1952 M135 GMC Inline 6 Hard to Crank Over

I have a brand new starter in this M135.
It turns over very easily without the spark plugs in.
It will intermittently turn over quickly and then when it’s about to fire it’s like it hits a brick wall, but the starter powers through it, what could be causing this?
I’ve attached a link to the video I posted to YouTube showing it fire up and then after it dies not being able to get it to start again.
Click the First Start Video link to see this run on YouTube.
First Start Video

Have you checked the ground from the batteries at the frame connection? Same with the ground strap from the starter if it has one and the ground strap from the engine to the frame.

Barrman said:

Have you checked the ground from the batteries at the frame connection? Same with the ground strap from the starter if it has one and the ground strap from the engine to the frame.

Click to expand...

The grounds definitely looks solid, they have the 1/0 cables going directly to the body in the battery box, continuing down to the frame beside the starter and across 4” from the frame to the starter, it’s a continuous path from the battery.
The motor does the near lock up thing when I add fuel to it.
I’ve got a toggle switch for the fuel pump and if I leave that off, eventually the motor turns over easily, like it’s Hydro locking or something when it has fuel going to it.

Check for too much timing advance just in case.

Can you take a video clip with sound to see what the engine is doing and sounds like?

cattlerepairman said:

Can you take a video clip with sound to see what the engine is doing and sounds like?

Click to expand...

The link to first start video brings you to YouTube.. the video has sound.

Aha! I did not see the link; I had clicked on the picture!

Once it runs, it runs fine, mosquito smoke screen notwithstanding.

Simple things first...how good is the battery and does it provide enough CCA? When you hook up a starter pack to the battery and then crank the truck, does that fix the issue? If so...battery most likely.
I see you had your pickup hooked up with starter cables in the video. Normally, that should give enough OOMPH but a good starter pack is often superior to the starter cables.

When the cranking develops a "gallop" or "hits a wall" I'd think of a valve train issue (stuck valves) or a flywheel/toothed ring issue (maybe tons of rodent material in there?). A corroded cylinder wall is possible as well, but after some running I would expect that to go away.

You replaced the starter. Can't hurt to deliberately clean and freshen all the grounds as well. They can look ok but corroded bolts can really cut down on current.

cattlerepairman said:

Aha! I did not see the link; I had clicked on the picture!

Once it runs, it runs fine, mosquito smoke screen notwithstanding.

Simple things first...how good is the battery and does it provide enough CCA? When you hook up a starter pack to the battery and then crank the truck, does that fix the issue? If so...battery most likely.
I see you had your pickup hooked up with starter cables in the video. Normally, that should give enough OOMPH but a good starter pack is often superior to the starter cables.

When the cranking develops a "gallop" or "hits a wall" I'd think of a valve train issue (stuck valves) or a flywheel/toothed ring issue (maybe tons of rodent material in there?). A corroded cylinder wall is possible as well, but after some running I would expect that to go away.

You replaced the starter. Can't hurt to deliberately clean and freshen all the grounds as well. They can look ok but corroded bolts can really cut down on current.

Click to expand...

The battery I had hooked up directly to the battery cables was a little low, 11.9 V, the batteries I had hooked to the jumpers from the other truck we’re fully charged and put out 1370 cold cranking amps each, but it’s jumper cables, not a lot of contact surface on either end.
I unfortunately killed the new starter in the short bit of time I tried to get the machine running after it stopped the last time, so when I take that out I will pull off the grounds and clean them up.
With the jump pack (Noco GBX155 4250A) or being jumpstarted with the truck it doesn’t make a difference for the hitting the wall.
The one thing that does make a difference is if I leave the fuel pump off and the system runs out of fuel it turns over freely, but the second it’s about to fire it hits that wall which makes me think that maybe the spark is happening just a little bit too soon.
All the smoke that you saw while the vehicle is running was likely because I filled all of the cylinders up with sea foam, left it in there for 24 hours and then turned the engine over to spit the stuff out.
I’ll take the starter in to get repaired, clean off the grounds replace the bolts, put one of the good batteries that are in my truck with the 1300 cold cranking amps in the 6 x 6 and then leave the fuel pump off while turning the engine over and if it turns over freely no problem turn on the fuel pump and see if it will start easier that way.
When I did the oil change, the oil looked like it had been used in a diesel engine, thin viscosity, but very black.
I’ll try to figure out how to get the timing right, I’ve been around diesel engines most of my life so I’ll have to figure out which way to turn the distributor and by how much.
Thank you for your reply and suggestions, I appreciate it.

