The Stovebolt Site Forums The Shop Area Engine Shop GMC 9430 engine troubles

Hello All from Alberta,
I am new to the forum, but have been viewing for a while now. I joined now that I have hit a snag with my project!

I recently bought an original 1952 GMC 9430. I started tinkering with the motor to see if it is salvageable. I drained and replaced the oil making sure to coat the rocker arm assembly, and sprayed Marvel Mystery oil into the cylinders liberally. By then I could easily roll the engine over by grabbing the belt. So I rotated it several times to help move the oil around. All seemed good...

Next I hooked up the 6v battery and attempted to turn it over with plug wires off, just to see if the starter had life. It sounded as if the engine turned over slightly. I did this one more time, and it made the same noise. Each time was for a split second. Unfortunately, I did not have my helper near by to tell me what went on under the hood.

So upon a third try, nothing happened. I ruled out electrical, and then realized the engine was stuck. I used to be able to easily turn it by hand, but now it wont budge even if I get some leverage on the crankshaft pulley.

Does anyone have any ideas of what happened? Could something in the driveline be stuck and causing this? I verified that the truck was in neutral before I tried starting, so I am not sure what is wrong. Could the starter have something to do with it?

It is either a 216 or a 235 (It has two acorn nut valve cover and low pressure oil gauge, but short side cover and manifold with "235" stamped onto it - a mystery for another thread). Thanks in advance for your time.

James

Are the spark plugs removed? If not, it's possible you could have liquid in one of the cylinders, causing a hydraulic lock. Recently, I've been using a very nice little borescope that plugs into a USB port on my laptop, and it gives a very clear full-screen view of what's going on inside an engine. The probe will fit into any hole that's at least 5MM in diameter, even a .22 caliber rifle barrel. Going through a spark plug hole gives me an excellent view of a cylinder and there's even a 90 degree mirror available to attach to the lens. I've also used it through an oil drain plug hole to inspect a crankcase.

The nice part- - - -the whole setup is available on Ebay with a CD setup disc to interface with the computer and only cost $35.00!
Jerry

Ok, well I am definitely looking into that borescope tonight haha.

That was my first suspicion, so I removed all 6 plugs and still no difference. To me it really feels like something mechanical is preventing the motor from rotating...

You should be able to visually determine that the starter is not the problem if the lever in the top of the starter has returned to the proper position.
If you are not familiar with what has been done to this engine by the previous owner, I would stop right now and take off the valve cover, then the oil pan to make sure that someone didn't take something apart and did not tighten it back up.
Carl

Carl,

I think you are on to something. I did notice that after I pushed the foot pedal in, it did not return all the way. Of course, that also meant that the lever did not either. It is now resting against the starter switch, but the switch is not fully depressed.

Do you know why this would cause the engine to stick if the starter lever did not return? Thanks.

James

I figured out the problem. I expect others might some day face the same thing so I thought I would share the experience.

I removed the starter to find a major mouse house inside the bell housing surrounding the flywheel. The vent ports on the housing are the perfect size for them to get in. This is where most of my bench seat ended up after the mice got to it, haha. I removed the little pan on the housing and sucked it out with the vacuum. Side note: If anyone knows the part name of this pan please let me know as I need a new one.

What was preventing the starter from disengaging was some of the seat fibers were impacted between the teeth of the ring gear. Amazingly this was enough to prevent the ring gear and starter gear from meshing properly, which caused the engine to stick when turned. I dug out all the fibers and cleaned up the ring gear and it all rolls smoothly with the starter lever engaged.

Man don't you love it when it's a simple cheap fix. There has been many a project put on hold by those stupid mice. Good job and thanks for letting us know what fixed the problem.

James,
welcome to the Stovebolt. You will find that GMC 9430 to be a lot of fun, just like I did. My mice had a more traditional place for the seat cushion material, and that was above the head liner! I am looking forward to see photos of your truck.