Runaway starter question:

[Sistersoldia]

I have a 1986 m1008 with what looks to be the original starter relay (i know... i know...) and this morning, after cranking for longer than normal ( i could tell the battery was starting to wear down - its 9 degrees here)
the starter continued to crank after releasing the key. Thanks to you guys i recognized the doom that had befallen me, and i reached under the dash and quickly removed the starter relay.
To my surprise, the starter continued cranking !!! I popped the hood and ran around frantically grabbing battery connections as the starter ground on slower and slower - and in a feat of superhuman strength i managed to pull off the front positive connection and everything stopped.
I wanted to see just how screwed i was and if I had fried my starter, so i re-installed the starter relay & the battery terminal and hit the key again...same result: The starter ran away- i pulled the relay..still cranking until i removed the front positive terminal.

My question is: What the Heck ? Shouldnt the removal of the starter relay stop everything dead ? or is this possibly a stuck solenoid or something on the starter itself that is continuing to power it without the relay?
The starter apparently isnt completely fried, but im hesitant to just throw a new relay in and expect my problems to be over with. Any guidance would be appreciated - im a bit of a mechanical novice but not a compleat moron so ill try to keep up. Thanks to all !

 

[Warthog]

Read the CUCV Helpful Threads sticky. There is a thread dedicated to the starter run-on and replacement of the starter relay.

Your relay is most likely stuck closed and your starter solenoid has bad contacts. Replace both.

 

[Sistersoldia]

Will Do Warthog - Thanks. I might as well do some (light ?) reading, as going to work this A.M. seems to not be an option.

 

[swbradley1]

I was debating on whether to post that very thing but I waited for expert to post.

 

[Sistersoldia]

Interestingly enough - I found this as I went to pull the starter. That is the heat shield - MINUS the accompanying starter bracket to hold it in place, slicing into the big power cable going to the starter. And yes it sparked when i got moving it around. I was wondering why i didnt smoke my wiring harness when i pulled only the front battery POS connection and that stopped the starter from running. From my now extensive research- i expected 12V to be fed backwards thru the system and the resulting fireworks.
So.. Long story short - I decided to hook everything up and run the same procedure I had done twice before - all the same, except THIS time - after i pulled the front battery connections, I heard sizzling and smoke started pouring out of the 12V wires near the GP relay. I luckily had loosened ALL the battery terminals at this point, and quickly disconnected the rear terminals too.
So after calling myself every name in the book, I wonder if that stupid heat shield was actually drawing a little current and saved my system from backfeeding somehow until I 'fixed' it.
I doubt it but I thought this story would be interesting reading - and yet another reason to make sure you have the proper mounting bracket for your starter eh ?

Anyway - starter is off the truck and going to the rebuilder 1st thing Monday. Im guessing its a cheap aftermarket - I cant find any markings on it whatsoever. I have a really good electrical guy here and I'm thinking he can rebuild the solenoid with better- quality parts than it originally had ? Thanks again moderators - you guys are great.

 

[goldneagle]

You were lucky you didn't burn yourself pulling the positive clamp off the battery. I had a runaway started on my M936 and I got severe burns on my hand from grabbing the clamp to stop the starter. FYI if your battery does not provide enough voltage the starter will pull more amps and could weld the solenoid at the back contacts. Happened on the wrecker. Luckily for me once I put "good" batteries in it was good to go again.

 

[Sistersoldia]

I think you make a good point Goldneagle - the batteries were a little low from the cold and short-cycling them on small trips. I also have a leaky Injection pump issue which means some extra cranking is needed occasionally.
All these things together mean paying the piper sooner or later.
I was pretty quick on my feet getting to the batteries but Lucky is Right !

 

[goldneagle]

I think you make a good point Goldneagle - the batteries were a little low from the cold and short-cycling them on small trips. I also have a leaky Injection pump issue which means some extra cranking is needed occasionally.
All these things together mean paying the piper sooner or later.
I was pretty quick on my feet getting to the batteries but Lucky is Right !

I have the same issue with a leaky IP. Mine leaks where the throttle shaft goes into the IP. I replaced my mechanical fuel pump and that helped keep the fuel from draining back towards the fuel tank and letting air into the line. I just had a electric fuel pump installed inline closer to the fuel tank. Now each time I turn the key on (while waiting for the glow plugs to cycle) the electric pump purges the system for easier starting.

If you look under the truck on the inside frame on the passenger side, behind the transmission you will see a metal shield bolted there. There is room under it to mount the fuel pump. Check my thread on M1008 mods.

 

[Warthog]

You will need some 12ga fusible link wire to fix the sizzle. The Fusible Link 101 thread has all the details on how to replace it.

I would guess that who ever replaced the starter decided that the support bracket was not needed so it was canned.

