I just picked up my first Cummins not too long ago. It's a 91 D250. It seemed like there was an excessive amount of oil on the front components. After checking it out I found that there is a hole about half an inch or so in diameter located in the middle between the harmonic balancer, the water pump, and the fan pulley. The hole is on the passenger side of the fan pulley and you can clearly feel the timing gear through it. I assumed that it might be a cam sensor, but I don't think that my truck (a 1991 manufactured in September of '90) would have one.

Is it an accessory that someone attempted to drill? I found cam sensors that appear to fit from newer model cummmins, but they look like they may ride to deep and contact the timing gear. Has anyone had any experience with this, or know of a best way to plug this hole with minimum impact to the engine?

Here's a crude pic for reference:

 

That was the old way of keeping the KDP from falling out. A jig was bolted to the timing case and a hole was drilled through it and into the timing case. I forget what was used to block the pin but it went through that hole that you have.

As you may know there's very little pressure to speak of within the case. I'd bet you could find a rubber plug to put in there, put some RTV silicone under the top's flange and it would seal just fine.

 

Thanks for the help. I didn't realize people actually drilled into the side of the timing case to keep the KDP in. I always thought the case came off to remove it no matter what.

I think I'll just seal it up nicely. Thanks for the tip.

 

You don't remove the dowel pin. It's needed in the assembly. You fashion a retainer to keep it in place.
a. There's a bolt nearby that will hold an elongated washer over the pin.
b. Redneck way, drill though the timing cover and hold the pin in place with a toggle bolt, probably sealed with bubble gum.

So, at least peek through the hole with a mirror and make sure your dowel pin isn't walking out of it's home hole.

 

I can't really tell, but that sure looks like the sensor hole from the Marine timing case. We just had someone here on the first gen board talk about theirs, last fall I think? Anyway, I believe theirs was a 91 as well.

 

That is not a KDP kill hole. That is a hole for a Hall effect tach sensor used in some marine and industrial applications. There should be an aluminum plug in this hole. They deleted this hole in the intercooled motors.

 

He stated it was on the pass. side of the fan hub, so that would make it impossible for it to be the KDP. My 89 motor does not have one of those.

 

Is this what you are referring to?

There is just a cover with a bolt securing it.









Quote:
I can't really tell, but that sure looks like the sensor hole from the Marine timing case. We just had someone here on the first gen board talk about theirs, last fall I think? Anyway, I believe theirs was a 91 as well.


Quote:
That is not a KDP kill hole. That is a hole for a Hall effect tach sensor used in some marine and industrial applications. There should be an aluminum plug in this hole. They deleted this hole in the intercooled motors.

So what all have you heard about this?

I have ask people at Cummins Cal Pacific and nobody knew what it was used for, I am looking for a way to install a good tachometer on my engine, if it was a hall effect sensor then how many pulses would be counted off the gear teeth and what style tach would be used?

All of the tachometer drives I have seen on stationary AG and fire pumps mount in place of the oil fill pipe and drives off the nut of the injection pump gear.

Jim

 

"I am looking for a way to install a good tachometer on my engine, if it was a hall effect sensor then how many pulses would be counted off the gear teeth and what style tach would be used?"

Depending on the tip width of the actually sensor it should see every tooth on the gear. So total teeth on gear=pulses/revolution.

 

The flat teardrop cover has a plug piece thet goes into the hole sealed with an o-ring.

 

So what determined what engines got this?

 

Any idea where to find this teardrop piece with an o-ring? I recently sealed the hole, but I'd prefer to do it correctly/factory.