nd lead directly across (below) from it is ground. The 3rd lead on the left is the important one as that keys the starter solenoid. The 4th lead on the right side as shown in the diagram is what is still puzzling me. This goes up to the auxilary bus routing through the thermo switch (wire #3 RED-2Y (SXL)).
Why is the thermo switch on the starter relay? Is this an attempt to disable the starter system while the glow plugs are heating? If it is then that does not work as I can key the starter while the plugs are still heating (glow plug light on) even though I don't due that as a norm.
During my troubleshooting, I will be in the area of the doghead relay and may go ahead and tie the two leads together or better yet eliminate these cables to the relay if it is not needed for the 12 volt trucks. The shorter and less number of cables the better in any circuit.
Thanks for the continued assistance.
jimm1009

 

[doghead]

I think you are misreading a fusible link, for a thermo switch?

There is no thermal cutout in the starting circuit.

 

[jimm1009]

An update. I removed all the connectors from the two buss bars and cleaned everything and applied a very light coat of dielectric grease and then wiped most of that off (too much greas attracts dirt).
There was not ground cable on the tranny although there is one now.
The only ground cable from the engine was attached to the right rear corner
and it was just a little loose at the engine side.
I cleaned those connections too and then reconnected everything.
I then purchased a battery cable with ring connectors only and installed this more forward in an area where I could grab another bolt going into the block and also back at the negative buss bar.

I disconnected the glow plug relay to take them out of the system and then I bumped the key about 10 times. The engine has not run since around 08:00 today and at the time of the test and completion it was around 16:00 today.

Each time the starter engaged with no hesitation.
I will drive it around and get it hot and then try it again to see if there is a heat related issue still present.
I did not get under the dash today as I ran out of time (wife was timing me) so I quit for the day.

If anyone has any more information on the other lead from the starter relay as I described above please post it here.
I will update the thread tomorrow as soon as I can drive it around.
jimm1009

 

[jimm1009]

I think that you are right. After closer examination of the print it does say THERMO HW. I guess that that is a link and not the switch.

jimm1009

 

[Abbylind]

I was poking around under the hood one day and pushed the hot wire to the starter from the battery. I noticed arcing coming from the wire near the starter. Closer examination showed it had chafed the insulation off the wire. A little electrical tape and I covered the wire with some wire split loom. The arcing could cause the starter to short and no crank or slow crank and... eventually a lotta smoke!

 

[jimm1009]

It is also very close to the exhaust manifold no matter where is is positioned so that is always a concern. It is always a hot wire too as this cable is directly connected to the batteries through the miltary buss bar arrangement.
In my case that is what caused my last OEM starter to finally go T.U. when the relay stuck in the closed position (on).
jimm1009

 

[roveroverme]

That's some interesting bit of info, thanks I'll remember that.