Troubleshooting Help Needed - Distributor Not Rotating

[Bravo2Uniform]

Troubleshooting Help Needed - Distributor Shaft Not Rotating

My M38a1 was running correctly but suddenly / abruptly quit running. Problem - no spark. Began troubleshooting.

I noticed, between attempting to start and troubleshooting that the rotor button was in the same place. I verified this by attempting to start again - the button remained in the same place.

What gives (or doesn't give as the case may be)? I am stumped.

 

[NDT]

You must mean "distributor rotor"?? The only way for your distributor to stop turning is for the tab to break off the end of the shaft. Does the rotor turn freely? It should not.

 

[Bravo2Uniform]

You must mean "distributor rotor"?? The only way for your distributor to stop turning is for the tab to break off the end of the shaft. Does the rotor turn freely? It should not.

Thanks for the nomenclature correction, my mistake. I'm a little flustered.

No, the shaft will not turn freely at all. I assume that means it is still engaged on the oil pump. There is no wiggle or play.

No matter how long I let it try to start, the rotor button is still in the same place, though. So is the issue in the body of the distributor?

 

[NDT]

See if your valves are moving. Another possibility is that the cam driven gear lost all it's fiber teeth. The cam drives the oil pump.

 

[Bravo2Uniform]

See if your valves are moving. Another possibility is that the cam driven gear lost all it's fiber teeth. The cam drives the oil pump.

I will. Thanks for your help, it is really appreciated.

 

[clinto]

So, on the F134, the crank spins the cam via the fiber gear NDT mentioned. The cam then spins the oil pump, which engages with a gear halfway down the cam. The distributor shaft fits into a recess in the top of the oil pump drive shaft. The good thing about this is that there is no timing chain. The bad thing is that you actually have to time the oil pump to the engine!

So, if the engine turns and the distributor doesn't, then the cam gear is stripped, the distributor shaft broke, or the oil pump shaft broke. I will bet you a cold Heineken at the Ga Rally this year that the cam gear is stripped. If so, order one and then put an oil pressure gauge on it and verify the engine has good pressure. They are a "fiber" material so they can wear out. See below:

A customer's M38A1:

Here you can see the end of the distributor and how it fits into the top of the oil pump.



Below you can see the stripped cam gear and how it engages with the crank gear. I had to use a puller to remove it. You can also see how knife edge the remaining teeth are.


Look how much thicker the teeth are on the new one.



Timing the cam to the crank. Kind of important.

 

[Bravo2Uniform]

Nut Came Off the Double Pulley (Harmonic Balancer)

So, on the F134, the crank spins the cam via the fiber gear NDT mentioned. The cam then spins the oil pump, which engages with a gear halfway down the cam. The distributor shaft fits into a recess in the top of the oil pump drive shaft. The good thing about this is that there is no timing chain. The bad thing is that you actually have to time the oil pump to the engine!
So, if the engine turns and the distributor doesn't, then the cam gear is stripped, the distributor shaft broke, or the oil pump shaft broke. I will bet you a cold Heineken at the Ga Rally this year that the cam gear is stripped. If so, order one and then put an oil pressure gauge on it and verify the engine has good pressure. They are a "fiber" material so they can wear out. /QUOTE]

OK, interesting wrinkle that may help isolate the problem. The nut holding the harmonic balancer (not sure if that is the correct nomenclature, it's the double belt pulley at the bottom) vibrated off a day or two ago. I saw the pulley wobbling and shut down the vehicle. Lying directly below the harmonic balancer was its nut. I put it back on.

Is that a coincidence or does it indicate what might have happened?

 

[NDT]

I say unrelated, what say you clinto

 

[clinto]

It's unrelated, all those stupid F134 pulleys are out of whack and no one repros them and with them all being bent, I suspect a great many sling the nut off.

 

[SturmTyger380]

When you do get into see the fiber gears make sure that the oil spray jet is not clogged and it is spraying oil on the gears. It's in the photo that clinto posted. The rusty tower looking thing near the gears with the screw slot on the top of it. It should have an opening that allows oil to be sprayed on the gears.

 

[jeepsguy]

I had one that had the shaft lock up. That caused the drive tab on the end of the shaft to shear off. Pull the distributor out and check. You can get a new shaft or lube up the old one and rebuild the drive tab.

 

[Bravo2Uniform]

I had one that had the shaft lock up. That caused the drive tab on the end of the shaft to shear off. Pull the distributor out and check. You can get a new shaft or lube up the old one and rebuild the drive tab.

Bingo! That's the same thing issue I have. Thanks!

 

[Bravo2Uniform]

 

[NDT]

When you pull the oil pump to remove the broken piece, make sure you mark where the teeth end up so you can orient the pump rotor in the same position when you replace it.

 

[clinto]

So the distributor doesn't turn freely?

You can rebuild them. Pretty simple.

 

[Bravo2Uniform]

When you pull the oil pump to remove the broken piece, make sure you mark where the teeth end up so you can orient the pump rotor in the same position when you replace it.

A lot of work for such a tiny piece of metal!

 

[NDT]

Could you fish it out through the block with your magnet?

 

[jeepsguy]

Hi. I had one where the distr. shaft froze in place causing the drive tab to shear off. I pulled the distr., freed up the shaft, lubed it again and had the tab rebuilt by a friend with a machine shop.

 

[Jeeagle]

Plan for the worse, but always, always check for the simplest solutions first!

 

[Bravo2Uniform]

Could you fish it out through the block with your magnet?

That's what I did. Man, I was not looking forward to tearing into that oil pump assembly. I got my endoscope that works with my phone and fished the magnet in and voila!