 

[goldneagle]

You need to replace the starter bracket. Otherwise you risk the starter housing braking or broken starter bolts. I have a dimension drawing of the starter bracket if you cannot locate one.

 

[Sistersoldia]

Goldneagle - I have tried looking on here for exact dimensions of that bracket (its the gear-reduction type) but cant find anything but rough drawings. That would be great info if I cant source one locally.
Warthog - I reconnected everything (why do I keep doing that) after removing the starter and relay and turned the key on - all my idiot lights are still working. So maybe i didnt totally melt those links ? The GEN wires are what seemed to get really hot.
Even so, im sure i weakened them substantially and will need to replace them ASAP.
Wow everything on this truck is such a steep learning curve for a carpenter - Im DEFINITELY not a mechanic. Im still amazed however by how many things I have been able to fix on my own with a LOT of help from you all.
Thanks again

 

[goldneagle]

Goldneagle - I have tried looking on here for exact dimensions of that bracket (its the gear-reduction type) but cant find anything but rough drawings. That would be great info if I cant source one locally.
Warthog - I reconnected everything (why do I keep doing that) after removing the starter and relay and turned the key on - all my idiot lights are still working. So maybe i didnt totally melt those links ? The GEN wires are what seemed to get really hot.
Even so, im sure i weakened them substantially and will need to replace them ASAP.
Wow everything on this truck is such a steep learning curve for a carpenter - Im DEFINITELY not a mechanic. Im still amazed however by how many things I have been able to fix on my own with a LOT of help from you all.
Thanks again

The gear reduction brackets are still available. Its the full size starter brackets that are rare. I will look up the part # and post it here.

 

[Sistersoldia]

New bracket is GM 23502557 - Ive been reading this crap and the TM's and going out to the truck all day. But Hey ! it got up to 33 degrees it wasnt all bad !

 

[scottladdy]

Electric Fuel Pump Oil Pressure Safety Switch

I just had a electric fuel pump installed inline closer to the fuel tank.

If you install an electric fuel pump, for safety's sake install an oil pressure safety switch.

When properly installed, power is supplied to the pump only when cranking or when the engine is running. This type of safety switch utilizes oil pressure to determine if the engine is running or not.

You don't want the fuel pump running if the engine stops due to a ruptured fuel line for example. That would be "bad".

 

[cucvrus]

Also from the looks of the picture showing the positive cable on the starter. The starter heat shield is cutting its way thru the insulation of the positive cable. That would also be a bad thing. I think the positive cable may be clocked wrong when it was installed. Check it out. Good luck with your project.

 

[Sistersoldia]

Also from the looks of the picture showing the positive cable on the starter. The starter heat shield is cutting its way thru the insulation of the positive cable. That would also be a bad thing. I think the positive cable may be clocked wrong when it was installed. Check it out. Good luck with your project.

I was definitely cutting the insulation - I thought it had severed the cable itself with the vibration, but the insulation is really thick and the copper is fine.
I couldnt even get a socket on the nut for that cable it was so twisted around - once the motor was free I could get an open-end wrench on it and it did seem attached strangely.
I'm sure the newer starter didnt fit the old bracket so the previous owner said "oh well" and deleted it.

 

[goldneagle]

If you install an electric fuel pump, for safety's sake install an oil pressure safety switch.

When properly installed, power is supplied to the pump only when cranking or when the engine is running. This type of safety switch utilizes oil pressure to determine if the engine is running or not.

You don't want the fuel pump running if the engine stops due to a ruptured fuel line for example. That would be "bad".

Mine is set to only come on if the key is turned on. I may put a manual switch on the dash in case I need to leave the key on for unlocking the steering wheel when the truck is being flat towed.

 

[Sistersoldia]

Well - got my starter looked at today - it was missing the stop collar in the nose (for lack of the proper term for it) which is probably why it wouldnt disengage. It probably cracked and eventually broke off at some point. My alternator guy (electrical motor savant) says that engaging the starter before it's totally wound down from the last attempt will actually throw that bendix wayy harder than its supposed to go because of the added centrifugal force.
He also said whoever rebuilt it last time "forgot" a few shims and such inside and the starter was wearing a hole into itself inside. Im afraid i cant describe exactly what the problem was, but he showed me the insides where it was wearing against the housing and it wasnt pretty. The solenoid also had some burn marks inside so we replaced it as well. The GM dealer nearby will have new starter bolts and my 'missing' starter support bracket as well in the next day or so.
A coil of fusible link wire and some connectors, oh and a heavy duty starter relay also went in the shopping bag today. Not fixed, but im feeling better already !

 

[Warthog]

A worn out starter is hard to diagnose. Glad you have an expert working on it.

 

[rsh4364]

I get my AC/Delco starter bolts from Rock Auto in groups of five for much cheaper than dealership.