I understand you looking at the ignition timing. You essentially feel that there is at least one cylinder prematurely firing, thereby "stopping" the cranking.
I am more leaning towards valve train/pushrods. My secondary suspicion is starter - especially, since it gave up the ghost after your starting attempts. Sure, lots of cranking is a workout, but a fresh starter should be able to take plenty of abuse and heat. Methinks, the thing could have been defective, with a bad spot, right out of the box. Not uncommon, these days!
We will find out who is closer!
FWIW, for the Deuce, a modern gear reduction starter fits. Not sure about the Gold Comet engine, but it is likely that there is a modern starter model that is more powerful and reliable.

The motor turns over just fine if I don’t add fuel, it almost turns over like there’s no spark plugs in it.
Once I turn on the fuel pump and it gets to the compression to pop is where it seems to hit a wall, like the compression stroke is just too much and the starter has to push through it, I’m not sure if you can hear that in the video attached to this thread.
The starter was rebuilt. If there is a more modern gear reduction starter that would be great, I just haven’t found anybody to point me in that direction yet.
There is a lever in the cab that you need to pull to push the solenoid to get it to turn over, but maybe the modern starter will bypass that whole situation.
Hopefully with the engine running and the fresh new oil if it is valve train with the heat cycle it might loosen things up.
I couldn’t hear any loud knocking or ticking, but then again with the exhaust manifold being cracked it was pretty loud.
I guess while I have the time because the starter will need to be rebuilt, I might as well take off the valve cover and see if there’s anything completely obvious going on under there.
The engine doesn’t make any noise or knocking when the spark plugs are out, turns over smooth as silk.

When this happens to me, it's a timing issue. It does sound like you also have other problems, which isn't a surprise on an old truck. All I can do is encourage you at this point, since I have no direct experience with the M135 (though I daydream about having one).
Please keep us posted.
BDGR

Are you trying to run on 12 volts instead of 24 volts?

The system was converted to 12 V, the starter is a 12 V. I’ve got a pair of commercial 4D batteries on the way and I’ll upgrade the wires from 1/0 to 3/0, clean up all of the grounds so I’ve got all the help and pushing power going to the starter to see what happens.
If you watch the video, it seems to run fine when it’s running, and even tried to idle nice and low, but it hasn’t run in 30 years so I’ll put some sea foam in the fuel and hopefully on the next round of trying to get it started after the starter is rebuilt it will clean itself out and run smoothly.

The system was converted to 12 V, the starter is a 12 V. I’ve got a pair of commercial 4D batteries on the way and I’ll upgrade the wires from 1/0 to 3/0, clean up all of the grounds so I’ve got all the help and pushing power going to the starter to see what happens.
If you watch the video, it seems to run fine when it’s running, and even tried to idle nice and low, but it hasn’t run in 30 years so I’ll put some sea foam in the fuel and hopefully on the next round of trying to get it started after the starter is rebuilt it will clean itself out and run smoothly.

Are you sure the carb isn’t flooding the motor and causing to to hydrolock ??

That is an absolute possibility and it would make a lot of sense, if I leave the fuel pump off and turn it over it turns over no problem at all, turning the pump on gets it to start to fire and then it quickly does the Hydro locking…
I’ll take a closer look at the carburetor, something does seem off between the accelerator pedal and the carburetor, if you clicked on the video to see it fire up it was idling super high and that might not be because it just started, it could be because the accelerator somehow stuck on.